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Sample records for pronounced purine sequence

  1. Indirect Readout of DNA Sequence at the Primary-kink Site in the CAP-DNA Complex: Recognition of Pyrimidine-Purine and Purine-Purine Steps

    SciTech Connect

    Napoli,A.; Lawson, C.; Ebright, R.; Berman, H.

    2006-01-01

    The catabolite activator protein (CAP) bends DNA in the CAP-DNA complex, typically introducing a sharp DNA kink, with a roll angle of {approx}40 deg and a twist angle of {approx}20 deg, between positions 6 and 7 of the DNA half-site, 5'-A1A2A3T4G5T6G7A8T9C10T11-3' ('primary kink'). In previous work, we showed that CAP recognizes the nucleotide immediately 5' to the primary-kink site, T6, through an 'indirect-readout' mechanism involving sequence effects on energetics of primary-kink formation. Here, to understand further this example of indirect readout, we have determined crystal structures of CAP-DNA complexes containing each possible nucleotide at position 6. The structures show that CAP can introduce a DNA kink at the primary-kink site with any nucleotide at position 6. The DNA kink is sharp with the consensus pyrimidine-purine step T{sub 6}G{sub 7}, and the non-consensus pyrimidine-purine step C{sub 6}G{sub 7} (roll angles of {approx}42 deg, twist angles of {approx}16 deg), but is much less sharp with the non-consensus purine-purine steps A{sub 6}G{sub 7} and G{sub 6}G{sub 7} (roll angles of {approx}20 deg, twist angles of {approx}17 deg). We infer that CAP discriminates between consensus and non-consensus pyrimidine-purine steps at positions 6-7 solely based on differences in the energetics of DNA deformation, but that CAP discriminates between the consensus pyrimidine-purine step and non-consensus purine-purine steps at positions 6-7 both based on differences in the energetics of DNA deformation and based on qualitative differences in DNA deformation. The structures further show that CAP can achieve a similar, {approx}46 deg per DNA half-site, overall DNA bend through a sharp DNA kink, a less sharp DNA kink, or a smooth DNA bend. Analysis of these and other crystal structures of CAP-DNA complexes indicates that there is a large, {approx}28 deg per DNA half-site, out-of-plane component of CAP-induced DNA bending in structures not constrained by end-to-end DNA

  2. Complete genome sequence of Bacillus amyloliquefaciens XH7, which exhibits production of purine nucleosides.

    PubMed

    Yang, Huilin; Liao, Yuling; Wang, Bin; Lin, Ying; Pan, Li

    2011-10-01

    Here, we report the complete annotated genome sequence of Bacillus amyloliquefaciens XH7, which is used to produce purine nucleosides in industry. The genome sequence will allow for the characterization of the molecular mechanisms underlying its beneficial properties.

  3. Association of poly-purine/poly-pyrimidine sequences with meiotic recombination hot spots

    PubMed Central

    Bagshaw, Andrew TM; Pitt, Joel PW; Gemmell, Neil J

    2006-01-01

    Background Meiotic recombination events have been found to concentrate in 1–2.5 kilo base regions, but these recombination hot spots do not share a consensus sequence and why they occur at specific sites is not fully understood. Some previous evidence suggests that poly-purine/poly-pyrimidine (poly-pu/py) tracts (PPTs), a class of sequence with distinctive biochemical properties, could be involved in recombination, but no general association of PPTs with meiotic recombination hot spots has previously been reported. Results We used computational methods to investigate in detail the relationship between PPTs and hot spots. We show statistical associations of PPT frequency with hot spots of meiotic recombination initiating lesions, double-strand breaks, in the genome of the yeast S. cerevisiae and with experimentally well characterized human meiotic recombination hot spots. Supporting a possible role of poly-pu/py-rich sequences in hot spot recombination, we also found that all three single nucleotide polymorphisms previously shown to be associated with human hot spot activity changes occur within sequence contexts of 14 bp or longer that are 85% or more poly-pu/py and at least 70% G/C. These polymorphisms are all close to the hot spot mid points. Comparing the sequences of experimentally characterized human hot spots with the orthologous regions of the chimpanzee genome previously shown not to contain hot spots, we found that in all five cases in which comparisons for the hot spot central regions are possible with publicly available sequence data, there are differences near the human hot spot mid points within sequences 14 bp or longer consisting of more than 80% poly-pu/py and at least 50% G/C. Conclusion Our results, along with previous evidence for the unique biochemical properties and recombination-stimulating potential of poly-pu/py-rich sequences, suggest that the possible functional involvement of this type of sequence in meiotic recombination hot spots

  4. Factors associated with a purine-rich exonic splicing enhancer sequence in Xenopus oocyte nucleus

    SciTech Connect

    Masuyama, Kaoru; Taniguchi, Ichiro; Okawa, Katsuya; Ohno, Mutsuhito . E-mail: hitoohno@virus.kyoto-u.ac.jp

    2007-08-03

    Purine-rich exonic splicing enhancers (ESEs) stimulate splicing of the adjacent introns with suboptimal splice sites. To elucidate the mechanism regarding ESEs, factors specifically associated with ESEs in HeLa cell nuclear extracts were previously investigated, and shown to include SR (serine/arginine-rich) proteins. However, factors associated with ESEs in vivo have not yet been explored. Here we show that a GAA repeat RNA sequence, a typical ESE, is associated in Xenopus oocyte nuclei with at least one SR protein, SF2/ASF, as was expected. Moreover, components of SF3a/b complexes, U2 snRNA, and U2AF{sup 65} were also found to be associated with the ESE in the nucleus. Since SF3a/b complexes are the constituents of the 17S U2 snRNP, these results suggest that the 17S U2 snRNP is associated with the ESE in the nucleus, probably through bridging interactions of U2AF and SR proteins. The identified factors may represent a functional splicing enhancer complex in vivo.

  5. Pronounced population genetic differentiation in the rock bream Oplegnathus fasciatus inferred from mitochondrial DNA sequences.

    PubMed

    Xiao, Yongshuang; Li, Jun; Ren, Guijing; Ma, Daoyuan; Wang, Yanfeng; Xiao, ZhiZhong; Xu, Shihong

    2016-05-01

    The population genetic structure of the rock bream (Oplegnathus fasciatus) along the coastal waters of China was estimated based on three mtDNA fragments (D-loop, COI, and Cytb). A total of 112 polymorphic sites were checked, which defined 63 haplotypes. A pattern with high levels of haplotype diversity (hCOI = 0.886 ± 0.034, hCytb = 0.874 ± 0.023) and low levels of nucleotide diversity (лCOI = 0.009 ± 0.005, лCytb = 0.006 ± 0.003) was detected based on the COI and Cytb fragments, and high levels of genetic diversity (hD-loop = 0.995 ± 0.007, лD-loop = 0.021 ± 0.011) were detected from the mtDNA D-loop. The population genetic diversity of O. fasciatus in south China was significantly higher than those of north China. Three genealogical clades were checked in the O. fasciatus populations based on the NJ and MST analyses of mtDNA COI gene sequence, and the genetic distances among the clades ranged from 0.018 to 0.025. Significant population genetic differentiation was also checked based on the Fst (0.331, p = 0.000) and exact p (0.000) test analyses. No significant population differentiations were checked based on mtDNA D-loop and Cytb fragments. Using a variety of phylogenetic methods, coalescent reasoning, and molecular dating interpreted in conjunction with paleoclimatic and physiographic evidences, we inferred that the genetic make-up of extant populations of O. fasciatus was shaped by Pleistocene environmental impacts on the historical demography of this species. Coalescent analyses (neutrality tests, mismatch distribution analysis, and Bayesian skyline analyses) showed that the species along coastline of China has experienced population expansions originated in its most recent history at about 169-175 kya before present.

  6. Expression of a cDNA sequence encoding human purine nucleoside phosphorylase in rodent and human cells.

    PubMed Central

    McIvor, R S; Goddard, J M; Simonsen, C C; Martin, D W

    1985-01-01

    A cDNA sequence which contains the entire coding region for human purine nucleoside phosphorylase (PNP) was recombined for selection and expression in mammalian cells. Plasmids containing either the simian virus 40 early promoter or the mouse metallothionein promoter positioned just upstream of the PNP coding sequence were constructed. These plasmids also contained the gene for a methotrexate-resistant dihydrofolate reductase, allowing for selection and amplification of positive transferrents after transfection of cells by the DNA-calcium phosphate coprecipitation technique. Expression of human PNP activity was readily detected in both mouse (L) and CHO cells by isoelectric focusing of cell extracts followed by histochemical staining for PNP activity. The simian virus 40 early promoter directed considerable expression of human PNP activity in CHO cells but only scant activity in mouse cells. The mouse metallothionein promoter was not successful in effecting human PNP expression in CHO cells but provided substantial human PNP activity in mouse cells and was inducible by incubation with zinc. HeLa cell transferrents were isolated and screened for the presence of transferred PNP cDNA sequences by Southern hybridization analysis. RNA transcripts derived from the transferred PNP cDNA were identified in one of these cell lines. Images PMID:3929070

  7. Purine and pyrimidine metabolism.

    PubMed

    Zöllner, N

    1982-09-01

    The pathways of purine biosynthesis and degradation have been elucidated during the last 30 years; the regulation of the mechanisms involved is not yet fully understood, particularly with respect to quantitative aspects. Research into inborn errors of purine metabolism has provided valuable insights into purine synthesis and salvage pathways. Nutrition experiments using purine-free formula diets and supplements with defined purine sources permit precise descriptions of the influence of various dietary purines on uric acid formation. Supplements of dietary purines produce dose-proportional increases in plasma uric acid concentrations, uric acid pool size and renal uric acid excretion. The magnitude of these increases depends on the type of purine compound administered, which may limit the value of food tables for human dietetics. Purine content of food must be related not only to weight but also to energy and to protein, particularly if new foodstuffs or a vegetarian diet are ingested. Dietary purines appear to influence the biosynthesis of pyrimidines. In contrast to dietary purines, pyrimidines in the diet, if administered as nucleosides or nucleotides, are utilized in animals for the synthesis of nucleic acids. Much further work is necessary for a better understanding of the inter-relationships of purine and pyrimidine metabolism.

  8. Structure/Function Analysis of DNA-glycosylases That Repair Oxidized Purines and Pyrimidines and the Influence of Surrounding DNA Sequence on Their Interactions

    SciTech Connect

    Wallace, Susan S.

    2005-08-22

    The overall goal of this project was to elucidate the structure/function relationships between oxidized DNA bases and the DNA repair enzymes that recognize and remove them. The NMR solution structure of formamidopyrimidine DNA glycosylase (Fpg) that recognizes oxidized DNA purines was to be determined. Furthermore, the solution structures of DNA molecules containing specific lesions recognized by Fpg was to be determined in sequence contexts that either facilitate or hinder this recognition. These objectives were in keeping with the long-term goals of the Principal Investigator's laboratory, that is, to understand the basic mechanisms that underpin base excision repair processing of oxidative DNA lesions and to elucidate the interactions of unrepaired lesions with DNA polymerases. The results of these two DNA transactions can ultimately determine the fate of the cell. These objectives were also in keeping with the goals of our collaborator, Dr. Michael Kennedy, who is studying the repair and recognition of damaged DNA. Overall the goals of this project were congruent with those of the Department of Energy's Health Effects and Life Sciences Research Program, especially to the Structural Biology, the Human Genome and the Health Effects Programs. The mission of the latter Program includes understanding the biological effects and consequences of DNA damages produced by toxic agents in the many DOE waste sites so that cleanup can be accomplished in a safe, effective and timely manner.

  9. [Determination of purine compounds and purine bases in food].

    PubMed

    Colling, M; Wolfram, G

    1987-10-01

    The total purine content and the content of RNA, DNA, nucleotides, nucleosides and free purine bases has been determined in commercial raw food. After hydrolysing food samples with acid, the total purine content is enzymatically determined as uric acid. For the determination of the nucleic acid content, a method is chosen that allows for the analysis of the composition of nucleic acids. The amount of purine bound in nucleic acids and of purine bound in nucleotides, nucleosides and free bases is very different. The content of nucleic acids is especially high in the innards of veal, pork and beef. In these samples the quantity of purine bound in nucleotides, nucleosides and bases is very small. In trout and herring, however, more purine is bound in RNA and DNA. The same is true of roe, pork and beef muscle. Peas and beans have the lowest total purine content of all the samples examined.

  10. Isolation of fast purine nucleotide synthase ribozymes.

    PubMed

    Lau, Matthew W L; Cadieux, Kelly E C; Unrau, Peter J

    2004-12-08

    Here we report the in vitro selection of fast ribozymes capable of promoting the synthesis of a purine nucleotide (6-thioguanosine monophosphate) from tethered 5-phosphoribosyl 1-pyrophosphate (PRPP) and 6-thioguanine ((6S)Gua). The two most proficient purine synthases have apparent efficiencies of 284 and 230 M(-1) min(-1) and are both significantly more efficient than pyrimidine nucleotide synthase ribozymes selected previously by a similar approach. Interestingly, while both ribozymes showed good substrate discrimination, one ribozyme had no detectable affinity for 6-thioguanine while the second had a K(m) of approximately 80 muM, indicating that these ribozymes use considerably different modes of substrate recognition. The purine synthases were isolated after 10 rounds of selection from two high-diversity RNA pools. The first pool contained a long random sequence region. The second pool contained random sequence elements interspersed with the mutagenized helical elements of a previously characterized 4-thiouridine synthase ribozyme. While nearly all of the ribozymes isolated from this biased pool population appeared to have benefited from utilizing one of the progenitor's helical elements, little evidence for more complicated secondary structure preservation was evident. The discovery of purine synthases, in addition to pyrimidine synthases, demonstrates the potential for nucleotide synthesis in an 'RNA World' and provides a context from which to study small molecule RNA catalysis.

  11. Triple, MPEG-conjugated, helix-forming oligonucleotides (TRIPEGXs): liquid-phase synthesis of natural and chimeric "all-purine" sequences linked to high molecular weight poly(ethylene glycols).

    PubMed

    Ballico, M; Drioli, S; Morvan, F; Xodo, L; Bonora, G M

    2001-01-01

    Long "all-purine" oligonucleotides, up to the 20mer, known to be active as antigene effectors, conjugated to high molecular weight monomethoxy poly(ethylene glycol)s (MPEG)s, were successfully synthesized. Through a liquid-phase, MPEG-supported process, both natural and chimeric sequences containing selected phosphorothioate backbone modifications were obtained, purified, and characterized. To follow their cellular trafficking, a fluorescent probe was linked by soluble supported organic reactions to the 5'-terminus, and the efficiency of the different synthetic procedures for the introduction of a fluorescein moiety was compared. The usefulness of the fluorescent marker was estimated by laser confocal microscopy that ascertains that the MPEG-conjugation enhances the oligonucleotide capacity to cross the cellular membranes and to be accumulated inside the nuclei.

  12. Detection of purine cytosine permease of S. cerevisiae: use of antibodies against a synthetic peptide corresponding to a predicted sequence in the N-terminal domain of the protein.

    PubMed

    Grandier-Vazeille, X; Neaud, V; Geoffre, S

    1993-12-15

    A synthetic peptide, selected in the predicted N-terminal amino-acid sequence of the purine cytosine permease (gene FCY2), linked to albumins proved a remarkably good immunogen in rabbits. In ELISA, sera reacted with the synthetic peptide and with specific proteins of plasma-membrane-enriched fractions of mutant Saccharomyces cerevisiae pAB strains (amplified FCY2 gene) with high titers and high avidity. Western blots of plasma membrane proteins of pAB strain probed with antisera showed two bands: a major (45 kDa) and minor band (50 kDa). On the contrary, plasma-membrane-enriched fractions of mutant S. cerevisiae pJDB strain (deficient in FCY2 gene) gave no signal when probed in the same conditions. These results demonstrate the specificity of the antisera and also suggest that the 45 kDa and 50 kDa proteins are both products of the FCY2 gene.

  13. Purine alkaloids in Paullinia.

    PubMed

    Weckerle, Caroline S; Stutz, Michael A; Baumann, Thomas W

    2003-10-01

    Among the few purine alkaloid-containing genera consumed as stimulants, Paullinia is the least investigated with respect to both chemotaxonomy and within-the-plant allocation of caffeine and its allies. Since purine alkaloids (PuA) have been proved to be valuable marker compounds in chemotaxonomy, 34 species of Paullinia and related genera were screened for them, but only one, P. pachycarpa, was positive in addition to the already known P. cupana and P. yoco. The PuA allocation in P. pachycarpa was examined and found to be restricted to theobromine in the stem, leaves and flowers. Moreover, the theobromine concentration in the stem cortex increased significantly towards the base of the plant. Since the stem cortex of P. yoco is traditionally used by the natives of Colombia and Ecuador to prepare a caffeine-rich beverage, we suspected that within the genus Paullinia the PuA are preferentially allocated to the older parts of the stem and not to young shoots like e.g., in the coffee plant (Coffea spp.). Indeed, the axis (greenhouse) of P. cupana (guaraná), known for its caffeine-rich seeds, exhibited a basipetal PuA gradient (0.005-0.145%). Moreover, the analysis of young cortex samples (herbarium) and of one piece of old stem (museum collection) revealed the same for P. yoco, even though we found much less (0.5 vs 2.5%) caffeine in the old cortex as compared to the only two analyses in 1926 of similar material. However, this discrepancy may be explained by the high variability of the PuA pattern we detected among yoco, the diversity of which the Indians take advantage.

  14. Importance of purine and pyrimidine content of local nucleotide sequences (six bases long) for evolution of the human immunodeficiency virus type 1.

    PubMed Central

    Doi, H

    1991-01-01

    Human immunodeficiency virus type 1 evolves rapidly, and random base change is thought to act as a major factor in this evolution. However, segments of the viral genome differ in their variability: there is the highly variable env gene, particularly hypervariable regions located within env, and, in contrast, the conservative gag and pol genes. Computer analysis of the nucleotide sequences of human immunodeficiency virus type 1 isolates reveals that base substitution in this virus is nonrandom and affected by local nucleotide sequences. Certain local sequences 6 base pairs long are excessively frequent in the hypervariable regions. These sequences exhibit base-substitution hotspots at specific positions in their 6 bases. The hotspots tend to be nonsilent letters of codons in the hypervariable regions--thus leading to marked amino acid substitutions there. Conversely, in the conservative gag and pol genes the hotspots tend to be silent letters because of a difference in codon frame from the hypervariable regions. Furthermore, base substitutions in the local sequences that frequently appear in the conservative genes occurred at a low level, even within the variable env. Thus, despite the high variability of this virus, the conservative genes and their products could be conserved. These may be some of the strategies evolved in human immunodeficiency virus type 1 to allow for positive-selection pressures, such as the host immune system, and negative-selection pressures on the conservative gene products. Images PMID:1924392

  15. Purine and pyrimidine metabolism in man V

    SciTech Connect

    Nyhan, W.L.; Thompson, L.F.; Watts, R.W.E.

    1986-01-01

    This book comprises the proceedings of the Fifth International Symposium on Human Purine and Pyrimidine Metabolism. Its papers are organized under the following categories: adenosine receptors; purine receptors and the central nervous system; nucleoside and base transport; studies with antimetabolites; deoxynucleotide and nucleoside toxicity and metabolism; enzymes; purine and pyrimidine metabolism during lymphocyte differentiation; purine metabolism in skeletal muscle; purine nucleotide metabolism in the heart; purine and pyrimidine metabolism in primary cell cultures and in parasites; nucleoside kinases and drug activation; phosphoribosylpyrophosphate; S-adenosylmethionine metabolism; and the metabolic effects of interferon.

  16. Base excision of oxidative purine and pyrimidine DNA damage in Saccharomyces cerevisiae by a DNA glycosylase with sequence similarity to endonuclease III from Escherichia coli.

    PubMed

    Eide, L; Bjørås, M; Pirovano, M; Alseth, I; Berdal, K G; Seeberg, E

    1996-10-01

    One gene locus on chromosome I in Saccharomyces cerevisiae encodes a protein (YAB5_YEAST; accession no. P31378) with local sequence similarity to the DNA repair glycosylase endonuclease III from Escherichia coli. We have analyzed the function of this gene, now assigned NTG1 (endonuclease three-like glycosylase 1), by cloning, mutant analysis, and gene expression in E. coli. Targeted gene disruption of NTG1 produces a mutant that is sensitive to H2O2 and menadione, indicating that NTG1 is required for repair of oxidative DNA damage in vivo. Northern blot analysis and expression studies of a NTG1-lacZ gene fusion showed that NTG1 is induced by cell exposure to different DNA damaging agents, particularly menadione, and hence belongs to the DNA damage-inducible regulon in S. cerevisiae. When expressed in E. coli, the NTG1 gene product cleaves plasmid DNA damaged by osmium tetroxide, thus, indicating specificity for thymine glycols in DNA similarly as is the case for EndoIII. However, NTG1 also releases formamidopyrimidines from DNA with high efficiency and, hence, represents a glycosylase with a novel range of substrate recognition. Sequences similar to NTG1 from other eukaryotes, including Caenorhabditis elegans, Schizosaccharomyces pombe, and mammals, have recently been entered in the GenBank suggesting the universal presence of NTG1-like genes in higher organisms. S. cerevisiae NTG1 does not have the [4Fe-4S] cluster DNA binding domain characteristic of the other members of this family.

  17. Structure of grouper iridovirus purine nucleoside phosphorylase

    SciTech Connect

    Kang, You-Na; Zhang, Yang; Allan, Paula W.; Parker, William B.; Ting, Jing-Wen; Chang, Chi-Yao; Ealick, Steven E.

    2010-02-01

    The crystal structure of purine nucleoside phosphorylase from grouper iridovirus was solved at 2.38 Å resolution. Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of purine ribonucleosides to the corresponding free bases and ribose 1-phosphate. The crystal structure of grouper iridovirus PNP (givPNP), corresponding to the first PNP gene to be found in a virus, was determined at 2.4 Å resolution. The crystals belonged to space group R3, with unit-cell parameters a = 193.0, c = 105.6 Å, and contained four protomers per asymmetric unit. The overall structure of givPNP shows high similarity to mammalian PNPs, having an α/β structure with a nine-stranded mixed β-barrel flanked by a total of nine α-helices. The predicted phosphate-binding and ribose-binding sites are occupied by a phosphate ion and a Tris molecule, respectively. The geometrical arrangement and hydrogen-bonding patterns of the phosphate-binding site are similar to those found in the human and bovine PNP structures. The enzymatic activity assay of givPNP on various substrates revealed that givPNP can only accept 6-oxopurine nucleosides as substrates, which is also suggested by its amino-acid composition and active-site architecture. All these results suggest that givPNP is a homologue of mammalian PNPs in terms of amino-acid sequence, molecular mass, substrate specificity and overall structure, as well as in the composition of the active site.

  18. Purine metabolism in Toxoplasma gondii

    SciTech Connect

    Krug, E.C.; Marr, J.J.; Berens, R.L.

    1989-06-25

    We have studied the incorporation and interconversion of purines into nucleotides by freshly isolated Toxoplasma gondii. They did not synthesize nucleotides from formate, glycine, or serine. The purine bases hypoxanthine, xanthine, guanine, and adenine were incorporated at 9.2, 6.2, 5.1, and 4.3 pmol/10(7) cells/h, respectively. The purine nucleosides adenosine, inosine, guanosine, and xanthosine were incorporated at 110, 9.0, 2.7, and 0.3 pmol/10(7) cells/h, respectively. Guanine, xanthine, and their respective nucleosides labeled only guanine nucleotides. Inosine, hypoxanthine, and adenine labeled both adenine and guanine nucleotide pools at nearly equal ratios. Adenosine kinase was greater than 10-fold more active than the next most active enzyme in vitro. This is consistent with the metabolic data in vivo. No other nucleoside kinase or phosphotransferase activities were found. Phosphorylase activities were detected for guanosine and inosine; no other cleavage activities were detected. Deaminases were found for adenine and guanine. Phosphoribosyltransferase activities were detected for all four purine nucleobases. Interconversion occurs only in the direction of adenine to guanine nucleotides.

  19. Was adenine the first purine?

    NASA Technical Reports Server (NTRS)

    Schwartz, Alan W.; Bakker, C. G.

    1989-01-01

    Oligomerization of HCN (1 molar) in the presence of added formaldehyde (0.5 molar) produced an order of magnitude more 8-hydroxymethyladenine than adenine or any other biologically significant purine. This result suggests that on the prebiotic earth, nucleoside analogs may have been synthesized directly in more complex mixtures of HCN with other aldehydes.

  20. Was adenine the first purine?

    NASA Technical Reports Server (NTRS)

    Schwartz, Alan W.; Bakker, C. G.

    1989-01-01

    Oligomerization of HCN (1 molar) in the presence of added formaldehyde (0.5 molar) produced an order of magnitude more 8-hydroxymethyladenine than adenine or any other biologically significant purine. This result suggests that on the prebiotic earth, nucleoside analogs may have been synthesized directly in more complex mixtures of HCN with other aldehydes.

  1. Dephosphorylation of purine mononucleotides by alkaline phosphatases. Substrate specificity and inhibition patterns.

    PubMed

    Jensen, M H

    1979-11-09

    Three purine mononucleotides, adenosine-, inosine- and guanosine monophosphate, were used as substrates at pH 7.4 and at 10.4 for three alkaline phosphatases (orthophosphoric-monoester phosphohydrolase (acid optimum), EC 3.1.3.1) containing similar phosphate-binding serine groups at their esteratic sites. Substrate specificity was found for the enzymes from calf intestine and bovine liver. Alkaline phosphatase from Escherichia coli was nonspecific. A substrate-dependent and pronounced inhibition with the purine analogue 1,3-dimethyl xanthine was found for the enzymes from intestine and liver, but not for alkaline phosphatase from E. coli. A substrate-independent and pronounced inhibition was found for all three enzymes with the phosphomonoester p-nitrophenol phosphate as the inhibitor. Alkaline phosphatases may play an important role in the regulation of the intracellular content of purine mononucleotides.

  2. Comparison of the effects of UV irradiation on 5-methyl-substituted and unsubstituted pyrimidines in alternating pyrimidine-purine sequences in DNA.

    PubMed

    Zuo, S; Boorstein, R J; Cunningham, R P; Teebor, G W

    1995-09-12

    We previously demonstrated the UV-induced formation of cytosine hydrate in DNA and its deamination product, uracil hydrate, via their release from the DNA backbone by the DNA glycosylase activity of Escherichia coli endonuclease III. Subsequently, endonuclease III-mediated release of thymine hydrate from UV-irradiated poly(dA-dT) was reported. Therefore, we asked whether 5-methylcytosine residues in DNA underwent photohydration and deamination to thymine hydrate in analogy to UV-induced deamination of cytosine. An alternating DNA copolymer containing 5-methylcytosine was irradiated with UVC and incubated with endonuclease III. No 5-methylcytosine hydrate was released. Instead, UV-induced nonenzymatic release of 5-methylcytosine occurred. Similarly, incubation of UV-irradiated poly(dA-dT) with endonuclease III did not release thymine hydrate; nonenzymatic release of thymine occurred. Nonenzymatic release of 5-methylpyrimidines was oxygen dependent, enhanced by ferric ion and inhibited by free radical scavengers. In contrast, photohydration of cytosine was oxygen independent, and only small amounts of cytosine were nonenzymatically released. Thus, 5-methylpyrimidine residues within alternating Pu-Py sequences in DNA do not undergo photohydration, but instead undergo cleavage of their N-glycosyl bonds yielding abasic (AP) sites. The inability to repair such AP sites may explain the UV sensitivity of E. coli xthnfo mutants, which lack AP endonuclease activity. We suggest that N-glycosyl bond cleavage is mediated by radical species formed via transfer of an electron from UV-excited triplet 5-methylpyrimidines to ground state oxygen and/or ferric ions.

  3. Structure and mechanism of purine binding riboswitches

    PubMed Central

    Batey, Robert T.

    2013-01-01

    A riboswitch is a non-protein coding sequence capable of directly binding a small molecule effector without the assistance of accessory proteins to regulate expression of the mRNA in which it is embedded. Currently, over 20 different classes of riboswitches have been validated in bacteria with the promise of many more to come, making them an important means of regulation of the genome in the bacterial kingdom. Strikingly, half of the known riboswitches recognize effector compounds that contain a purine or related moiety. In the last decade significant progress has been made to determine how riboswitches specifically recognize these compounds against the background of many other similar cellular metabolites and transduce this signal into a regulatory response. Of the known riboswitches, the purine family containing guanine, adenine, and 2’-deoxyguanosine binding classes are the most extensively studied, serving as a simple and useful paradigm for understanding how these regulatory RNAs function. This review provides a comprehensive summary of the current state of knowledge regarding the structure and mechanism of these riboswitches, as well as insights into how they might be exploited as therapeutic targets and novel biosensors. PMID:22850604

  4. The interaction of aflatoxins with purines and purine nucleosides

    PubMed Central

    Clifford, Janet I.; Rees, K. R.

    1967-01-01

    From measurements of thermal hyperchromicity and the behaviour of an aflatoxin–DNA mixture on a Sephadex column it was concluded that aflatoxin B1 is capable of weak binding to single-stranded DNA. The interactions of the aflatoxins (B1, G1 and G2) with nucleosides result in difference spectra and suggest that the purine bases and the amino group play a role in the binding of all the aflatoxins to DNA. PMID:6032981

  5. Mechanism of purine antimetabolites and purine nucleodise imbalance

    SciTech Connect

    Duan, D.S.

    1989-01-01

    Purine starvation is responsible for the cytotoxic effects of many purine antimetabolites. Guanine nucleotide depletion leads to a drastic DNA synthesis inhibition while adenine nucleotide depletion interferes with other vital functions before inhibiting DNA synthesis. To investigate the mechanism of these distinct effects, kinetics studies of adenine and guanine tracer incorporation into nucleotide pools and DNA were performed in S-49 cells. To address the question whether the cellular dGTP pool is compartmentalized, ({sup 14}C)Gua and ({sup 3}H)Guo tracer experiments were performed in a double mutant S-49 cell line, dGuo-L, with purine nucleoside phosphorylase (PNP) deficiency and dGTP feedback resistant ribonucleotide reductase (RR). While RR inhibition by dGTP was proposed as the cytotoxic mechanism in PNP immunodeficiency, additional effects of dGuo were studied in S-49 cells and human peripheral blood T lymphocytes (PBTL). RNA synthesis but not DNA synthesis was among the earliest targets of dGuo toxicity, and dGuo exerted cytotoxicity in resting PBTL before DNA synthesis. Three transformed T cells lines, PEER, HPB-ALL and HPB-MLT, were selected and characterized for cell surface markers and their sensitivities to dAdo and deoxycoformycin, an ADA inhibitor.

  6. [Total purine content in selected foods].

    PubMed

    Wolfram, G; Colling, M

    1987-12-01

    For the dietary treatment of hyperuricemia and gout, it is necessary to know the total purine content of food. A new method determining the purine content enzymatically, as uric acid, allows routine analysis. Many foods of animal and plant origin were brought in usual or alternative stores and analysed.

  7. [Purine in common plant food in China].

    PubMed

    Rong, Shengzhong; Zou, Lina; Wang, Zhaoxu; Pan, Hongzhi; Yang, Yuexin

    2012-01-01

    To determine the content of purine in plant food in China with HPLC. HPLC analysis was applied on Waters Atlantis T3 column (4.6mm x 250mm x 5 microm), using 10.0 mmol/L NH4COOH (pH 3.6) and CH3OH (99%/1%) as mobile phase and running at a flow rate of 1.0 ml/min. The column temperature was 30 degrees C, and the detection wavelength was at 254nm. The content of purine varied significantly in different kinds of plant food. The content of purine in dried fungi and dried legumes and legume products was higher than that in other food, the content of purine in vegetables and vegetable products and fruits and fruit products was low. As a whole, the content of purine was: dried fungi and algae > dried legumes and legume products > nuts and fresh > seeds fungi and algae > cereal and cereals products > vegetables and vegetable products > fruit and fruit products > tubers, starches and products. The content of purine of dried fungi and algae and dried legumes and legume products in plant food was high. The content of purine was varied significantly in different kinds of plant food.

  8. Kinetics of luminol sonochemiluminescence quenched by purines.

    PubMed

    Wang, Jian; Lai, Yongquan; Chen, Meili; Jiang, Zhou; Chen, Guonan

    2013-01-01

    A homogeneous chemiluminescence (CL) reaction was initiated by ultrasound irradiation. Luminol sonochemiluminescence (SCL) reaction kinetics were determined under pseudo-first-order conditions, and the reaction followed the model for simple rise-fall kinetics. In addition, SCL quenching reactions induced by purines were also investigated in which the interactions between luminol and purines were analysed using the Stern-Volmer (S-V) mechanism. The results implied that the high rate constant of luminol CL quenched by purines may be attributed to ground state interactions originating from hydrogen bonding. Copyright © 2012 John Wiley & Sons, Ltd.

  9. Microwave-assisted synthesis of C-8 aryl and heteroaryl inosines and determination of their inhibitory activities against Plasmodium falciparum purine nucleoside phosphorylase.

    PubMed

    Gigante, Alba; Priego, Eva-María; Sánchez-Carrasco, Paula; Ruiz-Pérez, Luis Miguel; Vande Voorde, Johan; Camarasa, María-José; Balzarini, Jan; González-Pacanowska, Dolores; Pérez-Pérez, María-Jesús

    2014-07-23

    8-Arylinosines have been scarcely studied for therapeutic purposes, probably due to difficulties in their synthesis. The recently described direct arylation reaction at position 8 of purine nucleosides has been employed to synthesize a series of 8-aryl and 8-pyridylinosines. These compounds have been studied for hydrolytic stability and subjected to biological evaluation. Three compounds have shown a pronounced specific inhibition of Plasmodium falciparum-encoded purine nucleoside phosphorylase, an important target for antimalarial chemotherapy.

  10. Genetics Home Reference: purine nucleoside phosphorylase deficiency

    MedlinePlus

    ... patients with purine nucleoside phosphorylase deficiency. Nucleosides Nucleotides Nucleic Acids. 2004 Oct;23(8-9):1411-5. Erratum in: Nucleosides Nucleotides Nucleic Acids. 2005;24(4):303. Citation on PubMed Nyhan ...

  11. T.C.G triplet in an antiparallel purine.purine.pyrimidine DNA triplex. Conformational studies by NMR.

    PubMed

    Dittrich, K; Gu, J; Tinder, R; Hogan, M; Gao, X

    1994-04-12

    The antiparallel purine.purine.pyrimidine DNA triplex, RRY6, which contains a T.C.G inverted triplet in the center of the sequence, was examined by proton and phosphorous two-dimensional NMR spectroscopy. The local conformation of the T.C.G triplet (T4.C11.G18) and the effect of this triplet on the global helical structure were analyzed in detail. The formation of the T.C.G triplet is confirmed by a set of cross-strand NOEs, including unusual cross-strand NOEs between the third strand and the pyrimidine strand as opposed to the purine strand of the duplex. NMR data suggest that the T.C.G triplet may be present in an equilibrium between a non-hydrogen-bonded form and a T(O4)-C(NH2) hydrogen-bonded form and that there is a distortion of the in-plane alignment of the three bases. The flanking G.G.C base triplets are well-defined on the 5'-side of T4, but somewhat interrupted on the 3'-side of T4. The effect of the third strand binding on the Watson-Crick duplex was probed by an NMR study of the free duplex RY6. NMR parameters are affected mostly around the T.C.G inversion site. The perturbations extend to at least two adjacent base triplets on either side. The binding of the third purine strand and the accommodation of a central T.C.G inversion in RRY6 does not require a readjustment in sugar pucker, which remains in the range of C2'-endo. 31P resonances of RRY6 distribute over a range of 2.2 ppm. The H-P coupling patterns of the third strand differ from those of the duplex. General spectral patterns defined by the marker protons of the RRY and YRY triplexes are compared.

  12. Dietary purines in vegetarian meat analogues.

    PubMed

    Havlik, Jaroslav; Plachy, Vladimir; Fernandez, Javier; Rada, Vojtech

    2010-11-01

    The meat alternatives market offers a wide range of products resembling meat in taste, flavour or texture but based on vegetable protein sources. These high protein-low purine foods may find application in a low purine or purine-free diet, which is sometimes suggested for subjects with increased serum urate levels, i.e. hyperuricaemia. We determined purine content (uric acid, adenine, guanine, hypoxanthine, xanthine) in 39 commercially available meat substitutes and evaluated them in relation to their protein content. Some of the products contained a comparable sum of adenine and hypoxanthine per protein as meat. Analysis of variance showed an influence of protein source used. Mycoprotein-based products had significantly higher contents (2264 mg kg(-1)) of adenine and hypoxanthine per kg of 100% protein than soybean-based products (1648 mg kg(-1)) or mixtures consisting of soybean protein and wheat protein (1239 mg kg(-1)). Protein-rich vegetable-based meat substitutes might be generally accepted as meat alternatives for individuals on special diets. The type of protein used to manufacture these products determines the total content of purines, which is relatively higher in the case of mycoprotein or soybean protein, while appearing lower in wheat protein and egg white-based products. These are therefore more suitable for dietary considerations in a low-purine diet for hyperuricaemic subjects. 2010 Society of Chemical Industry

  13. Riboswitch Structure: an Internal Residue Mimicking the Purine Ligand

    SciTech Connect

    Delfosse, V.; Bouchard, P; Bonneau, E; Dagenais, P; Lemay, J; Lafontaine, D; Legault, P

    2009-01-01

    The adenine and guanine riboswitches regulate gene expression in response to their purine ligand. X-ray structures of the aptamer moiety of these riboswitches are characterized by a compact fold in which the ligand forms a Watson-Crick base pair with residue 65. Phylogenetic analyses revealed a strict restriction at position 39 of the aptamer that prevents the G39-C65 and A39-U65 combinations, and mutational studies indicate that aptamers with these sequence combinations are impaired for ligand binding. In order to investigate the rationale for sequence conservation at residue 39, structural characterization of the U65C mutant from Bacillus subtilis pbuE adenine riboswitch aptamer was undertaken. NMR spectroscopy and X-ray crystallography studies demonstrate that the U65C mutant adopts a compact ligand-free structure, in which G39 occupies the ligand-binding site of purine riboswitch aptamers. These studies present a remarkable example of a mutant RNA aptamer that adopts a native-like fold by means of ligand mimicking and explain why this mutant is impaired for ligand binding. Furthermore, this work provides a specific insight into how the natural sequence has evolved through selection of nucleotide identities that contribute to formation of the ligand-bound state, but ensures that the ligand-free state remains in an active conformation.

  14. Prebiotic syntheses of purines and pyrimidines.

    PubMed

    Basile, B; Lazcano, A; Oró, J

    1984-01-01

    The work done in many laboratories during the last two decades has confirmed that hydrogen cyanide and cyanoacetylene are the two major precursors for the prebiotic synthesis of purines and pyrimidines, respectively. Although several different pathways for the synthesis of purines have been described, they are all variations of the initial mechanism proposed by Oró and Kimball, where hydrogen cyanide leads first to the formation of a 4,5-di-substituted imidazole derivative, and then to the closing of the purine ring with a C1 compound. A number of experiments have shown that purines and pyrimidines can also be obtained from methane, ammonia (nitrogen), and water mixtures, provided an activating source of energy (radiation, electric discharges, etc.) is available. However, in this case the yields are lower by about two orders of magnitude because of the intermediate formation of hydrogen cyanide and cyanoacetylene. The latter two compounds have been found in interstellar space, Titan and other bodies of the solar system. They were probably present in the primordial parent bodies from the solar nebula in concentrations of 10(-2) to 10(-3) M as inferred from recent calculations by Miller and coworkers obtained for the Murchison meteorite. These concentrations should have been sufficient to generate relatively large amounts of purine and pyrimidine bases on the primitive Earth.

  15. Prebiotic syntheses of purines and pyrimidines

    NASA Technical Reports Server (NTRS)

    Basile, B.; Oro, J.; Lazcano, A.

    1984-01-01

    The results of experimental and theoretical investigations of the prebiotic synthesis of purines and pyramidines are surveyed. Topics examined include the synthesis of purines from HCN via 4,5-disubstituted imidazole derivatives in aqueous solutions or liquid NH3, simultaneous formation of amino acids and purines by electron irradiation of CH4-NH3-H2O mixtures, synthesis of pyrimadines from cynoacetylene, energetics, formation of bases under anhydrous or concentrated conditions, formation of bases under dilute conditions, Fischer-Tropsch-type reactions, and the role of activated intermediates. It is pointed out that the precursor compounds have been detected in the interstellar medium, on Titan, and in other solar-system bodies, and that solar-nebula HCN concentrations of the order of 1-10 mM have been estimated on the basis of meteorite measurements.

  16. Prebiotic syntheses of purines and pyrimidines

    NASA Technical Reports Server (NTRS)

    Basile, B.; Oro, J.; Lazcano, A.

    1984-01-01

    The results of experimental and theoretical investigations of the prebiotic synthesis of purines and pyramidines are surveyed. Topics examined include the synthesis of purines from HCN via 4,5-disubstituted imidazole derivatives in aqueous solutions or liquid NH3, simultaneous formation of amino acids and purines by electron irradiation of CH4-NH3-H2O mixtures, synthesis of pyrimadines from cynoacetylene, energetics, formation of bases under anhydrous or concentrated conditions, formation of bases under dilute conditions, Fischer-Tropsch-type reactions, and the role of activated intermediates. It is pointed out that the precursor compounds have been detected in the interstellar medium, on Titan, and in other solar-system bodies, and that solar-nebula HCN concentrations of the order of 1-10 mM have been estimated on the basis of meteorite measurements.

  17. Purine nucleoside phosphorylase deficiency in a patient with spastic paraplegia and recurrent infections.

    PubMed

    Ozkinay, Ferda; Pehlivan, Sacide; Onay, Huseyin; van den Berg, Paul; Vardar, Fadil; Koturoglu, Guldane; Aksu, Guzide; Unal, Durisehvar; Tekgul, Hasan; Can, Sema; Ozkinay, Cihangir

    2007-06-01

    Purine nucleoside phosphorylase deficiency is a rare autosomal recessive immunodeficiency disease. The characteristic features of the disease include severe T cell immune defects with recurrent infections, a failure to thrive, and progressive neurological findings. To date, 35 cases of purine nucleosidase phosphorylase deficiency have been reported worldwide. A 2-year-old female patient was hospitalized due to recurrent infections starting from 6 months and a fever that had continued for a month. The parents were first cousins. Physical examination showed a failure to thrive, herpetic lesions around the lips, painful lesions on the tongue and the buccal mucosa, lung infection, and spastic paraparesis in the lower extremities. She had motor and mental retardation. Laboratory tests revealed lymphopenia; low CD3, CD4, and CD8 counts; normal immunoglobulin levels; low uric acid; and very low purine nucleoside phosphorylase enzyme activity (1.4 nmol/h/mg; normal range, 490-1530). DNA sequencing of the purine nucleosidase phosphorylase gene revealed a missense homozygous mutation, a G to A transition at exon 4 position 64 (349G>A transition), which led to a substitution of alanine by threonine at codon 117 (Ala117Thr). Both parents were heterozygous for the mutation. This is the second purine nucleosidase phosphorylase deficient case to have been presented and carrying this mutation worldwide. Various antibiotics, antifungal drugs, and intravenous immunoglobulin were used to treat the infections during her 3 months. This form of treatment proved to be unresponsive, resulting in her subsequent death at 26 months of age.

  18. Functional and Structural Characterization of Purine Nucleoside Phosphorylase from Kluyveromyces lactis and Its Potential Applications in Reducing Purine Content in Food.

    PubMed

    Mahor, Durga; Priyanka, Anu; Prasad, Gandham S; Thakur, Krishan Gopal

    2016-01-01

    Consumption of foods and beverages with high purine content increases the risk of hyperuricemia, which causes gout and can lead to cardiovascular, renal, and other metabolic disorders. As patients often find dietary restrictions challenging, enzymatically lowering purine content in popular foods and beverages offers a safe and attractive strategy to control hyperuricemia. Here, we report structurally and functionally characterized purine nucleoside phosphorylase (PNP) from Kluyveromyces lactis (KlacPNP), a key enzyme involved in the purine degradation pathway. We report a 1.97 Å resolution crystal structure of homotrimeric KlacPNP with an intrinsically bound hypoxanthine in the active site. KlacPNP belongs to the nucleoside phosphorylase-I (NP-I) family, and it specifically utilizes 6-oxopurine substrates in the following order: inosine > guanosine > xanthosine, but is inactive towards adenosine. To engineer enzymes with broad substrate specificity, we created two point variants, KlacPNPN256D and KlacPNPN256E, by replacing the catalytically active Asn256 with Asp and Glu, respectively, based on structural and comparative sequence analysis. KlacPNPN256D not only displayed broad substrate specificity by utilizing both 6-oxopurines and 6-aminopurines in the order adenosine > inosine > xanthosine > guanosine, but also displayed reversal of substrate specificity. In contrast, KlacPNPN256E was highly specific to inosine and could not utilize other tested substrates. Beer consumption is associated with increased risk of developing gout, owing to its high purine content. Here, we demonstrate that KlacPNP and KlacPNPN256D could be used to catalyze a key reaction involved in lowering beer purine content. Biochemical properties of these enzymes such as activity across a wide pH range, optimum activity at about 25°C, and stability for months at about 8°C, make them suitable candidates for food and beverage industries. Since KlacPNPN256D has broad substrate specificity, a

  19. Functional and Structural Characterization of Purine Nucleoside Phosphorylase from Kluyveromyces lactis and Its Potential Applications in Reducing Purine Content in Food

    PubMed Central

    Mahor, Durga; Priyanka, Anu; Prasad, Gandham S; Thakur, Krishan Gopal

    2016-01-01

    Consumption of foods and beverages with high purine content increases the risk of hyperuricemia, which causes gout and can lead to cardiovascular, renal, and other metabolic disorders. As patients often find dietary restrictions challenging, enzymatically lowering purine content in popular foods and beverages offers a safe and attractive strategy to control hyperuricemia. Here, we report structurally and functionally characterized purine nucleoside phosphorylase (PNP) from Kluyveromyces lactis (KlacPNP), a key enzyme involved in the purine degradation pathway. We report a 1.97 Å resolution crystal structure of homotrimeric KlacPNP with an intrinsically bound hypoxanthine in the active site. KlacPNP belongs to the nucleoside phosphorylase-I (NP-I) family, and it specifically utilizes 6-oxopurine substrates in the following order: inosine > guanosine > xanthosine, but is inactive towards adenosine. To engineer enzymes with broad substrate specificity, we created two point variants, KlacPNPN256D and KlacPNPN256E, by replacing the catalytically active Asn256 with Asp and Glu, respectively, based on structural and comparative sequence analysis. KlacPNPN256D not only displayed broad substrate specificity by utilizing both 6-oxopurines and 6-aminopurines in the order adenosine > inosine > xanthosine > guanosine, but also displayed reversal of substrate specificity. In contrast, KlacPNPN256E was highly specific to inosine and could not utilize other tested substrates. Beer consumption is associated with increased risk of developing gout, owing to its high purine content. Here, we demonstrate that KlacPNP and KlacPNPN256D could be used to catalyze a key reaction involved in lowering beer purine content. Biochemical properties of these enzymes such as activity across a wide pH range, optimum activity at about 25°C, and stability for months at about 8°C, make them suitable candidates for food and beverage industries. Since KlacPNPN256D has broad substrate specificity, a

  20. Radical-induced purine lesion formation is dependent on DNA helical topology.

    PubMed

    Terzidis, Michael A; Prisecaru, Andreea; Molphy, Zara; Barron, Niall; Randazzo, Antonio; Dumont, Elise; Krokidis, Marios G; Kellett, Andrew; Chatgilialoglu, Chryssostomos

    2016-11-01

    Herein we report the quantification of purine lesions arising from gamma-radiation sourced hydroxyl radicals (HO(•)) on tertiary dsDNA helical forms of supercoiled (SC), open circular (OC), and linear (L) conformation, along with single-stranded folded and non-folded sequences of guanine-rich DNA in selected G-quadruplex structures. We identify that DNA helical topology and folding plays major, and unexpected, roles in the formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxo-dA), along with tandem-type purine lesions 5',8-cyclo-2'-deoxyguanosine (5',8-cdG) and 5',8-cyclo-2'-deoxyadenosine (5',8-cdA). SC, OC, and L dsDNA conformers together with folded and non-folded G-quadruplexes d[TGGGGT]4 (TG4T), d[AGGG(TTAGGG)3] (Tel22), and the mutated tel24 d[TTGGG(TTAGGG)3A] (mutTel24) were exposed to HO(•) radicals and purine lesions were then quantified via stable isotope dilution LC-MS/MS analysis. Purine oxidation in dsDNA follows L > OC ≫ SC indicating greater damage towards the extended B-DNA topology. Conversely, G-quadruplex sequences were significantly more resistant toward purine oxidation in their unfolded states as compared with G-tetrad folded topologies; this effect is confirmed upon comparative analysis of Tel22 (∼50% solution folded) and mutTel24 (∼90% solution folded). In an effort to identify the accessibly of hydroxyl radicals to quadruplex purine nucleobases, G-quadruplex solvent cavities were then modeled at 1.33 Å with evidence suggesting that folded G-tetrads may act as potential oxidant traps to protect against chromosomal DNA damage.

  1. [Effect of cooking on the purine content of foods].

    PubMed

    Colling, M; Wolfram, G

    1987-12-01

    The total purine content and the content of purines bound in RNA and DNA was determined in selected food (veal meat, pork meat, pork liver, pork spleen, soja meat). Raw and boiled food samples were analysed. During preparation of food the total purine content is changed by losses of water or of purines into cooking water. Simultaneously, a great part of nucleic acids is hydrolysed.

  2. A New HPLC Purine Assay for Quantifying Microbial Flow

    USDA-ARS?s Scientific Manuscript database

    A HPLC method was developed to quantify the purines adenine and guanine and their metabolites xanthine and hypoxanthine in hydrolysates of isolated bacteria and omasal digesta and to assess the effect of using either purines only, or purines plus metabolites, as microbial markers for estimating micr...

  3. The pronounced seasonality of global groundwater recharge

    NASA Astrophysics Data System (ADS)

    Jasechko, Scott; Birks, S. Jean; Gleeson, Tom; Wada, Yoshihide; Fawcett, Peter J.; Sharp, Zachary D.; McDonnell, Jeffrey J.; Welker, Jeffrey M.

    2014-11-01

    Groundwater recharged by meteoric water supports human life by providing two billion people with drinking water and by supplying 40% of cropland irrigation. While annual groundwater recharge rates are reported in many studies, fewer studies have explicitly quantified intra-annual (i.e., seasonal) differences in groundwater recharge. Understanding seasonal differences in the fraction of precipitation that recharges aquifers is important for predicting annual recharge groundwater rates under changing seasonal precipitation and evapotranspiration regimes in a warming climate, for accurately interpreting isotopic proxies in paleoclimate records, and for understanding linkages between ecosystem productivity and groundwater recharge. Here we determine seasonal differences in the groundwater recharge ratio, defined here as the ratio of groundwater recharge to precipitation, at 54 globally distributed locations on the basis of 18O/16O and 2H/1H ratios in precipitation and groundwater. Our analysis shows that arid and temperate climates have wintertime groundwater recharge ratios that are consistently higher than summertime groundwater recharge ratios, while tropical groundwater recharge ratios are at a maximum during the wet season. The isotope-based recharge ratio seasonality is consistent with monthly outputs from a global hydrological model (PCR-GLOBWB) for most, but not all locations. The pronounced seasonality in groundwater recharge ratios shown in this study signifies that, from the point of view of predicting future groundwater recharge rates, a unit change in winter (temperate and arid regions) or wet season (tropics) precipitation will result in a greater change to the annual groundwater recharge rate than the same unit change to summer or dry season precipitation.

  4. Total purine and purine base content of common foodstuffs for facilitating nutritional therapy for gout and hyperuricemia.

    PubMed

    Kaneko, Kiyoko; Aoyagi, Yasuo; Fukuuchi, Tomoko; Inazawa, Katsunori; Yamaoka, Noriko

    2014-01-01

    Purines are natural substances found in all of the body's cells and in virtually all foods. In humans, purines are metabolized to uric acid, which serves as an antioxidant and helps to prevent damage caused by active oxygen species. A continuous supply of uric acid is important for protecting human blood vessels. However, frequent and high intake of purine-rich foods reportedly enhances serum uric acid levels, which results in gout and could be a risk factor for cardiovascular disease, kidney disease, and metabolic syndrome. In Japan, the daily intake of dietary purines is recommended to be less than 400 mg to prevent gout and hyperuricemia. We have established an HPLC method for purine analysis and determined purines in a total of 270 foodstuffs. A relatively small number of foods contained concentrated amounts of purines. For the most part, purine-rich foods are also energy-rich foods, and include animal meats, fish meats, organs such as the liver and fish milt, and yeast. When the ratio of the four purine bases (adenine, guanine, hypoxanthine, and xanthine) was compared, two groups of foods were identified: one that contained mainly adenine and guanine and one that contained mainly hypoxanthine. For patients with gout and hyperuricemia, the amount of total purines and the types of purines consumed, particularly hypoxanthine, are important considerations. In this context, the data from our analysis provide a purine content reference, and thereby clinicians and patients could utilize that reference in nutritional therapy for gout and hyperuricemia.

  5. Characterization of purine catabolic pathway genes in coelacanths.

    PubMed

    Forconi, Mariko; Biscotti, Maria Assunta; Barucca, Marco; Buonocore, Francesco; De Moro, Gianluca; Fausto, Anna Maria; Gerdol, Marco; Pallavicini, Alberto; Scapigliati, Giuseppe; Schartl, Manfred; Olmo, Ettore; Canapa, Adriana

    2014-09-01

    Coelacanths are a critically valuable species to explore the gene changes that took place in the transition from aquatic to terrestrial life. One interesting and biologically relevant feature of the genus Latimeria is ureotelism. However not all urea is excreted from the body; in fact high concentrations are retained in plasma and seem to be involved in osmoregulation. The purine catabolic pathway, which leads to urea production in Latimeria, has progressively lost some steps, reflecting an enzyme loss during diversification of terrestrial species. We report the results of analyses of the liver and testis transcriptomes of the Indonesian coelacanth Latimeria menadoensis and of the genome of Latimeria chalumnae, which has recently been fully sequenced in the framework of the coelacanth genome project. We describe five genes, uricase, 5-hydroxyisourate hydrolase, parahox neighbor B, allantoinase, and allantoicase, each coding for one of the five enzymes involved in urate degradation to urea, and report the identification of a putative second form of 5-hydroxyisourate hydrolase that is characteristic of the genus Latimeria. The present data also highlight the activity of the complete purine pathway in the coelacanth liver and suggest its involvement in the maintenance of high plasma urea concentrations.

  6. De novo purine nucleotide synthesis in the rat small and large intestine: effect of dietary protein and purines.

    PubMed

    LeLeiko, N S; Bronstein, A D; Baliga, B S; Munro, H N

    1983-05-01

    This study assessed the pathway for de novo purine nucleotide synthesis in rat small intestinal and colonic mucosal cells, and determined the effects of dietary purines and protein on de novo purine nucleotide synthetic activity in the small intestine in vitro. Incubation of small intestinal mucosal scrapings with [14C]glycine failed to show an active pathway of de novo synthesis; in contrast, the colon showed incorporation of [14C]glycine into RNA. Rats fed a diet deficient in purines demonstrated increased incorporation of [14C]glycine into RNA-adrenine in small intestinal mucosal cells. Measurement of glutamine-amidophosphoribosyltransferase demonstrated that, regardless of the purine content of the diet, enzyme activity in the small intestine is significantly lower than in the colon or liver. The results indicate that, in the small intestine of the rat, there is an inactive de novo pathway of purine nucleotide biosynthesis that can be stimulated when purines are omitted from the diet.

  7. Structural Biology of the Purine Biosynthetic Pathway

    PubMed Central

    Zhang, Yang; Morar, Mariya; Ealick, Steven E.

    2008-01-01

    Purine biosynthesis requires ten enzymatic transformations to generate inosine monophosphate. PurF, PurD, PurL, PurM, PurC, and PurB are common to all pathways, while PurN or PurT, PurK/PurE-I or PurE-II, PurH or PurP, and PurJ or PurO catalyze the same steps in different organisms. X-ray crystal structures are available for all 15 purine biosynthetic enzymes, including seven ATP-dependent enzymes, two amidotransferases and two tetrahydrofolate-dependent enzymes. Here we summarize the structures of the purine biosynthetic enzymes, discuss similarities and differences, and present arguments for pathway evolution. Four of the ATP-dependent enzymes belong to the ATP-grasp superfamily and two to the PurM superfamily. The amidotransferases are unrelated with one utilizing an NTN-glutaminase and the other utilizing a triad glutaminase. Likewise the tetrahydrofolate-dependent enzymes are unrelated. Ancestral proteins may have included a broad specificity enzyme instead of PurD, PurT, PurK, PurC, and PurP, and a separate enzyme instead of PurM and PurL. PMID:18712276

  8. Purines: forgotten mediators in traumatic brain injury.

    PubMed

    Jackson, Edwin K; Boison, Detlev; Schwarzschild, Michael A; Kochanek, Patrick M

    2016-04-01

    Recently, the topic of traumatic brain injury has gained attention in both the scientific community and lay press. Similarly, there have been exciting developments on multiple fronts in the area of neurochemistry specifically related to purine biology that are relevant to both neuroprotection and neurodegeneration. At the 2105 meeting of the National Neurotrauma Society, a session sponsored by the International Society for Neurochemistry featured three experts in the field of purine biology who discussed new developments that are germane to both the pathomechanisms of secondary injury and development of therapies for traumatic brain injury. This included presentations by Drs. Edwin Jackson on the novel 2',3'-cAMP pathway in neuroprotection, Detlev Boison on adenosine in post-traumatic seizures and epilepsy, and Michael Schwarzschild on the potential of urate to treat central nervous system injury. This mini review summarizes the important findings in these three areas and outlines future directions for the development of new purine-related therapies for traumatic brain injury and other forms of central nervous system injury. In this review, novel therapies based on three emerging areas of adenosine-related pathobiology in traumatic brain injury (TBI) were proposed, namely, therapies targeting 1) the 2',3'-cyclic adenosine monophosphate (cAMP) pathway, 2) adenosine deficiency after TBI, and 3) augmentation of urate after TBI. © 2016 International Society for Neurochemistry.

  9. Ligand Binding and Conformational Changes in the Purine-Binding Riboswitch Aptamer Domains

    NASA Astrophysics Data System (ADS)

    Noeske, Jonas; Buck, Janina; Wöhnert, Jens; Schwalbe, Harald

    Riboswitches are highly structured mRNA elements that regulate gene expression upon specific binding of small metabolite molecules. The purine-binding riboswitches bind different purine ligands by forming both canonical Watson—Crick and non-canonical intermolecular base pairs, involving a variety of hydrogen bonds between the riboswitch aptamer domain and the purine ligand. Here, we summarize work on the ligand binding modes of both purine-binding aptamer domains, their con-formational characteristics in the free and ligand-bound forms, and their ligand-induced folding. The adenine- and guanine-binding riboswitch aptamer domains display different conformations in their free forms, despite nearly identical nucleotide loop sequences that form a loop—loop interaction in the ligand-bound forms. Interestingly, the stability of helix II is crucial for the formation of the loop—loop interaction in the free form. A more stable helix II in the guanine riboswitch leads to a preformed loop—loop interaction in its free form. In contrast, a less stable helix II in the adenine riboswitch results in a lack of this loop—loop interaction in the absence of ligand and divalent cations.

  10. The Effects of Azathioprine (Imuran) on Purine Synthesis in Clinical Disorders of Purine Metabolism*

    PubMed Central

    Kelley, William N.; Rosenbloom, Frederick M.; Seegmiller, J. Edwin

    1967-01-01

    Azathioprine, a purine analogue, significantly suppressed the purine synthesis de novo of two gouty patients manifesting overproduction of uric acid, as well as three of four gouty patients who showed normal uric acid production. This suppression is taken as evidence that phosphoribosyl-pyrophosphate amidotransferase, the rate-controlling step in purine synthesis de novo, has a normal sensitivity to feedback inhibitors in the patients who responded to the drug. Two children afflicted with the familial disorder of hyperuricemia, choreo-athetosis, and self-mutilation described by Lesch and Nyhan showed no reduction in the activity of the biosynthetic pathway in response to azathioprine. This inability to respond to azathioprine can be directly related to the absence in these patients of the enzyme hypoxanthine-guanine phosphoribosyltransferase which is required for conversion of the drug or its metabolites to the biochemically active ribonucleotide form. PMID:16695929

  11. Purines 2010: Adenine Nucleosides and Nucleotides in Biomedicine.

    PubMed

    Sereda, Michal J

    2010-08-01

    The Purines 2010: Adenine Nucleosides and Nucleotides in Biomedicine meeting, held in Tarragona, Spain, included topics covering new findings in the field of purinergic signaling and the development of purine-based drugs. This conference report highlights selected presentations on developments in purinerigic signaling, medicinal chemistry, the therapeutic potential of purine-based drugs, and the role of purines and adenosine receptors in neurodegenerative disorders, sickle cell disease, bone homeostasis, pulmonary fibrosis and pain. Investigational drugs discussed include CF-101 (Can-Fite BioPharma Ltd/NIH/Kwang Dong Pharmaceutical Co Ltd/Seikagaku Corp) and denufosol tetrasodium (Cystic Fibrosis Foundation Therapeutics Inc/Inspire Pharmaceuticals Inc).

  12. Exclusion of RNA strands from a purine motif triple helix.

    PubMed Central

    Semerad, C L; Maher, L J

    1994-01-01

    Research concerning oligonucleotide-directed triple helix formation has mainly focused on the binding of DNA oligonucleotides to duplex DNA. The participation of RNA strands in triple helices is also of interest. For the pyrimidine motif (pyrimidine.purine.pyrimidine triplets), systematic substitution of RNA for DNA in one, two, or all three triplex strands has previously been reported. For the purine motif (purine.purine.pyrimidine triplets), studies have shown only that RNA cannot bind to duplex DNA. To extend this result, we created a DNA triple helix in the purine motif and systematically replaced one, two, or all three strands with RNA. In dramatic contrast to the general accommodation of RNA strands in the pyrimidine triple helix motif, a stable triplex forms in the purine motif only when all three of the substituent strands are DNA. The lack of triplex formation among any of the other seven possible strand combinations involving RNA suggests that: (i) duplex structures containing RNA cannot be targeted by DNA oligonucleotides in the purine motif; (ii) RNA strands cannot be employed to recognize duplex DNA in the purine motif; and (iii) RNA tertiary structures are likely to contain only isolated base triplets in the purine motif. Images PMID:7529405

  13. Anopheles gambiae Purine Nucleoside Phosphorylase: Catalysis, Structure, and Inhibition

    SciTech Connect

    Taylor,E.; Rinaldo-Matthis, A.; Li, L.; Ghanem, M.; Hazleton, K.; Cassera, M.; Almo, S.; Schramm, V.

    2007-01-01

    The purine salvage pathway of Anopheles gambiae, a mosquito that transmits malaria, has been identified in genome searches on the basis of sequence homology with characterized enzymes. Purine nucleoside phosphorylase (PNP) is a target for the development of therapeutic agents in humans and purine auxotrophs, including malarial parasites. The PNP from Anopheles gambiae (AgPNP) was expressed in Escherichia coli and compared to the PNPs from Homo sapiens (HsPNP) and Plasmodium falciparum (PfPNP). AgPNP has kcat values of 54 and 41 s-1 for 2'-deoxyinosine and inosine, its preferred substrates, and 1.0 s-1 for guanosine. However, the chemical step is fast for AgPNP at 226 s-1 for guanosine in pre-steady-state studies. 5'-Deaza-1'-aza-2'-deoxy-1'-(9-methylene)-Immucillin-H (DADMe-ImmH) is a transition-state mimic for a 2'-deoxyinosine ribocation with a fully dissociated N-ribosidic bond and is a slow-onset, tight-binding inhibitor with a dissociation constant of 3.5 pM. This is the tightest-binding inhibitor known for any PNP, with a remarkable Km/Ki* of 5.4 x 107, and is consistent with enzymatic transition state predictions of enhanced transition-state analogue binding in enzymes with enhanced catalytic efficiency. Deoxyguanosine is a weaker substrate than deoxyinosine, and DADMe-Immucillin-G is less tightly bound than DADMe-ImmH, with a dissociation constant of 23 pM for AgPNP as compared to 7 pM for HsPNP. The crystal structure of AgPNP was determined in complex with DADMe-ImmH and phosphate to a resolution of 2.2 Angstroms to reveal the differences in substrate and inhibitor specificity. The distance from the N1' cation to the phosphate O4 anion is shorter in the AgPNP{center_dot}DADMe-ImmH{center_dot}PO4 complex than in HsPNP{center_dot}DADMe-ImmH{center_dot}SO4, offering one explanation for the stronger inhibitory effect of DADMe-ImmH for AgPNP.

  14. Distinct Purine Distribution in Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Smith, Karen E.; Cleaves, Henderson J.; Ruzicka, Josef; Stern, Jennifer C.; Glavin, Daniel P.; House, Christopher H.; Dworkin, Jason P.

    2011-01-01

    Carbonaceous chondrite meteorites are known to contain a diverse suite of organic compounds, many of which are essential components of biochemistry. Amino acids, which are the monomers of proteins, have been extensively studied in such meteorites (e.g. Botta and Bada 2002; Pizzarello et aI., 2006). The origin of amino acids in meteorites has been firmly established as extraterrestrial based on their detection typically as racemic mixtures of amino acids, the presence of many non-protein amino acids, and non-terrestrial values for compound-specific deuterium, carbon, and nitrogen isotopic measurements. In contrast to amino acids, nucleobases in meteorites have been far less studied. Nucleobases are substituted one-ring (pyrimidine) or two-ring (purine) nitrogen heterocyclic compounds and serve as the information carriers of nucleic acids and in numerous coenzymes. All of the purines (adenine, guanine, hypoxanthine, and xanthine) and pyrimidines (uracil) previously reported in meteorites are biologically common and could be interpreted as the result of terrestrial contamination (e.g. van del' Velden and Schwartz, 1974.) Unlike other meteoritic organics, there have been no observations of stochastic molecular diversity of purines and pyrimidines in meteorites, which has been a criterion for establishing extraterrestrial origin. Maltins et al. (2008) performed compound-specific stable carbon isotope measurements for uracil and xanthine in the Murchison meteorite. They assigned a non-terrestrial origin for these nucleobases; however, the possibility that interfering indigenous molecules (e.g. carboxylic acids) contributed to the 13C-enriched isotope values for these nucleobases cannot be completely ruled out. Thus, the origin of these meteoritic nucleobases has never been established unequivocally. Here we report on our investigation of extracts of II different carbonaceous chondrites covering various petrographic types (Cl, CM, and CR) and degrees of aqueous alteration

  15. Structure, stability, and thermodynamics of a short intermolecular purine-purine-pyrimidine triple helix

    SciTech Connect

    Pilch, D.S.; Shafer, R.H. ); Levenson, C. )

    1991-06-25

    The authors have investigated the structure and physical chemistry of the d(C{sub 3}T{sub 4}C{sub 3}){center dot}2(d(G{sub 3}A{sub 4}G{sub 3})) triple helix by polyacrylamide gel electrophoresis (PAGE), {sup 1}H NMR, and ultraviolet (UV) absorption spectroscopy. The triplex was stabilized with MgCl{sub 2} at neutral pH. PAGE studies verify the stoichiometry of the strands comprising the triplex and indicate that the orientation of the third strand in purine-purine-pyrimidine (pur-pur-pyr) triplexes is antiparallel with respect to the purine strand of the underlying duplex. Imino proton NMR spectra provide evidence for the existence of new purine-purine (pur{center dot}pur) hydrogen bonds, in addition to those of the Watson-Crick (W-C) base pairs, in the triplex structure. These new hydrogen bonds are likely to correspond to the interaction between third-strand guanine NH1 imino protons and the N7 atoms of guanine residues on the puring strand of the underlying duplex. Thermal denaturation of the triplex proceeds to single strands in one step, under the conditions used in this study. Binding of the third strand appears to enhance the thermal stability of the duplex by 1-3 C, depending on the DNA concentration. This marked enhancement in stability, coupled with the lack of an acidic pH requirement, suggests that pur-pur-pyr triplexes are appealing choices for use in applications involving oligonucleotide targeting of duplex DNA in vitro and in vivo.

  16. Purine inhibitors of protein kinases, G proteins and polymerases

    DOEpatents

    Gray, Nathanael S.; Schultz, Peter; Kim, Sung-Hou; Meijer, Laurent

    2001-07-03

    The present invention relates to purine analogs that inhibit, inter alia, protein kinases, G-proteins and polymerases. In addition, the present invention relates to methods of using such purine analogs to inhibit protein kinases, G-proteins, polymerases and other cellular processes and to treat cellular proliferative diseases.

  17. Extracellular purines, purinergic receptors and tumor growth

    PubMed Central

    Di Virgilio, F; Adinolfi, E

    2017-01-01

    Virtually, all tumor cells as well as all immune cells express plasma membrane receptors for extracellular nucleosides (adenosine) and nucleotides (ATP, ADP, UTP, UDP and sugar UDP). The tumor microenvironment is characterized by an unusually high concentration of ATP and adenosine. Adenosine is a major determinant of the immunosuppressive tumor milieu. Sequential hydrolysis of extracellular ATP catalyzed by CD39 and CD73 is the main pathway for the generation of adenosine in the tumor interstitium. Extracellular ATP and adenosine mold both host and tumor responses. Depending on the specific receptor activated, extracellular purines mediate immunosuppression or immunostimulation on the host side, and growth stimulation or cytotoxicity on the tumor side. Recent progress in this field is providing the key to decode this complex scenario and to lay the basis to harness the potential benefits for therapy. Preclinical data show that targeting the adenosine-generating pathway (that is, CD73) or adenosinergic receptors (that is, A2A) relieves immunosuppresion and potently inhibits tumor growth. On the other hand, growth of experimental tumors is strongly inhibited by targeting the P2X7 ATP-selective receptor of cancer and immune cells. This review summarizes the recent data on the role played by extracellular purines (purinergic signaling) in host–tumor interaction and highlights novel therapeutic options stemming from recent advances in this field. PMID:27321181

  18. Allosteric Modulation of Purine and Pyrimidine Receptors

    PubMed Central

    Jacobson, Kenneth A.; Gao, Zhan-Guo; Göblyös, Anikó; IJzerman, Adriaan P.

    2011-01-01

    Among the purine and pyrimidine receptors, the discovery of small molecular allosteric modulators has been most highly advanced for the A1 and A3 ARs. These AR modulators have allosteric effects that are structurally separated from the orthosteric effects in SAR studies. The benzoylthiophene derivatives tend to act as allosteric agonists, as well as selective positive allosteric modulators (PAMs) of the A1 AR. A 2-amino-3-aroylthiophene derivative T-62 has been under development as a PAM of the A1 AR for the treatment of chronic pain. Several structurally distinct classes of allosteric modulators of the human A3 AR have been reported: 3-(2-pyridinyl)isoquinolines, 2,4-disubstituted quinolines, 1H-imidazo-[4,5-c]quinolin-4-amines, endocannabinoid 2-arachidonylglycerol and the food dye Brilliant Black BN. Site-directed mutagenesis of A1 and A3 ARs has identified residues associated with the allosteric effect, distinct from those that affect orthosteric binding. A few small molecular allosteric modulators have been reported for several of the P2X ligand-gated ion channels and the G protein-coupled P2Y receptor nucleotides. Metal ion modulation of the P2X receptors has been extensively explored. The allosteric approach to modulation of purine and pyrimidine receptors looks promising for development of drugs that are event-specific and site-specific in action. PMID:21586360

  19. The influence of exocyclic substituents of purine bases on DNA curvature.

    PubMed Central

    Diekmann, S; von Kitzing, E; McLaughlin, L; Ott, J; Eckstein, F

    1987-01-01

    Complementary oligonucleotides with 5' overhanging deoxyguanosine or deoxycytidine stretches, respectively, of the general form 5'-d(GGGCAARAAC).5'-d(CCCGTTYTTG), where R represents the bases adenine (A), hypoxanthine (base of inosine nucleoside, I), purine (R), 2-aminopurine (n2R), or 2,6-diaminopurine (n2,6(2)R) and where Y represents the pyrimidine bases thymine (T) or cytosine (C), have been chemically synthesized. After hybridization of complementary fragments, they were ligated to form multimers and analyzed by polyacrylamide gel electrophoresis. Anomalous gel migration was observed for the sequences 5'-d(AARAA) when the R.Y base pair was dA.dT, dI.dC, or dR.dT. All of these base pairs lack at least the amino group at position 2 of the purine base. The degree of anomalous gel migration was also related to the substituent at position 6 of the purine base. An amino group at position 6 was more effective than a carbonyl or a hydrogen in inducing anomalous gel migration. Additionally, the fragments 5'-d(GGGCAIAIAC).5'-d(CCCGTCTCTG), 5'-d(GGGCAIIIAC).5'-d(CCCGTCCCTG), and 5'-d(GGGCIIAIIC).5'-d(CCCGCCTCCG) were prepared in which increasing numbers of dA.dT base pairs are replaced by dI.dC base pairs. The degree of gel-migration anomaly of these sequences correlates with the number of dA.dT base pairs left in the five-base purine block. The data support the hypothesis that within the deoxyadenosine tracts, the base pairs fold into the minor groove at position 2 of the base to balance for the NH2 groups at position 6. This hypothesis explains the formation of a B'-form DNA structure for the deoxyadenosine tracts as well as DNA curvature. Images PMID:3479789

  20. Prolonged fasting increases purine recycling in post-weaned northern elephant seals.

    PubMed

    Soñanez-Organis, José Guadalupe; Vázquez-Medina, José Pablo; Zenteno-Savín, Tania; Aguilar, Andres; Crocker, Daniel E; Ortiz, Rudy M

    2012-05-01

    Northern elephant seals are naturally adapted to prolonged periods (1-2 months) of absolute food and water deprivation (fasting). In terrestrial mammals, food deprivation stimulates ATP degradation and decreases ATP synthesis, resulting in the accumulation of purines (ATP degradation byproducts). Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) salvages ATP by recycling the purine degradation products derived from xanthine oxidase (XO) metabolism, which also promotes oxidant production. The contributions of HGPRT to purine recycling during prolonged food deprivation in marine mammals are not well defined. In the present study we cloned and characterized the complete and partial cDNA sequences that encode for HGPRT and xanthine oxidoreductase (XOR) in northern elephant seals. We also measured XO protein expression and circulating activity, along with xanthine and hypoxanthine plasma content in fasting northern elephant seal pups. Blood, adipose and muscle tissue samples were collected from animals after 1, 3, 5 and 7 weeks of their natural post-weaning fast. The complete HGPRT and partial XOR cDNA sequences are 771 and 345 bp long and encode proteins of 218 and 115 amino acids, respectively, with conserved domains important for their function and regulation. XOR mRNA and XO protein expression increased 3-fold and 1.7-fold with fasting, respectively, whereas HGPRT mRNA (4-fold) and protein (2-fold) expression increased after 7 weeks in adipose tissue and muscle. Plasma xanthine (3-fold) and hypoxanthine (2.5-fold) levels, and XO (1.7- to 20-fold) and HGPRT (1.5- to 1.7-fold) activities increased during the last 2 weeks of fasting. Results suggest that prolonged fasting in elephant seal pups is associated with increased capacity to recycle purines, which may contribute to ameliorating oxidant production and enhancing the supply of ATP, both of which would be beneficial during prolonged food deprivation and appear to be adaptive in this species.

  1. Prolonged fasting increases purine recycling in post-weaned northern elephant seals

    PubMed Central

    Soñanez-Organis, José Guadalupe; Vázquez-Medina, José Pablo; Zenteno-Savín, Tania; Aguilar, Andres; Crocker, Daniel E.; Ortiz, Rudy M.

    2012-01-01

    SUMMARY Northern elephant seals are naturally adapted to prolonged periods (1–2 months) of absolute food and water deprivation (fasting). In terrestrial mammals, food deprivation stimulates ATP degradation and decreases ATP synthesis, resulting in the accumulation of purines (ATP degradation byproducts). Hypoxanthine-guanine phosphoribosyl transferase (HGPRT) salvages ATP by recycling the purine degradation products derived from xanthine oxidase (XO) metabolism, which also promotes oxidant production. The contributions of HGPRT to purine recycling during prolonged food deprivation in marine mammals are not well defined. In the present study we cloned and characterized the complete and partial cDNA sequences that encode for HGPRT and xanthine oxidoreductase (XOR) in northern elephant seals. We also measured XO protein expression and circulating activity, along with xanthine and hypoxanthine plasma content in fasting northern elephant seal pups. Blood, adipose and muscle tissue samples were collected from animals after 1, 3, 5 and 7 weeks of their natural post-weaning fast. The complete HGPRT and partial XOR cDNA sequences are 771 and 345 bp long and encode proteins of 218 and 115 amino acids, respectively, with conserved domains important for their function and regulation. XOR mRNA and XO protein expression increased 3-fold and 1.7-fold with fasting, respectively, whereas HGPRT mRNA (4-fold) and protein (2-fold) expression increased after 7 weeks in adipose tissue and muscle. Plasma xanthine (3-fold) and hypoxanthine (2.5-fold) levels, and XO (1.7- to 20-fold) and HGPRT (1.5- to 1.7-fold) activities increased during the last 2 weeks of fasting. Results suggest that prolonged fasting in elephant seal pups is associated with increased capacity to recycle purines, which may contribute to ameliorating oxidant production and enhancing the supply of ATP, both of which would be beneficial during prolonged food deprivation and appear to be adaptive in this species. PMID

  2. Purine Salvage in Two Halophilic Archaea: Characterization of Salvage Pathways and Isolation of Mutants Resistant to Purine Analogs

    PubMed Central

    Stuer-Lauridsen, Birgitte; Nygaard, Per

    1998-01-01

    In exponentially growing cultures of the extreme halophile Halobacterium halobium and the moderate halophile Haloferax volcanii, growth characteristics including intracellular protein levels, RNA content, and nucleotide pool sizes were analyzed. This is the first report on pool sizes of nucleoside triphosphates, NAD, and PRPP (5-phosphoribosyl-α-1-pyrophosphate) in archaea. The presence of a number of salvage and interconversion enzymes was determined by enzymatic assays. The levels varied significantly between the two organisms. The most significant difference was the absence of GMP reductase activity in H. halobium. The metabolism of exogenous purines was investigated in growing cultures. Both purine bases and nucleosides were readily taken up and were incorporated into nucleic acids. Growth of both organisms was affected by a number of inhibitors of nucleotide synthesis. H. volcanii was more sensitive than H. halobium, and purine base analogs were more toxic than nucleoside analogs. Growth of H. volcanii was inhibited by trimethoprim and sulfathiazole, while these compounds had no effect on the growth of H. halobium. Spontaneous mutants resistant to purine analogs were isolated. The most frequent cause of resistance was a defect in purine phosphoribosyltransferase activity coupled with reduced purine uptake. A single phosphoribosyltransferase seemed to convert guanine as well as hypoxanthine to nucleoside monophosphates, and another phosphoribosyltransferase had specificity towards adenine. The differences in the metabolism of purine bases and nucleosides and the sensitivity to purine analogs between the two halobacteria were reflected in differences in purine enzyme levels. Based on our results, we conclude that purine salvage and interconversion pathways differ just as much between the two archaeal species as among archaea, bacteria, and eukarya. PMID:9457844

  3. Purine metabolism in adenosine deaminase deficiency.

    PubMed Central

    Mills, G C; Schmalstieg, F C; Trimmer, K B; Goldman, A S; Goldblum, R M

    1976-01-01

    Purine and pyrimidine metabolites were measured in erythrocytes, plasma, and urine of a 5-month-old infant with adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) deficiency. Adenosine and adenine were measured using newly devised ion exchange separation techniques and a sensitive fluorescence assay. Plasma adenosine levels were increased, whereas adenosine was normal in erythrocytes and not detectable in urine. Increased amounts of adenine were found in erythrocytes and urine as well as in the plasma. Erythrocyte adenosine 5'-monophosphate and adenosine diphosphate concentrations were normal, but adenosine triphosphate content was greatly elevated. Because of the possibility of pyrimidine starvation, pyrimidine nucleotides (pyrimidine coenzymes) in erythrocytes and orotic acid in urine were measured. Pyrimidine nucleotide concentrations were normal, while orotic acid was not detected. These studies suggest that the immune deficiency associated with adenosine deaminase deficiency may be related to increased amounts of adenine, adenosine, or adenine nucleotides. PMID:1066699

  4. Acceleration of purine degradation by periodontal diseases.

    PubMed

    Barnes, V M; Teles, R; Trivedi, H M; Devizio, W; Xu, T; Mitchell, M W; Milburn, M V; Guo, L

    2009-09-01

    Periodontal diseases, such as gingivitis and periodontitis, are characterized by bacterial plaque accumulation around the gingival crevice and the subsequent inflammation and destruction of host tissues. To test the hypothesis that cellular metabolism is altered as a result of host-bacteria interaction, we performed an unbiased metabolomic profiling of gingival crevicular fluid (GCF) collected from healthy, gingivitis, and periodontitis sites in humans, by liquid and gas chromatography mass spectrometry. The purine degradation pathway, a major biochemical source for reactive oxygen species (ROS) production, was significantly accelerated at the disease sites. This suggests that periodontal-disease-induced oxidative stress and inflammation are mediated through this pathway. The complex host-bacterial interaction was further highlighted by depletion of anti-oxidants, degradation of host cellular components, and accumulation of bacterial products in GCF. These findings provide new mechanistic insights and a panel of comprehensive biomarkers for periodontal disease progression.

  5. Adaptive role of increased frequency of polypurine tracts in mRNA sequences of thermophilic prokaryotes.

    PubMed

    Paz, Arnon; Mester, David; Baca, Ivan; Nevo, Eviatar; Korol, Abraham

    2004-03-02

    The mechanism of an organism's adaptation to high temperatures has been investigated intensively in recent years. It was suggested that the macromolecules of thermophilic microorganisms (especially proteins) have structural features that enhance their thermostability. We compared mRNA sequences of 72 fully sequenced prokaryotic proteomes (14 thermophilic and 58 mesophilic species). Although the differences between the percentage of adenine plus guanine content of whole mRNAs of different prokaryotic species are much lower than those of guanine plus cytosine content, the thermophile purine-pyrimidine (R/Y) ratio within their mRNAs is significantly higher than that of the mesophiles. The first and third codon positions of both thermophiles and mesophiles are purine-biased, with the bias more pronounced by the thermophiles. Thermophile mRNAs that display the highest R/Y ratio (1.43-1.69) are those of the ribosomal proteins, histone-like proteins, DNA-dependent RNA polymerase subunits, and heat-shock proteins. Within mesophilic prokaryotes and five eukaryotic species, the R/Y ratio of the mRNAs of heat-shock proteins is higher than their average over coding part of the genome. Polypurine tracts (R)(n) (with n > or = 5) are much more abundant within the thermophile mRNAs compared with mesophiles. Between two sequential pure-purinic codons of thermophile mRNAs, there is a rather strong tendency for the occurrence of adenine but not guanine tracts. The data suggest that mixed adenine.guanine and polyadenine tracts in mRNAs increase the thermostability beyond the contribution of amino acids encoded by purine tracts, which highlights the importance of ecological stress in the evolution of genome architecture.

  6. Purine salvage in the apicomplexan Sarcocystis neurona, and generation of hypoxanthine-xanthine-guanine phosphoribosyltransferase-deficient clones for positive-negative selection of transgenic parasites.

    PubMed

    Dangoudoubiyam, Sriveny; Zhang, Zijing; Howe, Daniel K

    2014-09-01

    Sarcocystis neurona is an apicomplexan parasite that causes severe neurological disease in horses and marine mammals. The Apicomplexa are all obligate intracellular parasites that lack purine biosynthesis pathways and rely on the host cell for their purine requirements. Hypoxanthine-xanthine-guanine phosphoribosyltransferase (HXGPRT) and adenosine kinase (AK) are key enzymes that function in two complementary purine salvage pathways in apicomplexans. Bioinformatic searches of the S. neurona genome revealed genes encoding HXGPRT, AK and all of the major purine salvage enzymes except purine nucleoside phosphorylase. Wild-type S. neurona were able to grow in the presence of mycophenolic acid (MPA) but were inhibited by 6-thioxanthine (6-TX), suggesting that the pathways involving either HXGPRT or AK are functional in this parasite. Prior work with Toxoplasma gondii demonstrated the utility of HXGPRT as a positive-negative selection marker. To enable the use of HXGPRT in S. neurona, the SnHXGPRT gene sequence was determined and a gene-targeting plasmid was transfected into S. neurona. SnHXGPRT-deficient mutants were selected with 6-TX, and single-cell clones were obtained. These Sn∆HXG parasites were susceptible to MPA and could be complemented using the heterologous T. gondii HXGPRT gene. In summary, S. neurona possesses both purine salvage pathways described in apicomplexans, thus allowing the use of HXGPRT as a positive-negative drug selection marker in this parasite.

  7. Determination and profiling of purines in foods by using HPLC and LC-MS.

    PubMed

    Inazawa, K; Sato, A; Kato, Y; Yamaoka, N; Fukuuchi, T; Yasuda, M; Mawatari, K; Nakagomi, K; Kaneko, K

    2014-01-01

    Purines in food are known to raise serum uric acid levels. We determined the purine content of sweet potato and beef by high-performance liquid chromatography and liquid chromatography-mass spectrometry. The purine content of the samples was 118-1,034 μmol/100 g. The total purine content was also divided into purine bases, nucleosides, nucleotides, and nucleic acids. Our results suggest that differences in total purine content and in the ratio of purine types between vegetables and beef cause a difference in elevation of serum uric acid levels.

  8. Enzymic cleavage of purine ultraviolet photoproducts formed at biologically significant wavelengths

    SciTech Connect

    Gallagher, P.E.; Duker, N.J.

    1986-05-01

    A paradox of ultraviolet carcinogenesis research has been that maximal absorption and mutagenesis occurs at 254 nm irradiation, while the greatest tumor yield in irradiated animals has been at wavelengths between 275 and 300 nm. Ambient actinic radiation contains mostly wavelengths above 280 nm with no substantial 254 nm component. Therefore, the authors investigated formation of DNA damage by 250-400 nm irradiation. Irradiated, 3'-end-labeled, 92 base pair sequence of the human alphoid segment was incubated with endonuclease v, purified from T4-infected E. coli, or with a crude extract of M. luteus. Analysis by gel electrophoresis showed that besides pyrimidine photodimers, previously unreported photoproducts were incised. These are not 6-4'(pyrimidin-2'-one)-pyrimidines, apurinic or apyrimidinic sites, or ring-opened purines. The new products are at specific purine loci and are formed in quantities similar to pyridimine dimers. The optimal wavelengths for their formation are 275-295 nm, similar to the maximum peak of actinic carcinogenesis. The enzyme incising these products is inactivated by different heating conditions than the pyrimidine dimer-DNA glycosylase, and they appear to be separable by column chromatography. The authors propose that a novel family of photoproducts, possibly purine-containing dimers, are incised by previously uncharacterized DNA repair enzymes.

  9. Thermodynamic examination of 1- to 5-nt purine bulge loops in RNA and DNA constructs

    PubMed Central

    Strom, Shane; Shiskova, Evgenia; Hahm, Yaeeun

    2015-01-01

    Bulge loops are common features of RNA structures that are involved in the formation of RNA tertiary structures and are often sites for interactions with proteins and ions. Minimal thermodynamic data currently exist on the bulge size and sequence effects. Using thermal denaturation methods, thermodynamic properties of 1- to 5-nt adenine and guanine bulge loop constructs were examined in 10 mM MgCl2 or 1 M KCl. The ΔG37∘ loop parameters for 1- to 5-nt purine bulge loops in RNA constructs were between 3.07 and 5.31 kcal/mol in 1 M KCl buffer. In 10 mM magnesium ions, the ΔΔG° values relative to 1 M KCl were 0.47–2.06 kcal/mol more favorable for the RNA bulge loops. The ΔG37∘ loop parameters for 1- to 5-nt purine bulge loops in DNA constructs were between 4.54 and 5.89 kcal/mol. Only 4- and 5-nt guanine constructs showed significant change in stability for the DNA constructs in magnesium ions. A linear correlation is seen between the size of the bulge loop and its stability. New prediction models are proposed for 1- to 5-nt purine bulge loops in RNA and DNA in 1 M KCl. We show that a significant stabilization is seen for small bulge loops in RNA in the presence of magnesium ions. A prediction model is also proposed for 1- to 5-nt purine bulge loop RNA constructs in 10 mM magnesium chloride. PMID:26022248

  10. Thermodynamic examination of 1- to 5-nt purine bulge loops in RNA and DNA constructs.

    PubMed

    Strom, Shane; Shiskova, Evgenia; Hahm, Yaeeun; Grover, Neena

    2015-07-01

    Bulge loops are common features of RNA structures that are involved in the formation of RNA tertiary structures and are often sites for interactions with proteins and ions. Minimal thermodynamic data currently exist on the bulge size and sequence effects. Using thermal denaturation methods, thermodynamic properties of 1- to 5-nt adenine and guanine bulge loop constructs were examined in 10 mM MgCl(2) or 1 M KCl. The [Formula: see text] loop parameters for 1- to 5-nt purine bulge loops in RNA constructs were between 3.07 and 5.31 kcal/mol in 1 M KCl buffer. In 10 mM magnesium ions, the ΔΔG° values relative to 1 M KCl were 0.47-2.06 kcal/mol more favorable for the RNA bulge loops. The [Formula: see text] loop parameters for 1- to 5-nt purine bulge loops in DNA constructs were between 4.54 and 5.89 kcal/mol. Only 4- and 5-nt guanine constructs showed significant change in stability for the DNA constructs in magnesium ions. A linear correlation is seen between the size of the bulge loop and its stability. New prediction models are proposed for 1- to 5-nt purine bulge loops in RNA and DNA in 1 M KCl. We show that a significant stabilization is seen for small bulge loops in RNA in the presence of magnesium ions. A prediction model is also proposed for 1- to 5-nt purine bulge loop RNA constructs in 10 mM magnesium chloride. © 2015 Strom et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  11. Trophic effects of purines in neurons and glial cells.

    PubMed

    Rathbone, M P; Middlemiss, P J; Gysbers, J W; Andrew, C; Herman, M A; Reed, J K; Ciccarelli, R; Di Iorio, P; Caciagli, F

    1999-12-01

    In addition to their well known roles within cells, purine nucleotides such as adenosine 5' triphosphate (ATP) and guanosine 5' triphosphate (GTP), nucleosides such as adenosine and guanosine and bases, such as adenine and guanine and their metabolic products xanthine and hypoxanthine are released into the extracellular space where they act as intercellular signaling molecules. In the nervous system they mediate both immediate effects, such as neurotransmission, and trophic effects which induce changes in cell metabolism, structure and function and therefore have a longer time course. Some trophic effects of purines are mediated via purinergic cell surface receptors, whereas others require uptake of purines by the target cells. Purine nucleosides and nucleotides, especially guanosine, ATP and GTP stimulate incorporation of [3H]thymidine into DNA of astrocytes and microglia and concomitant mitosis in vitro. High concentrations of adenosine also induce apoptosis, through both activation of cell-surface A3 receptors and through a mechanism requiring uptake into the cells. Extracellular purines also stimulate the synthesis and release of protein trophic factors by astrocytes, including bFGF (basic fibroblast growth factor), nerve growth factor (NGF), neurotrophin-3, ciliary neurotrophic factor and S-100beta protein. In vivo infusion into brain of adenosine analogs stimulates reactive gliosis. Purine nucleosides and nucleotides also stimulate the differentiation and process outgrowth from various neurons including primary cultures of hippocampal neurons and pheochromocytoma cells. A tonic release of ATP from neurons, its hydrolysis by ecto-nucleotidases and subsequent re-uptake by axons appears crucial for normal axonal growth. Guanosine and GTP, through apparently different mechanisms, are also potent stimulators of axonal growth in vitro. In vivo the extracellular concentration of purines depends on a balance between the release of purines from cells and their re

  12. Potential chemotherapeutic targets in the purine metabolism of parasites.

    PubMed

    el Kouni, Mahmoud H

    2003-09-01

    Parasites are responsible for a wide variety of infectious diseases in human as well as in domestic and wild animals, causing an enormous health and economical blight. Current containment strategies are not entirely successful and parasitic infections are on the rise. In the absence of availability of antiparasitic vaccines, chemotherapy remains the mainstay for the treatment of most parasitic diseases. However, there is an urgent need for new drugs to prevent or combat some major parasitic infections because of lack of a single effective approach for controlling the parasites (e.g., trypanosomiasis) or because some serious parasitic infections developed resistance to presently available drugs (e.g., malaria). The rational design of a drug is usually based on biochemical and physiological differences between pathogens and host. Some of the most striking differences between parasites and their mammalian host are found in purine metabolism. Purine nucleotides can be synthesized by the de novo and/or the so-called "salvage" pathways. Unlike their mammalian host, most parasites studied lack the pathways for de novo purine biosynthesis and rely on the salvage pathways to meet their purine demands. Moreover, because of the great phylogenic separation between the host and the parasite, there are in some cases sufficient distinctions between corresponding enzymes of the purine salvage from the host and the parasite that can be exploited to design specific inhibitors or "subversive substrates" for the parasitic enzymes. Furthermore, the specificities of purine transport, the first step in purine salvage, diverge significantly between parasites and their mammalian host. This review highlights the unique transporters and enzymes responsible for the salvage of purines in parasites that could constitute excellent potential targets for the design of safe and effective antiparasitic drugs.

  13. Biosensor measurement of purine release from cerebellar cultures and slices.

    PubMed

    Wall, Mark; Eason, Robert; Dale, Nicholas

    2010-09-01

    We have previously described an action-potential and Ca(2+)-dependent form of adenosine release in the molecular layer of cerebellar slices. The most likely source of the adenosine is the parallel fibres, the axons of granule cells. Using microelectrode biosensors, we have therefore investigated whether cultured granule cells (from postnatal day 7-8 rats) can release adenosine. Although no purine release could be detected in response to focal electrical stimulation, purine (adenosine, inosine or hypoxanthine) release occurred in response to an increase in extracellular K(+) concentration from 3 to 25 mM coupled with addition of 1 mM glutamate. The mechanism of purine release was transport from the cytoplasm via an ENT transporter. This process did not require action-potential firing but was Ca(2+)dependent. The major purine released was not adenosine, but was either inosine or hypoxanthine. In order for inosine/hypoxanthine release to occur, cultures had to contain both granule cells and glial cells; neither cellular component was sufficient alone. Using the same stimulus in cerebellar slices (postnatal day 7-25), it was possible to release purines. The release however was not blocked by ENT blockers and there was a shift in the Ca(2+) dependence during development. This data from cultures and slices further illustrates the complexities of purine release, which is dependent on cellular composition and developmental stage.

  14. The effect of cyclophosphamide and gamma irradiation on adenosine deaminase and purine nucleoside phosphorylase in mice

    SciTech Connect

    Hosek, B.; Bohaecek, J.; Sikulova, J. )

    1991-01-01

    Changes in ADA and PNP activities in the spleens and thymuses of mice were studied after a single administration of cyclophosphamide and after whole-body gamma irradiation, applied alone or three days after CY application, In the first days after the treatment the enzyme activities were significantly depressed with the exception of ADA in the spleen, where a high elevation in relation to controls was observed. During the regeneration period a pronounced rise of PNP activity in the spleen occurred mainly after a combined application of CY and irradiation. In the thymus the regeneration was manifested by a mild increase of both ADA and PNP activities towards control values. The findings suggest that the expressive changes of ADA and PNP activities, participating in the purine salvage pathway, may, after a cytotoxic treatment, influence the nucleotide pool and DNA synthesis in lymphoid organs.

  15. Metabolic Reprogramming During Purine Stress in the Protozoan Pathogen Leishmania donovani

    SciTech Connect

    Martin, Jessica L.; Yates, Phillip A.; Soysa, Radika; Alfaro, Joshua F.; Yang, Feng; Burnum-Johnson, Kristin E.; Petyuk, Vladislav A.; Weitz, Karl K.; Camp, David G.; Smith, Richard D.; Wilmarth, Phillip A.; David, Larry L.; Ramasamy, Gowthaman; Myler, Peter J.; Carter, Nicola S.

    2014-02-27

    The ability of Leishmania to survive in their insect or mammalian host is dependent upon an ability to sense and adapt to changes in the microenvironment. However, little is known about the molecular mechanisms underlying the parasite response to environmental changes, such as nutrient availability. To elucidate nutrient stress response pathways in Leishmania donovani, we have used purine starvation as the paradigm. The salvage of purines from the host milieu is obligatory for parasite replication; nevertheless, purine-starved parasites can persist in culture without supplementary purine for over 3 months, indicating that the response to purine starvation is robust and engenders parasite survival under conditions of extreme scarcity. To understand metabolic reprogramming during purine starvation we have employed global approaches. Whole proteome comparisons between purine-starved and purine-replete parasites over a 6-48 h span have revealed a temporal and coordinated response to purine starvation. Purine transporters and enzymes involved in acquisition at the cell surface are upregulated within a few hours of purine removal from the media, while other key purine salvage components are upregulated later in the time-course and more modestly. After 48 h, the proteome of purine-starved parasites is extensively remodeled and adaptations to purine stress appear tailored to deal with both purine deprivation and general stress. To probe the molecular mechanisms affecting proteome remodeling in response to purine starvation, comparative RNA-seq analyses, qRT-PCR, and luciferase reporter assays were performed on purine-starved versus purine-replete parasites. While the regulation of a minority of proteins tracked with changes at the mRNA level, for many regulated proteins it appears that proteome remodeling during purine stress occurs primarily via translational and/or post-translational mechanisms.

  16. Metabolic Reprogramming during Purine Stress in the Protozoan Pathogen Leishmania donovani

    PubMed Central

    Soysa, Radika; Alfaro, Joshua F.; Yang, Feng; Burnum-Johnson, Kristin E.; Petyuk, Vladislav A.; Weitz, Karl K.; Camp, David G.; Smith, Richard D.; Wilmarth, Phillip A.; David, Larry L.; Ramasamy, Gowthaman; Myler, Peter J.; Carter, Nicola S.

    2014-01-01

    The ability of Leishmania to survive in their insect or mammalian host is dependent upon an ability to sense and adapt to changes in the microenvironment. However, little is known about the molecular mechanisms underlying the parasite response to environmental changes, such as nutrient availability. To elucidate nutrient stress response pathways in Leishmania donovani, we have used purine starvation as the paradigm. The salvage of purines from the host milieu is obligatory for parasite replication; nevertheless, purine-starved parasites can persist in culture without supplementary purine for over three months, indicating that the response to purine starvation is robust and engenders parasite survival under conditions of extreme scarcity. To understand metabolic reprogramming during purine starvation we have employed global approaches. Whole proteome comparisons between purine-starved and purine-replete parasites over a 6–48 h span have revealed a temporal and coordinated response to purine starvation. Purine transporters and enzymes involved in acquisition at the cell surface are upregulated within a few hours of purine removal from the media, while other key purine salvage components are upregulated later in the time-course and more modestly. After 48 h, the proteome of purine-starved parasites is extensively remodeled and adaptations to purine stress appear tailored to deal with both purine deprivation and general stress. To probe the molecular mechanisms affecting proteome remodeling in response to purine starvation, comparative RNA-seq analyses, qRT-PCR, and luciferase reporter assays were performed on purine-starved versus purine-replete parasites. While the regulation of a minority of proteins tracked with changes at the mRNA level, for many regulated proteins it appears that proteome remodeling during purine stress occurs primarily via translational and/or post-translational mechanisms. PMID:24586154

  17. Characterizing substrate properties of purine-related compounds with purine metabolism enzymes for enzymatic peak-shift HPLC method.

    PubMed

    Fukuuchi, T; Morimura, A; Kawatani, M; Yamamoto, K; Yamaoka, N; Kaneko, K

    2014-01-01

    We have extended peak-shift method for measuring purine bases to make it suitable for other purine-related compounds. We optimized the reactions of the purine metabolism enzymes 5'-nucleotidase (EC 3.1.3.5), purine nucleoside phosphorylase (PNP) (EC 2.4.2.1), xanthine oxidase (XO) (EC 1.17.3.2), urate hydroxylase (EC 1.7.3.3), adenosine deaminase (ADA) (EC 3.5.4.4), and guanine deaminase (EC 3.5.4.3) by determining their substrate specificity and reaction kinetics. These enzymes eliminate the five purine base peaks (adenine, guanine, hypoxanthine, xanthine, and uric acid) and four nucleosides (adenosine, guanosine, inosine, and xanthosine). The bases and nucleosides can be identified and accurately quantified by comparing the chromatograms before and after treatment with the enzymes. Elimination of the individual purine compound peaks was complete in a few minutes. However, when there were multiple substrates, such as for XO, and when the metabolites were purine compounds, such as for PNP and ADA, it took longer to eliminate the peaks. The optimum reaction conditions for the peak-shift assay methods were an assay mixture containing the substrate (10 μL, 0.1 mg/mL), the combined enzyme solution (10 μL each, optimum concentration), and 50 mM sodium phosphate (up to 120 μL, pH 7.4). The mixture was incubated for 60 minutes at 37°C. This method should be suitable for determining the purine content of a variety of samples, without interference from impurities.

  18. Catalase increases ethanol oxidation through the purine catabolism in rat liver.

    PubMed

    Villalobos-García, Daniel; Hernández-Muñoz, Rolando

    2017-08-01

    Hepatic ethanol oxidation increases according to its concentration and is raised to near-saturation levels of alcohol dehydrogenase (ADH); therefore, re-oxidation of NADH becomes rate limiting in ethanol metabolism by the liver. Adenosine is able to increase liver ethanol oxidation in both in vivo and in vitro conditions; the enhancement being related with the capacity of the nucleoside to accelerate the transport of cytoplasmic reducing equivalents to mitochondria, by modifying the subcellular distribution of the malate-aspartate shuttle components. In the present study, we explored the putative effects of adenosine and other purines on liver ethanol oxidation mediated by non-ADH pathways. Using the model of high precision-cut rat liver slices, a pronounced increase of ethanol oxidation was found in liver slices incubated with various intermediates of the purine degradation pathway, from adenosine to uric acid (175-230%, over controls). Of these, urate had the strongest (230%), whereas xanthine had the less pronounced effect (178% over controls). The enhancement was not abolished by 4-methylpyrazole, indicating that the effect was independent of alcohol dehydrogenase. Conversely, aminotriazole, a catalase inhibitor, completely abolished the effect, pointing out that this enhanced ethanol oxidation is mediated by catalase activity. It is concluded that the H2O2 needed for catalase activity is derived from the oxidation of (hypo)xanthine by xanthine oxidase and the oxidation of urate by uricase. The present and previous data led us to propose that, depending on the metabolic conditions, adenosine might be able to stimulate the metabolism of ethanol through different pathways. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Learning to Pronounce Words: The Limitations of Analogies.

    ERIC Educational Resources Information Center

    Bruck, Maggie; Treiman, Rebecca

    1992-01-01

    Examines the degree to which teaching beginning readers to use various types of analogies helps them pronounce new words and nonwords. Finds that, although beginning readers can use analogies, they rely to a large extent on correspondences between individual phonemes and graphemes to decode new words. (RS)

  20. Peculiarities of carnosine metabolism in a patient with pronounced homocarnosinemia.

    PubMed

    Kramarenko, G G; Markova, E D; Ivanova-Smolenskaya, I A; Boldyrev, A A

    2001-10-01

    The article describes a case of homocarnosinemia with increased liquor and plasma content of homocarnosine, increased urinary excretion of homocarnosine, and low activity of serum carnosinase. These metabolic disturbances were accompanied by moderate neurological disorders. Changes in carnosine metabolism in family members were less pronounced and not accompanied by neuropathological symptoms.

  1. Targeting a Novel Plasmodium falciparum Purine Recycling Pathway with Specific Immucillins

    SciTech Connect

    Ting, L; Shi, W; Lewandowicz, A; Singh, V; Mwakingwe, A; Birck, M R; Taylor Ringia, E A; Bench, G; Madrid, D C; Tyler, P C; Evans, G B; Furneaux, R H; Schramm, V L; Kim, K

    2004-05-19

    Plasmodium falciparum is unable to synthesize purine bases and relies upon purine salvage and purine recycling to meet its purine needs. We report that purines formed as products of the polyamine pathway are recycled in a novel pathway in which 5'-methylthioinosine is generated by adenosine deaminase. The action of P. falciparum purine nucleoside phosphorylase is a convergent step of purine salvage, converting both 5'-methylthioinosine and inosine to hypoxanthine. We used accelerator mass spectrometry to verify that 5'-methylthioinosine is an active nucleic acid precursor in P. falciparum. Prior studies have shown that inhibitors of purine salvage enzymes kill malaria, but potent malaria-specific inhibitors of these enzymes have not previously been described. 5'-methylthio-Immucillin-H, a transition state analogue inhibitor that is selective for malarial over human purine nucleoside phosphorylase, kills P. falciparum in culture. Immucillins are currently in clinical trials for other indications and may have application as antimalarials.

  2. A role for adenine nucleotides in the sensing mechanism to purine starvation in Leishmania donovani.

    PubMed

    Martin, Jessica L; Yates, Phillip A; Boitz, Jan M; Koop, Dennis R; Fulwiler, Audrey L; Cassera, Maria Belen; Ullman, Buddy; Carter, Nicola S

    2016-07-01

    Purine salvage by Leishmania is an obligatory nutritional process that impacts both cell viability and growth. Previously, we have demonstrated that the removal of purines in culture provokes significant metabolic changes that enable Leishmania to survive prolonged periods of purine starvation. In order to understand how Leishmania sense and respond to changes in their purine environment, we have exploited several purine pathway mutants, some in which adenine and guanine nucleotide metabolism is uncoupled. While wild type parasites grow in any one of a variety of naturally occurring purines, the proliferation of these purine pathway mutants requires specific types or combinations of exogenous purines. By culturing purine pathway mutants in high levels of extracellular purines that are either permissive or non-permissive for growth and monitoring for previously defined markers of the adaptive response to purine starvation, we determined that adaptation arises from a surveillance of intracellular purine nucleotide pools rather than from a direct sensing of the extracellular purine content of the environment. Specifically, our data suggest that perturbation of intracellular adenine-containing nucleotide pools provides a crucial signal for inducing the metabolic changes necessary for the long-term survival of Leishmania in a purine-scarce environment. © 2016 John Wiley & Sons Ltd.

  3. Purine-rich foods intake and recurrent gout attacks

    PubMed Central

    Zhang, Yuqing; Chen, Clara; Choi, Hyon; Chaisson, Christine; Hunter, David; Niu, Jingbo; Neogi, Tuhina

    2014-01-01

    Objective To examine and quantify the relation between purine intake and the risk of recurrent gout attacks among gout patients. Methods The authors conducted a case-crossover study to examine associations of a set of putative risk factors with recurrent gout attacks. Individuals with gout were prospectively recruited and followed online for 1 year. Participants were asked about the following information when experiencing a gout attack: the onset date of the gout attack, clinical symptoms and signs, medications (including antigout medications), and presence of potential risk factors (including daily intake of various purine-containing food items) during the 2-day period prior to the gout attack. The same exposure information was also assessed over 2-day control periods. Results This study included 633 participants with gout. Compared with the lowest quintile of total purine intake over a 2-day period, OR of recurrent gout attacks were 1.17, 1.38, 2.21 and 4.76, respectively, with each increasing quintile (p for trend <0.001). The corresponding OR were 1.42, 1.34, 1.77 and 2.41 for increasing quintiles of purine intake from animal sources (p for trend <0.001), and 1.12, 0.99, 1.32 and 1.39 from plant sources (p=0.04), respectively. The effect of purine intake persisted across subgroups by sex, use of alcohol, diuretics, allopurinol, NSAIDs and colchicine. Conclusions The study findings suggest that acute purine intake increases the risk of recurrent gout attacks by almost fivefold among gout patients. Avoiding or reducing amount of purine-rich foods intake, especially of animal origin, may help reduce the risk of gout attacks. PMID:22648933

  4. Ophidian envenomation strategies and the role of purines.

    PubMed

    Aird, Steven D

    2002-04-01

    Snake envenomation employs three well integrated strategies: prey immobilization via hypotension, prey immobilization via paralysis, and prey digestion. Purines (adenosine, guanosine and inosine) evidently play a central role in the envenomation strategies of most advanced snakes. Purines constitute the perfect multifunctional toxins, participating simultaneously in all three envenomation strategies. Because they are endogenous regulatory compounds in all vertebrates, it is impossible for any prey organism to develop resistance to them. Purine generation from endogenous precursors in the prey explains the presence of many hitherto unexplained enzyme activities in snake venoms: 5'-nucleotidase, endonucleases (including ribonuclease), phosphodiesterase, ATPase, ADPase, phosphomonoesterase, and NADase. Phospholipases A(2), cytotoxins, myotoxins, and heparinase also participate in purine liberation, in addition to their better known functions. Adenosine contributes to prey immobilization by activation of neuronal adenosine A(1) receptors, suppressing acetylcholine release from motor neurons and excitatory neurotransmitters from central sites. It also exacerbates venom-induced hypotension by activating A(2) receptors in the vasculature. Adenosine and inosine both activate mast cell A(3) receptors, liberating vasoactive substances and increasing vascular permeability. Guanosine probably contributes to hypotension, by augmenting vascular endothelial cGMP levels via an unknown mechanism. Novel functions are suggested for toxins that act upon blood coagulation factors, including nitric oxide production, using the prey's carboxypeptidases. Leucine aminopeptidase may link venom hemorrhagic metalloproteases and endogenous chymotrypsin-like proteases with venom L-amino acid oxidase (LAO), accelerating the latter. The primary function of LAO is probably to promote prey hypotension by activating soluble guanylate cyclase in the presence of superoxide dismutase. LAO's apoptotic

  5. Asymmetric purine-pyrimidine distribution in cellular small RNA population of papaya

    PubMed Central

    2012-01-01

    Background The small RNAs (sRNA) are a regulatory class of RNA mainly represented by the 21 and 24-nucleotide size classes. The cellular sRNAs are processed by RNase III family enzyme dicer (Dicer like in plant) from a self-complementary hairpin loop or other type of RNA duplexes. The papaya genome has been sequenced, but its microRNAs and other regulatory RNAs are yet to be analyzed. Results We analyzed the genomic features of the papaya sRNA population from three sRNA deep sequencing libraries made from leaves, flowers, and leaves infected with Papaya Ringspot Virus (PRSV). We also used the deep sequencing data to annotate the micro RNA (miRNA) in papaya. We identified 60 miRNAs, 24 of which were conserved in other species, and 36 of which were novel miRNAs specific to papaya. In contrast to the Chargaff’s purine-pyrimidine equilibrium, cellular sRNA was significantly biased towards a purine rich population. Of the two purine bases, higher frequency of adenine was present in 23nt or longer sRNAs, while 22nt or shorter sRNAs were over represented by guanine bases. However, this bias was not observed in the annotated miRNAs in plants. The 21nt species were expressed from fewer loci but expressed at higher levels relative to the 24nt species. The highly expressed 21nt species were clustered in a few isolated locations of the genome. The PRSV infected leaves showed higher accumulation of 21 and 22nt sRNA compared to uninfected leaves. We observed higher accumulation of miRNA* of seven annotated miRNAs in virus-infected tissue, indicating the potential function of miRNA* under stressed conditions. Conclusions We have identified 60 miRNAs in papaya. Our study revealed the asymmetric purine-pyrimidine distribution in cellular sRNA population. The 21nt species of sRNAs have higher expression levels than 24nt sRNA. The miRNA* of some miRNAs shows higher accumulation in PRSV infected tissues, suggesting that these strands are not totally functionally redundant. The

  6. Purine receptor mediated actin cytoskeleton remodeling of human fibroblasts

    PubMed Central

    Goldman, Nanna; Chandler-Militello, Devin; Langevin, Helene; Nedergaard, Maiken; Takano, Takahiro

    2013-01-01

    Earlier studies have shown that activation of adenosine A1 receptors on peripheral pain fibers contributes to acupuncture-induced suppression of painful input. In addition to adenosine, acupuncture triggers the release of other purines, including ATP and ADP that may bind to purine receptors on nearby fibroblasts. We here show that purine agonists trigger increase in cytosolic Ca 2+ signaling in a cultured human fibroblasts cell line. The profile of agonist-induced Ca2+ increases indicates that the cells express functional P2yR2 and P2yR4 receptors, as well as P2yR1 and P2xR7 receptors. Unexpectedly, purine-induced Ca2+ signaling was associated with a remodeling of the actin cytoskeleton. ATP induced a transient loss in F-actin stress fiber. The changes of actin cytoskeleton occurred slowly and peaked at 10 min after agonist exposure. Inhibition of ATP-induced increases in Ca2+ by cyclopiazonic acid blocked receptor-mediated cytoskeleton remodeling. The Ca2+ ionophore failed to induce cytoskeletal remodeling despite triggering robust increases in cytosolic Ca2+. These observations indicate that purine signaling induces transient changes in fibroblast cytoarchitecture that could be related to the beneficial effects of acupuncture. PMID:23462235

  7. Isolation of Purines and Pyrimidines from the Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. K.

    2003-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth's prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines'. These compounds play a major role in terrestrial biochemistry and are integral components of proteins, DNA and RNA. In this study we developed a new extraction technique using sublimation in order to isolate purines and pyrimidines from Murchison2, which is cleaner and more time efficient that traditional methods3. Several purines including adenine, guanine, hypoxanthine and xanthine were positively identified by high performance liquid chromatography and ultraviolet absorption detection in our Murchison extracts. The purines detected in Murchison do not correlate with the distribution of nucleobases found in geological environments on Earth4. Moreover, the abundance of extraterrestrial amino acids and the low level of terrestrial amino acid contaminants found in Murchison', support the idea that the purines in t h s meteorite are extraterrestrial in origin.

  8. Isolation of Purines and Pyrimidines from the Murchison Meteorite

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. K.

    2003-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth's prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines'. These compounds play a major role in terrestrial biochemistry and are integral components of proteins, DNA and RNA. In this study we developed a new extraction technique using sublimation in order to isolate purines and pyrimidines from Murchison2, which is cleaner and more time efficient that traditional methods3. Several purines including adenine, guanine, hypoxanthine and xanthine were positively identified by high performance liquid chromatography and ultraviolet absorption detection in our Murchison extracts. The purines detected in Murchison do not correlate with the distribution of nucleobases found in geological environments on Earth4. Moreover, the abundance of extraterrestrial amino acids and the low level of terrestrial amino acid contaminants found in Murchison', support the idea that the purines in t h s meteorite are extraterrestrial in origin.

  9. 8-Phosphorus substituted isosteres of purine and deazapurines.

    PubMed Central

    Khwaja, T A; Pande, H

    1979-01-01

    Synthesis of 8-phosphorus substituted isosteres of purine [pyrimidino (4,5-d)-1,3,2-diazaphosphole], 1-deazapurine [pyridino (2,3-d)-1,3,2-diazaphosphole] and 3-deazapurine [pyridino (4,5-d)-1,3,2-diazaphosphole] has been achieved by the reaction of equimolar amounts of triphenylphosphite and 4,5-diaminopyrimidine, 2,3-diaminopyridine and 3,4-diaminopyridine, respectively. These compounds hydrolyzed (cleavage of the phosphorus-nitrogen bounds) in aqueous solutions to provide the corresponding diaminopyrimidine or diaminopyridines. These three new basic ring systems constitute the first reported synthesis of purines in which ring carbon atom is substituted with a phosphorus atom. 8-Phosphorus substituted purine at a concentration of 4 X 10(-4)M caused a 50% inhibition in the growth of leukemia L1210 cells in culture. The biochemical rationale for the synthesis of these compounds is discussed. PMID:493140

  10. Plasticity in the purine-thiamine metabolic network of Salmonella.

    PubMed

    Bazurto, Jannell V; Downs, Diana M

    2011-02-01

    In Salmonella enterica, 5-aminoimidazole ribonucleotide (AIR) is the precursor of the 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) pyrophosphate moiety of thiamine and the last intermediate in the common HMP/purine biosynthetic pathway. AIR is synthesized de novo via five reactions catalyzed by the purF, -D, -T, -G, and -I gene products. In vivo genetic analysis demonstrated that in the absence of these gene products AIR can be generated if (i) methionine and lysine are in the growth medium, (ii) PurC is functional, and (iii) 5-amino-4-imidazolecarboxamide ribotide (AICAR) has accumulated. This study provides evidence that the five steps of the common HMP/purine biosynthetic pathway can be bypassed in the synthesis of AIR and thus demonstrates that thiamine synthesis can be uncoupled from the early purine biosynthetic pathway in bacteria.

  11. Arthrobacter oxydans as a biocatalyst for purine deamination.

    PubMed

    Médici, Rosario; Lewkowicz, Elizabeth S; Iribarren, Adolfo M

    2008-12-01

    Deaminases are enzymes that catalyze the hydrolysis of amino groups of nucleosides or their bases. Because these enzymes play important roles in nucleotide metabolism, they are relevant targets in anticancer and antibacterial therapies. Mammalian deaminases are commercially available but the use of bacterial whole cells, especially as biocatalysts, is continuously growing because of their economical benefits. Moreover, deaminases are useful for the preparative chemoenzymatic transformation of nucleoside and base analogues into a variety of derivatives. The purine deaminase activities of Arthrobacter oxydans, a gram-positive bacterium utilized widely in bioremediation, were studied. The presence of adenosine, adenine and guanine deaminases was demonstrated and some purine bases and nucleosides were analyzed as substrates. Using A. oxydans whole cells as the biocatalyst, different purine compounds such as the anti-HIV, 2',3'-dideoxyinosine (73%, 2 h) were obtained.

  12. Gene expression control by Bacillus anthracis purine riboswitches.

    PubMed

    Kirchner, Marion; Schneider, Sabine

    2017-02-16

    In all kingdoms of life, cellular replication relies on the presence of nucleosides and nucleotides, the building blocks of nucleic acids and the main source of energy. In bacteria, the availability of metabolites sometimes directly regulates the expression of enzymes and proteins involved in purine salvage, biosynthesis and uptake through riboswitches. Riboswitches are located in bacterial mRNAs and can control gene expression by conformational changes in response to ligand binding. We have established an inverse reporter gene system in Bacillus subtilis that allows us to monitor riboswitch-controlled gene expression. We used it to investigate the activity of five potential purine riboswitches from B. anthracis in response to different purines and pyrimidines. Furthermore, in vitro studies on the aptamer domains of the riboswitches reveal their variation in guanine binding affinity ranging from nM to µM. These data do not only provide insight into metabolite sensing but can also aid to engineer artificial cell regulatory systems.

  13. Recombinant purine nucleoside phosphorylases from thermophiles: preparation, properties and activity towards purine and pyrimidine nucleosides.

    PubMed

    Zhou, Xinrui; Szeker, Kathleen; Janocha, Bernd; Böhme, Thomas; Albrecht, Dirk; Mikhailopulo, Igor A; Neubauer, Peter

    2013-03-01

    Thermostable nucleoside phosphorylases are attractive biocatalysts for the synthesis of modified nucleosides. Hence we report on the recombinant expression of three 'high molecular mass' purine nucleoside phosphorylases (PNPs) derived from the thermophilic bacteria Deinococcus geothermalis, Geobacillus thermoglucosidasius and from the hyperthermophilic archaeon Aeropyrum pernix (5'-methythioadenosine phosphorylase; ApMTAP). Thermostability studies, kinetic analysis and substrate specificities are reported. The PNPs were stable at their optimal temperatures (DgPNP, 55 °C; GtPNP, 70 °C; ApMTAP, activity rising to 99 °C). Substrate properties were investigated for natural purine nucleosides [adenosine, inosine and their C2'-deoxy counterparts (activity within 50-500 U·mg(-1))], analogues with 2'-amino modified 2'-deoxy-adenosine and -inosine (within 0.1-3 U·mg(-1)) as well as 2'-deoxy-2'-fluoroadenosine (9) and its C2'-arabino diastereomer (10, within 0.01-0.03 U·mg(-1)). Our results reveal that the structure of the heterocyclic base (e.g. adenine or hypoxanthine) can play a critical role in the phosphorolysis reaction. The implications of this finding may be helpful for reaction mechanism studies or optimization of reaction conditions. Unexpectedly, the diastereomeric 2'-deoxyfluoro adenine ribo- and arabino-nucleosides displayed similar substrate properties. Moreover, cytidine and 2'-deoxycytidine were found to be moderate substrates of the prepared PNPs, with substrate activities in a range similar to those determined for 2'-deoxyfluoro adenine nucleosides 9 and 10. C2'-modified nucleosides are accepted as substrates by all recombinant enzymes studied, making these enzymes promising biocatalysts for the synthesis of modified nucleosides. Indeed, the prepared PNPs performed well in preliminary transglycosylation reactions resulting in the synthesis of 2'-deoxyfluoro adenine ribo- and arabino- nucleosides in moderate yield (24%). © 2013 The Authors Journal

  14. Advances in purine and pyrimidine metabolism in health and diseases.

    PubMed

    Hirano, Michio; Peters, Godefridus J

    2016-12-01

    In June, 2015, the Purine and Pyrimidine Society organized the 16th biennial symposium on Purine and Pyrimidine metabolism at the Faculty House of Columbia University, New York City. This exciting meeting focused on these important molecules, new developments in inborn errors of metabolism; therapeutic analogs. In addition, the biochemistry of mammalian and non-mammalian systems were discussed. Due to significant advances in molecular medicine, the boundaries between clinical and basic sciences have merged into exciting translational research, of which a small portion was highlighted in the presymposium.

  15. Molecular and Genetic Analyses of Drosophila Prat, Which Encodes the First Enzyme of De Novo Purine Biosynthesis

    PubMed Central

    Clark, D. V.

    1994-01-01

    The Drosophila Prat gene encodes phosphoribosylamidotransferase (PRAT), the enzyme that performs the first committed step of the de novo purine nucleotide biosynthesis pathway. Using information from amino acid sequence alignments of PRAT from other organisms, a polymerase chain reaction-based approach was employed to clone Prat. Amino acid sequence alignment of Drosophila PRAT with PRAT from bacteria, yeast, and vertebrates indicates that it is most identical (at least 60%) to the vertebrate PRATs. It shares putative amino-terminal propeptide and ironbinding domains seen only in Bacillus subtilis and vertebrate PRATs. Prat was localized to the right arm of chromosome 3 at polytene band 84E1-2. Owing to the fact that this region had been well characterized previously, Prat was localized to a 30-kilobase region between two deficiency break-points. By making the prediction that Prat would have a similar ``purine syndrome'' phenotype as mutations in the genes ade2 and ade3, which encode enzymes downstream in the pathway, five alleles of Prat were isolated. Three of the alleles were identified as missense mutations. A comparison of PRAT enzyme activity with phenotype in three of the mutants indicates that a reduction to 40% of the wild-type allele's activity is sufficient to cause the purine syndrome, suggesting that PRAT activity is limiting in Drosophila. PMID:8150282

  16. A purine nucleoside phosphorylase in Solanum tuberosum L. (potato) with specificity for cytokinins contributes to the duration of tuber endodormancy.

    PubMed

    Bromley, Jennifer R; Warnes, Barbara J; Newell, Christine A; Thomson, Jamie C P; James, Celia M; Turnbull, Colin G N; Hanke, David E

    2014-03-01

    StCKP1 (Solanum tuberosum cytokinin riboside phosphorylase) catalyses the interconversion of the N9-riboside form of the plant hormone CK (cytokinin), a subset of purines, with its most active free base form. StCKP1 prefers CK to unsubstituted aminopurines. The protein was discovered as a CK-binding activity in extracts of tuberizing potato stolon tips, from which it was isolated by affinity chromatography. The N-terminal amino acid sequence matched the translation product of a set of ESTs, enabling a complete mRNA sequence to be obtained by RACE-PCR. The predicted polypeptide includes a cleavable signal peptide and motifs for purine nucleoside phosphorylase activity. The expressed protein was assayed for purine nucleoside phosphorylase activity against CKs and adenine/adenosine. Isopentenyladenine, trans-zeatin, dihydrozeatin and adenine were converted into ribosides in the presence of ribose 1-phosphate. In the opposite direction, isopentenyladenosine, trans-zeatin riboside, dihydrozeatin riboside and adenosine were converted into their free bases in the presence of Pi. StCKP1 had no detectable ribohydrolase activity. Evidence is presented that StCKP1 is active in tubers as a negative regulator of CKs, prolonging endodormancy by a chill-reversible mechanism.

  17. The Purine-Utilizing Bacterium Clostridium acidurici 9a: A Genome-Guided Metabolic Reconsideration

    PubMed Central

    Hartwich, Katrin; Poehlein, Anja; Daniel, Rolf

    2012-01-01

    Clostridium acidurici is an anaerobic, homoacetogenic bacterium, which is able to use purines such as uric acid as sole carbon, nitrogen, and energy source. Together with the two other known purinolytic clostridia C. cylindrosporum and C. purinilyticum, C. acidurici serves as a model organism for investigation of purine fermentation. Here, we present the first complete sequence and analysis of a genome derived from a purinolytic Clostridium. The genome of C. acidurici 9a consists of one chromosome (3,105,335 bp) and one small circular plasmid (2,913 bp). The lack of candidate genes encoding glycine reductase indicates that C. acidurici 9a uses the energetically less favorable glycine-serine-pyruvate pathway for glycine degradation. In accordance with the specialized lifestyle and the corresponding narrow substrate spectrum of C. acidurici 9a, the number of genes involved in carbohydrate transport and metabolism is significantly lower than in other clostridia such as C. acetobutylicum, C. saccharolyticum, and C. beijerinckii. The only amino acid that can be degraded by C. acidurici is glycine but growth on glycine only occurs in the presence of a fermentable purine. Nevertheless, the addition of glycine resulted in increased transcription levels of genes encoding enzymes involved in the glycine-serine-pyruvate pathway such as serine hydroxymethyltransferase and acetate kinase, whereas the transcription levels of formate dehydrogenase-encoding genes decreased. Sugars could not be utilized by C. acidurici but the full genetic repertoire for glycolysis was detected. In addition, genes encoding enzymes that mediate resistance against several antimicrobials and metals were identified. High resistance of C. acidurici towards bacitracin, acriflavine and azaleucine was experimentally confirmed. PMID:23240052

  18. Purine utilization by Klebsiella oxytoca M5al: genes for ring-oxidizing and -opening enzymes.

    PubMed

    Pope, Scott D; Chen, Li-Ling; Stewart, Valley

    2009-02-01

    The enterobacterium Klebsiella oxytoca uses a variety of inorganic and organic nitrogen sources, including purines, nitrogen-rich compounds that are widespread in the biosphere. We have identified a 23-gene cluster that encodes the enzymes for utilizing purines as the sole nitrogen source. Growth and complementation tests with insertion mutants, combined with sequence comparisons, reveal functions for the products of these genes. Here, we report our characterization of 12 genes, one encoding guanine deaminase and the others encoding enzymes for converting (hypo)xanthine to allantoate. Conventionally, xanthine dehydrogenase, a broadly distributed molybdoflavoenzyme, catalyzes sequential hydroxylation reactions to convert hypoxanthine via xanthine to urate. Our results show that these reactions in K. oxytoca are catalyzed by a two-component oxygenase (HpxE-HpxD enzyme) homologous to Rieske nonheme iron aromatic-ring-hydroxylating systems, such as phthalate dioxygenase. Our results also reveal previously undescribed enzymes involved in urate oxidation to allantoin, catalyzed by a flavoprotein monooxygenase (HpxO enzyme), and in allantoin conversion to allantoate, which involves allantoin racemase (HpxA enzyme). The pathway also includes the recently described PuuE allantoinase (HpxB enzyme). The HpxE-HpxD and HpxO enzymes were discovered independently by de la Riva et al. (L. de la Riva, J. Badia, J. Aguilar, R. A. Bender, and L. Baldoma, J. Bacteriol. 190:7892-7903, 2008). Thus, several enzymes in this K. oxytoca purine utilization pathway differ from those in other microorganisms. Isofunctional homologs of these enzymes apparently are encoded by other species, including Acinetobacter, Burkholderia, Pseudomonas, Saccharomyces, and Xanthomonas.

  19. Endophytic bacteria from Pinellia ternata, a new source of purine alkaloids and bacterial manure.

    PubMed

    Liu, Yonghong; Liu, Wenting; Liang, Zongsuo

    2015-01-01

    Pinellia ternata (Thunb.) Berit., a perennial herb belonging to Araceae, is one of the few medicinal plants to produce purine alkaloids. It is speculated that endophytic bacteria from P. ternata may produce guanosine or inosine. However, there is no report about endophytic bacteria in P. ternata. In this study, endophytic bacteria were isolated from P. ternata and examined for the first time. This study finds a novel way to increase the yield of P. ternata herb, and to provide some new alkaloid producers. Plant material includes leaves, tubers, and roots of cultivated and wild P. ternata. The dilutions were smeared onto beef extract-peptone medium and cultured at 28 °C in darkness for 48-72 h. Co-culture treatments were prepared by inoculating 100 mL liquid 1/2 MS medium with bacterial culture broth at concentrations of 0 (control), 0.5%, and 1.5% (v/v). Of the 34 endophytic bacterial colonies isolated from P. ternata leaves, roots, and tubers, five strains were able to produce purine alkaloids. Results from 16s rDNA sequence analysis indicated that the bacteria belonged to Bacillus cereus, Aranicola proteolyticus, Serratia liquefaciens, Bacillus thuringiensis, and Bacillus licheniformis. Co-culture with living Serratia liquefaciens cells increased PLB growth by 58-71%. Co-culture with living Bacillus licheniformis cells increased PLB growth by 4-11%. This study provides a novel way for improving the yield of P. ternata herb, and for the production of purine alkaloids by the fermentation industry.

  20. 40 CFR 721.4685 - Substituted purine metal salt (generic name).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Substituted purine metal salt (generic... Specific Chemical Substances § 721.4685 Substituted purine metal salt (generic name). (a) Chemical... as a substituted purine metal salt (PMN P-95-175) is subject to reporting under this section for the...

  1. 40 CFR 721.4685 - Substituted purine metal salt (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Substituted purine metal salt (generic... Specific Chemical Substances § 721.4685 Substituted purine metal salt (generic name). (a) Chemical... as a substituted purine metal salt (PMN P-95-175) is subject to reporting under this section for the...

  2. 40 CFR 721.4685 - Substituted purine metal salt (generic name).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Substituted purine metal salt (generic... Specific Chemical Substances § 721.4685 Substituted purine metal salt (generic name). (a) Chemical... as a substituted purine metal salt (PMN P-95-175) is subject to reporting under this section for the...

  3. 40 CFR 721.4685 - Substituted purine metal salt (generic name).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Substituted purine metal salt (generic... Specific Chemical Substances § 721.4685 Substituted purine metal salt (generic name). (a) Chemical... as a substituted purine metal salt (PMN P-95-175) is subject to reporting under this section for the...

  4. 40 CFR 721.4685 - Substituted purine metal salt (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Substituted purine metal salt (generic... Specific Chemical Substances § 721.4685 Substituted purine metal salt (generic name). (a) Chemical... as a substituted purine metal salt (PMN P-95-175) is subject to reporting under this section for the...

  5. Inhibition and Structure of Toxoplasma gondii Purine Nucleoside Phosphorylase

    PubMed Central

    Donaldson, Teraya M.; Cassera, María B.; Ho, Meng-Chiao; Zhan, Chenyang; Merino, Emilio F.; Evans, Gary B.; Tyler, Peter C.; Almo, Steven C.; Schramm, Vern L.

    2014-01-01

    The intracellular pathogen Toxoplasma gondii is a purine auxotroph that relies on purine salvage for proliferation. We have optimized T. gondii purine nucleoside phosphorylase (TgPNP) stability and crystallized TgPNP with phosphate and immucillin-H, a transition-state analogue that has high affinity for the enzyme. Immucillin-H bound to TgPNP with a dissociation constant of 370 pM, the highest affinity of 11 immucillins selected to probe the catalytic site. The specificity for transition-state analogues indicated an early dissociative transition state for TgPNP. Compared to Plasmodium falciparum PNP, large substituents surrounding the 5′-hydroxyl group of inhibitors demonstrate reduced capacity for TgPNP inhibition. Catalytic discrimination against large 5′ groups is consistent with the inability of TgPNP to catalyze the phosphorolysis of 5′-methylthioinosine to hypoxanthine. In contrast to mammalian PNP, the 2′-hydroxyl group is crucial for inhibitor binding in the catalytic site of TgPNP. This first crystal structure of TgPNP describes the basis for discrimination against 5′-methylthioinosine and similarly 5′-hydroxy-substituted immucillins; structural differences reflect the unique adaptations of purine salvage pathways of Apicomplexa. PMID:24585883

  6. Purines and neuronal excitability: links to the ketogenic diet.

    PubMed

    Masino, S A; Kawamura, M; Ruskin, D N; Geiger, J D; Boison, D

    2012-07-01

    ATP and adenosine are purines that play dual roles in cell metabolism and neuronal signaling. Acting at the A(1) receptor (A(1)R) subtype, adenosine acts directly on neurons to inhibit excitability and is a powerful endogenous neuroprotective and anticonvulsant molecule. Previous research showed an increase in ATP and other cell energy parameters when an animal is administered a ketogenic diet, an established metabolic therapy to reduce epileptic seizures, but the relationship among purines, neuronal excitability and the ketogenic diet was unclear. Recent work in vivo and in vitro tested the specific hypothesis that adenosine acting at A(1)Rs is a key mechanism underlying the success of ketogenic diet therapy and yielded direct evidence linking A(1)Rs to the antiepileptic effects of a ketogenic diet. Specifically, an in vitro mimic of a ketogenic diet revealed an A(1)R-dependent metabolic autocrine hyperpolarization of hippocampal neurons. In parallel, applying the ketogenic diet in vivo to transgenic mouse models with spontaneous electrographic seizures revealed that intact A(1)Rs are necessary for the seizure-suppressing effects of the diet. This is the first direct in vivo evidence linking A(1)Rs to the antiepileptic effects of a ketogenic diet. Other predictions of the relationship between purines and the ketogenic diet are discussed. Taken together, recent research on the role of purines may offer new opportunities for metabolic therapy and insight into its underlying mechanisms.

  7. Purines and Neuronal Excitability: Links to the Ketogenic Diet

    PubMed Central

    Masino, SA; Kawamura, M; Ruskin, DN; Geiger, JD; Boison, D

    2011-01-01

    ATP and adenosine are purines that play dual roles in cell metabolism and neuronal signaling. Acting at the A1 receptor (A1R) subtype, adenosine acts directly on neurons to inhibit excitability and is a powerful endogenous neuroprotective and anticonvulsant molecule. Previous research showed an increase in ATP and other cell energy parameters when an animal is administered a ketogenic diet, an established metabolic therapy to reduce epileptic seizures, but the relationship among purines, neuronal excitability and the ketogenic diet was unclear. Recent work in vivo and in vitro tested the specific hypothesis that adenosine acting at A1Rs is a key mechanism underlying the success of ketogenic diet therapy and yielded direct evidence linking A1Rs to the antiepileptic effects of a ketogenic diet. Specifically, an in vitro mimic of a ketogenic diet revealed an A1R-dependent metabolic autocrine hyperpolarization of hippocampal neurons. In parallel, applying the ketogenic diet in vivo to transgenic mouse models with spontaneous electrographic seizures revealed that intact A1Rs are necessary for the seizure-suppressing effects of the diet. This is the first direct in vivo evidence linking A1Rs to the antiepileptic effects of a ketogenic diet. Other predictions of the relationship between purines and the ketogenic diet are discussed. Taken together, recent research on the role of purines may offer new opportunities for metabolic therapy and insight into its underlying mechanisms. PMID:21880467

  8. Distinct Distribution of Purines in CM and CR Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Stern, Jennifer C.; Glavin, Daniel P.; Smith, Karen E.; Martin, Mildred G.; Dworkin, Jason P.

    2010-01-01

    Carbonaceous meteorites contain a diverse suite of organic molecules and delivered pre biotic organic compounds, including purines and pyrimidines, to the early Earth (and other planetary bodies), seeding it with the ingredients likely required for the first genetic material. We have investigated the distribution of nucleobases in six different CM and CR type carbonaceous chondrites, including fivc Antarctic meteorites never before analyzed for nucleobases. We employed a traditional formic acid extraction protocol and a recently developed solid phase extraction method to isolate nucleobases. We analyzed these extracts by high performance liquid chromatography with UV absorbance detection and tandem mass spectrometry (HPLC-UV -MS/MS) targeting the five canonical RNAIDNA bases and hypoxanthine and xanthine. We detected parts-per-billion levels of nucleobases in both CM and CR meteorites. The relative abundances of the purines found in Antarctic CM and CR meteorites were clearly distinct from each other suggesting that these compounds are not terrestrial contaminants. One likely source of these purines is formation by HCN oligomerization (with other small molecules) during aqueous alteration inside the meteorite parent body. The detection of the purines adenine (A), guanine (0), hypoxanthine (HX), and xanthine (X) in carbonaceous meteorites indicates that these compounds should have been available on the early Earth prior to the origin of the first genetic material.

  9. Distinct Distribution of Purines in CM and CR Carbonaceous Chondrites

    NASA Technical Reports Server (NTRS)

    Callahan, Michael P.; Stern, Jennifer C.; Glavin, Daniel P.; Smith, Karen E.; Martin, Mildred G.; Dworkin, Jason P.

    2010-01-01

    Carbonaceous meteorites contain a diverse suite of organic molecules and delivered pre biotic organic compounds, including purines and pyrimidines, to the early Earth (and other planetary bodies), seeding it with the ingredients likely required for the first genetic material. We have investigated the distribution of nucleobases in six different CM and CR type carbonaceous chondrites, including fivc Antarctic meteorites never before analyzed for nucleobases. We employed a traditional formic acid extraction protocol and a recently developed solid phase extraction method to isolate nucleobases. We analyzed these extracts by high performance liquid chromatography with UV absorbance detection and tandem mass spectrometry (HPLC-UV -MS/MS) targeting the five canonical RNAIDNA bases and hypoxanthine and xanthine. We detected parts-per-billion levels of nucleobases in both CM and CR meteorites. The relative abundances of the purines found in Antarctic CM and CR meteorites were clearly distinct from each other suggesting that these compounds are not terrestrial contaminants. One likely source of these purines is formation by HCN oligomerization (with other small molecules) during aqueous alteration inside the meteorite parent body. The detection of the purines adenine (A), guanine (0), hypoxanthine (HX), and xanthine (X) in carbonaceous meteorites indicates that these compounds should have been available on the early Earth prior to the origin of the first genetic material.

  10. Purine nucleoside transport and metabolism in isolated rat jejunum.

    PubMed Central

    Stow, R A; Bronk, J R

    1993-01-01

    1. The absorption and metabolism of purine nucleosides and their constituent bases has been investigated by perfusion through the lumen of isolated loops of rat jejunum. In control perfusions and those with luminal purines or purine nucleosides, high-performance liquid chromatography (HPLC) revealed uric acid as the only detectable purine in the mucosal epithelial layer and the serosal secretions unless the xanthine oxidase inhibitor allopurinol was present. 2. Adenosine (0.5 mM) was quantitatively deaminated to inosine in the lumen after perfusion for 30 min. 3. Luminal inosine and hypoxanthine (0.15-1.0 mM) increased the serosal uric acid concentration significantly (P < 0.001); at 0.5 and 1.0 mM the nucleoside gave a significantly greater (P < 0.01) rate of serosal uric acid appearance than the base. 4. Luminal guanosine (0.05-0.50 mM) and guanine (0.05-0.15 mM) increased the serosal uric acid concentration significantly (P < 0.001); with 0.15 mM nucleoside the serosal uric acid appeared significantly faster (P < 0.01) than it did from the base. 5. Luminal allopurinol (0.3 mM) inhibited xanthine oxidase by 80% and reduced serosal purine appearance significantly (P < 0.01) from luminal guanine, hypoxanthine and inosine. With allopurinol, guanosine (0.1 and 0.15 mM) and inosine (0.1-1.0 mM) gave significantly higher (P < 0.01) total serosal purine concentrations than their respective bases. 6. Inosine and guanosine were cleaved to their respective bases plus ribose phosphate by the action of a cytoplasmic nucleoside phosphorylase, which was found to have widely different Michaelis constants (Km; 318 +/- 45 and 41.4 +/- 3.6 microM for inosine and guanosine, respectively) and maximum velocities (Vmax; 79.3 +/- 4.0 and 20.5 +/- 0.05 mumol min-1 (mg protein)-1 for inosine and guanosine, respectively). 7. We conclude that hypoxanthine and guanine absorbed by rat small intestine are oxidized to uric acid which is released in the serosa. The corresponding nucleosides are

  11. Purine metabolism is dysregulated in patients with major depressive disorder.

    PubMed

    Ali-Sisto, Toni; Tolmunen, Tommi; Toffol, Elena; Viinamäki, Heimo; Mäntyselkä, Pekka; Valkonen-Korhonen, Minna; Honkalampi, Kirsi; Ruusunen, Anu; Velagapudi, Vidya; Lehto, Soili M

    2016-08-01

    The purine cycle and altered purinergic signaling have been suggested to play a role in major depressive disorder (MDD). Nevertheless, data on this topic are scarce. Based on previous studies, we hypothesized that compared with non-depressed controls, MDD patients have distinct purine metabolite profiles. The samples comprised 99 MDD patients and 253 non-depressed controls, aged 20-71 years. Background data were collected with questionnaires. Fasting serum samples were analyzed using ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) to determine seven purine cycle metabolites belonging to the purine cycle. We investigated the levels of these metabolites in three settings: (1) MDD patients vs. non-depressed controls and (2) remitted vs. non-remitted MDD patients, and also (3) within-group changes in metabolite levels during the follow-up period. In logistic regression adjusted for age, gender, smoking, alcohol use, physical exercise, glycosylated hemoglobin, and high-density lipoprotein cholesterol, lower levels of inosine (OR 0.89, 95% CI 0.82-0.97) and guanosine (OR 0.32, 95% CI 0.17-0.59), and higher levels of xanthine (OR 2.21, 95% CI 1.30-3.75) were associated with MDD vs. the non-depressed group. Levels of several metabolites changed significantly during the follow-up period in the MDD group, but there were no differences between remitted and non-remitted groups. We observed altered purine metabolism in MDD patients compared with non-depressed controls. Furthermore, our observations suggest that circulating xanthine may accumulate in MDD patients. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Molecular and biochemical characterization of caffeine synthase and purine alkaloid concentration in guarana fruit.

    PubMed

    Schimpl, Flávia Camila; Kiyota, Eduardo; Mayer, Juliana Lischka Sampaio; Gonçalves, José Francisco de Carvalho; da Silva, José Ferreira; Mazzafera, Paulo

    2014-09-01

    Guarana seeds have the highest caffeine concentration among plants accumulating purine alkaloids, but in contrast with coffee and tea, practically nothing is known about caffeine metabolism in this Amazonian plant. In this study, the levels of purine alkaloids in tissues of five guarana cultivars were determined. Theobromine was the main alkaloid that accumulated in leaves, stems, inflorescences and pericarps of fruit, while caffeine accumulated in the seeds and reached levels from 3.3% to 5.8%. In all tissues analysed, the alkaloid concentration, whether theobromine or caffeine, was higher in young/immature tissues, then decreasing with plant development/maturation. Caffeine synthase activity was highest in seeds of immature fruit. A nucleotide sequence (PcCS) was assembled with sequences retrieved from the EST database REALGENE using sequences of caffeine synthase from coffee and tea, whose expression was also highest in seeds from immature fruit. The PcCS has 1083bp and the protein sequence has greater similarity and identity with the caffeine synthase from cocoa (BTS1) and tea (TCS1). A recombinant PcCS allowed functional characterization of the enzyme as a bifunctional CS, able to catalyse the methylation of 7-methylxanthine to theobromine (3,7-dimethylxanthine), and theobromine to caffeine (1,3,7-trimethylxanthine), respectively. Among several substrates tested, PcCS showed higher affinity for theobromine, differing from all other caffeine synthases described so far, which have higher affinity for paraxanthine. When compared to previous knowledge on the protein structure of coffee caffeine synthase, the unique substrate affinity of PcCS is probably explained by the amino acid residues found in the active site of the predicted protein.

  13. Roles of the amino group of purine bases in the thermodynamic stability of DNA base pairing.

    PubMed

    Nakano, Shu-ichi; Sugimoto, Naoki

    2014-08-05

    The energetic aspects of hydrogen-bonded base-pair interactions are important for the design of functional nucleotide analogs and for practical applications of oligonucleotides. The present study investigated the contribution of the 2-amino group of DNA purine bases to the thermodynamic stability of oligonucleotide duplexes under different salt and solvent conditions, using 2'-deoxyriboinosine (I) and 2'-deoxyribo-2,6-diaminopurine (D) as non-canonical nucleotides. The stability of DNA duplexes was changed by substitution of a single base pair in the following order: G • C > D • T ≈ I • C > A • T > G • T > I • T. The apparent stabilization energy due to the presence of the 2-amino group of G and D varied depending on the salt concentration, and decreased in the water-ethanol mixed solvent. The effects of salt concentration on the thermodynamics of DNA duplexes were found to be partially sequence-dependent, and the 2-amino group of the purine bases might have an influence on the binding of ions to DNA through the formation of a stable base-paired structure. Our results also showed that physiological salt conditions were energetically favorable for complementary base recognition, and conversely, low salt concentration media and ethanol-containing solvents were effective for low stringency oligonucleotide hybridization, in the context of conditions employed in this study.

  14. Purine nucleoside phosphorylase from Pseudoalteromonas sp. Bsi590: molecular cloning, gene expression and characterization of the recombinant protein.

    PubMed

    Li, Xiaohui; Jiang, Xinyin; Li, Huirong; Ren, Daming

    2008-05-01

    The gene encoding purine nucleoside phosphorylase (PNP) from the cold-adapted marine bacterium Pseudoalteromonas sp. Bsi590 was identified, cloned and expressed in Escherichia coli. The gene encodes a polypeptide of 233 amino acids with a calculated molecular weight of 25,018 Da. Pseudoalteromonas sp. Bsi590 PNP (PiPNP) shares 60% amino sequence identity and conservation of amino acid residues involved in catalysis with mesophilic Escherichia coli deoD-encoded purine nucleoside phosphorylase (EcPNP). N-terminal his-tagged PiPNP and EcPNP were purified to apparent homogeneity using Ni2+-chelating column. Compared with EcPNP, PiPNP possessed a lower temperature optimum and thermal stability. As for PNP enzymes in general, PiPNP and EcPNP displayed complicated kinetic properties; PiPNP possessed higher Km and catalytic efficiency (kcat/Km) compared to EcPNP at 37 degrees C. Substrate specificity results showed PiPNP catalyzed the phosphorolytic cleavage of 6-oxopurine and 6-aminopurine nucleosides (or 2-deoxynucleosides), and to a lesser extent purine arabinosides. PiPNP showed a better activity with inosine while no activity toward pyrimidine nucleosides. The protein conformation was analyzed by temperature perturbation difference spectrum. Results showed that PiPNP had lower conformation transition point temperature than EcPNP; phosphate buffer and KCl had significant influence on PiPNP protein conformation stability and thermostability.

  15. Pronounced genetic diversity in tropical epiphyllous lichen fungi.

    PubMed

    Baloch, Elisabeth; Grube, Martin

    2009-05-01

    Lowland tropical habitats harbour an unexplored genetic diversity of epiphyllous fungi. In the shade of rainforest understoreys, lichenized fungi are specialized to an ephemeral habitat where they produce little vegetative biomass and develop reproductive structures early. In a first population genetic study of epiphyllous lichen fungi, we analysed the intraspecific genetic diversity of five leaf-colonizing lichen mycobiont species. Sampling focused on a lowland perhumid forest plot in Costa Rica, with additional collections from other localities throughout the country. In all species we detected sympatric occurrence of highly diverged haplotypes. Haplotypes belonging to distinct clades in networks were also found on the same leaf, clearly indicating multiple independent colonization events on single leaves. Despite the unusually high genetic diversity of these leaf-colonizing tropical fungi, we did not detect pronounced spatial structure of the haplotype distribution between geographical regions. The observed patterns suggest that the diversity of foliicolous lichens could be much higher than expected, with several cryptic genetic lineages within each morphologically characterized species.

  16. Purification and characterization of purine nucleoside phosphorylase from Proteus vulgaris.

    PubMed Central

    Surette, M; Gill, T; MacLean, S

    1990-01-01

    Purine nucleoside phosphorylase was isolated and purified from cell extracts of Proteus vulgaris recovered from spoiling cod fish (Gadus morhua). The molecular weight and isoelectric point of the enzyme were 120,000 +/- 2,000 and pH 6.8. The Michaelis constant for inosine as substrate was 3.9 x 10(-5). Guanosine also served as a substrate (Km = 2.9 x 10(-5). However, the enzyme was incapable of phosphorylizing adenosine. Adenosine proved to be useful as a competitive inhibitor and was used as a ligand for affinity chromatography of purine nucleoside phosphorylase following initial purification steps of gel filtration and ion-exchange chromatography. PMID:2111121

  17. Infrared Spectroscopy of Charge Transfer Complexes of Purines and Pyrimidines

    SciTech Connect

    Rathod, Pravinsinh I.; Oza, A. T.

    2011-10-20

    The FTIR spectra of charge transfer complexes of purines and pyrimidines with organic acceptors such as TCNQ, TCNE, DDQ, chloranil and iodine are obtained and studied in the present work. Adenine, guanine, thymine, cytosine and uracil are the purines and pyrimidines which are found as constituent of DNA and RNA. Charge transfer induced hydrogen bonding is concluded on the basis of indirect transitions observed in the infrared range in these CTCs. Some CTCs show gaussian bands revealing delocalization of charge carriers. The CTCs show interband transition in three-dimensions rather than two-dimensions unlike CTCs of amino acids. There is no extended hydrogen bonded network spanning the whole crystal. This leads to indirect transition due to locally deformed lattice furnishing a phonon-assisted transition.

  18. The salivary purine nucleosidase of the mosquito, Aedes aegypti.

    PubMed

    Ribeiro, José M C; Valenzuela, Jesus G

    2003-01-01

    A cDNA clone originating from adult female Aedes aegypti mosquitoes was found with substantial similarity to nucleosidases of the EC 3.2.2.1 enzyme class. Although this type of enzyme is unusual in animals, abundant enzyme activity was found in salivary homogenates of this mosquito, but not in salivary homogenates of the mosquitoes Anopheles gambiae and Culex quinquefasciatus, or the sand fly Lutzomyia longipalpis. Aedes salivary homogenate hydrolyses inosine and guanosine to hypoxanthine and xanthine plus the ribose moiety, but does not hydrolyse the pyrimidines uridine and cytidine, thus characterizing the presence of a purine nucleosidase activity. The enzyme is present in oil-induced saliva, indicating that it is secreted. Male Ae. aegypti salivary gland homogenates (SGH) have very low purine nucleosidase activity, suggesting that the enzyme plays a role in mosquito blood feeding. A novel isocratic HPLC method to separate nucleosides and their bases is described.

  19. Infrared Spectroscopy of Charge Transfer Complexes of Purines and Pyrimidines

    NASA Astrophysics Data System (ADS)

    Rathod, Pravinsinh I.; Oza, A. T.

    2011-10-01

    The FTIR spectra of charge transfer complexes of purines and pyrimidines with organic acceptors such as TCNQ, TCNE, DDQ, chloranil and iodine are obtained and studied in the present work. Adenine, guanine, thymine, cytosine and uracil are the purines and pyrimidines which are found as constituent of DNA and RNA. Charge transfer induced hydrogen bonding is concluded on the basis of indirect transitions observed in the infrared range in these CTCs. Some CTCs show gaussian bands revealing delocalization of charge carriers. The CTCs show interband transition in three-dimensions rather than two-dimensions unlike CTCs of amino acids. There is no extended hydrogen bonded network spanning the whole crystal. This leads to indirect transition due to locally deformed lattice furnishing a phonon-assisted transition.

  20. Fine targeting of purine salvage in Cryptosporidium parasites.

    PubMed

    Hyde, John E

    2008-08-01

    The apicomplexan pathogen Cryptosporidium parvum poses major logistical problems in the search for effective drug treatments. These treatments are required urgently because this parasite can cause severe disease and death in immunocompromised individuals and young children. In a recent study, the dependence of Cryptosporidium parasites on a single salvage pathway that leads to essential purine derivatives has been exploited and inhibitors have been identified that selectively target a key enzyme in this salvage process, inosine 5'-monophosphate dehydrogenase.

  1. A novel enzymatic approach in the production of food with low purine content using Arxula adeninivorans endogenous and recombinant purine degradative enzymes.

    PubMed

    Jankowska, Dagmara A; Trautwein-Schult, Anke; Cordes, Arno; Bode, Rüdiger; Baronian, Keith; Kunze, Gotthard

    2015-01-01

    The purine degradation pathway in humans ends with uric acid, which has low water solubility. When the production of uric acid is increased either by elevated purine intake or by impaired kidney function, uric acid will accumulate in the blood (hyperuricemia). This increases the risk of gout, a disease described in humans for at least 1000 years. Many lower organisms, such as the yeast Arxula adeninivorans, possess the enzyme, urate oxidase that converts uric acid to 5-hydroxyisourate, thus preventing uric acid accumulation. We have examined the complete purine degradation pathway in A. adeninivorans and analyzed enzymes involved. Recombinant adenine deaminase, guanine deaminase, urate oxidase and endogenous xanthine oxidoreductase have been investigated as potential additives to degrade purines in the food. Here, we review the current model of the purine degradation pathway of A. adeninivorans and present an overview of proposed enzyme system with perspectives for its further development.

  2. A novel enzymatic approach in the production of food with low purine content using Arxula adeninivorans endogenous and recombinant purine degradative enzymes

    PubMed Central

    Jankowska, Dagmara A; Trautwein-Schult, Anke; Cordes, Arno; Bode, Rüdiger; Baronian, Keith; Kunze, Gotthard

    2015-01-01

    The purine degradation pathway in humans ends with uric acid, which has low water solubility. When the production of uric acid is increased either by elevated purine intake or by impaired kidney function, uric acid will accumulate in the blood (hyperuricemia). This increases the risk of gout, a disease described in humans for at least 1000 years. Many lower organisms, such as the yeast Arxula adeninivorans, possess the enzyme, urate oxidase that converts uric acid to 5-hydroxyisourate, thus preventing uric acid accumulation. We have examined the complete purine degradation pathway in A. adeninivorans and analyzed enzymes involved. Recombinant adenine deaminase, guanine deaminase, urate oxidase and endogenous xanthine oxidoreductase have been investigated as potential additives to degrade purines in the food. Here, we review the current model of the purine degradation pathway of A. adeninivorans and present an overview of proposed enzyme system with perspectives for its further development. PMID:25513995

  3. Enantioselective and Regiodivergent Addition of Purines to Terminal Allenes: Synthesis of Abacavir.

    PubMed

    Thieme, Niels; Breit, Bernhard

    2017-02-01

    The rhodium-catalyzed atom-economic asymmetric N-selective intermolecular addition of purine derivatives to terminal allenes is reported. Branched allylic purines were obtained in high yields, regioselectivity and outstanding enantioselectivity utilizing a Rh/Josiphos catalyst. Conversely, linear selective allylation of purines could be realized in good to excellent regio- and E/Z-selectivity with a Pd/dppf catalyst system. Furthermore, the new methodology was applied to a straightforward asymmetric synthesis of carbocyclic nucleoside abacavir.

  4. A complex of nuclear proteins mediates SR protein binding to a purine-rich splicing enhancer.

    PubMed Central

    Yeakley, J M; Morfin, J P; Rosenfeld, M G; Fu, X D

    1996-01-01

    A purine-rich splicing enhancer from a constitutive exon has been shown to shift the alternative splicing of calcitonin/CGRP pre-mRNA in vivo. Here, we demonstrate that the native repetitive GAA sequence comprises the optimal enhancer element and specifically binds a saturable complex of proteins required for general splicing in vitro. This complex contains a 37-kDa protein that directly binds the repetitive GAA sequence and SRp40, a member of the SR family of non-snRNP splicing factors. While purified SR proteins do not stably bind the repetitive GAA element, exogenous SR proteins become associated with the GAA element in the presence of nuclear extracts and stimulate GAA-dependent splicing. These results suggest that repetitive GAA sequences enhance splicing by binding a protein complex containing a sequence-specific RNA binding protein and a general splicing activator that, in turn, recruit additional SR proteins. This type of mechanism resembles the tra/tra-2-dependent recruitment of SR proteins to the Drosophila doublesex alternative splicing regulatory element. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 PMID:8755518

  5. Determination of purine contents of alcoholic beverages using high performance liquid chromatography.

    PubMed

    Kaneko, Kiyoko; Yamanobe, Tomoyo; Fujimori, Shin

    2009-08-01

    The purine contents of alcoholic beverages were determined in order to utilize them in the dietary care of gout and hyperuricemia. In the management of these diseases, restriction of both alcohol and purine intake are important. The method employed in this study is a quantitative determination of purine contents by HPLC. Alcoholic beverages were hydrolyzed to corresponding purine bases, which were then separated by HPLC, and base peaks were identified using an enzymatic peak-shift technique. This method is sufficiently accurate and reproducible to examine the purine contents of various alcoholic beverages that patients consume. Purine contents were as follows: spirits, 0.7-26.4 micromol/L; regular beer, 225.0-580.2 micromol/L; low-malt beer, 193.4-267.9 micromol/L; low-malt and low-purine beer, 13.3 micromol/L; other liquors, 13.1-818.3 micromol/L. Some local and low-alcohol beers were found to contain about 2.5 times more purines than regular beer. As some alcoholic beverages contain considerable amounts of purines, we recommend that excess consumption of these beverages be avoided. These data should be useful in the management of hyperuricemia and gout, not only for patients but also for physicians. (c) 2009 John Wiley & Sons, Ltd.

  6. Experimental and theoretical dipole moments of purines in their ground and lowest excited singlet states

    NASA Astrophysics Data System (ADS)

    Aaron, Jean-Jacques; Diabou Gaye, Mame; Párkányi, Cyril; Cho, Nam Sook; Von Szentpály, László

    1987-01-01

    The ground-state dipole moments of seven biologically important purines (purine, 6-chloropurine, 6-mercaptopurine, hypoxanthine, theobromine, theophylline and caffeine) were determined at 25°C in acetic acid (all the above compounds with the exception of purine) and in ethyl acetate (purine, theophylline and caffeine). Because of its low solubility, it was not possible to measure the dipole moment of uric acid. The first excited singlet-state dipole moments were obtained on the basis of the Bakhshiev and Chamma—Viallet equations using the variation of the Stokes shift with the solvent dielectric constant-refractive index term. The theoretical dipole moments for all the purines listed above and including uric acid were calculated by combining the use of the PPP (π-LCI-SCF-MO) method for the π-contribution to the overall dipole moment with the σ-contribution obtained as a vector sum of the σbond moments and group moments. The experimental and theoretical values were compared with the data available in the literature for some of the purines under study. For several purines, the calculations were carried out for different tautomeric forms. Excited singlet-state dipole moments are smaller than the ground-state values by 0.8 to 2.2 Debye units for all purines under study with the exception of 6-chloropurine. The effects of the structure upon the ground- and excited-state dipole moments of the purines are discussed.

  7. Homochiral Selectivity in RNA Synthesis: Montmorillonite-catalyzed Quaternary Reactions of D, L-Purine with D, L- Pyrimidine Nucleotides

    NASA Astrophysics Data System (ADS)

    Joshi, Prakash C.; Aldersley, Michael F.; Ferris, James P.

    2011-06-01

    Selective adsorption of D, L-ImpA with D, L-ImpU on the platelets of montmorillonite demonstrates an important reaction pathway for the origin of homochirality in RNA synthesis. Our earlier studies have shown that the individual reactions of D, L-ImpA or D, L-ImpU on montmorillonite catalyst produced oligomers which were only partially inhibited by the incorporation of both D- and L-enantiomers. Homochirality in these reactions was largely due to the formation of cyclic dimers that cannot elongate. We investigated the quaternary reactions of D, L-ImpA with D, L-ImpU on montmorillonite. The chain length of these oligomers increased from 9-mer to 11-mer as observed by HPLC, with a concominant increase in the yield of linear dimers and higher oligomers in the reactions involving D, L-ImpA with D, L-ImpU as compared to the similar reactions carried out with D-enantiomers only. The formation of cyclic dimers of U was completely inhibited in the quaternary reactions. The yield of cyclic dimers of A was reduced from 60% to 10% within the dimer fraction. 12 linear dimers and 3 cyclic dimers were isolated and characterized from the quaternary reaction. The homochirality and regioselectivity of dimers were 64.1% and 71.7%, respectively. Their sequence selectivity was shown by the formation of purine-pyrimidine (54-59%) linkages, followed by purine-purine (29-32%) linkages and pyrimidine-pyrimidine (9-13%) linkages. Of the 16 trimers detected, 10 were homochiral with an overall homochirality of 73-76%. In view of the greater homochirality, sequence- and regio- selectivity, the quaternary reactions on montmorillonite demonstrate an unexpectedly favorable route for the prebiotic synthesis of homochiral RNA compared with the separate reactions of enantiomeric activated mononucleotides.

  8. Gene set analysis of purine and pyrimidine antimetabolites cancer therapies.

    PubMed

    Fridley, Brooke L; Batzler, Anthony; Li, Liang; Li, Fang; Matimba, Alice; Jenkins, Gregory D; Ji, Yuan; Wang, Liewei; Weinshilboum, Richard M

    2011-11-01

    Responses to therapies, either with regard to toxicities or efficacy, are expected to involve complex relationships of gene products within the same molecular pathway or functional gene set. Therefore, pathways or gene sets, as opposed to single genes, may better reflect the true underlying biology and may be more appropriate units for analysis of pharmacogenomic studies. Application of such methods to pharmacogenomic studies may enable the detection of more subtle effects of multiple genes in the same pathway that may be missed by assessing each gene individually. A gene set analysis of 3821 gene sets is presented assessing the association between basal messenger RNA expression and drug cytotoxicity using ethnically defined human lymphoblastoid cell lines for two classes of drugs: pyrimidines [gemcitabine (dFdC) and arabinoside] and purines [6-thioguanine and 6-mercaptopurine]. The gene set nucleoside-diphosphatase activity was found to be significantly associated with both dFdC and arabinoside, whereas gene set γ-aminobutyric acid catabolic process was associated with dFdC and 6-thioguanine. These gene sets were significantly associated with the phenotype even after adjusting for multiple testing. In addition, five associated gene sets were found in common between the pyrimidines and two gene sets for the purines (3',5'-cyclic-AMP phosphodiesterase activity and γ-aminobutyric acid catabolic process) with a P value of less than 0.0001. Functional validation was attempted with four genes each in gene sets for thiopurine and pyrimidine antimetabolites. All four genes selected from the pyrimidine gene sets (PSME3, CANT1, ENTPD6, ADRM1) were validated, but only one (PDE4D) was validated for the thiopurine gene sets. In summary, results from the gene set analysis of pyrimidine and purine therapies, used often in the treatment of various cancers, provide novel insight into the relationship between genomic variation and drug response.

  9. Gene set analysis of purine and pyrimidine antimetabolites cancer therapies

    PubMed Central

    Fridley, Brooke L.; Batzler, Anthony; Li, Liang; Li, Fang; Matimba, Alice; Jenkins, Gregory D.; Ji, Yuan; Wang, Liewei; Weinshilboum, Richard M.

    2011-01-01

    Objective Responses to therapies, either with regards to toxicities or efficacy, are expected to involve complex relationships of gene products within the same molecular pathway or functional gene set. Therefore, pathways or gene sets, as opposed to single genes, may better reflect the true underlying biology and may be more appropriate units for analysis of pharmacogenomic studies. Application of such methods to pharmacogenomic studies may enable the detection of more subtle effects of multiple genes in the same pathway that may be missed by assessing each gene individually. Methods A gene set analysis of 3,821 gene sets is presented assessing the association between basal mRNA expression and drug cytotoxicity using ethnically defined human lymphoblastoid cell lines for two classes of drugs: pyrimidines (dFdC and AraC) and purines (6-TG and 6-MP). Results The gene set nucleoside-diphosphatase activity was found to be significantly associated with both dFdC and AraC, while gene set gamma-aminobutyric acid catabolic process was associated with dFdC and 6-TG. These gene sets were significantly associated with the phenotype even after adjusting for multiple testing. In addition, five associated gene sets were found in common between the pyrimidines and two gene sets for the purines (3′,5′-cyclic-AMP phosphodiesterase activity and gamma-aminobutyric acid catabolic process) with p < 0.0001. Functional validation was attempted with 4 genes each in gene sets for thiopurine and pyrimidine anti-metabolites. All four genes selected from the pyrimidine gene sets (PSME3, CANT1, ENTPD6, ADRM1) were validated, but only one (PDE4D) was validated for the thiopurine gene sets. Conclusions In summary, results from the gene set analysis of pyrimidine and purine therapies, used often in the treatment of various cancers, provide novel insight into the relationship between genomic variation and drug response. PMID:21869733

  10. Computer-generated Model of Purine Nucleoside Phosphorylase (PNP)

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Purine Nucleoside Phosphorylase (PNP) is an important target enzyme for the design of anti-cancer and immunosuppressive drugs. Bacterial PNP, which is slightly different from the human enzyme, is used to synthesize chemotherapuautic agents. Knowledge of the three-dimensional structure of the bacterial PNP molecule is useful in efforts to engineer different types of PNP enzymes, that can be used to produce new chemotherapeutic agents. This picture shows a computer model of bacterial PNP, which looks a lot like a display of colorful ribbons. Principal Investigator was Charles Bugg.

  11. INTERMOLECULAR FORCES IN ASSOCIATION OF PURINES WITH POLYBENZENOID HYDROCARBONS.

    PubMed

    PULLMAN, B; CLAVERIE, P; CAILLET, J

    1965-03-12

    The interactions in solution between purine or pyrimidine bases and polybenzenoid aromatic hydrocarbons probably consist in a vertical, stacking-type physical association. By molecular orbital calculations the role of the Van der Waals-London intermolecular forces in these interactions is determined. The electrostatic dipole-dipole forces are negligible, the polarization (or induction) dipole-induced dipole forces are contributory, but most important are the dispersion (or fluctuation) forces. This loose, physical type of interaction should not show any specificity with respect to the carcinogenic activity of the hydrocarbons.

  12. Computer-generated Model of Purine Nucleoside Phosphorylase (PNP)

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Purine Nucleoside Phosphorylase (PNP) is an important target enzyme for the design of anti-cancer and immunosuppressive drugs. Bacterial PNP, which is slightly different from the human enzyme, is used to synthesize chemotherapuautic agents. Knowledge of the three-dimensional structure of the bacterial PNP molecule is useful in efforts to engineer different types of PNP enzymes, that can be used to produce new chemotherapeutic agents. This picture shows a computer model of bacterial PNP, which looks a lot like a display of colorful ribbons. Principal Investigator was Charles Bugg.

  13. Associations between purine metabolites and monoamine neurotransmitters in first-episode psychosis

    PubMed Central

    Yao, Jeffrey K.; Dougherty, George G.; Reddy, Ravinder D.; Matson, Wayne R.; Kaddurah-Daouk, Rima; Keshavan, Matcheri S.

    2013-01-01

    Schizophrenia (SZ) is a biochemically complex disorder characterized by widespread defects in multiple metabolic pathways whose dynamic interactions, until recently, have been difficult to examine. Rather, evidence for these alterations has been collected piecemeal, limiting the potential to inform our understanding of the interactions amongst relevant biochemical pathways. We herein review perturbations in purine and neurotransmitter metabolism observed in early SZ using a metabolomic approach. Purine catabolism is an underappreciated, but important component of the homeostatic response of mitochondria to oxidant stress. We have observed a homeostatic imbalance of purine catabolism in first-episode neuroleptic-naïve patients with SZ (FENNS). Precursor and product relationships within purine pathways are tightly correlated. Although some of these correlations persist across disease or medication status, others appear to be lost among FENNS suggesting that steady formation of the antioxidant uric acid (UA) via purine catabolism is altered early in the course of illness. As is the case for within-pathway correlations, there are also significant cross-pathway correlations between respective purine and tryptophan (TRP) pathway metabolites. By contrast, purine metabolites show significant cross-pathway correlation only with tyrosine, and not with its metabolites. Furthermore, several purine metabolites (UA, guanosine, or xanthine) are each significantly correlated with 5-hydroxyindoleacetic acid (5-HIAA) in healthy controls, but not in FENNS at baseline or 4-week after antipsychotic treatment. Taken together, the above findings suggest that purine catabolism strongly associates with the TRP pathways leading to serotonin (5-hydroxytryptamine, 5-HT) and kynurenine metabolites. The lack of a significant correlation between purine metabolites and 5-HIAA, suggests alterations in key 5-HT pathways that may both be modified by and contribute to oxidative stress via purine

  14. Morphine enhances the release of /sup 3/H-purines from rat brain cerebral cortical prisms

    SciTech Connect

    Wu, P.H.; Phillis, J.W.; Yuen, H.

    1982-10-01

    In vitro experiments have shown that /sup 3/H-purines can be released from /sup 3/H-adenosine preloaded rat brain cortical prisms by a KCl-evoked depolarization. The KCl-evoked release of /sup 3/H-purines is dependent on the concentration of KCl present in the superfusate. At concentrations of 10(-7) approximately 10(-5)M morphine did not influence the basal release of /sup 3/H-purines from the prisms, although it enhanced the KCl-evoked release of /sup 3/H-purines. The enhancement of KCl-evoked /sup 3/H-purine release by morphine was concentration-dependent and was antagonized by naloxone, suggesting the involvement of opiate receptors. Uptake studies with rat brain cerebral cortical synaptosomes show that morphine is a very weak inhibitor of adenosine uptake. Comparisons with dipyridamole, a potent inhibitor of adenosine uptake, suggest that this low level of inhibition of the uptake did not contribute significantly to the release of /sup 3/H-purine by morphine seen in our experiments. It is therefore suggested that morphine enhances KCl-evoked /sup 3/H-purine release by an interaction with opiate receptors and that the resultant increase in extracellular purine (adenosine) levels may account for some of the actions of morphine.

  15. The electrochemical properties of the purine bases : at the interface between biological conjugates to inorganic surfaces

    NASA Technical Reports Server (NTRS)

    Hays, Charles C.

    2003-01-01

    The study of the charge transfer and interfacial reactions of the purine bases in physiological solutions provides valuable knowledge, as these processes are relevant to the origins of life. It has been proposed that the adsorption of the adsorption of the purine bases on an inorganic surface could serve as a template for specifying the arrangement of amino acids in peptides.

  16. Purine import into malaria parasites as a target for antimalarial drug development.

    PubMed

    Frame, I J; Deniskin, Roman; Arora, Avish; Akabas, Myles H

    2015-04-01

    Infection with Plasmodium species parasites causes malaria. Plasmodium parasites are purine auxotrophs. In all life cycle stages, they require purines for RNA and DNA synthesis and other cellular metabolic processes. Purines are imported from the host erythrocyte by equilibrative nucleoside transporters (ENTs). They are processed via purine salvage pathway enzymes to form the required purine nucleotides. The Plasmodium falciparum genome encodes four putative ENTs (PfENT1-4). Genetic, biochemical, and physiologic evidence suggest that PfENT1 is the primary purine transporter supplying the purine salvage pathway. Protein mass spectrometry shows that PfENT1 is expressed in all parasite stages. PfENT1 knockout parasites are not viable in culture at purine concentrations found in human blood (<10 μM). Thus, PfENT1 is a potential target for novel antimalarial drugs, but no PfENT1 inhibitors have been identified to test the hypothesis. Identifying inhibitors of PfENT1 is an essential step to validate PfENT1 as a potential antimalarial drug target.

  17. The electrochemical properties of the purine bases : at the interface between biological conjugates to inorganic surfaces

    NASA Technical Reports Server (NTRS)

    Hays, Charles C.

    2003-01-01

    The study of the charge transfer and interfacial reactions of the purine bases in physiological solutions provides valuable knowledge, as these processes are relevant to the origins of life. It has been proposed that the adsorption of the adsorption of the purine bases on an inorganic surface could serve as a template for specifying the arrangement of amino acids in peptides.

  18. Purine derivate content and amino acid profile in larval stages of three edible insects.

    PubMed

    Bednářová, Martina; Borkovcová, Marie; Komprda, Tomáš

    2014-01-15

    Considering their high content of protein, insects are a valuable alternative protein source. However, no evaluation of their purine content has so far been done. High content of purine derivates may lead to the exclusion of such food from the diet of people with specific diseases. The aim of this study was to analyse the content of selected purine derivates and amino acid profile in the three insect species most often used for entomophagy in Europe and compare them with the purine content in egg white and chicken breast. The content of individual purine derivates and their total content were significantly dependent on insect species. The purine content in all three species was significantly higher (P < 0.05) than in egg white, but some values were significantly lower (P < 0.05) than in chicken breast. The total protein content was 548.9 g kg(-1) dry matter (DM) in mealworm (Tenebrio molitor), 551.6 g kg(-1) DM in superworm (Zophobas atratus) and 564.9 g kg(-1) DM in cricket (Gryllus assimilis). Larvae of mealworm and superworm are protein-rich and purine-low meat alternatives. In contrast, cricket nymphs are protein-rich and purine-rich and cannot be recommended for people with hyperuricemia or gout. © 2013 Society of Chemical Industry.

  19. Effect of dietary purines on the pharmacokinetics of orally administered ribavirin.

    PubMed

    Li, Linghui; Koo, Seok Hwee; Limenta, Lie Michael George; Han, Li; Hashim, Khadijah Binte; Quek, Hung Hiang; Lee, Edmund Jon Deoon

    2009-06-01

    Ribavirin is found to be absorbed in the intestine through the human concentrative nucleoside transporter 2 (hCNT2). Cellular uptake of ribavirin was strongly inhibited by purine nucleoside in an in vitro study. This study aims to examine the effects of dietary purine on the pharmacokinetics of orally administered ribavirin in vivo. Twenty healthy participants were enrolled in a randomized, 2-period crossover study. Participants were administered a single 600-mg oral dose of ribavirin after either a high-purine meal or a low-purine meal. Serial blood samples were collected predose and over 144 hours after dosing. Ribavirin concentrations were measured by liquid chromatography/tandem mass spectrometry. In comparison with corresponding plasma values of ribavirin following a high-purine meal, C(max), AUC(0-144) and AUC(0-infinity) of ribavirin following a low-purine meal were 136% (90% confidence internal [CI]: 120%-155%), 134% (90% CI: 118%-153%), and 139% (90% CI: 120%-159%), respectively. This study indicates that dietary purines have an effect on ribavirin absorption. Dosage regimens of ribavirin might need to be adjusted according to the purine content of the meal.

  20. Leishmania Metacyclogenesis Is Promoted in the Absence of Purines

    PubMed Central

    Serafim, Tiago Donatelli; Figueiredo, Amanda Braga; Costa, Pedro Augusto Carvalho; Marques-da-Silva, Eduardo Almeida; Gonçalves, Ricardo; de Moura, Sandra Aparecida Lima; Gontijo, Nelder Figueiredo; da Silva, Sydnei Magno; Michalick, Marilene Suzan Marques; Meyer-Fernandes, José Roberto; de Carvalho, Roberto Paes; Uliana, Silvia Reni Bortolin; Fietto, Juliana Lopes Rangel; Afonso, Luís Carlos Crocco

    2012-01-01

    Leishmania parasites, the causative agent of leishmaniasis, are transmitted through the bite of an infected sand fly. Leishmania parasites present two basic forms known as promastigote and amastigote which, respectively, parasitizes the vector and the mammalian hosts. Infection of the vertebrate host is dependent on the development, in the vector, of metacyclic promastigotes, however, little is known about the factors that trigger metacyclogenesis in Leishmania parasites. It has been generally stated that “stressful conditions” will lead to development of metacyclic forms, and with the exception of a few studies no detailed analysis of the molecular nature of the stress factor has been performed. Here we show that presence/absence of nucleosides, especially adenosine, controls metacyclogenesis both in vitro and in vivo. We found that addition of an adenosine-receptor antagonist to in vitro cultures of Leishmania amazonensis significantly increases metacyclogenesis, an effect that can be reversed by the presence of specific purine nucleosides or nucleobases. Furthermore, our results show that proliferation and metacyclogenesis are independently regulated and that addition of adenosine to culture medium is sufficient to recover proliferative characteristics for purified metacyclic promastigotes. More importantly, we show that metacyclogenesis was inhibited in sand flies infected with Leishmania infantum chagasi that were fed a mixture of sucrose and adenosine. Our results fill a gap in the life cycle of Leishmania parasites by demonstrating how metacyclogenesis, a key point in the propagation of the parasite to the mammalian host, can be controlled by the presence of specific purines. PMID:23050028

  1. Lie Markov models with purine/pyrimidine symmetry.

    PubMed

    Fernández-Sánchez, Jesús; Sumner, Jeremy G; Jarvis, Peter D; Woodhams, Michael D

    2015-03-01

    Continuous-time Markov chains are a standard tool in phylogenetic inference. If homogeneity is assumed, the chain is formulated by specifying time-independent rates of substitutions between states in the chain. In applications, there are usually extra constraints on the rates, depending on the situation. If a model is formulated in this way, it is possible to generalise it and allow for an inhomogeneous process, with time-dependent rates satisfying the same constraints. It is then useful to require that, under some time restrictions, there exists a homogeneous average of this inhomogeneous process within the same model. This leads to the definition of "Lie Markov models" which, as we will show, are precisely the class of models where such an average exists. These models form Lie algebras and hence concepts from Lie group theory are central to their derivation. In this paper, we concentrate on applications to phylogenetics and nucleotide evolution, and derive the complete hierarchy of Lie Markov models that respect the grouping of nucleotides into purines and pyrimidines-that is, models with purine/pyrimidine symmetry. We also discuss how to handle the subtleties of applying Lie group methods, most naturally defined over the complex field, to the stochastic case of a Markov process, where parameter values are restricted to be real and positive. In particular, we explore the geometric embedding of the cone of stochastic rate matrices within the ambient space of the associated complex Lie algebra.

  2. B Family DNA Polymerases Asymmetrically Recognize Pyrimidines and Purines

    PubMed Central

    Lund, Travis J.; Cavanaugh, Nisha A.; Joubert, Nicolas; Urban, Milan; Patro, Jennifer N.; Hocek, Michal; Kuchta, Robert D.

    2011-01-01

    We utilized a series of pyrimidine analogues modified at O2, N-3, and N4/O4 to determine if two B family DNA polymerases, human DNA polymerase α and herpes simplex virus I DNA polymerase, choose whether or not to polymerize pyrimidine dNTPs using the same mechanisms they use for purine dNTPs. Removing O2 of a pyrimidine dNTP vastly decreased incorporation by these enzymes and also compromised fidelity in the case of C analogues, while removing O2 from the templating base had more modest effects. Removing the Watson-Crick hydrogen bonding groups of N-3 and N4/O4 greatly impaired polymerization, both of the resulting dNTP analogues as well as polymerization of natural dNTPs opposite these pyrimidine analogues when present in the template strand. Thus, the Watson-Crick hydrogen bonding groups of a pyrimidine clearly play an important role in enhancing correct dNTP polymerization, but are not essential for preventing misincorporation. These studies also indicate that DNA polymerases recognize bases extremely asymmetrically, both in terms of whether they are a purine or pyrimidine and whether they are in the template or are the incoming dNTP. The mechanistic implications of these results regarding how polymerases discriminate between right and wrong dNTPs are discussed. PMID:21761848

  3. Deregulation of purine pathway in Bacillus subtilis and its use in riboflavin biosynthesis

    PubMed Central

    2014-01-01

    Background Purine nucleotides are essential metabolites for living organisms because they are involved in many important processes, such as nucleic acid synthesis, energy supply, and biosynthesis of several amino acids and riboflavin. Owing to the pivotal roles of purines in cell physiology, the pool of intracellular purine nucleotides must be maintained under strict control, and hence the de novo purine biosynthetic pathway is tightly regulated by transcription repression and inhibition mechanism. Deregulation of purine pathway is essential for this pathway engineering in Bacillus subtilis. Results Deregulation of purine pathway was attempted to improve purine nucleotides supply, based on a riboflavin producer B. subtilis strain with modification of its rib operon. To eliminate transcription repression, the pur operon repressor PurR and the 5’-UTR of pur operon containing a guanine-sensing riboswitch were disrupted. Quantitative RT-PCR analysis revealed that the relative transcription levels of purine genes were up-regulated about 380 times. Furthermore, site-directed mutagenesis was successfully introduced into PRPP amidotransferase (encoded by purF) to remove feedback inhibition by homologous alignment and analysis. Overexpression of the novel mutant PurF (D293V, K316Q and S400W) significantly increased PRPP amidotransferase activity and triggered a strong refractory effect on purine nucleotides mediated inhibition. Intracellular metabolite target analysis indicated that the purine nucleotides supply in engineered strains was facilitated by a stepwise gene-targeted deregulation. With these genetic manipulations, we managed to enhance the metabolic flow through purine pathway and consequently increased riboflavin production 3-fold (826.52 mg/L) in the purF-VQW mutant strain. Conclusions A sequential optimization strategy was applied to deregulate the rib operon and purine pathway of B. subtilis to create genetic diversities and to improve riboflavin production

  4. A p-coumaroyl esterase from Rhizoctonia solani with a pronounced chlorogenic acid esterase activity.

    PubMed

    Nieter, Annabel; Kelle, Sebastian; Linke, Diana; Berger, Ralf G

    2017-07-25

    Extracellular esterase activity was detected in submerged cultures of Rhizoctonia solani grown in the presence of sugar beet pectin or Tween 80. Putative type B feruloyl esterase (FAE) coding sequences found in the genome data of the basidiomycete were heterologously expressed in Pichia pastoris. Recombinant enzyme production on the 5-L bioreactor scale (Rs pCAE: 3245UL(-1)) exceeded the productivity of the wild type strain by a factor of 800. Based on substrate specificity profiling, the purified recombinant Rs pCAE was classified as a p-coumaroyl esterase (pCAE) with a pronounced chlorogenic acid esterase side activity. The Rs pCAE was also active on methyl cinnamate, caffeate and ferulate and on feruloylated saccharides. The unprecedented substrate profile of Rs pCAE together with the lack of sequence similarity to known FAEs or pCAEs suggested that the Rs pCAE represents a new type of enzyme. Hydroxycinnamic acids were released from agro-industrial side-streams, such as destarched wheat bran (DSWB), sugar beet pectin (SBP) and coffee pulp (CP). Overnight incubation of coffee pulp with the Rs pCAE resulted in the efficient release of p-coumaric (100%), caffeic (100%) and ferulic acid (85%) indicating possible applications for the valorization of food processing wastes and for the enhanced degradation of lignified biomass. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. A nuclear factor that binds purine-rich, single-stranded oligonucleotides derived from S1-sensitive elements upstream of the CFTR gene and the MUC1 gene.

    PubMed Central

    Hollingsworth, M A; Closken, C; Harris, A; McDonald, C D; Pahwa, G S; Maher, L J

    1994-01-01

    We have identified two regions of non-random purine/pyrimidine strand asymmetry that were nearly identical in sequence in the 5' flanking (promoter) regions of the human cystic fibrosis transmembrane conductance regulator (CFTR) gene and the human MUC1 gene. These regions contain perfect mirror repeat elements, a sequence motif previously found to be associated with the formation of H-DNA conformations. In this report we demonstrate that a single-stranded non-B DNA conformation exists at low pH in supercoiled plasmids containing the similar mirror repeat elements, and that S1 nuclease digestion maps the single-stranded region to the position of the mirror repeats. In addition, we identify a nuclear protein of approximately 27 kD that binds to single-stranded oligonucleotides corresponding to the purine-rich strand of this region, but not to the pyrimidine-rich strands or to double-stranded oligonucleotides with corresponding purine/pyrimidine strand asymmetry. Images PMID:7513081

  6. Identification of genes containing expanded purine repeats in the human genome and their apparent protective role against cancer.

    PubMed

    Singh, Himanshu Narayan; Rajeswari, Moganty R

    2016-01-01

    Purine repeat sequences present in a gene are unique as they have high propensity to form unusual DNA-triple helix structures. Friedreich's ataxia is the only human disease that is well known to be associated with DNA-triplexes formed by purine repeats. The purpose of this study was to recognize the expanded purine repeats (EPRs) in human genome and find their correlation with cancer pathogenesis. We developed "PuRepeatFinder.pl" algorithm to identify non-overlapping EPRs without pyrimidine interruptions in the human genome and customized for searching repeat lengths, n ≥ 200. A total of 1158 EPRs were identified in the genome which followed Wakeby distribution. Two hundred and ninety-six EPRs were found in geneic regions of 282 genes (EPR-genes). Gene clustering of EPR-genes was done based on their cellular function and a large number of EPR-genes were found to be enzymes/enzyme modulators. Meta-analysis of 282 EPR-genes identified only 63 EPR-genes in association with cancer, mostly in breast, lung, and blood cancers. Protein-protein interaction network analysis of all 282 EPR-genes identified proteins including those in cadherins and VEGF. The two observations, that EPRs can induce mutations under malignant conditions and that identification of some EPR-gene products in vital cell signaling-mediated pathways, together suggest the crucial role of EPRs in carcinogenesis. The new link between EPR-genes and their functionally interacting proteins throws a new dimension in the present understanding of cancer pathogenesis and can help in planning therapeutic strategies. Validation of present results using techniques like NGS is required to establish the role of the EPR genes in cancer pathology.

  7. Absorption and intermediary metabolism of purines and pyrimidines in lactating dairy cows.

    PubMed

    Stentoft, Charlotte; Røjen, Betina Amdisen; Jensen, Søren Krogh; Kristensen, Niels B; Vestergaard, Mogens; Larsen, Mogens

    2015-02-28

    About 20 % of ruminal microbial N in dairy cows derives from purines and pyrimidines; however, their intermediary metabolism and contribution to the overall N metabolism has sparsely been described. In the present study, the postprandial patterns of net portal-drained viscera (PDV) and hepatic metabolism were assessed to evaluate purine and pyrimidine N in dairy cows. Blood was sampled simultaneously from four veins with eight hourly samples from four multi-catheterised Holstein cows. Quantification of twenty purines and pyrimidines was performed with HPLC-MS/MS, and net fluxes were estimated across the PDV, hepatic tissue and total splanchnic tissue (TSP). Concentration differences between veins of fifteen purine and pyrimidine nucleosides (NS), bases (BS) and degradation products (DP) were different from zero (P≤ 0·05), resulting in the net PDV releases of purine NS (0·33-1·3 mmol/h), purine BS (0·0023-0·018 mmol/h), purine DP (7·0-7·8 mmol/h), pyrimidine NS (0·30-2·8 mmol/h) and pyrimidine DP (0·047-0·77 mmol/h). The hepatic removal of purine and pyrimidine was almost equivalent to the net PDV release, resulting in no net TSP release. One exception was uric acid (7·9 mmol/h) from which a large net TSP release originated from the degradation of purine NS and BS. A small net TSP release of the pyrimidine DP β-alanine and β-aminoisobutyric acid (-0·032 to 0·37 mmol/h) demonstrated an outlet of N into the circulating N pool. No effect of time relative to feeding was observed (P>0·05). These data indicate that considerable amounts of N are lost in the dairy cow due to prominent intermediary degradation of purines, but that pyrimidine N is reusable to a larger extent.

  8. PRESENCE OF PURINE METABOLITES IN OMASAL DIGESTA AND BACTERIA: NEW ANALYTICAL METHOD AND EFFECTS ON MICROBIAL FLOWS

    USDA-ARS?s Scientific Manuscript database

    A new HPLC method was developed to determine concentrations of purines [adenine (A) and guanine (G)], and their metabolites [xanthine (X) and hypoxanthine (HX)] in omasal digesta and bacterial samples and to assess the effect of using either purines (TP) or purines plus their metabolites (PM) as mic...

  9. NMR studies of the stable mismatch purine-thymine in the self-complementary d(CGPuAATTTCG) duplex in solution

    SciTech Connect

    Ikuta, S.; Eritja, R.; Kaplan, B.E.; Itakura, K.

    1987-09-08

    One- and two-dimensional nuclear Overhauser effect experiments demonstrate that a single hydrogen bond between a T imino proton and purine N3 is sufficient to hold the base pair dPu-dT in d(CGPuAATTTCG) by a Watson-Crick fashion rather than a Hoogsteen type. In addition, the dPu-dT base pair is well stacked with neighboring base pairs. The spin-lattice relaxation measurements at 30 and 35/sup 0/C of two decamers, d(CGPuAATTTCG) and d(CGAAATTTCG), reveal that the elimination of two single hydrogen bonds of dA-dT base pairs (due to the substitution of adenine for purine) in the sequence results in an increase in the overall imino proton exchange rate from 7 to 36 s/sup -1/ at the site of mismatch.

  10. Synthesis and cytostatic activity of purine nucleosides derivatives of allofuranose.

    PubMed

    Besada, Pedro; Costas, Tamara; Teijeira, Marta; Terán, Carmen

    2010-12-01

    Several new purine nucleosides derivatives of allofuranose were prepared according to Vorbrüggen method, starting from 1,2,5,6-di-O-isopropylidene-α-D-allofuranose and using 1,2,3,5,6-pentaacetoxy-β-D-allofuranose as key intermediate. The synthesized allofuranosyl nucleosides, as well as some acetyl derivatives, were evaluated for their cytotoxicity in vitro in three human cancer cell lines (MCF-7, Hela-229 and HL-60). Among the studied compounds the 9-(2,3,5,6-tetra-O-acetyl-β-D-allofuranosyl)-2,6-dichloropurine (9) was the most potent one on the three cell lines evaluated, being its activity against HL-60 cells similar to cisplatin.

  11. [Metformin impact on purine metabolism in breast cancer].

    PubMed

    Shatova, O P; Butenko, Eu V; Khomutov, Eu V; Kaplun, D S; Sedakov, I Eu; Zinkovych, I I

    2016-03-01

    Large-scale epidemiological and clinical studies have demonstrated the efficacy of metformin in oncology practice. However, the mechanisms of implementation of the anti-tumor effect of this drug there is still need understanding. In this study we have investigated the effect of metformin on the activity of adenosine deaminase and respectively adenosinergic immunosuppression in tumors and their microenvironment. The material of the study was taken during surgery of breast cacer patients receiveing metformin, and also patients which did not take this drug. The adenosine deaminase activity and substrate (adenosine) and products (inosine, hypoxanthine) concentrations were determined by HPLC. Results of this study suggest that metformin significantly alters catabolism of purine nucleotides in the node breast adenocarcinoma tisue. However, the metformin-induced increase in the adenosine deaminase activity is not sufficient to reduce the level of adenosine in cancer tissue. Thus, in metformin treated patients the adenosine concentration remained unchanged, and inosine and hypoxanthine concentration significantly increased.

  12. Cyclin-dependent kinase inhibitors inspired by roscovitine: purine bioisosteres.

    PubMed

    Jorda, Radek; Paruch, Kamil; Krystof, Vladimír

    2012-01-01

    Roscovitine is a synthetic inhibitor of cyclin-dependent kinases that is currently undergoing clinical trials as a candidate drug for some oncological indications. Its discovery prompted many research teams to further optimize its structure or to initiate their own related but independent studies. This article reviews known roscovitine bioisosteres that have been prepared as CDK inhibitors using different core heterocycles. The individual bioisostere types have been described and explored to a different extent, which complicates direct comparisons of their biochemical activity - only six direct analogs containing different purine bioisosteres have been prepared and evaluated side by side with roscovitine. Only four types of bioisosteres have demonstrated improved biological properties, namely pyrazolo[ 1,5-a]-1,3,5-triazines, pyrazolo[1,5-a]pyrimidines, pyrazolo[1,5-a]pyridines and pyrazolo[4,3-d]pyrimidines.

  13. Antimalarial activity of thiosemicarbazones and purine derived nitriles

    PubMed Central

    Mallari, Jeremy P.; Guiguemde, Wendyam A.; Guy, R. Kiplin

    2009-01-01

    Malaria is a devastating illness caused by multiple species of the Plasmodium genus. The parasite’s food vacuole of falcipain proteases have been extensively studied as potential drug targets. Here we report the testing of two established cysteine protease inhibitor scaffolds against both chloroquine sensitive and chloroquine resistant parasites. A subset of purine derived nitriles killed the parasite with moderate potency, and these inhibitors do not seem to exert their antiproliferative effects as cysteine protease inhibitors. Compound potency was determined to be similar against both parasite strains, indicating a low probability of cross resistance with chloroquine. These compounds represent a novel antimalarial scaffold, and a potential starting point for the development new inhibitors. PMID:19447616

  14. The Attachment of Amino Fragment to Purine: Inner-Shell Structures And Spectra

    SciTech Connect

    Saha, Saumitra; Wang, Feng; MacNaughton, Janay B.; Moewes, Alex; Chong, Denalo P.; /British Columbia U.

    2009-05-11

    The impact of the amino fragment (-NH{sub 2}) attachment on the inner-shell structures and spectra of unsubstituted purine and the purine ring of adenine are studied. Density functional theory calculations, using the LB94/TZ2P//B3LYP/TZVP model, reveal significant site-dependent electronic structural changes in the inner shell of the species. A condensed Fukui function indicates that all of the N and C sites, except for N{sub (1)} and C{sub (5)}, demonstrate significant electrophilic reactivity (f > 0.5 in |e|) in the unsubstituted purine. Once the amino fragment binds to the C{sub (6)} position of purine to form adenine, the electrophilic reactivity of these N and C sites is greatly reduced. As expected, the C{sub (6)} position experiences substantial changes in energy and charge transfer, owing to the formation of the C-NH{sub 2} bond in adenine. The present study reveals that the N1s spectra of adenine inherit the N1s spectra of the unsubstituted purine, whereas the C1s spectra experience significant changes although purine and adenine have geometrically similar carbon frames. The findings also indicate that the attachment of the NH{sub 2} fragment to purine exhibits deeply rooted influences to the inner-shell structures of DNA/RNA bases. The present study suggests that some fragment-based methods may not be applicable to spectral analyses in the inner shell.

  15. Folate-Dependent Purine Nucleotide Biosynthesis in Humans1

    PubMed Central

    Baggott, Joseph E; Tamura, Tsunenobu

    2015-01-01

    Purine nucleotide biosynthesis de novo (PNB) requires 2 folate-dependent transformylases—5′-phosphoribosyl-glycinamide (GAR) and 5′-phosphoribosyl-5-aminoimidazole-4-carboxamide (AICAR) transformylases—to introduce carbon 8 (C8) and carbon 2 (C2) into the purine ring. Both transformylases utilize 10-formyltetrahydrofolate (10-formyl-H4folate), where the formyl-carbon sources include ring-2-C of histidine, 3-C of serine, 2-C of glycine, and formate. Our findings in human studies indicate that glycine provides the carbon for GAR transformylase (exclusively C8), whereas histidine and formate are the predominant carbon sources for AICAR transformylase (C2). Contrary to the previous notion, these carbon sources may not supply a general 10-formyl-H4folate pool, which was believed to equally provide carbons to C8 and C2. To explain these phenomena, we postulate that GAR transformylase is in a complex with the trifunctional folate-metabolizing enzyme (TFM) and serine hydroxymethyltransferase to channel carbons of glycine and serine to C8. There is no evidence for channeling carbons of histidine and formate to AICAR transformylase (C2). GAR transformylase may require the TFM to furnish 10-formyl-H4folate immediately after its production from serine to protect its oxidation to 10-formyldihydrofolate (10-formyl-H2folate), whereas AICAR transformylase can utilize both 10-formyl-H2folate and 10-formyl-H4folate. Human liver may supply AICAR to AICAR transformylase in erythrocytes/erythroblasts. Incorporation of ring-2-C of histidine and formate into C2 of urinary uric acid presented a circadian rhythm with a peak in the morning, which corresponds to the maximum DNA synthesis in the bone marrow, and it may be useful in the timing of the administration of drugs that block PNB for the treatment of cancer and autoimmune disease. PMID:26374178

  16. Structural and catalytic effects of an invariant purine substitution in the hammerhead ribozyme: implications for the mechanism of acid–base catalysis

    PubMed Central

    Schultz, Eric P.; Vasquez, Ernesto E.; Scott, William G.

    2014-01-01

    The hammerhead ribozyme catalyzes RNA cleavage via acid–base catalysis. Whether it does so by general acid–base catalysis, in which the RNA itself donates and abstracts protons in the transition state, as is typically assumed, or by specific acid–base catalysis, in which the RNA plays a structural role and proton transfer is mediated by active-site water molecules, is unknown. Previous biochemical and crystallographic experiments implicate an invariant purine in the active site, G12, as the general base. However, G12 may play a structural role consistent with specific base catalysis. To better understand the role of G12 in the mechanism of hammerhead catalysis, a 2.2 Å resolution crystal structure of a hammerhead ribozyme from Schistosoma mansoni with a purine substituted for G12 in the active site of the ribozyme was obtained. Comparison of this structure (PDB entry 3zd4), in which A12 is substituted for G, with three previously determined structures that now serve as important experimental controls, allows the identification of structural perturbations that are owing to the purine substitution itself. Kinetic measurements for G12 purine-substituted schistosomal hammerheads confirm a previously observed dependence of rate on the pK a of the substituted purine; in both cases inosine, which is similar to G in pK a and hydrogen-bonding properties, is unexpectedly inactive. Structural comparisons indicate that this may primarily be owing to the lack of the exocyclic 2-amino group in the G12A and G12I substitutions and its structural effect upon both the nucleotide base and phosphate of A9. The latter involves the perturbation of a previously identified and well characterized metal ion-binding site known to be catalytically important in both minimal and full-length hammerhead ribozyme sequences. The results permit it to be suggested that G12 plays an important role in stabilizing the active-site structure. This result, although not inconsistent with the

  17. Structural and catalytic effects of an invariant purine substitution in the hammerhead ribozyme: implications for the mechanism of acid-base catalysis.

    PubMed

    Schultz, Eric P; Vasquez, Ernesto E; Scott, William G

    2014-09-01

    The hammerhead ribozyme catalyzes RNA cleavage via acid-base catalysis. Whether it does so by general acid-base catalysis, in which the RNA itself donates and abstracts protons in the transition state, as is typically assumed, or by specific acid-base catalysis, in which the RNA plays a structural role and proton transfer is mediated by active-site water molecules, is unknown. Previous biochemical and crystallographic experiments implicate an invariant purine in the active site, G12, as the general base. However, G12 may play a structural role consistent with specific base catalysis. To better understand the role of G12 in the mechanism of hammerhead catalysis, a 2.2 Å resolution crystal structure of a hammerhead ribozyme from Schistosoma mansoni with a purine substituted for G12 in the active site of the ribozyme was obtained. Comparison of this structure (PDB entry 3zd4), in which A12 is substituted for G, with three previously determined structures that now serve as important experimental controls, allows the identification of structural perturbations that are owing to the purine substitution itself. Kinetic measurements for G12 purine-substituted schistosomal hammerheads confirm a previously observed dependence of rate on the pK(a) of the substituted purine; in both cases inosine, which is similar to G in pK(a) and hydrogen-bonding properties, is unexpectedly inactive. Structural comparisons indicate that this may primarily be owing to the lack of the exocyclic 2-amino group in the G12A and G12I substitutions and its structural effect upon both the nucleotide base and phosphate of A9. The latter involves the perturbation of a previously identified and well characterized metal ion-binding site known to be catalytically important in both minimal and full-length hammerhead ribozyme sequences. The results permit it to be suggested that G12 plays an important role in stabilizing the active-site structure. This result, although not inconsistent with the potential

  18. Evidence for purine nucleoside phosphorylase (PNP) release from rat C6 glioma cells.

    PubMed

    Giuliani, Patricia; Zuccarini, Mariachiara; Buccella, Silvana; Peña-Altamira, Luis Emiliano; Polazzi, Elisabetta; Virgili, Marco; Monti, Barbara; Poli, Alessandro; Rathbone, Michel P; Di Iorio, Patrizia; Ciccarelli, Renata; Caciagli, Francesco

    2017-04-01

    Intracellular purine turnover is mainly oriented to preserving the level of triphosphate nucleotides, fundamental molecules in vital cell functions that, when released outside cells, act as receptor signals. Conversely, high levels of purine bases and uric acid are found in the extracellular milieu, even in resting conditions. These compounds could derive from nucleosides/bases that, having escaped to cell reuptake, are metabolized by extracellular enzymes similar to the cytosolic ones. Focusing on purine nucleoside phosphorylase (PNP) that catalyzes the reversible phosphorolysis of purine (deoxy)-nucleosides/bases, we found that it is constitutively released from cultured rat C6 glioma cells into the medium, and has a molecular weight and enzyme activity similar to the cytosolic enzyme. Cell exposure to 10 μM ATP or guanosine triphosphate (GTP) increased the extracellular amount of all corresponding purines without modifying the levels/activity of released PNP, whereas selective activation of ATP P2Y1 or adenosine A2A metabotropic receptors increased PNP release and purine base formation. The reduction to 1% in oxygen supply (2 h) to cells decreased the levels of released PNP, leading to an increased presence of extracellular nucleosides and to a reduced formation of xanthine and uric acid. Conversely, 2 h cell re-oxygenation enhanced the extracellular amounts of both PNP and purine bases. Thus, hypoxia and re-oxygenation modulated in opposite manner the PNP release/activity and, thereby, the extracellular formation of purine metabolism end-products. In conclusion, extracellular PNP and likely other enzymes deputed to purine base metabolism are released from cells, contributing to the purinergic system homeostasis and exhibiting an important pathophysiological role. © 2017 International Society for Neurochemistry.

  19. Blood purine measurements as a rapid real-time indicator of reversible brain ischaemia.

    PubMed

    Tian, Faming; Bibi, Fakhra; Dale, Nicholas; Imray, Christopher H E

    2017-08-12

    To preserve the disequilibrium between ATP and ADP necessary to drive cellular metabolism, enzymatic pathways rapidly convert ADP to adenosine and the downstream purines inosine and hypoxanthine. During ischaemia, these same pathways result in the production of purines. We performed a prospective observational study to test whether purine levels in arterial blood might correlate with brain ischaemia. We made real-time perioperative measurements, via microelectrode biosensors, of the purine levels in untreated arterial blood from 18 patients undergoing regional anaesthetic carotid endarterectomy. Pre-operatively, the median purine level was 2.4 μM (95% CI 1.3-4.0 μM); during the cross-clamp phase, the purines rose to 6.7 μM (95% CI 4.7-11.5 μM) and fell back to 1.9 μM (95% CI 1.4-2.7 μM) in recovery. Three patients became unconscious during carotid clamping, necessitating insertion of a temporary carotid shunt to restore cerebral blood flow. In these, the pre-operative median purine level was 5.4 μM (range 4.7-6.1 μM), on clamping, 9.6 μM (range 9.4-16.1 μM); during shunting, purines fell to below the pre-operative level (1.4 μM, range 0.4-2.9 μM) and in recovery 1.8 μM (range 1.8-2.6 μM). Our results suggest that blood purines may be a sensitive real-time and rapidly produced indicator of brain ischaemia, even when there is no accompanying neurological obtundation.

  20. Comparison of nitrogen-15 and purines as microbial markers in continuous culture.

    PubMed

    Calsamiglia, S; Stern, M D; Firkins, J L

    1996-06-01

    Eight dual-flow continuous-culture fermenters were used in four replicated periods to compare the effects of diet and microbial marker on estimates of N metabolism in continuous culture of ruminal microorganisms. A basal diet was supplemented with urea and tryptone, soybean meal (SBM), lignosulfonate-treated SBM, corn gluten meal, blood meal (BM), hydrolyzed feather meal, fish meal (FM), or meat and bone meal (MBM). Microbial protein flow and protein degradation in fermenters were estimated using purines, purine N, and 15N in bacteria obtained from fermenter flasks or from the effluent. The ratio of purine N to total N in bacteria averaged .083 and was not affected (P > .05) by treatment. Dietary purine content (percentage of DM) ranged from .033 in BM to .084 in FM. Escape of feed purine N (percentage of total purine N flow) averaged 1.7% (SE = 2.9) and was not different (P > .05) among treatments. Bacterial N flows obtained using purines were more variable than estimates obtained using 15N. Bacterial N flows calculated using 15N in bacteria isolated from fermenters were more variable than those obtained using bacteria isolated from the effluent. The use of purines as a microbial marker resulted in lower estimates of protein degradation and smaller differences among treatments compared with use of 15N. Data suggest that escape of feed purine N seems to be a minor factor affecting calculation of bacterial N flow and that the use of 15N in effluent bacteria may be a more accurate procedure when using continuous-culture fermenters.

  1. Use of Analogues and the Substrate-Sensitivity of Mutants in Analysis of Purine Uptake and Breakdown in Aspergillus nidulans

    PubMed Central

    Darlington, A. J.; Scazzocchio, C.

    1967-01-01

    Aspergillus mutants resistant to various purine analogues (purine, 8-azaguanine, 2-thioxanthine, and 2-thiouric acid) are defective in at least one step of purine uptake or breakdown. The properties of these mutants show that there are two uptake systems for purines, one which mediates the uptake of hypoxanthine, guanine, and adenine, and the other, xanthine and uric acid. Allantoinase-less strains are sensitive to the toxic effects of allantoin accumulation. They are severely inhibited when grown in the presence of naturally occurring purines. Mutant strains derived from these, resistant to naturally occurring purines, may be isolated. These are either wild-type revertants, or carry a second metabolic block in the uptake or breakdown of purines. The properties of these double mutants confirm the interpretation of the nature of the analogue-resistant mutants. PMID:6025432

  2. [Quantum-chemical investigation of the elementary molecular mechanisms of pyrimidine-purine transversions].

    PubMed

    Brovarets', O O; Govorun D M

    2010-01-01

    Purine-purine mispairs of DNA (thus involving template base in anti-conformation along the glycosidic bond and base of the incoming nucleotide - in syn-conformation) leading to pyrimidine-purine "transversions"-type point mutations were revealed and characterized at the MP2/6-311++G(2df,pd)//B3LYP/6-311++G(d,p) level of theory in vacuum approach adequately modeling hydrophobic environment of the active centre of high-fidelity replicative DNA-polymerases.

  3. Novel N9-arenethenyl purines as potent dual Src/Abl tyrosine kinase inhibitors.

    PubMed

    Wang, Yihan; Shakespeare, William C; Huang, Wei-Sheng; Sundaramoorthi, Raji; Lentini, Scott; Das, Sasmita; Liu, Shuangying; Banda, Geeta; Wen, David; Zhu, Xiaotian; Xu, Qihong; Keats, Jeffrey; Wang, Frank; Wardwell, Scott; Ning, Yaoyu; Snodgrass, Joseph T; Broudy, Mark I; Russian, Karin; Dalgarno, David; Clackson, Tim; Sawyer, Tomi K

    2008-09-01

    Novel N(9)-arenethenyl purines, optimized potent dual Src/Abl tyrosine kinase inhibitors, are described. The key structural feature is a trans vinyl linkage at N(9) on the purine core which projects hydrophobic substituents into the selectivity pocket at the rear of the ATP site. Their synthesis was achieved through a Horner-Wadsworth-Emmons reaction of N(9)-phosphorylmethylpurines and substituted benzaldehydes or Heck reactions between 9-vinyl purines and aryl halides. Most compounds are potent inhibitors of both Src and Abl kinase, and several possess good oral bioavailability.

  4. Novel developments in metabolic disorders of purine and pyrimidine metabolism and therapeutic applications of their analogs.

    PubMed

    Torres, Rosa J; Peters, Godefridus J; Puig, Juan G

    2014-01-01

    The biennial 15th symposium on Purine and Pyrimidine metabolism was held in Madrid, June 2013 (PP13). During the meeting, several novel developments on the diagnosis, pathophysiology, and treatment of several inborn errors of purine and pyrimidine metabolism were presented. These ranged from new drugs for gout to enzyme replacement therapies for mitochondrial diseases. A relatively novel aspect in this meeting was the interest in purine and pyrimidine metabolism in nonmammalian systems, such as parasites, mycoplasms, and bacteria. Development of novel analogs for parasite infections, cardiovascular diseases, inflammatory diseases, and cancer were also discussed.

  5. The role of purine degradation in methane biosynthesis and energy production in Methanococcus vannielii

    SciTech Connect

    DeMoll, E.

    1990-10-22

    Research continues on the role of purine degradation in methane biosynthesis and energy production in Methanococcus vannielii. This report summarizes current progress of the research. Topics include: A survey of other methanogens for the purine degradation pathway; isolate and characterize the enzyme and products of formiminoglycine cleavage; ascertain the fate of glycine from the formiminoglycine cleavage; elucidate the route of incorporation of the formyl moiety of formiminoglycine into methane biosynthesis; determine the percent methane and amino acid synthesis from purine degradation; and related studies on xanthine dehydrogenase and pyrimidine degradation of M. Vannielii. (SM)

  6. Placental Hypomethylation Is More Pronounced in Genomic Loci Devoid of Retroelements

    PubMed Central

    Chatterjee, Aniruddha; Macaulay, Erin C.; Rodger, Euan J.; Stockwell, Peter A.; Parry, Matthew F.; Roberts, Hester E.; Slatter, Tania L.; Hung, Noelyn A.; Devenish, Celia J.; Morison, Ian M.

    2016-01-01

    The human placenta is hypomethylated compared to somatic tissues. However, the degree and specificity of placental hypomethylation across the genome is unclear. We assessed genome-wide methylation of the human placenta and compared it to that of the neutrophil, a representative homogeneous somatic cell. We observed global hypomethylation in placenta (relative reduction of 22%) compared to neutrophils. Placental hypomethylation was pronounced in intergenic regions and gene bodies, while the unmethylated state of the promoter remained conserved in both tissues. For every class of repeat elements, the placenta showed lower methylation but the degree of hypomethylation differed substantially between these classes. However, some retroelements, especially the evolutionarily younger Alu elements, retained high levels of placental methylation. Surprisingly, nonretrotransposon-containing sequences showed a greater degree of placental hypomethylation than retrotransposons in every genomic element (intergenic, introns, and exons) except promoters. The differentially methylated fragments (DMFs) in placenta and neutrophils were enriched in gene-poor and CpG-poor regions. The placentally hypomethylated DMFs were enriched in genomic regions that are usually inactive, whereas hypermethylated DMFs were enriched in active regions. Hypomethylation of the human placenta is not specific to retroelements, indicating that the evolutionary advantages of placental hypomethylation go beyond those provided by expression of retrotransposons and retrogenes. PMID:27172225

  7. Pronounceability: a measure of language samples based on children's mastery of the phonemes employed in them.

    PubMed

    Whissell, Cynthia

    2003-06-01

    56 samples (n > half a million phonemes) of names (e.g., men's, women's jets'), song lyrics (e.g., Paul Simon's, rap, Beatles'), poems (frequently anthologized English poems), and children's materials (books directed at children ages 3-10 years) were used to study a proposed new measure of English language samples--Pronounceability-based on children's mastery of some phonemes in advance of others. This measure was provisionally equated with greater "youthfulness" and "playfulness" in language samples and with less "maturity." Findings include the facts that women's names were less pronounceable than men's and that poetry was less pronounceable than song lyrics or children's materials. In a supplementary study, 13 university student volunteers' assessments of the youth of randomly constructed names was linearly related to how pronounceable each name was (eta = .8), providing construct validity for the interpretation of Pronounceability as a measure of Youthfulness.

  8. Solvent effects on the photochemistry of 4-aminoimidazole-5-carbonitrile, a prebiotically plausible precursor of purines.

    PubMed

    Szabla, Rafał; Sponer, Judit E; Sponer, Jiří; Sobolewski, Andrzej L; Góra, Robert W

    2014-09-07

    4-Aminoimidazole-5-carbonitrile (AICN) was suggested as a prebiotically plausible precursor of purine nucleobases and nucleotides. Although it can be formed in a sequence of photoreactions, AICN is immune to further irradiation with UV-light. We present state-of-the-art multi-reference quantum-chemical calculations of potential energy surface cuts and conical intersection optimizations to explain the molecular mechanisms underlying the photostability of this compound. We have identified the N-H bond stretching and ring-puckering mechanisms that should be responsible for the photochemistry of AICN in the gas phase. We have further considered the photochemistry of AICN-water clusters, while including up to six explicit water molecules. The calculations reveal charge transfer to solvent followed by formation of an H3O(+) cation, both of which occur on the (1)πσ* hypersurface. Interestingly, a second proton transfer to an adjacent water molecule leads to a (1)πσ*/S0 conical intersection. We suggest that this electron-driven proton relay might be characteristic of low-lying (1)πσ* states in chromophore-water clusters. Owing to its nature, this mechanism might also be responsible for the photostability of analogous organic molecules in bulk water.

  9. Cloning of three human multifunctional de novo purine biosynthetic genes by functional complementation of yeast mutations.

    PubMed Central

    Schild, D; Brake, A J; Kiefer, M C; Young, D; Barr, P J

    1990-01-01

    Functional complementation of mutations in the yeast Saccharomyces cerevisiae has been used to clone three multifunctional human genes involved in de novo purine biosynthesis. A HepG2 cDNA library constructed in a yeast expression vector was used to transform yeast strains with mutations in adenine biosynthetic genes. Clones were isolated that complement mutations in the yeast ADE2, ADE3, and ADE8 genes. The cDNA that complemented the ade8 (phosphoribosylglycinamide formyltransferase, GART) mutation, also complemented the ade5 (phosphoribosylglycinamide synthetase) and ade7 [phosphoribosylaminoimidazole synthetase (AIRS; also known as PAIS)] mutations, indicating that it is the human trifunctional GART gene. Supporting data include homology between the AIRS and GART domains of this gene and the published sequence of these domains from other organisms, and localization of the cloned gene to human chromosome 21, where the GART gene has been shown to map. The cDNA that complemented ade2 (phosphoribosylaminoimidazole carboxylase) also complemented ade1 (phosphoribosylaminoimidazole succinocarboxamide synthetase), supporting earlier data suggesting that in some organisms these functions are part of a bifunctional protein. The cDNA that complemented ade3 (formyltetrahydrofolate synthetase) is different from the recently isolated human cDNA encoding this enzyme and instead appears to encode a related mitochondrial enzyme. Images PMID:2183217

  10. Effect of purine alkaloids on the proliferation of lettuce cells derived from protoplasts.

    PubMed

    Sasamoto, Hamako; Fujii, Yoshiharu; Ashihara, Hiroshi

    2015-05-01

    To investigate the ecological role of caffeine, theobromine, theophylline and paraxanthine, which are released from purine alkaloid forming plants, the effects of these purine alkaloids on the division and colony formation of lettuce cells were assessed at concentrations up to 1 mM. Five days after treatment with 500 μM caffeine, theophylline and paraxanthine, division of isolated protoplasts was significantly inhibited. Thirteen days treatment with > 250 μM caffeine had a marked inhibitory effect on the colony formation of cells derived from the protoplasts. Other purine alkaloids also acted as inhibitors. The order of the inhibition was caffeine > theophylline > paraxanthine > theobromine. These observations suggest that a relatively low concentration of caffeine is toxic for proliferation of plant cells. In contrast, theobromine is a weak inhibitor of proliferation. Possible allelopathic roles of purine alkaloids in natural ecosystems are discussed.

  11. Structure of purine nucleoside phosphorylase (DeoD) from Bacillus anthracis

    SciTech Connect

    Grenha, Rosa; Levdikov, Vladimir M.; Fogg, Mark J.; Blagova, Elena V.; Brannigan, James A. Wilkinson, Anthony J.; Wilson, Keith S.

    2005-05-01

    The crystal structure of purine nucleoside phosphorylase (DeoD) from B. anthracis was solved by X-ray crystallography using molecular replacement and refined at a resolution of 2.24 Å. Protein structures from the causative agent of anthrax (Bacillus anthracis) are being determined as part of a structural genomics programme. Amongst initial candidates for crystallographic analysis are enzymes involved in nucleotide biosynthesis, since these are recognized as potential targets in antibacterial therapy. Purine nucleoside phosphorylase is a key enzyme in the purine-salvage pathway. The crystal structure of purine nucleoside phosphorylase (DeoD) from B. anthracis has been solved by molecular replacement at 2.24 Å resolution and refined to an R factor of 18.4%. This is the first report of a DeoD structure from a Gram-positive bacterium.

  12. Long-term follow-up after purine analogue therapy in hairy cell leukaemia.

    PubMed

    Else, Monica; Dearden, Claire E; Catovsky, Daniel

    2015-12-01

    Since 2006 when we last reviewed the literature concerning the use of purine analogues in hairy cell leukaemia (HCL), results from several new and updated series have been published. Here we examine these reports and consider their implications for patient management. The two purine analogues pentostatin and cladribine remain the first-line treatments of choice for all patients with HCL. Although they have not been compared in randomised trials, they appear to be equally effective. A complete response is important for the long-term outcome and we look at how best this can be achieved. Evidence is emerging which supports the use of either purine analogue plus an anti-CD20 monoclonal antibody after relapse, though questions remain concerning the scheduling of the monoclonal antibody. Patients refractory to the purine analogues may require alternative agents. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  13. Versatile synthesis and biological evaluation of novel 3’-fluorinated purine nucleosides

    PubMed Central

    Ren, Hang; Hatala, Paul J; Stevens, William C; He, Baicheng

    2015-01-01

    Summary A unified synthetic strategy accessing novel 3'-fluorinated purine nucleoside derivatives and their biological evaluation were achieved. Novel 3’-fluorinated analogues were constructed from a common 3’-deoxy-3’-fluororibofuranose intermediate. Employing Suzuki and Stille cross-coupling reactions, fifteen 3’-fluororibose purine nucleosides 1–15 and eight 3’-fluororibose 2-chloro/2-aminopurine nucleosides 16–23 with various substituents at position 6 of the purine ring were efficiently synthesized. Furthermore, 3’-fluorine analogs of natural products nebularine and 6-methylpurine riboside were constructed via our convergent synthetic strategy. Synthesized nucleosides were tested against HT116 (colon cancer) and 143B (osteosarcoma cancer) tumor cell lines. We have demonstrated 3’-fluorine purine nucleoside analogues display potent tumor cell growth inhibition activity at sub- or low micromolar concentration. PMID:26734098

  14. Extracellular-purine metabolism in blood vessels (part I). Extracellular-purine level in blood of patients with abdominal aortic aneurysm.

    PubMed

    Lecka, Joanna; Molski, Stanislaw; Komoszynski, Michal

    2010-09-01

    Adenosine and adenosine derivatives are the main regulators of purinoceptors (P1 and P2) mediated hemostasis and blood pressure. Since impaired hemostasis and high blood pressure lead to atherosclerosis and to the development of aneurysm, in this study we tested and compared the concentration of extracellular purines (e-purines) in the blood in of patients having abdominal aortic aneurysm with that from healthy volunteers. Whereas adenine nucleosides and nucleotides level in human blood plasma was analysed using reverse phase high performance liquid chromatography (HPLC), cholesterol concentration was estimated by an enzymatic assay. We did not find any correlation between e-purines concentration and the age of healthy volunteers. Furthermore, the sum level of e-purines (ATP, ADP, AMP, adenosine, and inosine) in the control group did not exceed 70 microM, while it was nearly two-fold higher in the blood of patients having abdominal aortic aneurysm, (123 microM). In a special case of people with Leriche Syndrome, a disease characterized by deep atherosclerotic changes, the e-purines level had further increased. Additionally, we also report typical atherosclerotic changes in the aorta using histological assays as well as total cholesterol rise. The significant rise in cholesterol concentration in the blood of the patients with abdominal aortas aneurysm, compared with the control groups, was not unique since 23% of the healthy people also exceeded the normal level of cholesterol. Therefore, our results strongly indicate that the estimation of e-purines concentration in the blood may serve as another indicator of atherosclerosis and warrant further consideration as a futuristic diagnostic tool.

  15. Revisiting the planarity of nucleic acid bases: Pyramidilization at glycosidic nitrogen in purine bases is modulated by orientation of glycosidic torsion

    PubMed Central

    Sychrovsky, Vladimir; Foldynova-Trantirkova, Silvie; Spackova, Nada; Robeyns, Koen; Van Meervelt, Luc; Blankenfeldt, Wulf; Vokacova, Zuzana; Sponer, Jiri; Trantirek, Lukas

    2009-01-01

    We describe a novel, fundamental property of nucleobase structure, namely, pyramidilization at the N1/9 sites of purine and pyrimidine bases. Through a combined analyses of ultra-high-resolution X-ray structures of both oligonucleotides extracted from the Nucleic Acid Database and isolated nucleotides and nucleosides from the Cambridge Structural Database, together with a series of quantum chemical calculations, molecular dynamics (MD) simulations, and published solution nuclear magnetic resonance (NMR) data, we show that pyramidilization at the glycosidic nitrogen is an intrinsic property. This property is common to isolated nucleosides and nucleotides as well as oligonucleotides—it is also common to both RNA and DNA. Our analysis suggests that pyramidilization at N1/9 sites depends in a systematic way on the local structure of the nucleoside. Of note, the pyramidilization undergoes stereo-inversion upon reorientation of the glycosidic bond. The extent of the pyramidilization is further modulated by the conformation of the sugar ring. The observed pyramidilization is more pronounced for purine bases, while for pyrimidines it is negligible. We discuss how the assumption of nucleic acid base planarity can lead to systematic errors in determining the conformation of nucleotides from experimental data and from unconstrained MD simulations. PMID:19786496

  16. De novo purine biosynthesis by two pathways in Burkitt lymphoma cells and in human spleen.

    PubMed

    Reem, G H

    1972-05-01

    This study was designed to answer the question whether human lymphocytes and spleen cells were capable of de novo purine biosynthesis. Experiments were carried out in cell-free extracts prepared from human spleen, and from a cell line established from Burkitt lymphoma. Burkitt lymphoma cells and human spleen cells could synthesize the first and second intermediates of the purine biosynthetic pathway. Cell-free extracts of all cell lines studied contained the enzyme systems which catalyze the synthesis of phosphoribosyl-1-amine, the first intermediate unique to the purine biosynthetic pathway and of phosphoribosyl glycinamide, the second intermediate of this pathway. Phosphoribosyl-1-amine could be synthesized in cell-free extracts from alpha-5-phosphoribosyl-1-pyrophosphate (PRPP) and glutamine, from PRPP and ammonia, and by an alternative pathway, directly from ribose-5-phosphate and ammonia. These findings suggest that extrahepatic tissues may be an important source for the de novo synthesis of purine ribonucleotide in man. They also indicate that ammonia may play an important role in purine biosynthesis. The alternative pathway for the synthesis of phosphoribosyl-1-amine from ribose-5-phosphate and ammonia was found to be subject to inhibition by the end products of the purine synthetic pathway, particularly by adenylic acid and to a lesser degree by guanylic acid. The alternative pathway for phosphoribosyl-1-amine synthesis from ribose-5-phosphate and ammonia may contribute significantly towards the regulation of the rate of de novo purine biosynthesis in the normal state, in metabolic disorders in which purines are excessively produced and in myeloproliferative diseases.

  17. A Targeted Metabolomics Assay to Measure Eight Purines in the Diet of Common Bottlenose Dolphins, Tursiops truncatus

    PubMed Central

    Ardente, AJ; Garrett, TJ; Wells, RS; Walsh, M; Smith, CR; Colee, J; Hill, RC

    2016-01-01

    Bottlenose dolphins managed under human care, human beings and Dalmatian dogs are prone to forming urate uroliths. Limiting dietary purine intake limits urate urolith formation in people and dogs because purines are metabolized to uric acid, which is excreted in urine. Managed dolphins develop ammonium urate nephroliths, whereas free-ranging dolphins do not. Free-ranging dolphins consume live fish, whereas managed dolphins consume different species that have been stored frozen and thawed. Differences in the purine content of fish consumed by dolphins under human care versus in the wild may be responsible for the difference in urolith prevalence. Commercially available purine assays measure only four purines, but reported changes in purines during frozen storage suggest that a wider range of metabolites should be measured when comparing fresh and stored fish. A method using high performance liquid chromatography with tandem mass spectrometry was developed to quantify eight purine metabolites in whole fish and squid commonly consumed by dolphins. The coefficient of variation within and among days was sometimes high for purines present in small amounts but was acceptable (≤ 25%) for guanine, hypoxanthine, and inosine, which were present in high concentrations. This expanded assay identified a total purine content up to 2.5 times greater than the total that would be quantified if only four purines were measured. Assuming additional purines are absorbed, these results suggest that additional purine metabolites should be measured to better understand the associated risk when fish or other purine-rich foods are consumed by people or animals prone to developing uroliths. PMID:27904786

  18. A Targeted Metabolomics Assay to Measure Eight Purines in the Diet of Common Bottlenose Dolphins, Tursiops truncatus.

    PubMed

    Ardente, A J; Garrett, T J; Wells, R S; Walsh, M; Smith, C R; Colee, J; Hill, R C

    2016-10-01

    Bottlenose dolphins managed under human care, human beings and Dalmatian dogs are prone to forming urate uroliths. Limiting dietary purine intake limits urate urolith formation in people and dogs because purines are metabolized to uric acid, which is excreted in urine. Managed dolphins develop ammonium urate nephroliths, whereas free-ranging dolphins do not. Free-ranging dolphins consume live fish, whereas managed dolphins consume different species that have been stored frozen and thawed. Differences in the purine content of fish consumed by dolphins under human care versus in the wild may be responsible for the difference in urolith prevalence. Commercially available purine assays measure only four purines, but reported changes in purines during frozen storage suggest that a wider range of metabolites should be measured when comparing fresh and stored fish. A method using high performance liquid chromatography with tandem mass spectrometry was developed to quantify eight purine metabolites in whole fish and squid commonly consumed by dolphins. The coefficient of variation within and among days was sometimes high for purines present in small amounts but was acceptable (≤ 25%) for guanine, hypoxanthine, and inosine, which were present in high concentrations. This expanded assay identified a total purine content up to 2.5 times greater than the total that would be quantified if only four purines were measured. Assuming additional purines are absorbed, these results suggest that additional purine metabolites should be measured to better understand the associated risk when fish or other purine-rich foods are consumed by people or animals prone to developing uroliths.

  19. Divergent prebiotic synthesis of pyrimidine and 8-oxo-purine ribonucleotides

    NASA Astrophysics Data System (ADS)

    Stairs, Shaun; Nikmal, Arif; Bučar, Dejan-Krešimir; Zheng, Shao-Liang; Szostak, Jack W.; Powner, Matthew W.

    2017-05-01

    Understanding prebiotic nucleotide synthesis is a long standing challenge thought to be essential to elucidating the origins of life on Earth. Recently, remarkable progress has been made, but to date all proposed syntheses account separately for the pyrimidine and purine ribonucleotides; no divergent synthesis from common precursors has been proposed. Moreover, the prebiotic syntheses of pyrimidine and purine nucleotides that have been demonstrated operate under mutually incompatible conditions. Here, we tackle this mutual incompatibility by recognizing that the 8-oxo-purines share an underlying generational parity with the pyrimidine nucleotides. We present a divergent synthesis of pyrimidine and 8-oxo-purine nucleotides starting from a common prebiotic precursor that yields the β-ribo-stereochemistry found in the sugar phosphate backbone of biological nucleic acids. The generational relationship between pyrimidine and 8-oxo-purine nucleotides suggests that 8-oxo-purine ribonucleotides may have played a key role in primordial nucleic acids prior to the emergence of the canonical nucleotides of biology.

  20. The Role of Gene Duplication in the Evolution of Purine Nucleotide Salvage Pathways

    NASA Astrophysics Data System (ADS)

    Becerra, Arturo; Lazcano, Antonio

    1998-10-01

    Purine nucleotides are formed de novo by a widespread biochemical route that may be of monophyletic origin, or are synthesized from preformed purine bases and nucleosides through different salvage pathways. Three monophyletic sets of purine salvage enzymes, each of which catalyzes mechanistically similar reactions, can be identified: (a) adenine-, xanthine-, hypoxanthine- and guanine-phosphoribosyltransferases, which are all homologous among themselves, as well as to nucleoside phosphorylases; (b) adenine deaminase, adenosine deaminase, and adenosine monophophate deaminase; and (c) guanine reductase and inosine monophosphate dehydrogenase. These homologies support the idea that substrate specificity is the outcome of gene duplication, and that the purine nucleotide salvage pathways were assembled by a patchwork process that probably took place before the divergence of the three cell domains (Bacteria, Archaea, and Eucarya). Based on the ability of adenine PRTase to catalyze the condensation of PRPP with 4-aminoimidazole-5-carboxamide (AICA), a simpler scheme of purine nucleotide biosynthesis is presented. This hypothetical route requires the prior evolution of PRPP biosynthesis. Since it has been argued that PRPP, nucleosides, and nucleotides are susceptible to hydrolysis, they are very unlikely prebiotic compounds. If this is the case, it implies that many purine salvage pathways appeared only after the evolution of phosphorylated sugar biosynthetic pathways made ribosides available.

  1. Arxula adeninivorans xanthine oxidoreductase and its application in the production of food with low purine content.

    PubMed

    Jankowska, D A; Trautwein-Schult, A; Cordes, A; Hoferichter, P; Klein, C; Bode, R; Baronian, K; Kunze, G

    2013-09-01

    Isolation and characterization of xanthine oxidoreductase and its application in the production of food with low purine content. The A. adeninivorans xanthine oxidoreductase is an inducible enzyme. The best inducers were identified by enzyme activity tests and real-time PCR and used to produce large amounts of the protein. Xanthine oxidoreductase was partially purified and biochemically characterized, showing pH and temperature optimum of 8·5 and 43°C, respectively. The enzyme decreased xanthine and hypoxanthine concentrations in yeast extract and was active simultaneously with other purine-degrading enzymes so that all of the substrates for uric acid production were reduced in a single step. It was shown that induced A. adeninivorans can produce sufficient amount of xanthine dehydrogenase and that the enzyme is able to reduce xanthine and hypoxanthine content in food, and when used in conjunction with other enzymes of the pathway, uric acid concentration is significantly reduced. Reduction in dietary purines is recommended to people suffering from hyperuricemia. Elimination of most purine-rich foods may affect balanced nutrition. Food with lowered purine concentration will assist in controlling the disease. This study is a continuation of previous studies that characterized and overexpressed other enzymes of the purine degradation pathway. © 2013 The Society for Applied Microbiology.

  2. Disruption of host antiviral resistances by gammaherpesvirus tegument proteins with homology to the FGARAT purine biosynthesis enzyme.

    PubMed

    Tsai, Kevin; Messick, Troy E; Lieberman, Paul M

    2015-10-01

    All known gammaherpesviruses encode at least one conserved tegument protein that contains sequence homology to the cellular purine biosynthesis enzyme: phosphoribosylformylglycineamide amidotransferase (FGARAT, or PFAS). While no enzymatic activity have been found on these viral FGARAT-homology proteins (vFGARAT), they are important for disarming host intrinsic antiviral machinery. Most vFGARAT proteins disrupt the intrinsic antiviral response-associated cellular subnuclear structure: ProMyelocytic Leukemia (PML) associated nuclear body (PML-NB). vFGARATs from different viruses target different components of PML-NB to prevent cellular repression of viral infection. In addition, vFGARATs of rhadinoviruses were recently found to oligomerize with the cellular FGARAT to deamidate RIG-I and repress inflammatory cytokine production. In this review we discuss the diverse mechanisms of antiviral response disruption by gammaherpesvirus vFGARATs and the significance of the enzyme homology domain. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Universal full-length nucleosome mapping sequence probe.

    PubMed

    Tripathi, Vijay; Salih, Bilal; Trifonov, Edward N

    2015-01-01

    For the computational sequence-directed mapping of the nucleosomes, the knowledge of the nucleosome positioning motifs - 10-11 base long sequences - and respective matrices of bendability, is not sufficient, since there is no justified way to fuse these motifs in one continuous nucleosome DNA sequence. Discovery of the strong nucleosome (SN) DNA sequences, with visible sequence periodicity allows derivation of the full-length nucleosome DNA bendability pattern as matrix or consensus sequence. The SN sequences of three species (A. thaliana, C. elegans, and H. sapiens) are aligned (512 sequences for each species), and long (115 dinucleotides) matrices of bendability derived for the species. The matrices have strong common property - alternation of runs of purine-purine (RR) and pyrimidine-pyrimidine (YY) dinucleotides, with average period 10.4 bases. On this basis the universal [R,Y] consensus of the nucleosome DNA sequence is derived, with exactly defined positions of respective penta- and hexamers RRRRR, RRRRRR, YYYYY, and YYYYYY.

  4. Antimalarial action of nitrobenzylthioinosine in combination with purine nucleoside antimetabolites.

    PubMed

    Gero, A M; Scott, H V; O'Sullivan, W J; Christopherson, R I

    1989-04-01

    The infection of human erythrocytes by two strains of the human malarial parasite, Plasmodium falciparum (FCQ-27 or the multi-drug-resistant strain K-1), markedly changed the transport characteristics of the nucleosides, adenosine and tubercidin, compared to uninfected erythrocytes. A component of the transport of these nucleosides was insensitive to the classical mammalian nucleoside transport inhibitor nitrobenzylthioinosine (NBMPR). In vitro studies with tubercidin demonstrated ID50 values of 0.43 and 0.51 microM for FCQ-27 and K-1, respectively. In addition, the nucleoside transport inhibitors NBMPR, nitrobenzylthioguanosine (NBTGR), dilazep and dipyridamole also independently exhibited antimalarial activity in vitro. The combination of tubercidin and NBMPR or NBTGR in vitro demonstrated synergistic activity, whilst tubercidin together with dilazep or dipyridamole showed subadditive activity. Analysis by HPLC indicated that NBMPR could permeate the infected cell membrane and provided evidence for the catabolism of NBMPR in vitro, with subsequent alteration of the purine pool in the infected erythrocyte. These observations further indicated the possibility of the utilization of cytotoxic nucleosides against P. falciparum infection in conjunction with a nucleoside transport inhibitor to protect the host tissue.

  5. Purines, a new class of agonists in salivary glands?

    PubMed

    Dehaye, J P; Moran, A; Marino, A

    1999-05-01

    The response of rat submandibular glands to extracellular purines was tested. In crude cellular suspensions, ATP increased the [Ca2+]i mostly by promoting uptake of extracellular calcium. ATP caused the pHi to drop, a response blocked by chloride channel inhibitors. ATP also inhibited the basal and isoproterenol-stimulated activity of the Na+ -K+ -2Cl-cotransporter. These effects were reproduced by benzoyl-ATP, an agonist of ionotropic purinoceptors. In pure ductal suspensions, ATP activated a metabotropic P2Y1 purinergic receptor coupled to phospholipase C and opened a non-specific cation channel coupled to a P2X7 receptor. Activation of these receptors stimulated a Ca2+ -dependent and a Ca2+ -independent phospholipase A2, the latter resulting in kallikrein secretion. We conclude that purinergic agonists can modulate the activity of both acinar and ductal phases of secretion. Activation of metabotropic receptors coupled to phospholipase C could lead to responses resembling those to muscarinic or adrenergic agonists. Activation of ionotropic receptors could stimulate new intracellular responses also involved in secretory function.

  6. Pathophysiological roles for purines: adenosine, caffeine and urate

    PubMed Central

    Morelli, Micaela; Carta, Anna R; Kachroo, Anil; Schwarzschild, Michael A.

    2011-01-01

    The motor symptoms of Parkinson's disease (PD) are due primarily to the degeneration of the dopaminergic neurons in the nigrostriatal pathway. However, several other brain areas and neurotransmitters other than dopamine such as noradrenaline, 5-hydroxytryptamine and acetylcholine are affected in the disease. Moreover, adenosine because of the extensive interaction of its receptors with the dopaminergic system has been implicated in the in the pathophysiology of the disease. Based on the involvement of these nondopaminergic neurotransmitters in PD and the sometimes severe adverse effects that limit the mainstay use of dopamine-based antiparkinsonian treatments, recent assessments have called for a broadening of therapeutic options beyond the traditional dopaminergic drug arsenal. In this review we describe the interactions between dopamine and adenosine receptors that underpin the preclinical and clinical rationale for pursuing adenosine A2A receptor antagonists as symptomatic and potentially neuroprotective treatment of PD. The review will pay particular attention to recent results regarding specific A2A receptor-receptor interactions and recent findings identifying urate, the end product of purine metabolism, as a novel prognostic biomarker and candidate neuroprotectant in PD. PMID:20696321

  7. From formamide to purine: an energetically viable mechanistic reaction pathway.

    PubMed

    Wang, Jing; Gu, Jiande; Nguyen, Minh Tho; Springsteen, Greg; Leszczynski, Jerzy

    2013-02-28

    A step-by-step mechanistic pathway following the transformation of formamide to purine through a five-membered ring intermediate has been explored by density functional theory computations. The highlight of the mechanistic route detailed here is that the proposed pathway represents the simplest reaction pathway. All necessary reactants are generated from a single starting compound, formamide, through energetically viable reactions. Several important reaction steps are involved in this mechanistic route: formylation-dehydration, Leuckart reduction, five- and six-membered ring-closure, and deamination. On the basis of the study of noncatalytic pathways, catalytic water has been found to provide energetically viable step-by-step mechanistic pathways. Among these reaction steps, five-member ring-closure is the rate-determining step. The energy barrier (ca. 42 kcal/mol) of this rate-control step is somewhat lower than the rate-determining step (ca. 44 kcal/mol) for a pyrimidine-based pathway reported previously. The mechanistic pathway reported herein is less energetically demanding than for previously proposed routes to adenine.

  8. [Hyperuricemia and disorders in content of amino acids-purine precursors in patients with autoimmune diseases and gout].

    PubMed

    Nikolenko, Iu I; Siniachenko, O V; Anan'eva, M N; Nikolenko, V Iu; Dubiaga, V V; Shchukin, I N

    2005-06-01

    Patients with system lupus erythematosus, rheumatic arthritis, chronic active hepatitis and gout were found to have considerable hyperuricemia and be decreased in aminoacides content, which are the predecessors of purine. Hyperactivity of xanthineoxidase and POL content were also revealed. The close correlation relation of purine indices of such patients has been observed. The obtained data allow applying methods of correction of immunity system and purine metabolism to these patients by introducing in a complex therapy inhibitors of xanthineoxidase.

  9. Helicobacter pylori Salvages Purines from Extracellular Host Cell DNA Utilizing the Outer Membrane-Associated Nuclease NucT

    PubMed Central

    Liechti, George W.

    2013-01-01

    Helicobacter pylori is a bacterial pathogen that establishes life-long infections in humans, and its presence in the gastric epithelium is strongly associated with gastritis, peptic ulcer disease, and gastric cancer. Having evolved in this specific gastric niche for hundreds of thousands of years, this microbe has become dependent on its human host. Bioinformatic analysis reveals that H. pylori has lost several genes involved in the de novo synthesis of purine nucleotides, and without this pathway present, H. pylori must salvage purines from its environment in order to grow. While the presence and abundance of free purines in various mammalian tissues has been loosely quantified, the concentration of purines present within the gastric mucosa remains unknown. There is evidence, however, that a significant amount of extracellular DNA is present in the human gastric mucosal layer as a result of epithelial cell turnover, and this DNA has the potential to serve as an adequate purine source for gastric purine auxotrophs. In this study, we characterize the ability of H. pylori to grow utilizing only DNA as a purine source. We show that this ability is independent of the ComB DNA uptake system, and that H. pylori utilization of DNA as a purine source is largely influenced by the presence of an outer membrane-associated nuclease (NucT). A ΔnucT mutant exhibits significantly reduced extracellular nuclease activity and is deficient in growth when DNA is provided as the sole purine source in laboratory growth media. These growth defects are also evident when this nuclease mutant is grown in the presence of AGS cells or in purine-free tissue culture medium that has been conditioned by AGS cells in the absence of fetal bovine serum. Taken together, these results indicate that the salvage of purines from exogenous host cell DNA plays an important role in allowing H. pylori to meet its purine requirements for growth. PMID:23893109

  10. Non-random distribution and co-localization of purine/pyrimidine-encoded information and transcriptional regulatory domains.

    PubMed

    Povinelli, C M

    1992-01-01

    In order to detect sequence-based information predictive for the location of eukaryotic transcriptional regulatory domains, the frequencies and distributions of the 36 possible purine/pyrimidine reverse complement hexamer pairs was determined for test sets of real and random sequences. The distribution of one of the hexamer pairs (RRYYRR/YYRRYY, referred to as M1) was further examined in a larger set of sequences (> 32 genes, 230 kb). Predominant clusters of M1 and the locations of eukaryotic transcriptional regulatory domains were found to be associated and non-randomly distributed along the DNA consistent with a periodicity of approximately 1.2 kb. In the context of higher ordered chromatin this would align promoters, enhancers and the predominant clusters of M1 longitudinally along one face of a 30 nm fiber. Using only information about the distribution of the M1 motif, 50-70% of a sequence could be eliminated as being unlikely to contain transcriptional regulatory domains with an 87% recovery of the regulatory domains present.

  11. Lactobacillus gasseri PA-3 Uses the Purines IMP, Inosine and Hypoxanthine and Reduces their Absorption in Rats.

    PubMed

    Yamada, Naruomi; Saito-Iwamoto, Chizuru; Nakamura, Marie; Soeda, Misato; Chiba, Yoshika; Kano, Hiroshi; Asami, Yukio

    2017-03-08

    Excessive intake of purine-rich foods elevates serum levels of uric acid. Animal and fish meats contain high amounts of inosine and its related purines, and the reduction of taking those purines is crucial for the improvement of serum uric acid levels. We previously showed that Lactobacillus gasseri PA-3 (PA-3) incorporates adenosine and its related purines and that oral treatment with PA-3 reduced adenosine absorption in rats. This study investigated whether PA-3 also incorporates IMP (inosine 5'-monophosphate), inosine, and hypoxanthine, and whether it reduces their absorption in rats. PA-3 was incubated in vitro with radioisotope (RI)-labeled IMP, inosine, and hypoxanthine, and the incorporation of these compounds by PA-3 was evaluated. In addition, rats were orally administered PA-3 along with RI-labeled inosine 5'-monophosphate, inosine, or hypoxanthine, and the ability of PA-3 to attenuate the absorption of these purines was determined. PA-3 incorporated all three purines and displayed greater proliferation in the presence than in the absence of these purines. Oral administration of PA-3 to rats reduced the absorption of IMP, inosine, and hypoxanthine. These results indicate that PA-3 reduces the absorption of purines contained in foods and it is expected that PA-3 contributes attenuation of the excessive intake of dietary purines.

  12. Lactobacillus gasseri PA-3 Uses the Purines IMP, Inosine and Hypoxanthine and Reduces Their Absorption in Rats

    PubMed Central

    Yamada, Naruomi; Saito-Iwamoto, Chizuru; Nakamura, Marie; Soeda, Misato; Chiba, Yoshika; Kano, Hiroshi; Asami, Yukio

    2017-01-01

    Excessive intake of purine-rich foods elevates serum levels of uric acid. Animal and fish meats contain high amounts of inosine and its related purines, and the reduction of taking those purines is crucial for the improvement of serum uric acid levels. We previously showed that Lactobacillus gasseri PA-3 (PA-3) incorporates adenosine and its related purines and that oral treatment with PA-3 reduced adenosine absorption in rats. This study investigated whether PA-3 also incorporates IMP (inosine 5′-monophosphate), inosine, and hypoxanthine, and whether it reduces their absorption in rats. PA-3 was incubated in vitro with radioisotope (RI)-labeled IMP, inosine, and hypoxanthine, and the incorporation of these compounds by PA-3 was evaluated. In addition, rats were orally administered PA-3 along with RI-labeled inosine 5′-monophosphate, inosine, or hypoxanthine, and the ability of PA-3 to attenuate the absorption of these purines was determined. PA-3 incorporated all three purines and displayed greater proliferation in the presence than in the absence of these purines. Oral administration of PA-3 to rats reduced the absorption of IMP, inosine, and hypoxanthine. These results indicate that PA-3 reduces the absorption of purines contained in foods and it is expected that PA-3 contributes attenuation of the excessive intake of dietary purines. PMID:28282902

  13. Autoimmune dysregulation and purine metabolism in adenosine deaminase deficiency.

    PubMed

    Sauer, Aisha Vanessa; Brigida, Immacolata; Carriglio, Nicola; Aiuti, Alessandro

    2012-01-01

    Genetic defects in the adenosine deaminase (ADA) gene are among the most common causes for severe combined immunodeficiency (SCID). ADA-SCID patients suffer from lymphopenia, severely impaired cellular and humoral immunity, failure to thrive, and recurrent infections. Currently available therapeutic options for this otherwise fatal disorder include bone marrow transplantation (BMT), enzyme replacement therapy with bovine ADA (PEG-ADA), or hematopoietic stem cell gene therapy (HSC-GT). Although varying degrees of immune reconstitution can be achieved by these treatments, breakdown of tolerance is a major concern in ADA-SCID. Immune dysregulation such as autoimmune hypothyroidism, diabetes mellitus, hemolytic anemia, and immune thrombocytopenia are frequently observed in milder forms of the disease. However, several reports document similar complications also in patients on long-term PEG-ADA and after BMT or GT treatment. A skewed repertoire and decreased immune functions have been implicated in autoimmunity observed in certain B-cell and/or T-cell immunodeficiencies, but it remains unclear to what extent specific mechanisms of tolerance are affected in ADA deficiency. Herein we provide an overview about ADA-SCID and the autoimmune manifestations reported in these patients before and after treatment. We also assess the value of the ADA-deficient mouse model as a useful tool to study both immune and metabolic disease mechanisms. With focus on regulatory T- and B-cells we discuss the lymphocyte subpopulations particularly prone to contribute to the loss of self-tolerance and onset of autoimmunity in ADA deficiency. Moreover we address which aspects of immune dysregulation are specifically related to alterations in purine metabolism caused by the lack of ADA and the subsequent accumulation of metabolites with immunomodulatory properties.

  14. Effects of NAD at purine receptors in isolated blood vessels.

    PubMed

    Alefishat, E; Alexander, S P H; Ralevic, V

    2015-03-01

    Nicotinamide adenine dinucleotide (NAD) belongs to the family of naturally occurring adenine dinucleotides, best known for their various intracellular roles. However, there is evidence that they can also be released from cells to act as novel extracellular signalling molecules. Relatively little is known about the extracellular actions of NAD, especially in the cardiovascular system. The present study investigated the actions of NAD in the rat thoracic aorta, porcine coronary artery and porcine mesenteric arteries, mounted in organ baths for isometric tension recording. In the rat thoracic aorta and porcine coronary artery, NAD caused endothelium-independent concentration-dependent vasorelaxations which were unaffected by palmitoylCoA, a P2Y1 receptor antagonist, but which were blocked by CGS15943, a non-selective adenosine receptor antagonist. In the porcine coronary artery, NAD-evoked relaxations were abolished by SCH58261, a selective A2A receptor antagonist. In the rat thoracic aorta, NAD-evoked relaxations were attenuated by A2A receptor antagonism with SCH58261 but were unaffected by an A2B receptor antagonist, MRS1754. In contrast, in the porcine mesenteric artery, NAD-evoked endothelium-independent contractions, which were unaffected by a P2 receptor antagonist, suramin, or by NF449, a P2X1 receptor antagonist, but were attenuated following P2X receptor desensitisation with αβ-meATP. In conclusion, the present results show that NAD can alter vascular tone through actions at purine receptors in three different arteries from two species; its molecular targets differ according to the type of blood vessel.

  15. Metabolic Engineering of the Purine Pathway for Riboflavin Production in Ashbya gossypii†

    PubMed Central

    Jiménez, Alberto; Santos, María A.; Pompejus, Markus; Revuelta, José L.

    2005-01-01

    Purine nucleotides are essential precursors for living organisms because they are involved in many important processes, such as nucleic acid synthesis, energy supply, and the biosynthesis of several amino acids and vitamins such as riboflavin. GTP is the immediate precursor for riboflavin biosynthesis, and its formation through the purine pathway is subject to several regulatory mechanisms in different steps. Extracellular purines repress the transcription of most genes required for de novo ATP and GTP synthesis. Additionally, three enzymes of the pathway, phosphoribosyl pyrophosphate (PRPP) amidotransferase, adenylosuccinate synthetase, and IMP dehydrogenase, are subject to feedback inhibition by their end products. Here we report the characterization and manipulation of the committed step in the purine pathway of the riboflavin overproducer Ashbya gossypii. We report that phosphoribosylamine biosynthesis in A. gossypii is negatively regulated at the transcriptional level by extracellular adenine. Furthermore, we show that ATP and GTP exert a strong inhibitory effect on the PRPP amidotransferase from A. gossypii. We constitutively overexpressed the AgADE4 gene encoding PRPP amidotransferase in A. gossypii, thereby abolishing the adenine-mediated transcriptional repression. In addition, we replaced the corresponding residues (aspartic acid310, lysine333, and alanine417) that have been described to be important for PRPP amidotransferase feedback inhibition in other organisms by site-directed mutagenesis. With these manipulations, we managed to enhance metabolic flow through the purine pathway and to increase the production of riboflavin in the triple mutant strain 10-fold (228 mg/liter). PMID:16204483

  16. Coordinate developmental regulation of purine catabolic enzyme expression in gastrointestinal and postimplantation reproductive tracts

    PubMed Central

    1991-01-01

    Using histochemical detection, we have visualized in situ the complete metabolic pathway for the degradation of purine nucleotides. From the tongue to the ileum, diverse epithelial cell types lining the lumen of the mouse gastrointestinal (GI) tract strongly coexpress each of the five key purine catabolic enzymes. Dramatic increases in the expression of each enzyme occurred during postnatal maturation of the GI tract. Using in situ hybridization, an intense accumulation of adenosine deaminase (ADA) mRNA was detected only within GI epithelial cells undergoing postmitotic differentiation. In a similar manner, at the developing maternal-fetal interface, high level expression of the purine catabolic pathway also occurred in a unique subset of maternal decidual cells previously known to express high levels of alkaline phosphatase and ADA. This induction occurred almost immediately after implantation in the periembryonic maternal decidual cells, shortly thereafter in antimesometrial decidual cells, and later in cells of the placental decidua basalis: all of which contain cell types thought to be undergoing programmed cell death. The expression of the pathway at the site of embryo implantation appears to be critical because its pharmacologic inhibition during pregnancy has been found to be embryolethal or teratogenic. Purine destruction at these nutritional interfaces (placenta and gastrointestinal tract) seem to override any potential economy of purine salvage, and may represent biochemical adaptation to nucleic acid breakdown occurring in the context of dietary digestion or extensive programmed cell death. PMID:1918135

  17. Extracellular conversion of guanine-based purines to guanosine specifically enhances astrocyte glutamate uptake.

    PubMed

    Frizzo, Marcos Emílio dos Santos; Antunes Soares, Félix Alexandre; Dall'Onder, Leonara Patrícia; Lara, Diogo Rizzato; Swanson, Raymond A; Souza, Diogo Onofre

    2003-05-16

    Guanosine (GUO) has been shown to stimulate glutamate uptake in primary astrocyte cultures. The purpose of this study was to determine the effect and specificity of guanine- or adenine-based purines on glutamate and GABA uptake in cultured astrocytes. Stimulatory effect on glutamate uptake was observed with GUO, GMP or GTP. Simultaneous exposure with these guanine-based purines did not show an additive effect. We also investigated a possible interconversion of guanine-based purines during incubation time. Action by GTP was excluded since the hydrolysis resistant GTP analog, GMP-PNP did not stimulate glutamate uptake. Addition of an ecto-5'-nucleotidase inhibitor abolished GMP-stimulatory effect on glutamate uptake, without affecting GUO action. Taken together, these results suggest that GUO is the guanine-based purines responsible for glutamate uptake activation. In addition, the stimulatory effect on glutamate uptake was not observed with adenine-based purines. Moreover, GABA uptake was not activated by GUO. These results point to specificity in the interaction between GUO and the astrocyte glutamate uptake system.

  18. Which Electronic and Structural Factors Control the Photostability of DNA and RNA Purine Nucleobases?

    NASA Astrophysics Data System (ADS)

    Pollum, Marvin; Reichardt, Christian; Crespo-Hernández, Carlos E.; Martínez-Fernández, Lara; Corral, Inés; Rauer, Clemens; Mai, Sebastian; Marquetand, Philipp; González, Leticia

    2015-06-01

    Following ultraviolet excitation, the canonical purine nucleobases, guanine and adenine, are able to efficiently dissipate the absorbed energy within hundreds of femtoseconds. This property affords these nucleobases with great photostability. Conversely, non-canonical purine nucleobases exhibit high fluorescence quantum yields or efficiently populate long-lived triplet excited states from which chemistry can occur. Using femtosecond broadband transient absorption spectroscopy in combination with ab initio static and surface hopping dynamics simulations we have determined the electronic and structural factors that regulate the excited state dynamics of the purine nucleobase derivatives. Importantly, we have uncovered that the photostability of the guanine and adenine nucleobases is not due to the structure of the purine core itself and that the substituent at the C6 position of the purine nucleobase plays a more important role than that at the C2 position in the ultrafast relaxation of deleterious electronic energy. [The authors acknowledge the CAREER program of the National Science Foundation (Grant No. CHE-1255084) for financial support.

  19. Identification of a chemoreceptor that specifically mediates chemotaxis toward metabolizable purine derivatives.

    PubMed

    Fernández, Matilde; Morel, Bertrand; Corral-Lugo, Andrés; Krell, Tino

    2016-01-01

    Chemotaxis is an essential mechanism that enables bacteria to move toward favorable ecological niches. Escherichia coli, the historical model organism for studying chemotaxis, has five well-studied chemoreceptors. However, many bacteria with different lifestyle have more chemoreceptors, most of unknown function. Using a high throughput screening approach, we identified a chemoreceptor from Pseudomonas putida KT2440, named McpH, which specifically recognizes purine and its derivatives, adenine, guanine, xanthine, hypoxanthine and uric acid. The latter five compounds form part of the purine degradation pathway, permitting their use as sole nitrogen sources. Isothermal titration calorimetry studies show that these six compounds bind McpH-Ligand Binding Domain (LBD) with very similar affinity. In contrast, non-metabolizable purine derivatives (caffeine, theophylline, theobromine), nucleotides, nucleosides or pyrimidines are unable to bind McpH-LBD. Mutation of mcpH abolished chemotaxis toward the McpH ligands identified - a phenotype that is restored by complementation. This is the first report on bacterial chemotaxis to purine derivatives and McpH the first chemoreceptor described that responds exclusively to intermediates of a catabolic pathway, illustrating a clear link between metabolism and chemotaxis. The evolution of McpH may reflect a saprophytic lifestyle, which would have exposed the studied bacterium to high concentrations of purines produced by nucleic acid degradation.

  20. Drosophila melanogaster Prat, a Purine de Novo Synthesis Gene, Has a Pleiotropic Maternal-Effect Phenotype

    PubMed Central

    Malmanche, Nicolas; Clark, Denise V.

    2004-01-01

    In Drosophila melanogaster, two genes, Prat and Prat2, encode the enzyme, amidophosphoribosyltransferase, that performs the first and limiting step in purine de novo synthesis. Only Prat mRNA is present in the female germline and 0- to 2-hr embryos prior to the onset of zygotic transcription. We studied the maternal-effect phenotype caused by Prat loss-of-function mutations, allowing us to examine the effects of decreased purine de novo synthesis during oogenesis and the early stages of embryonic development. In addition to the purine syndrome previously characterized, we found that Prat mutant adult females have a significantly shorter life span and are conditionally semisterile. The semisterility is associated with a pleiotropic phenotype, including egg chamber defects and later effects on embryonic and larval viability. Embryos show mitotic synchrony and/or nuclear content defects at the syncytial blastoderm stages and segmentation defects at later stages. The semisterility is partially rescued by providing Prat mutant females with an RNA-enriched diet as a source of purines. Our results suggest that purine de novo synthesis is a limiting factor during the processes of cellular or nuclear proliferation that take place during egg chamber and embryonic development. PMID:15611171

  1. Determination of purine contents in different parts of pork and beef by high performance liquid chromatography.

    PubMed

    Rong, Shengzhong; Zou, Lina; Zhang, Yannan; Zhang, Guangteng; Li, Xiaoxia; Li, Miaojing; Yang, Fenghua; Li, Chunmei; He, Yingjuan; Guan, Hongjun; Guo, Yupeng; Wang, Dong; Cui, Xinyu; Ye, Hongting; Liu, Fenghai; Pan, Hongzhi; Yang, Yuexin

    2015-03-01

    Determination of adenine, hypoxanthine, guanine and xanthine in different parts of pork and beef using high performance liquid chromatography was described. Chromatographic separation was carried out on Waters Atlantis T3 column (4.6 mm × 250 mm × 5 μm) with column temperature at 30 °C. The mobile phase contained 99% 10.0 mmol/L ammonium formate solution at pH 3.6 and 1.0% methanol. Chromatography was achieved at a flow rate of 1.0 mL/min and detection wavelength at 254 nm. The results indicated that total purine amounts in pork rump and beef sirloin were higher than those in other parts (P<0.05). The principal purine bases were hypoxanthine and adenine, and hypoxanthine content was the most highest in all samples (P<0.05). As pork rump and beef sirloin contain considerable amounts of total purine and uricogenic purine base, we suggest that excess consumption of them be avoid, whereas pork loin chop and beef rib eye are more suitable for a low-purine diet. Copyright © 2014 Elsevier Ltd. All rights reserved.

  2. Triple helix formation with purine-rich phosphorothioate-containing oligonucleotides covalently linked to an acridine derivative.

    PubMed Central

    Lacoste, J; François, J C; Hélène, C

    1997-01-01

    Purine-rich (GA)- and (GT)-containing oligophosphorothioates were investigated for their triplex-forming potential on a 23 bp DNA duplex target. In our system, GA-containing oligophosphorothioates (23mer GA-PS) were capable of triplex formation with binding affinities lower than (GA)-containing oligophosphodiesters (23mer GA-PO). The orientation of the third strand 23mers GA-PS and GA-PO was antiparallel to the purine strand of the duplex DNA target. In contrast, (GT)-containing oligophosphorothioates (23mer GT-PS) did not support triplex formation in either orientation, whereas the 23mer GT-PO oligophosphodiester demonstrated triplex formation in the antiparallel orientation. GA-PS oligonucleotides, in contrast to GT-PS oligonucleotides, were capable of self-association, but these self-associated structures exhibited lower stabilities than those formed with GA-PO oligonucleotides, suggesting that homoduplex formation (previously described for the 23mer GA-PO sequence by Noonberg et al.) could not fully account for the decrease in triplex stability when phosphorothioate linkages were used. The 23mer GA-PS oligonucleotide was covalently linked via its 5'-end to an acridine derivative (23mer Acr-GA-PS). In the presence of potassium cations, this conjugate demonstrated triplex formation with higher binding affinity than the unmodified 23mer GA-PS oligonucleotide and even than the 23mer GA-PO oligonucleotide. A (GA)-containing oligophosphodiester with two phosphorothioate linkages at both the 5'- and 3'-ends exhibited similar binding affinity to duplex DNA compared with the unmodified GA-PO oligophosphodiester. This capped oligonucleotide was more resistant to nucleases than the GA-PO oligomer and thus represents a good alternative for ex vivo applications of (GA)-containing, triplex-forming oligonucleotides, allowing a higher binding affinity for its duplex target without rapid cellular degradation. PMID:9115367

  3. Polymerase recognition of synthetic oligodeoxyribonucleotides incorporating degenerate pyrimidine and purine bases

    PubMed Central

    Hill, F.; Loakes, D.; Brown, D. M.

    1998-01-01

    A universal base that is capable of substituting for any of the four natural bases in DNA would be of great utility in both mutagenesis and recombinant DNA experiments. This paper describes the properties of oligonucleotides incorporating two degenerate bases, the pyrimidine base 6H,8H-3,4-dihydropyrimido[4,5-c][1,2]oxazin-7-one and the purine base N6-methoxy-2,6-diaminopurine, designated P and K, respectively. An equimolar mixture of the analogues P and K (called M) acts, in primers, as a universal base. The thermal stability of oligonucleotide duplexes were only slightly reduced when natural bases were replaced by P or K. Templates containing the modified bases were copied by Taq polymerase; P behaved as thymine in 60% of copying events and as cytosine in 40%, whereas K behaved as if it were guanine (13%) or adenine (87%). The dUTPase gene of Caenorhabditis elegans, which we have found to contain three nonidentical homologous repeats, was used as a model system to test the use of these bases in primers for DNA synthesis. A pair of oligodeoxyribonucleotides, each 20 residues long and containing an equimolar mixture of P and K at six positions, primed with high specificity both T7 DNA polymerase in sequencing reactions and Taq polymerase in PCRs; no nonspecific amplification was obtained on genomic DNA of C. elegans. Use of P and K can significantly reduce the complexity of degenerate oligonucleotide mixtures, and when used together, P and K can act as a universal base. PMID:9539724

  4. The Formation of Nucleobases from the Ultraviolet Photoirradiation of Purine in Simple Astrophysical Ice Analogues

    NASA Astrophysics Data System (ADS)

    Materese, Christopher K.; Nuevo, Michel; Sandford, Scott A.

    2017-08-01

    Nucleobases are the informational subunits of RNA and DNA and are essential to all known forms of life. The nucleobases can be divided into two groups of molecules: the pyrimidine-based compounds that include uracil, cytosine, and thymine, and the purine-based compounds that include adenine and guanine. Previous work in our laboratory has demonstrated that uracil, cytosine, thymine, and other nonbiological, less common nucleobases can form abiotically from the UV photoirradiation of pyrimidine in simple astrophysical ice analogues containing combinations of H2O, NH3, and CH4. In this work, we focused on the UV photoirradiation of purine mixed with combinations of H2O and NH3 ices to determine whether or not the full complement of biological nucleobases can be formed abiotically under astrophysical conditions. Room-temperature analyses of the resulting photoproducts resulted in the detection of adenine, guanine, and numerous other functionalized purine derivatives.

  5. Functionalized Solid Electrodes for Electrochemical Biosensing of Purine Nucleobases and Their Analogues: A Review

    PubMed Central

    Sharma, Vimal Kumar; Jelen, Frantisek; Trnkova, Libuse

    2015-01-01

    Interest in electrochemical analysis of purine nucleobases and few other important purine derivatives has been growing rapidly. Over the period of the past decade, the design of electrochemical biosensors has been focused on achieving high sensitivity and efficiency. The range of existing electrochemical methods with carbon electrode displays the highest rate in the development of biosensors. Moreover, modification of electrode surfaces based on nanomaterials is frequently used due to their extraordinary conductivity and surface to volume ratio. Different strategies for modifying electrode surfaces facilitate electron transport between the electrode surface and biomolecules, including DNA, oligonucleotides and their components. This review aims to summarize recent developments in the electrochemical analysis of purine derivatives, as well as discuss different applications. PMID:25594595

  6. The effect of purine and pyrimidine analogues and virazole on adenovirus replication.

    PubMed

    Scheffler, P; Haghchenas, D; Wigand, R

    1975-04-01

    The multiplication of adenovirus 19 in HeLa cells was inhibited by various purine and pyrimidine analogues and by virazole. The formation of infectious virus and of capsid proteins (haemagglutin, group-specific complement-fixing antigen) was inhibited to the same degree, while the viral cytopathic effect (CPE) was not inhibited. The reversibility of the inhibition after removal of the substances was more complete for purine than for pyrimidine analogues. The inhibition was counteracted by simulataneous addition of the corresponding nucleosides. Adenosine was more effected than guanosine against purine analogues; both were partially effective against virazole, but none of them against arabinofuranosyladenine. The time-dependence of inhibition, the ensuing eclipse period after removal of the inhibitors, and the successive application of two inhibitors led to the conclusion that most of them affect the viral multiplication mainly by inhibition of DNA synthesis. Azacytidine inhibits the synthesis of structural proteins as well.

  7. Analysis of mixtures of purines and pyrimidines by first- and second-derivative ultraviolet spectrometry.

    PubMed

    Aaron, J J; Gaye, M D

    1988-07-01

    Zero-order, first-derivative and second-derivative ultraviolet absorption spectra of a series of purines, pyrimidines and their binary mixtures in aqueous solution have been recorded at 298 K. It is shown that second-derivative spectra can be used for the identification of eight mixtures of purines and pyrimidines. Several graphical procedures are tested for evaluating derivative spectra in quantitative measurements of single compounds and mixtures. Linear log-log calibration plots are obtained with correlation coefficients generally larger than 0.99. Second-derivative spectra appear to provide a precise and simple method for determination of purines and pyrimidines, at concentrations ranging between 5 x 10(-6) and 5 x 10(-4)M.

  8. Three-dimensional structure of E. Coli purine nucleoside phosphorylase at 0.99 Å resolution

    NASA Astrophysics Data System (ADS)

    Timofeev, V. I.; Abramchik, Yu. A.; Zhukhlistova, N. E.; Muravieva, T. I.; Esipov, R. S.; Kuranova, I. P.

    2016-03-01

    Purine nucleoside phosphorylases (PNPs) catalyze the reversible phosphorolysis of nucleosides and are key enzymes involved in nucleotide metabolism. They are essential for normal cell function and can catalyze the transglycosylation. Crystals of E. coli PNP were grown in microgravity by the capillary counterdiffusion method through a gel layer. The three-dimensional structure of the enzyme was determined by the molecular-replacement method at 0.99 Å resolution. The structural features are considered, and the structure of E. coli PNP is compared with the structures of the free enzyme and its complexes with purine base derivatives established earlier. A comparison of the environment of the purine base in the complex of PNP with formycin A and of the pyrimidine base in the complex of uridine phosphorylase with thymidine revealed the main structural features of the base-binding sites. Coordinates of the atomic model determined with high accuracy were deposited in the Protein Data Bank (PDB_ID: 4RJ2).

  9. Purine enzyme activities in recent onset rheumatoid arthritis: are there differences between patients and healthy controls?

    PubMed Central

    Stolk, J N; Boerbooms, A M; De Abreu, R A; Kerstens, P J; de Koning, D G; de Graaf, R; Mulder, J; van de Putte, L B

    1996-01-01

    OBJECTIVE: Purine enzyme activities may predict the effectiveness of azathioprine treatment and be associated with increased deaths from infectious diseases. In rheumatoid arthritis, patients show variable responses to azathioprine and a higher percentage of death is caused by infections. The aim of the study was to investigate possible rheumatoid arthritis associated abnormalities of purine enzyme activities by measuring several of these enzymes in patients with recent onset rheumatoid arthritis before treatment with disease modifying antirheumatic drugs or prednisone. METHODS: 23 patients with recent onset rheumatoid arthritis and 28 healthy controls were studied. Activities of the enzymes 5'-nucleotidase, purine nucleoside phosphorylase (PNP), hypoxanthine guanine phosphoribosyltransferase (HGPRT), and thiopurine methyltransferase (TPMT) were measured. Assessment of disease activity and blood sampling for routine measurements and HLA typing were done simultaneously. RESULTS: Purine enzyme activities did not differ between patients and healthy controls. Enzyme activities had no significant relations with indices of disease activity or rheumatoid factor titre or with the rheumatoid arthritis associated HLA types. Activity of 5'nucleotidase decreased with age (P < or = 0.05) and was lower by about 27% (P = 0.007) in males than in females. CONCLUSIONS: In rheumatoid arthritis patients, neither the variability in azathioprine effectiveness nor the increased death rate from infections can be explained by pre-existing abnormalities in the activities of the purine enzymes 5'-nucleotidase, PNP, HGPRT, or TPMT at an early stage of the disease, before disease modifying antirheumatic drugs or prednisone treatment. Besides adjustment for age, results of studies involving purine 5' nucleotidase activity should also be adjusted for sex. PMID:8984938

  10. Inhibitors of the purine salvage pathway: a valuable approach for antiprotozoal chemotherapy?

    PubMed

    Berg, M; Van der Veken, P; Goeminne, A; Haemers, A; Augustyns, K

    2010-01-01

    For many years, the purine salvage pathway of parasitic protozoa has been regarded as an attractive chemotherapeutic target. Parasitic protozoa lack de novo synthesis and rely entirely on the purine salvage pathway to meet their purine demands. Because of the great phylogenetic difference between parasite and host, there are often sufficient distinctions that can be exploited to design specific inhibitors for the parasitic enzymes. As a result, this pathway has been thoroughly investigated over the last twenty years. It is only quite recently that the genome studies of Trypanosoma, Leishmania and Plasmodium have been published. Based on these genomic data however, the existence of by-pass mechanisms by other enzymes and transporter systems could be suggested. Taking into account such proposition, the question might arise as to whether inhibition of a single salvage enzyme will be able or not to cause parasite death or growth arrest. In this paper, the key enzymes in the purine salvage pathways of relevant pathogenic species from the genera Trypanosoma, Leishmania and Plasmodium are reviewed. Their potential as drug targets is critically evaluated and where possible, correlated to literature data on antiparasitic activity of their inhibitors. While many studies over the past ten years have yielded contradictory results, this review attempts to clarify these findings by discussing the latest elements of progress in the field. Additionally, as part of a broader discussion on substrate analogue types of inhibitors, special attention is paid to iminoribitol derivatives, serving as transition state analogues of nucleoside-processing enzymes and comprising the most potent inhibitors reported for purine salvage enzymes. More specifically, the development of three generations of immucillins and a newer series of N-(arylmethyl-) substituted iminoribitol derivatives will be discussed. Finally, this review also covers subversive substrates of salvage enzymes: compounds that

  11. Enhancement of the therapeutic effectiveness of methotrexate and protection of normal proliferating tissues with purines and pyrimidines.

    PubMed

    Harrap, K R; Taylor, G A; Browman, G P

    1977-07-01

    Mice can be protected against the toxicity arising from lethal doses of methotrexate with purine and pyrimidine combinations, but not with pyrimidine alone. Furthermore, methotrexate treatment of tumour-bearing mice, conjunction with purine/pyrimidine protection, can be more effective than conventional metotrexate/folinic acid treatment.

  12. Determination of four different purines and their content change in seafood by high-performance liquid chromatography.

    PubMed

    Qu, Xin; Sui, Jianxin; Mi, Nasha; Lin, Hong

    2017-01-01

    Seafood is regarded as a high-purine food that may induce gout, which has attracted extensive attention concerning its safety. Therefore, the aim of this study was to develop a simple and reliable method to determine the purine content in seafood and its change during storage to offer consumers healthy diet information. Chromatographic separation was carried out using Waters Atlantis dC18 column, and potassium phosphate monobasic solution (0.02 mol L(-1) , pH 3.6) as a mobile phase. The average recovery yields of four purines were 91.5-105.0%, and relative standard deviation values were around 1.8-6.5%. Shrimp and snail contained higher amounts of purine than fish and bivalves; the livers and skins of fish contained higher amounts of purine than muscles; and the main purine varied depending on the type of seafood. Also, purine content of seafood changed during storage. The purine content of seafood differed depending on species, body part and degree of freshness, which could recommend consumers a healthy diet, especially for people with hyperuricemia and gout. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  13. Genetic and proteomic analyses of a Xanthomonas campestris pv. campestris purC mutant deficient in purine biosynthesis and virulence.

    PubMed

    Yuan, Zhihui; Wang, Li; Sun, Shutao; Wu, Yao; Qian, Wei

    2013-09-20

    Bacterial proliferation in hosts requires activation of a number of housekeeping pathways, including purine de novo biosynthesis. Although inactivation of purine biosynthesis genes can attenuate virulence, it is unclear which biochemical or virulence factors are associated with the purine biosynthesis pathway in vivo. We report that inactivation of purC, a gene encoding phosphoribosylaminoimidazole-succinocarboxamide synthase, caused complete loss of virulence in Xanthomonas campestris pv. campestris, the causal agent of black rot disease of cruciferous plants. The purC mutant was a purine auxotroph; it could not grow on minimal medium, whereas addition of purine derivatives, such as hypoxanthine or adenine plus guanine, restored growth of the mutant. The purC mutation also significantly enhanced the production of an unknown purine synthesis associated pigment and extracellular polysaccharides by the bacterium. In addition, comparative proteomic analyses of bacteria grown on rich and minimal media revealed that the purC mutation affected the expression levels of diverse proteins involved in purine and pyrimidine synthesis, carbon and energy metabolisms, iron uptake, proteolysis, protein secretion, and signal transduction. These results provided clues to understanding the contributions of purine synthesis to bacterial virulence and interactions with host immune systems.

  14. Purine salvage pathways of Bacillus subtilis and effect of guanine on growth of GMP reductase mutants.

    PubMed Central

    Endo, T; Uratani, B; Freese, E

    1983-01-01

    We have isolated numerous mutants containing mutations in the salvage pathways of purine synthesis. The mutations cause deficiencies in adenine phosphoribosyltransferase (adeF), in hypoxanthine-guanine phosphoribosyltransferase (guaF), in adenine deaminase (adeC), in inosine-guanosine phosphorylase, (guaP), and in GMP reductase (guaC). The physiological properties of mutants containing one or more of these mutations and corresponding enzyme measurements have been used to derive a metabolic chart of the purine salvage pathway of Bacillus subtilis. PMID:6408059

  15. The role of purine degradation in methane biosynthesis and energy production in Methanococcus vannielii. Progress report

    SciTech Connect

    DeMoll, E.

    1998-11-01

    Firstly, characterization of a purine degrading pathway in Methanococcus vannielii was determined. The pathway is similar to that described for Clostridia. The M. vannielli pathway differs in a few respects from the Clostridial pathway. The pathway of Clostridia uses tetrahydrofolic acid (THF), whereas the pathway of M. vannielii uses tetrahydromethanopterin (H{sub 4}MPt) as a cofactor in the transfer of both the formimino moiety of formiminoglycine and apparently in the cleavage of glycine by a glycin decarboxylase type mechanism that is dependent upon at least H{sub 4}MPt and either NAD{sup +} or NADP{sup +}. Secondly, the relationship of purine degradation to methanogenesis was investigated.

  16. Synthesis of cycloalkyl substituted purine nucleosides via a metal-free radical route.

    PubMed

    Wang, Dong-Chao; Xia, Ran; Xie, Ming-Sheng; Qu, Gui-Rong; Guo, Hai-Ming

    2016-05-04

    An efficient route to synthesize cycloalkyl substituted purine nucleosides was developed. This metal-free C-H activation was accomplished by a tBuOOtBu initiated radical reaction. By adjusting the amount of tBuOOtBu and reaction time, the selective synthesis of C6-monocycloalkyl or C6,C8-dicycloalkyl substituted purine nucleosides could be realized. Furthermore, uracil and related nucleosides were also suitable substrates, giving the C5-cyclohexyl substituted uracil derivatives in good yields with excellent regioselectivities.

  17. meta-C-H Bromination on Purine Bases by Heterogeneous Ruthenium Catalysis.

    PubMed

    Warratz, Svenja; Burns, David J; Zhu, Cuiju; Korvorapun, Korkit; Rogge, Torben; Scholz, Julius; Jooss, Christian; Gelman, Dmitri; Ackermann, Lutz

    2017-02-01

    Methods for positionally selective remote C-H functionalizations are in high demand. Herein, we disclose the first heterogeneous ruthenium catalyst for meta-selective C-H functionalizations, which enabled remote halogenations with excellent site selectivity and ample scope. The versatile heterogeneous Ru@SiO2 catalyst was broadly applicable and could be easily recovered and reused, which set the stage for the direct fluorescent labeling of purines. In contrast to palladium, rhodium, iridium, or cobalt complexes, solely the ruthenium catalysis manifold provided access to meta-halogenated purine derivatives, illustrating the unique power of ruthenium C-H activation catalysis.

  18. Selective DNA purine base photooxidation by bis-terdentate iridium(III) polypyridyl and cyclometalated complexes.

    PubMed

    Jacques, Alexandre; Kirsch-De Mesmaeker, Andrée; Elias, Benjamin

    2014-02-03

    Two bis-terdentate iridium(III) complexes with polypyridyl and cyclometalated ligands have been prepared and characterized. Their spectroscopic and electrochemical properties have been studied, and a photophysical scheme addressing their properties is proposed. Different types of excited states have been considered to account for the deactivation processes in each complex. Interestingly, in the presence of mono- or polynucleotides, a photoinduced electron-transfer process from a DNA purine base (i.e., guanine or adenine) to the excited complex is shown through luminescence quenching experiments. For the first time, this work reports evidence for selective DNA purine bases oxidation by excited iridium(III) bis-terdentate complexes.

  19. Learning to Read: Developing Processes for Recognizing, Understanding and Pronouncing Written Words

    ERIC Educational Resources Information Center

    Stuart, Morag

    2006-01-01

    Major theories of how skilled readers recognize, understand and pronounce written words include processes for phonological recoding (i.e., translating segments of print to their corresponding segments of sound) and processes by which direct access is achieved from printed words to their meanings. If these are the processes employed in skilled…

  20. On the way to graphane-pronounced fluorescence of polyhydrogenated graphene.

    PubMed

    Schäfer, Ricarda A; Englert, Jan M; Wehrfritz, Peter; Bauer, Walter; Hauke, Frank; Seyller, Thomas; Hirsch, Andreas

    2013-01-07

    Chemistry meets graphane: a Birch-type reaction using frozen water as a gentle proton source causes the exfoliation of graphite and formation of hydrogenated graphene with electronically decoupled π-nanodomains. This highly functionalized graphene displays pronounced fluorescence. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Screening and Characterization of Purine Nucleoside Degrading Lactic Acid Bacteria Isolated from Chinese Sauerkraut and Evaluation of the Serum Uric Acid Lowering Effect in Hyperuricemic Rats

    PubMed Central

    Mei, Lu; Yuan, Lin; Xie, Ao; Yuan, Jieli

    2014-01-01

    Hyperuricemia is well known as the cause of gout. In recent years, it has also been recognized as a risk factor for arteriosclerosis, cerebrovascular and cardiovascular diseases, and nephropathy in diabetic patients. Foods high in purine compounds are more potent in exacerbating hyperuricemia. Therefore, the development of probiotics that efficiently degrade purine compounds is a promising potential therapy for the prevention of hyperuricemia. In this study, fifty-five lactic acid bacteria isolated from Chinese sauerkraut were evaluated for the ability to degrade inosine and guanosine, the two key intermediates in purine metabolism. After a preliminary screening based on HPLC, three candidate strains with the highest nucleoside degrading rates were selected for further characterization. The tested biological characteristics of candidate strains included acid tolerance, bile tolerance, anti-pathogenic bacteria activity, cell adhesion ability, resistance to antibiotics and the ability to produce hydrogen peroxide. Among the selected strains, DM9218 showed the best probiotic potential compared with other strains despite its poor bile resistance. Analysis of 16S rRNA sequences showed that DM9218 has the highest similarity (99%) to Lactobacillus plantarum WCFS1. The acclimated strain DM9218-A showed better resistance to 0.3% bile salt, and its survival in gastrointestinal tract of rats was proven by PCR-DGGE. Furthermore, the effects of DM9218-A in a hyperuricemia rat model were evaluated. The level of serum uric acid in hyperuricemic rat can be efficiently reduced by the intragastric administration of DM9218-A (P<0.05). The preventive treatment of DM9218-A caused a greater reduction in serum uric acid concentration in hyperuricemic rats than the later treatment (P<0.05). Our results suggest that DM9218-A may be a promising candidate as an adjunctive treatment in patients with hyperuricemia during the onset period of disease. DM9218-A also has potential as a probiotic

  2. Screening and characterization of purine nucleoside degrading lactic acid bacteria isolated from Chinese sauerkraut and evaluation of the serum uric acid lowering effect in hyperuricemic rats.

    PubMed

    Li, Ming; Yang, Dianbin; Mei, Lu; Yuan, Lin; Xie, Ao; Yuan, Jieli

    2014-01-01

    Hyperuricemia is well known as the cause of gout. In recent years, it has also been recognized as a risk factor for arteriosclerosis, cerebrovascular and cardiovascular diseases, and nephropathy in diabetic patients. Foods high in purine compounds are more potent in exacerbating hyperuricemia. Therefore, the development of probiotics that efficiently degrade purine compounds is a promising potential therapy for the prevention of hyperuricemia. In this study, fifty-five lactic acid bacteria isolated from Chinese sauerkraut were evaluated for the ability to degrade inosine and guanosine, the two key intermediates in purine metabolism. After a preliminary screening based on HPLC, three candidate strains with the highest nucleoside degrading rates were selected for further characterization. The tested biological characteristics of candidate strains included acid tolerance, bile tolerance, anti-pathogenic bacteria activity, cell adhesion ability, resistance to antibiotics and the ability to produce hydrogen peroxide. Among the selected strains, DM9218 showed the best probiotic potential compared with other strains despite its poor bile resistance. Analysis of 16S rRNA sequences showed that DM9218 has the highest similarity (99%) to Lactobacillus plantarum WCFS1. The acclimated strain DM9218-A showed better resistance to 0.3% bile salt, and its survival in gastrointestinal tract of rats was proven by PCR-DGGE. Furthermore, the effects of DM9218-A in a hyperuricemia rat model were evaluated. The level of serum uric acid in hyperuricemic rat can be efficiently reduced by the intragastric administration of DM9218-A (P<0.05). The preventive treatment of DM9218-A caused a greater reduction in serum uric acid concentration in hyperuricemic rats than the later treatment (P<0.05). Our results suggest that DM9218-A may be a promising candidate as an adjunctive treatment in patients with hyperuricemia during the onset period of disease. DM9218-A also has potential as a probiotic

  3. Infection of soybean and pea nodules by Rhizobium spp. purine auxotrophs in the presence of 5-aminoimidazole-4-carboxamide riboside.

    PubMed Central

    Newman, J D; Diebold, R J; Schultz, B W; Noel, K D

    1994-01-01

    Purine auxotrophs of various Rhizobium species are symbiotically defective, usually unable to initiate or complete the infection process. Earlier studies demonstrated that, in the Rhizobium etli-bean symbiosis, infection by purine auxotrophs is partially restored by supplementation of the plant medium with 5-amino-imidazole-4-carboxamide (AICA) riboside, the unphosphorylated form of the purine biosynthetic intermediate AICAR. The addition of purine to the root environment does not have this effect. In this study, purine auxotrophs of Rhizobium fredii HH303 and Rhizobium leguminosarum 128C56 (bv. viciae) were examined. Nutritional and genetic characterization indicated that each mutant was blocked in purine biosynthesis prior to the production of AICAR. R. fredii HH303 and R. leguminosarum 128C56 appeared to be deficient in AICA riboside transport and/or conversion into AICAR, and the auxotrophs derived from them grew very poorly with AICA riboside as a purine source. All of the auxotrophs elicited poorly developed, uninfected nodules on their appropriate hosts. On peas, addition of AICA riboside or purine to the root environment led to enhanced nodulation; however, infection threads were observed only in the presence of AICA riboside. On soybeans, only AICA riboside was effective in enhancing nodulation and promoting infection. Although AICA riboside supplementation of the auxotrophs led to infection thread development on both hosts, the numbers of bacteria recovered from the nodules were still 2 or more orders of magnitude lower than in fully developed nodules populated by wild-type bacteria. The ability to AICA riboside to promote infection by purine auxotrophs, despite serving as a very poor purine source for these strains, supports the hypothesis that AICAR plays a role in infection other than merely promoting bacterial growth. Images PMID:8195084

  4. Comparison of human erythrocyte purine nucleotide metabolism and blood purine and pyrimidine degradation product concentrations before and after acute exercise in trained and sedentary subjects.

    PubMed

    Dudzinska, Wioleta; Suska, M; Lubkowska, A; Jakubowska, K; Olszewska, M; Safranow, K; Chlubek, D

    2017-04-21

    This study aimed at evaluating the concentration of erythrocyte purine nucleotides (ATP, ADP, AMP, IMP) in trained and sedentary subjects before and after maximal physical exercise together with measuring the activity of purine metabolism enzymes as well as the concentration of purine (hypoxanthine, xanthine, uric acid) and pyrimidine (uridine) degradation products in blood. The study included 15 male elite rowers [mean age 24.3 ± 2.56 years; maximal oxygen uptake (VO2max) 52.8 ± 4.54 mL/kg/min; endurance and strength training 8.2 ± 0.33 h per week for 6.4 ± 2.52 years] and 15 sedentary control subjects (mean age 23.1 ± 3.41 years; VO2max 43.2 ± 5.20 mL/kg/min). Progressive incremental exercise testing until refusal to continue exercising was conducted on a bicycle ergometer. The concentrations of ATP, ADP, AMP, IMP and the activities of adenine phosphoribosyltransferase (APRT), hypoxanthine-guanine phosphoribosyltransferase (HGPRT) and phosphoribosyl pyrophosphate synthetase (PRPP-S) were determined in erythrocytes. The concentrations of hypoxanthine, xanthine, uric acid and uridine were determined in the whole blood before exercise, after exercise, and 30 min after exercise testing. The study demonstrated a significantly higher concentration of ATP in the erythrocytes of trained subjects which, in part, may be explained by higher metabolic activity on the purine re-synthesis pathway (significantly higher PRPP-S, APRT and HGPRT activities). The ATP concentration, just as the ATP/ADP ratio, as well as an exercise-induced increase in this ratio, correlates with the VO2max level in these subjects which allows them to be considered as the important factors characterising physical capacity and exercise tolerance. Maximal physical exercise in the group of trained subjects results not only in a lower post-exercise increase in the concentration of hypoxanthine, xanthine and uric acid but also in that of uridine. This indicates the possibility of

  5. Formation of A Novel Purine Metabolite through CYP3A4 Bioactivation and Glutathione Conjugation

    PubMed Central

    Apuy, Julius L.; Xiang, Cathie; Franc, Sarah; Hegde, Sayee G.; Hubbard, Robert; Zhao, Jingjing; Moghaddam, Mehran F.

    2016-01-01

    Background: The study of novel sites of metabolism is important in understanding new mechanisms of biotransformation of a particular moiety by metabolic enzymes. This information is valuable in designing metabolically-stable compounds with drug-like properties. It may also provide insights into the existence of active and reactive metabolites. Methods: We utilized small scale incubations to generate adequate amounts of the metabolite of interest. After purification, LC-MS/MS and Proton Nuclear Magnetic Resonance (1H-NMR) were utilized to unequivocally assign the novel site of glutathione conjugation on the purine ring system. Results: A proposed novel site of glutathione conjugation was investigated on a diaminopurine-containing molecule. It was demonstrated that the formation of the glutathione conjugate at the C-6 position of the purine ring system was due to the bioactivation of the compound to a di-imine intermediate by CYP3A4, followed by the nucleophilic addition of glutathione. Conclusion: S-glutathionylation at C-6 position of a purine was proven unequivocally. This previously unreported mechanism constitutes a novel biotransformation for purines. PMID:27165340

  6. Changes in Purines Concentration in the Cerebrospinal Fluid of Pregnant Women Experiencing Pain During Active Labor.

    PubMed

    Schmidt, André P; Böhmer, Ana E; Hansel, Gisele; Soares, Félix A; Oses, Jean P; Giordani, Alex T; Posso, Irimar P; Auler, José Otávio C; Mendes, Florentino F; Félix, Elaine A; Portela, Luís V; Souza, Diogo O

    2015-11-01

    Labor pain has been reported as a severe pain and can be considered as a model of acute visceral pain. It is well known that extracellular purines have an important role in pain signaling in the central nervous system. This study analyzes the relationship between extracellular purines and pain perception during active labor. A prospective observational study was performed. Cerebrospinal fluid (CSF) levels of the purines and their metabolites were compared between women at term pregnancy with labor pain (n = 49) and without labor pain (Caesarian section; n = 47). Control groups (healthy men and women without chronic or acute pain-n = 40 and 32, respectively) were also investigated. The CSF levels of adenosine were significantly lower in the labor pain group (P = 0.026) and negatively correlated with pain intensity measured by a visual analogue scale (r = -0.48, P = 0.0005). Interestingly, CSF levels of uric acid were significantly higher in healthy men as compared to women. Additionally, pregnant women showed increased CSF levels of ADP, GDP, adenosine and guanosine and reduced CSF levels of AMP, GTP, and uric acid as compared to non-pregnant women (P < 0.05). These findings suggest that purines, in special the nucleoside adenosine, are associated with pregnancy and labor pain.

  7. Photogeneration of 2-deoxyribonolactone in benzophenone-purine dyads. Formation of ketyl-C1' biradicals.

    PubMed

    Paris, Cecilia; Encinas, Susana; Belmadoui, Nourreddine; Climent, María J; Miranda, Miguel Angel

    2008-10-16

    Photolysis of the title dyads under aerobic conditions leads to a 2-deoxyribonolactone derivative. Laser flash photolysis reveals that the process occurs from the short-lived benzophenone-like triplet excited state. A mechanism involving intramolecular electron transfer with the purine bases (adenine, guanine, or 8-oxoadenine) as donors is proposed.

  8. The purine metabolite allantoin enhances abiotic stress tolerance through synergistic activation of abscisic acid metabolism.

    PubMed

    Watanabe, Shunsuke; Matsumoto, Mayumi; Hakomori, Yuki; Takagi, Hiroshi; Shimada, Hiroshi; Sakamoto, Atsushi

    2014-04-01

    Purine catabolism is regarded as a housekeeping function that remobilizes nitrogen for plant growth and development. However, emerging evidence suggests that certain purine metabolites might contribute to stress protection of plants. Here, we show that in Arabidopsis, the intermediary metabolite allantoin plays a role in abiotic stress tolerance via activation of abscisic acid (ABA) metabolism. The aln loss-of-function of ALN, encoding allantoinase, results in increased allantoin accumulation, genome-wide up-regulation of stress-related genes and enhanced tolerance to drought-shock and osmotic stress in aln mutant seedlings. This phenotype is not caused by a general response to purine catabolism inhibition, but rather results from a specific effect of allantoin. Allantoin activates ABA production both through increased transcription of NCED3, encoding a key enzyme in ABA biosynthesis, and through post-translational activation via high-molecular-weight complex formation of BG1, a β-glucosidase hydrolysing glucose-conjugated ABA. Exogenous application of allantoin to wild-type plants also activates the two ABA-producing pathways that lead to ABA accumulation and stress-responsive gene expression, but this effect is abrogated in ABA-deficient and BG1-knockout mutants. We propose that purine catabolism functions not only in nitrogen metabolism, but also in stress tolerance by influencing ABA production, which is mediated by the possible regulatory action of allantoin. © 2013 John Wiley & Sons Ltd.

  9. From Purines to Basic Biochemical Concepts: Experiments for High School Students

    ERIC Educational Resources Information Center

    Marini, Isabella; Ipata, Piero Luigi

    2007-01-01

    Many high school biology courses address mainly the molecular and cellular basis of life. The complexity that underlies the most essential processes is often difficult for the students to understand; possibly, in part, because of the inability to see and explore them. Six simple practical experiments on purine catabolism as a part of a…

  10. From Purines to Basic Biochemical Concepts: Experiments for High School Students

    ERIC Educational Resources Information Center

    Marini, Isabella; Ipata, Piero Luigi

    2007-01-01

    Many high school biology courses address mainly the molecular and cellular basis of life. The complexity that underlies the most essential processes is often difficult for the students to understand; possibly, in part, because of the inability to see and explore them. Six simple practical experiments on purine catabolism as a part of a…

  11. Purine and pyrimidine nucleosides preserve human astrocytoma cell adenylate energy charge under ischemic conditions.

    PubMed

    Balestri, Francesco; Giannecchini, Michela; Sgarrella, Francesco; Carta, Maria Caterina; Tozzi, Maria Grazia; Camici, Marcella

    2007-02-01

    The brain depends on both glycolysis and mitochondrial oxidative phosphorylation for maintenance of ATP pools. Astrocytes play an integral role in brain functions providing trophic supports and energy substrates for neurons. In this paper, we report that human astrocytoma cells (ADF) undergoing ischemic conditions may use both purine and pyrimidine nucleosides as energy source to slow down cellular damage. The cells are subjected to metabolic stress conditions by exclusion of glucose and incubation with oligomycin (an inhibitor of oxidative phosphorylation). This treatment brings about a depletion of the ATP pool, with a concomitant increase in the AMP levels, which results in a significant decrease of the adenylate energy charge. The presence of purine nucleosides in the culture medium preserves the adenylate energy charge, and improves cell viability. Besides purine nucleosides, also pyrimidine nucleosides, such as uridine and, to a lesser extent, cytidine, are able to preserve the ATP pool. The determination of lactate in the incubation medium indicates that nucleosides can preserve the ATP pool through anaerobic glycolysis, thus pointing to a relevant role of the phosphorolytic cleavage of the N-glycosidic bond of nucleosides which generates, without energy expense, the phosphorylated pentose, which through the pentose phosphate pathway and glycolysis can be converted to energetic intermediates also in the absence of oxygen. In fact, ADF cells possess both purine nucleoside phosphorylase and uridine phosphorylase activities.

  12. Targeting DNA repair with aphidicolin sensitizes primary chronic lymphocytic leukemia cells to purine analogs

    PubMed Central

    Starczewska, Eliza; Beyaert, Maxime; Michaux, Lucienne; Vekemans, Marie-Christiane; Saussoy, Pascale; Bol, Vanesa; Echarri, Ainhoa Arana; Smal, Caroline; Van Den Neste, Eric; Bontemps, Françoise

    2016-01-01

    Purine analogs are among the most effective chemotherapeutic drugs for the treatment of chronic lymphocytic leukemia (CLL). However, chemoresistance and toxicity limit their clinical use. Here, we report that the DNA polymerase inhibitor aphidicolin, which displayed negligible cytotoxicity as a single agent in primary CLL cells, markedly synergizes with fludarabine and cladribine via enhanced apoptosis. Importantly, synergy was recorded regardless of CLL prognostic markers. At the molecular level, aphidicolin enhanced purine analog-induced phosphorylation of p53 and accumulation of γH2AX, consistent with increase in DNA damage. In addition, aphidicolin delayed γH2AX disappearance that arises after removal of purine analogs, suggesting that aphidicolin causes an increase in DNA damage by impeding DNA damage repair. Similarly, aphidicolin inhibited UV-induced DNA repair known to occur primarily through the nucleotide excision repair (NER) pathway. Finally, we showed that fludarabine induced nuclear import of XPA, an indispensable factor for NER, and that XPA silencing sensitized cell lines to undergo apoptosis in response to fludarabine. Together, our data indicate that aphidicolin potentiates the cytotoxicity of purine analogs by inhibiting a DNA repair pathway that involves DNA polymerases, most likely NER, and provide a rationale for manipulating it to therapeutic advantage. PMID:27223263

  13. Participation of purines in the modulation of inflammatory response in rats experimentally infected by Cryptococcus neoformans.

    PubMed

    de Azevedo, Maria Isabel; Ferreiro, Laerte; Da Silva, Aleksandro S; Tonin, Alexandre A; Monteiro, Danieli Urach; Casali, Emerson A; Moritz, Cesar E J; Schirmbeck, Gabriel H; Cardoso, Valesca V; Flores, Mariana M; Fighera, Rafael; Stefani, Lenita M; Santurio, Janio M

    2016-10-01

    The present study was carried out to assess the participation of purines in the activation and modulation of inflammatory response of rats experimentally infected by Cryptococcus neoformans. Twenty four Wistar rats were divided into two groups of 12 animals each: Group A - uninfected control group and Group B - infected by C. neoformans. Blood was collected 20 and 50 days post-infection (PI) from six animals of each group in order to verify purine levels (adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), adenosine (ADO), inosine (INO), hypoxanthine (HYPO), xanthine (XAN) and uric acid (URIC)). ATP levels were significantly increased (P < 0.05) in serum from infected animals on days 20 and 50 PI, as well as adenosine levels after 20 days PI on rats. On day 50 PI, levels of adenosine and uric acid were also reduced, but the levels of inosine and xanthine increased in animals infected by the fungus (P < 0.05). Therefore, it was possible to conclude that the purine levels in serum were altered and that these changes may be able to influence the pathogenesis of the disease caused by C. neoformans due the participation of purines (ATP and adenosine main) in the activation and modulation of inflammatory response.

  14. Metabolism of purine alkaloids and xanthine in leaves of maté (Ilex paraguariensis).

    PubMed

    Yin, Yuling; Katahira, Riko; Ashihara, Hiroshi

    2015-05-01

    Accumulation and metabolism of purine alkaloids in leaves of maté (Ilex paraguariensis) were investigated. In winter, leaves accumulated caffeine but not theobromine, indicating that caffeine is the end product of purine alkaloid synthesis in maté. To elucidate the purine alkaloid metabolism in maté leaves, the metabolic fate of [8-(14)C]theobromine, [8-(14)C]theophylline, [8-(14)C]caffeine and [8-(14)C] xanthine was investigated in the leaf disks of young and mature leaves. In young maté leaves, significant amounts of theobromine and theophylline were utilized for caffeine biosynthesis, but the conversion was not observed in mature leaves. A small amount of theophylline was converted to theobromine. Practically no caffeine catabolism was detected in maté leaves during a 24 h-incubation. Catabolism of theobromine and theophylline via 3-methylxanthine was observed mainly in mature leaves. Xanthine was catabolised extensively via ureides in both young and mature leaves, but limited amounts are also utilized for the synthesis of theobromine, theophylline and caffeine. Possible pathways for the metabolism of purine alkaloids in maté leaves are discussed.

  15. Modular Synthesis of Constrained Ethyl (cEt) Purine and Pyrimidine Nucleosides.

    PubMed

    Blade, Helen; Bradley, Derek; Diorazio, Louis; Evans, Timothy; Hayter, Barry R; Howell, Gareth P

    2015-05-15

    A modular and scalable approach to pyrimidine- and purine-containing constrained ethyl (cEt) nucleosides is demonstrated. Minimizing stereochemical adjustments and protecting group manipulations, diacetone glucose is converted to two representative cEt nucleosides via a functionalized, common intermediate. The retrosynthetic approach to this complex class of drug precursors offers clear benefits over existing routes based on step count and efficiency.

  16. Synthesis and evaluation of the substrate activity of C-6 substituted purine ribosides with E. coli purine nucleoside phosphorylase: palladium mediated cross-coupling of organozinc halides with 6-chloropurine nucleosides.

    PubMed

    Hassan, Abdalla E A; Abou-Elkhair, Reham A I; Riordan, James M; Allan, Paula W; Parker, William B; Khare, Rashmi; Waud, William R; Montgomery, John A; Secrist, John A

    2012-01-01

    A series of C-6 alkyl, cycloalkyl, and aryl-9-(β-d-ribofuranosyl)purines were synthesized and their substrate activities with Escherichia coli purine nucleoside phosphorylase (E. coli PNP) were evaluated. (Ph(3)P)(4)Pd-mediated cross-coupling reactions of 6-chloro-9-(2,3,5-tri-O-acetyl-β-d-ribofuranosyl)-purine (6) with primary alkyl (Me, Et, n-Pr, n-Bu, isoBu) zinc halides followed by treatment with NH(3)/MeOH gave the corresponding 6-alkyl-9-(β-d-ribofuranosyl)purine derivatives 7-11, respectively, in good yields. Reactions of 6 with cycloalkyl(propyl, butyl, pentyl)zinc halides and aryl (phenyl, 2-thienyl)zinc halides gave under similar conditions the corresponding 6-cyclopropyl, cyclobutyl, cyclopentyl, phenyl, and thienyl -9-(β-d-ribofuranosyl)purine derivatives 12-16, respectively in high yields. E. coli PNP showed a high tolerance to the steric and hydrophobic environment at the 6-position of the synthesized purine ribonucleosides. Significant cytotoxic activity was observed for 8, 12, 15, and 16. Evaluation of 12 and 16 against human tumor xenografts in mice did not demonstrate any selective antitumor activity. In addition, 6-methyl-9-(β-d-arabinofuranosyl)purine (18) was prepared and evaluated. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  17. Pronounced minimum of the thermodynamic Casimir forces of O(n) symmetric film systems: analytic theory.

    PubMed

    Dohm, Volker

    2014-09-01

    Thermodynamic Casimir forces of film systems in the O(n) universality classes with Dirichlet boundary conditions are studied below bulk criticality. Substantial progress is achieved in resolving the long-standing problem of describing analytically the pronounced minimum of the scaling function observed experimentally in ^{4}He films (n=2) by Garcia and Chan [Phys. Rev. Lett. 83, 1187 (1999)] and in Monte Carlo simulations for the three-dimensional Ising model (n=1) by O. Vasilyev et al. [Europhys. Lett. 80, 60009 (2007)]. Our finite-size renormalization-group approach describes the film systems as the limit of finite-slab systems with vanishing aspect ratio. This yields excellent agreement with the depth and the position of the minimum for n=1 and semiquantitative agreement with the minimum for n=2. Our theory also predicts a pronounced minimum for the n=3 Heisenberg universality class.

  18. Pronounced gender and age differences are evident in personal health care spending per person.

    PubMed

    Cylus, Jonathan; Hartman, Micah; Washington, Benjamin; Andrews, Kimberly; Catlin, Aaron

    2011-01-01

    This paper examines differences in national health care spending by gender and age. Our research found significant variations in per person spending by gender across age groups, health services, and types of payers. For example, in 2004 per capita health care spending for females was 32 percent more than for males. Per capita differences were most pronounced among the working-age population, largely because of spending for maternity care. Except for children, total spending for and by females was greater than that for and by males, for most services and payers. The gender difference in total spending was most pronounced in the elderly, as a result of the longer life expectancy of women.

  19. Prosthetic improvement of pronounced buccally positioned zygomatic implants: a clinical report.

    PubMed

    Bacchi, Ataís; Santos, Mateus Bertolini Fernandes dos; Pimentel, Marcele Jardim; Nóbilo, Mauro Antonio de Arruda; Consani, Rafael Leonardo Xediek

    2014-08-01

    This report presents a prosthetic technique for the improvement of surgically positioned, buccally placed zygomatic implants with the use of custom abutments for improved retention screw position and an esthetic implant reconstruction. The patient presented four zygomatic implants with pronounced buccal inclination. The anterior implants were inclined toward the location where the anterior artificial teeth should be placed during rehabilitation. As the manufacturer does not provide angulated abutments, we attempted the waxing and overcasting of a prosthetic abutment, repositioning the access holes of the prosthetic screws to a more palatal position. This clinical report demonstrates that abutment customization could be an interesting way to relocate the access holes of the prosthetic screws in cases of zygomatic implants with pronounced buccal inclination. © 2014 by the American College of Prosthodontists.

  20. Purine nucleobase transport in human erythrocytes. Reinvestigation with a novel "inhibitor-stop" assay.

    PubMed

    Domin, B A; Mahony, W B; Zimmerman, T P

    1988-07-05

    A novel "inhibitor-stop" method for the determination of initial rates of purine nucleobase transport in human erythrocytes has been developed, based on the addition of seven assay volumes of cold 19 mM papaverine to terminate influx. In view of our finding that the initial velocities of adenine, guanine, and hypoxanthine influx into human erythrocytes were linear for only 4-6 s at 37 degrees C, the present method has been used to reexamine the kinetics of purine nucleobase transport in these cells. Initial influx rates of all three purine nucleobases were shown to be the result of concurrent facilitated and nonfacilitated diffusion. The nonfacilitated influx rates could be estimated either from the linear concentration dependence of nucleobase influx at high concentrations of permeant or from residual influx rates which were not inhibited by the presence of co-permeants. Appropriate corrections for nonfacilitated diffusion were made to the influx rates observed at low nucleobase concentrations. Kinetic analyses indicated that adenine (Km = 13 +/- 1 microM, n = 7), guanine (Km = 37 +/- 2 microM, n = 5), and hypoxanthine (Km = 180 +/- 12 microM, n = 6) were mutually competitive substrates for transport. The Ki values obtained with each nucleobase as an inhibitor of the influx of the other nucleobases were similar to their respective Km values for influx. Furthermore, the transport of the purine nucleobases was not inhibited by nucleosides (uridine, inosine) or by inhibitors of nucleoside transport (6-[(4-nitrobenzyl)thio]-9-beta-D-ribofuranosylpurine, dilazep, dipyridamole). It is concluded that all three purine nucleobases share a common facilitated transport system in human erythrocytes which is functionally distinct from the nucleoside transporter.

  1. Plasma Hypoxanthine-Guanine Phosphoribosyl Transferase Activity in Bottlenose Dolphins Contributes to Avoiding Accumulation of Non-recyclable Purines.

    PubMed

    López-Cruz, Roberto I; Crocker, Daniel E; Gaxiola-Robles, Ramón; Bernal, Jaime A; Real-Valle, Roberto A; Lugo-Lugo, Orlando; Zenteno-Savín, Tania

    2016-01-01

    Marine mammals are exposed to ischemia/reperfusion and hypoxia/reoxygenation during diving. During oxygen deprivation, adenosine triphosphate (ATP) breakdown implies purine metabolite accumulation, which in humans is associated with pathological conditions. Purine recycling in seals increases in response to prolonged fasting and ischemia. Concentrations of metabolites and activities of key enzymes in purine metabolism were examined in plasma and red blood cells from bottlenose dolphins (Tursiops truncatus) and humans. Hypoxanthine and inosine monophosphate concentrations were higher in plasma from dolphins than humans. Plasma hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity in dolphins suggests an elevated purine recycling rate, and a mechanism for avoiding accumulation of non-recyclable purines (xanthine and uric acid). Red blood cell concentrations of hypoxanthine, adenosine diphosphate, ATP and guanosine triphosphate were lower in dolphins than in humans; adenosine monophosphate and nicotinamide adenine dinucleotide concentrations were higher in dolphins. HGPRT activity in red blood cells was higher in humans than in dolphins. The lower concentrations of purine catabolism and recycling by-products in plasma from dolphins could be beneficial in providing substrates for recovery of ATP depleted during diving or vigorous swimming. These results suggest that purine salvage in dolphins could be a mechanism for delivering nucleotide precursors to tissues with high ATP and guanosine triphosphate requirements.

  2. Plasma Hypoxanthine-Guanine Phosphoribosyl Transferase Activity in Bottlenose Dolphins Contributes to Avoiding Accumulation of Non-recyclable Purines

    PubMed Central

    López-Cruz, Roberto I.; Crocker, Daniel E.; Gaxiola-Robles, Ramón; Bernal, Jaime A.; Real-Valle, Roberto A.; Lugo-Lugo, Orlando; Zenteno-Savín, Tania

    2016-01-01

    Marine mammals are exposed to ischemia/reperfusion and hypoxia/reoxygenation during diving. During oxygen deprivation, adenosine triphosphate (ATP) breakdown implies purine metabolite accumulation, which in humans is associated with pathological conditions. Purine recycling in seals increases in response to prolonged fasting and ischemia. Concentrations of metabolites and activities of key enzymes in purine metabolism were examined in plasma and red blood cells from bottlenose dolphins (Tursiops truncatus) and humans. Hypoxanthine and inosine monophosphate concentrations were higher in plasma from dolphins than humans. Plasma hypoxanthine-guanine phosphoribosyl transferase (HGPRT) activity in dolphins suggests an elevated purine recycling rate, and a mechanism for avoiding accumulation of non-recyclable purines (xanthine and uric acid). Red blood cell concentrations of hypoxanthine, adenosine diphosphate, ATP and guanosine triphosphate were lower in dolphins than in humans; adenosine monophosphate and nicotinamide adenine dinucleotide concentrations were higher in dolphins. HGPRT activity in red blood cells was higher in humans than in dolphins. The lower concentrations of purine catabolism and recycling by-products in plasma from dolphins could be beneficial in providing substrates for recovery of ATP depleted during diving or vigorous swimming. These results suggest that purine salvage in dolphins could be a mechanism for delivering nucleotide precursors to tissues with high ATP and guanosine triphosphate requirements. PMID:27375492

  3. Arxula adeninivorans recombinant guanine deaminase and its application in the production of food with low purine content.

    PubMed

    Trautwein-Schult, Anke; Jankowska, Dagmara; Cordes, Arno; Hoferichter, Petra; Klein, Christina; Matros, Andrea; Mock, Hans-Peter; Baronian, Keith; Bode, Rüdiger; Kunze, Gotthard

    2014-01-01

    Purines of exogenous and endogenous sources are degraded to uric acid in human beings. Concentrations >6.8 mg uric acid/dl serum cause hyperuricemia and its symptoms. Pharmaceuticals and the reduction of the intake of purine-rich food are used to control uric acid levels. A novel approach to the latter proposition is the enzymatic reduction of the purine content of food by purine-degrading enzymes. Here we describe the production of recombinant guanine deaminase by the yeast Arxula adeninivorans LS3 and its application in food. In media supplemented with nitrogen sources hypoxanthine or adenine, guanine deaminase (AGDA) gene expression is induced and intracellular accumulation of guanine deaminase (Agdap) protein occurs. The characteristics of the guanine deaminase isolated from wild-type strain LS3 and a transgenic strain expressing the AGDA gene under control of the strong constitutive TEF1 promoter were determined and compared. Both enzymes were dimeric and had temperature optima of 55°C with high substrate specificity for guanine and localisation in both the cytoplasm and vacuole of yeast. The enzyme was demonstrated to reduce levels of guanine in food. A mixture of guanine deaminase and other purine degradation enzymes will allow the reduction of purines in purine-rich foods. © 2014 S. Karger AG, Basel.

  4. Synthesis and antimycobacterial activity of N-(2-aminopurin-6-yl) and N-(purin-6-yl) amino acids and dipeptides.

    PubMed

    Krasnov, Victor P; Vigorov, Alexey Yu; Musiyak, Vera V; Nizova, Irina A; Gruzdev, Dmitry A; Matveeva, Tatyana V; Levit, Galina L; Kravchenko, Marionella A; Skornyakov, Sergey N; Bekker, Olga B; Danilenko, Valery N; Charushin, Valery N

    2016-06-01

    Synthetic routes to novel N-(purin-6-yl)- and N-(2-aminopurin-6-yl) conjugates with amino acids and glycine-containing dipeptides were developed. In vitro testing of 42 new and known compounds made it possible to reveal a series of N-(purin-6-yl)- and N-(2-aminopurin-6-yl) conjugates exhibiting significant antimycobacterial activity against Mycobacterium tuberculosis H37Rv, Mycobacterium avium, Mycobacterium terrae, and multidrug-resistant M. tuberculosis strain isolated from tuberculosis patients in the Ural region (Russia). N-(2-Aminopurin-6-yl)- and N-(purin-6-yl)-glycyl-(S)-glutamic acids were the most active compounds.

  5. Sequence- and Regio-Selectivity in the Montmorillonite-Catalyzed Synthesis of RNA

    NASA Astrophysics Data System (ADS)

    Ertem, Gözen; Ferris, James P.

    2000-10-01

    The six binary montmorillonite clay-catalyzed reactions of the 5'-phosphorimidazolides of adenosine, cytidine, guanosine and uridine were performed and the eight dimers from each reaction were separated and analyzed by HPLC. A 16-51-fold higher yield of the 5'-purine-pyrimidine dimers over that of the 5'-pyrimidine-purines was observed. The total yield of the 5'-purine-pyrimidine dimers was in the 50-70% range while that of the 5'-pyrimidine-purine dimers was 1.3-7.0%. Less sequence selectivity was observed in the homodimers formed. Regioselectivity for the formation of 3', 5'-phosphodiester bonds over that found in the absence of clay was observed. The 5'-purine-pyrimidine, 5'-pyrimidine-pyrimidine and 5'-purine-purine dimers had 3', 5'-links in about half of their phosphodiester bonds. The percent phosphodiester links in the 5'-pyrimidine-pyrimidine dimers was 18%, a value close to that observed in the absence of the montmorillonite catalyst. The montmorillonite-catalyzed reaction of all four activated nucleotides was performed and the 24 products were separated and analyzed. The trends observed in the binary reactions were confirmed and the results also showed that the relative reactivity of the activated monomers was A>G>C>U in the ratio 8.2: 4.8: 1.3: 1 respectively. No 5'-pyrimidine-purines with a 5'-U and pG^3'pU, pC^3'pA and pC^3'pG were detected. These studies suggest that a limited population of RNAs would have formed in catalyzed prebiotic reactions.

  6. Sequence-dependent dynamics of duplex DNA: the applicability of a dinucleotide model.

    PubMed Central

    Okonogi, T M; Alley, S C; Reese, A W; Hopkins, P B; Robinson, B H

    2002-01-01

    The short-time (submicrosecond) bending dynamics of duplex DNA were measured to determine the effect of sequence on dynamics. All measurements were obtained from a single site on duplex DNA, using a single, site-specific modified base containing a rigidly tethered, electron paramagnetic resonance active spin probe. The observed dynamics are interpreted in terms of single-step sequence-dependent bending force constants, determined from the mean squared amplitude of bending relative to the end-to-end vector using the modified weakly bending rod model. The bending dynamics at a single site are a function of the sequence of the nucleotides constituting the duplex DNA. We developed and examined several dinucleotide-based models for flexibility. The models indicate that the dominant feature of the dynamics is best explained in terms of purine- and pyrimidine-type steps, although distinction is made among all 10 unique steps: It was found that purine-purine steps (which are the same as pyrimidine-pyrimidine steps) were near average in flexibility, but the pyrimidine-purine steps (5' to 3') were nearly twice as flexible, whereas purine-pyrimidine steps were more than half as flexible as average DNA. Therefore, the range of stepwise flexibility is approximately fourfold and is characterized by both the type of base pair step (pyrimidine/purine combination) and the identity of the bases within the pair (G, A, T, or C). All of the four models considered here underscore the complexity of the dependence of dynamics on DNA sequence with certain sequences not satisfactorily explainable in terms of any dinucleotide model. These findings provide a quantitative basis for interpreting the dynamics and kinetics of DNA-sequence-dependent biological processes, including protein recognition and chromatin packaging. PMID:12496111

  7. Thermodynamic and kinetic characterization of ligand binding to the purine riboswitch aptamer domain.

    PubMed

    Gilbert, Sunny D; Stoddard, Colby D; Wise, Sarah J; Batey, Robert T

    2006-06-09

    Riboswitches are cis-acting genetic regulatory elements found commonly in bacterial mRNAs that consist of a metabolite-responsive aptamer domain coupled to a regulatory switch. Purine riboswitches respond to intracellular concentrations of either adenine or guanine/hypoxanthine to control gene expression. The aptamer domain of the purine riboswitch contains a pyrimidine residue (Y74) that forms a Watson-Crick base-pairing interaction with the bound purine nucleobase ligand that discriminates between adenine and guanine. We sought to understand the structural basis of this specificity and the mechanism of ligand recognition by the purine riboswitch. Here, we present the 2,6-diaminopurine-bound structure of a C74U mutant of the xpt-pbuX guanine riboswitch, along with a detailed thermodynamic and kinetic analysis of nucleobase recognition by both the native and mutant riboswitches. These studies demonstrate clearly that the pyrimidine at position 74 is the sole determinant of purine riboswitch specificity. In addition, the mutant riboswitch binds adenine and adenine derivatives well compared with the guanine-responsive riboswitch. Under our experimental conditions, 2,6-diaminopurine binds the RNA with DeltaH=-40.3 kcal mol(-1), DeltaS=-97.6 cal mol(-1)K(-1), and DeltaG=-10.73 kcal mol(-1). A kinetic determination of the slow rate (0.15 x 10(5)M(-1)s(-1) and 2.1 x 10(5)mM(-1)s(-1) for 2-aminopurine binding the adenine-responsive mutant riboswitch and 7-deazaguanine-binding guanine riboswitch, respectively) of association under varying experimental conditions allowed us to propose a mechanism for ligand recognition by the purine riboswitch. A conformationally dynamic unliganded state for the binding pocket is stabilized first by the Watson-Crick base pairing between the ligand and Y74, and by the subsequent ordering of the J2/3 loop, enclosing the ligand within the three-way junction.

  8. Hypouricemic effects of novel concentrative nucleoside transporter 2 inhibitors through suppressing intestinal absorption of purine nucleosides.

    PubMed

    Hiratochi, Masahiro; Tatani, Kazuya; Shimizu, Kazuo; Kuramochi, Yu; Kikuchi, Norihiko; Kamada, Noboru; Itoh, Fumiaki; Isaji, Masayuki

    2012-09-05

    We have developed concentrative nucleoside transporter 2 (CNT2) inhibitors as a novel pharmacological approach for improving hyperuricemia by inhibiting intestinal absorption of purines. Dietary purine nucleosides are absorbed in the small intestines by CNTs expressed in the apical membrane. In humans, the absorbed purine nucleosides are rapidly degraded to their final end product, uric acid, by xanthine oxidase. Based on the expression profile of human CNTs in digestive tract tissues, we established a working hypothesis that mainly CNT2 contributes to the intestinal absorption of purine nucleosides. In order to confirm this possibility, we developed CNT2 inhibitors and found that (2R,3R,4S,5R)-2-(6-amino-8-{[3'-(3-aminopropoxy)-biphenyl-4-ylmethyl]-amino}-9H-purin-9-yl)-5-hydroxymethyl-tetrahydrofuran-3,4-diol (KGO-2142) and 1-[3-(5-{[1-((2R,3R,4S,5R)-3,4-dihydroxy-5-hydroxymethyl-tetrahydrofuran-2-yl)-1H-benzimidazol-2-ylamino]-methyl}-2-ethoxyphenoxy)-propyl]-piperidine-4-carboxylic acid amide (KGO-2173) were inhibitory. These CNT2 inhibitors had potent inhibitory activity against inosine uptake via human CNT2, but they did not potently interfere with nucleoside uptake via human CNT1, CNT3 or equilibrative nucleoside transporters (ENTs) in vitro. After oral administration of KGO-2173 along with [(14)C]-inosine, KGO-2173 significantly decreased the urinary excretion of radioactivity at 6 and 24h in rats. Since dietary purine nucleosides are not utilized in the body and are excreted into the urine rapidly, this decrease in radioactivity in the urine represented the inhibitory activity of KGO-2173 toward the absorption of [(14)C]-inosine in the small intestines. KGO-2142 almost completely inhibited dietary RNA-induced hyperuricemia and the increase in urinary excretion of uric acid in cebus monkeys. These novel CNT2 inhibitors, KGO-2142 and KGO-2173, could be useful therapeutic options for the treatment of hyperuricemia. Copyright © 2012 Elsevier B.V. All rights

  9. Pronouncing the names of the moons of Saturn, or pulling teeth from Tethys

    NASA Astrophysics Data System (ADS)

    Consolmagno, G.; Reiche, H.

    The moons of Saturn, so Woody Allen recently observed [Allen, 1979], do not come up in conversation very often. This may be one reason why most people, planetary scientists included, have trouble pronouncing their names.Our troubles, however, stem not merely from the fact that these names are unfamiliar, or even that they are of non-English origin. After all, the same is true of many terms in technology and medicine [cf. Nybakken, 1959; Reiche, 1959]. They stem from the fact that they are drawn from Greco-Roman mythology and so possess the three chief difficulties troubling those who strive for ‘correct’ pronunciation anywhere in this area.

  10. A Dual-Route Model that Learns to Pronounce English Words

    NASA Technical Reports Server (NTRS)

    Remington, Roger W.; Miller, Craig S.; Null, Cynthia H. (Technical Monitor)

    1995-01-01

    This paper describes a model that learns to pronounce English words. Learning occurs in two modules: 1) a rule-based module that constructs pronunciations by phonetic analysis of the letter string, and 2) a whole-word module that learns to associate subsets of letters to the pronunciation, without phonetic analysis. In a simulation on a corpus of over 300 words the model produced pronunciation latencies consistent with the effects of word frequency and orthographic regularity observed in human data. Implications of the model for theories of visual word processing and reading instruction are discussed.

  11. Periodontal status of mandibular incisors after pronounced orthodontic advancement during adolescence: a follow-up evaluation.

    PubMed

    Artun, J; Grobéty, D

    2001-01-01

    The purpose of this study was to analyze whether pronounced orthodontic advancement of the mandibular incisors during Class II correction in the mixed dentition results in gingival recession. Through mandibular superimposition of the pretreatment and posttreatment cephalograms of 67 Class II patients who were treated with reverse headgear to the mandibular dentition, 45 patients with a minimum of a 1-mm advancement of the cementoenamel junction (CEJ; mean, 2.18 +/- 0.87) and a minimum of a 2-mm advancement of the incisal edge (mean, 3.87 +/- 1.34) were identified. Using the same protocol in Class II patients, 30 individuals who finished treatment at a similar time and age, but without reverse headgear and with no advancement of the CEJ (mean -0.43, SD 0.53) and a maximum of 1-mm advancement of the incisal edge (mean -0.26, SD 1.15) were identified. Before treatment, the mandibular incisors were more retruded, relative to the line from point A to pogonion and relative to the mandibular plane in the patients with pronounced advancement than in those with no advancement of the mandibular incisors; no differences were found at the time of appliance removal. A total of 30 patients with pronounced advancement and 21 patients with no advancement could meet for a follow-up examination a mean period of 7.83 years (SD, 4.44) and 9.38 years (SD, 4.39) after treatment, respectively. Clinical examinations at the time of follow-up revealed no differences in the amount of recession, the width of attached gingiva, the length of supracrestal connective tissue attachment, the probing pocket depth, and gingival bleeding index or visible plaque index of the mandibular incisors between the patients in the 2 groups. An examination of color slides demonstrated no differences in the number of mandibular incisors that developed recession from before treatment to after treatment and from after treatment to follow-up. Measurement of mandibular incisor crown height on the study models

  12. A Dual-Route Model that Learns to Pronounce English Words

    NASA Technical Reports Server (NTRS)

    Remington, Roger W.; Miller, Craig S.; Null, Cynthia H. (Technical Monitor)

    1995-01-01

    This paper describes a model that learns to pronounce English words. Learning occurs in two modules: 1) a rule-based module that constructs pronunciations by phonetic analysis of the letter string, and 2) a whole-word module that learns to associate subsets of letters to the pronunciation, without phonetic analysis. In a simulation on a corpus of over 300 words the model produced pronunciation latencies consistent with the effects of word frequency and orthographic regularity observed in human data. Implications of the model for theories of visual word processing and reading instruction are discussed.

  13. Nonrandom distribution of cryptic repeating triplets of purines and pyrimidines (RNY)(n) in gp120 of HIV Type1.

    PubMed

    De Crignis, Elisa; Guglietta, Silvia; Foley, Brian T; Negroni, Matteo; Di Narzo, Antonio Fabio; Waelti Da Costa, Vreneli; Cavassini, Matthias; Bart, Pierre-Alexandre; Pantaleo, Giuseppe; Graziosi, Cecilia

    2012-05-01

    We have analyzed purine (R) and pyrimidine (Y) codon patterns in variable and constant regions of HIV-1 gp120 in seven patients infected with different HIV-1 subtypes and naive to antiretroviral therapy. We have calculated the relative frequency of each in-frame codon RNY, YNR, RNR, and YNY (N=any nucleotide) in variable and constant regions of gp120, in the sequence within indels and at indels' flanking sites. Our data show that hypervariable regions V1, V2, V4, and V5 are characterized by the presence of long stretches of RNY codons constituting the majority of the sequence portion within insertions/deletions. In full-length gp120 and within inserted/deleted fragments the number of AVT (V=A, C, G) codons did not exceed 50% of the total RNY codons. RNY strings in variable regions spanned up to 21 codons and were always in frame. In contrast, RNY strings in constant regions were mostly out of frame and their length was limited to five codons. The frequency of the codon RNY was found to be significantly higher in variable regions (p<0.0001; t-test), within indels, and at indels' flanking sites (p<0.0001; χ(2) test). Analysis of the distribution of RNY strings equal to or longer than five codons in the full genome of HXB2 also shows that these sequences are mostly out of frame, unless they contain a potential N-glycosylation site or an asparagine. These data suggest that cryptic repeats of RNY may play a role in the genesis of multiple base insertions and deletions in hypervariable regions of gp120.

  14. Characterization of a purine permease family gene OsPUP7 involved in growth and development control in rice.

    PubMed

    Qi, Zhuyun; Xiong, Lizhong

    2013-11-01

    In this study, PUP-type cytokinin transporter genes were identified in rice (Oryza sativa L.). The Oryza sativa purine permease (OsPUP) family has 12 members that show similar predicted protein sequences with AtPUPs. To reveal the functions of OsPUP genes, we searched the T-DNA mutant library of rice and found one mutant for the member OsPUP7. The T-DNA insertion caused a new transcript that encodes a protein with 26 amino acids different from the native OsPUP7 at the C-terminus. The mutant showed multiple phenotypic changes including increased plant height, big seeds, and delayed flowering. The mutant also showed increased sensitivity to drought and salt stresses and treatments with kinetin and abscisic acid. OsPUP7 is expressed mainly in the vascular bundle, pistil, and stamens. The measurement of cytokinins (CKs) showed that CK content in the mutant spikelets accumulated higher than that in the wild type. Moreover, uptake experiment in the yeast fcy2 mutant suggested that OsPUP7 has the ability to transport caffeine, a CK derivative. Our results indicate that the PUP transport system also exists in rice, and OsPUP7 has an important role in the transport of CK, thus affecting developmental process and stress responses. © 2013 Institute of Botany, Chinese Academy of Sciences.

  15. Amide-controlled, one-pot synthesis of tri-substituted purines generates structural diversity and analogues with trypanocidal activity.

    PubMed

    Pineda de las Infantas y Villatoro, Maria J; Unciti-Broceta, Juan D; Contreras-Montoya, Rafael; Garcia-Salcedo, Jose A; Gallo Mezo, Miguel A; Unciti-Broceta, Asier; Diaz-Mochon, Juan J

    2015-03-16

    A novel one-pot synthesis of tri-substituted purines and the discovery of purine analogues with trypanocidal activity are reported. The reaction is initiated by a metal-free oxidative coupling of primary alkoxides and diaminopyrimidines with Schiff base formation and subsequent annulation in the presence of large N,N-dimethylamides (e.g. N,N-dimethylpropanamide or larger). This synthetic route is in competition with a reaction previously-reported by our group, allowing the generation of a combinatorial library of tri-substituted purines by the simple modification of the amide and the alkoxide employed. Among the variety of structures generated, two purine analogues displayed trypanocidal activity against the protozoan parasite Trypanosoma brucei with IC50 < 5 μM, being each of those compounds obtained through each of the synthetic pathways.

  16. Akt Phosphorylation and Regulation of Transketolase Is a Nodal Point for Amino Acid Control of Purine Synthesis

    PubMed Central

    Saha, Arindam; Connelly, Stephen; Jiang, Jingjing; Zhuang, Shunhui; Amador, Deron T.; Phan, Tony; Pilz, Renate B.; Boss, Gerry R.

    2014-01-01

    SUMMARY The phosphatidylinositol 3-kinase (PI3K)/Akt pathway integrates environmental clues to regulate cell growth and survival. We showed previously that depriving cells of a single essential amino acid rapidly and reversibly arrests purine synthesis. Here we demonstrate that amino acids via mTORC2 and IκB kinase regulate Akt activity, and Akt association and phosphorylation of transketolase (TKT), a key enzyme of the non-oxidative pentose phosphate pathway (PPP). Akt phosphorylates TKT on Thr382, markedly enhancing enzyme activity and increasing carbon flow through the non-oxidative PPP, thereby increasing purine synthesis. Mice fed a lysine-deficient diet for two days show decreased Akt activity, TKT activity, and purine synthesis in multiple organs. These results provide a new mechanism whereby Akt coordinates amino acid availability with glucose utilization, purine synthesis, and RNA and DNA synthesis. PMID:24981175

  17. Akt phosphorylation and regulation of transketolase is a nodal point for amino acid control of purine synthesis.

    PubMed

    Saha, Arindam; Connelly, Stephen; Jiang, Jingjing; Zhuang, Shunhui; Amador, Deron T; Phan, Tony; Pilz, Renate B; Boss, Gerry R

    2014-07-17

    The phosphatidylinositol 3-kinase (PI3K)/Akt pathway integrates environmental clues to regulate cell growth and survival. We showed previously that depriving cells of a single essential amino acid rapidly and reversibly arrests purine synthesis. Here we demonstrate that amino acids via mammalian target of rapamycin 2 and IκB kinase regulate Akt activity and Akt association and phosphorylation of transketolase (TKT), a key enzyme of the nonoxidative pentose phosphate pathway (PPP). Akt phosphorylates TKT on Thr382, markedly enhancing enzyme activity and increasing carbon flow through the nonoxidative PPP, thereby increasing purine synthesis. Mice fed a lysine-deficient diet for 2 days show decreased Akt activity, TKT activity, and purine synthesis in multiple organs. These results provide a mechanism whereby Akt coordinates amino acid availability with glucose utilization, purine synthesis, and RNA and DNA synthesis. Copyright © 2014 Elsevier Inc. All rights reserved.

  18. SPAD chlorophyll meter reading can be pronouncedly affected by chloroplast movement.

    PubMed

    Nauš, Jan; Prokopová, Jitka; Rebíček, Jiří; Spundová, Martina

    2010-09-01

    Non-destructive assessment of chlorophyll content has recently been widely done by chlorophyll meters based on measurement of leaf transmittance (e.g. the SPAD-502 chlorophyll meter measures the leaf transmittance at 650 and 940 nm). However, the leaf transmittance depends not only on the content of chlorophylls but also on their distribution in leaves. The chlorophyll distribution within leaves is co-determined by chloroplast arrangement in cells that depends on light conditions. When tobacco leaves were exposed to a strong blue light (about 340 μmol of photons m⁻² s⁻¹), a very pronounced increase in the leaf transmittance was observed as chloroplasts migrated from face position (along cell walls perpendicular to the incident light) to side position (along cell walls parallel to the incoming light) and the SPAD reading decreased markedly. This effect was more pronounced in the leaves of young tobacco plants compared with old ones; the difference between SPAD values in face and side position reached even about 35%. It is shown how the chloroplast movement changes a relationship between the SPAD readings and real chlorophyll content. For an elimination of the chloroplast movement effect, it can be recommended to measure the SPAD values in leaves with a defined chloroplasts arrangement.

  19. Determination of Caffeine and Other Purine Compounds in Food and Pharmaceuitcals by Micellar Electrokinetic Chrmoatography

    NASA Astrophysics Data System (ADS)

    Vogt, Carla; Contradi, S.; Rohde, E.

    1997-09-01

    Capillary elctrophoresis is a modern separation technique, especially the extremely high efficiencies and minimal requirements with regard to buffers, samples and solvents lead to a dramatic increase of applications in the last few years. This paper offers an introduction to the technique of micellar elektrokinetic chromatography as a special kind of capillary electrophoresis. Caffeine and other purine compounds have been determined in foodstuff (tea, coffee, cocoa) as well as in pharmaceutical formulations. Different sample preparation procedures which have been developed with regard to the special properties of the sample matrices are discussed in the paper.This preparation facilitates the separation in many cases. So students have to solve a relatively simple separation problem by variation of buffer pH, buffer components and separation parameters. By doing a calibration for the analyzed purine compounds they will learn about reproducibility in capillary electrophoresis.

  20. Direct Isolation of Purines and Pyrimidines from Nucleic Acids Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Schubert, Michael; Bada, Jeffrey L.

    2003-01-01

    A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (approx. 0.5 Torr) at temperatures of >150 C. With the exception of guanine, approximately 60 -75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 C. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.

  1. 9H-Purine Scaffold Reveals Induced-Fit Pocket Plasticity of the BRD9 Bromodomain

    PubMed Central

    2015-01-01

    The 2-amine-9H-purine scaffold was identified as a weak bromodomain template and was developed via iterative structure based design into a potent nanomolar ligand for the bromodomain of human BRD9 with small residual micromolar affinity toward the bromodomain of BRD4. Binding of the lead compound 11 to the bromodomain of BRD9 results in an unprecedented rearrangement of residues forming the acetyllysine recognition site, affecting plasticity of the protein in an induced-fit pocket. The compound does not exhibit any cytotoxic effect in HEK293 cells and displaces the BRD9 bromodomain from chromatin in bioluminescence proximity assays without affecting the BRD4/histone complex. The 2-amine-9H-purine scaffold represents a novel template that can be further modified to yield highly potent and selective tool compounds to interrogate the biological role of BRD9 in diverse cellular systems. PMID:25703523

  2. Abiotic synthesis of purines and other heterocyclic compounds by the action of electrical discharges

    NASA Technical Reports Server (NTRS)

    Yuasa, S.; Flory, D.; Basile, B.; Oro, J.

    1984-01-01

    The synthesis of purines and pyrimidines using Oparin-Urey-type primitive earth atmospheres has been demonstrated by reacting methane, ethane, and ammonia in electrical discharges. Adenine, guaine, 4-aminoimidazole-5-carboxamide (AICA), and isocytosine have been identified by UV spectrometry and paper chromatography as the products of the reaction. The total yields of the identified heterocyclic compounds are 0.0023 percent. It is concluded that adenine synthesis occurs at a much lower concentration of hydrogen cyanide than has been shown by earlier studies. Pathways for the synthesis of purines from hydrogen cyanide are discussed, and a comparison of the heterocyclic compounds that have been identified in meteorites and in prebiotic reactions is presented.

  3. Purine derivatives as potent Bruton’s tyrosine kinase (BTK) inhibitors for autoimmune diseases

    SciTech Connect

    Shi, Qing; Tebben, Andrew; Dyckman, Alaric J.; Li, Hedy; Liu, Chunjian; Lin, James; Spergel, Steve; Burke, James R.; McIntyre, Kim W.; Olini, Gilbert C.; Strnad, Joann; Surti, Neha; Muckelbauer, Jodi K.; Chang, Chiehying; An, Yongmi; Cheng, Lin; Ruan, Qian; Leftheris, Katerina; Carter, Percy H.; Tino, Joseph; De Lucca, George V.

    2014-05-01

    Investigation of various heterocyclic core isosteres of imidazopyrazines 1 & 2 yielded purine derivatives 3 & 8 as potent and selective BTK inhibitors. Subsequent SAR studies of the purine series led to the discovery of 20 as a leading compound. Compound 20 is very selective when screened against a panel of 400 kinases and is a potent inhibitor in cellular assays of human B cell function including B-Cell proliferation and CD86 cell surface expression and exhibited in vivo efficacy in a mouse PCA model. Its X-ray co-crystal structure with BTK shows that the high selectivity is gained from filling a BTK specific lipophilic pocket. However, physical and ADME properties leading to low oral exposure hindered further development.

  4. Direct Isolation of Purines and Pyrimidines from Nucleic Acids Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Schubert, Michael; Bada, Jeffrey L.

    2003-01-01

    A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (approx. 0.5 Torr) at temperatures of >150 C. With the exception of guanine, approximately 60 -75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 C. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.

  5. Synthesis of Novel N9-Substituted Purine Derivatives from Polymer Supported α-Amino Acids.

    PubMed

    Vanda, David; Jorda, Radek; Lemrová, Barbora; Volná, Tereza; Kryštof, Vladimír; McMaster, Claire; Soural, Miroslav

    2015-07-13

    Solid-phase synthesis of purine derivatives bearing an α-amino acid motif in position 9 is described herein. Polymer supported amines were acylated with various Fmoc-α-amino acids and, after cleavage of the protecting group, arylation with 4,6-dichloro-5-nitropyrimidine or 2,4-dichloro-5-nitropyrimidine was performed. The second chlorine atom was replaced with various amines. Subsequent reduction of the nitro group, followed by reaction with aldehydes, afforded the purine scaffold. After cleavage from the polymer support, the target compounds were obtained in very good crude purity, good overall yields, and excellent enantiomeric purity. The anticancer activity of prepared compounds was tested in vitro against human cancer cell lines MCF7 and K562, and they were found to have mild, but clear dose-dependent effects.

  6. A high-yielding, strictly regioselective prebiotic purine nucleoside formation pathway.

    PubMed

    Becker, Sidney; Thoma, Ines; Deutsch, Amrei; Gehrke, Tim; Mayer, Peter; Zipse, Hendrik; Carell, Thomas

    2016-05-13

    The origin of life is believed to have started with prebiotic molecules reacting along unidentified pathways to produce key molecules such as nucleosides. To date, a single prebiotic pathway to purine nucleosides had been proposed. It is considered to be inefficient due to missing regioselectivity and low yields. We report that the condensation of formamidopyrimidines (FaPys) with sugars provides the natural N-9 nucleosides with extreme regioselectivity and in good yields (60%). The FaPys are available from formic acid and aminopyrimidines, which are in turn available from prebiotic molecules that were also detected during the Rosetta comet mission. This nucleoside formation pathway can be fused to sugar-forming reactions to produce pentosides, providing a plausible scenario of how purine nucleosides may have formed under prebiotic conditions. Copyright © 2016, American Association for the Advancement of Science.

  7. The prebiotic synthesis of modified purines and their potential role in the RNA world

    NASA Technical Reports Server (NTRS)

    Levy, M.; Miller, S. L.; Bada, J. L. (Principal Investigator)

    1999-01-01

    Modified purines are found in all organisms in the tRNA, rRNA, and even DNA, raising the possibility of an early role for these compounds in the evolution of life. These include N6-methyladenine, 1-methyladenine, N6,N6-dimethyladenine, 1-methylhypoxanthine, 1-methylguanine, and N2-methylguanine. We find that these bases as well as a number of nonbiological modified purines can be synthesized from adenine and guanine by the simple reaction of an amine or an amino group with adenine and guanine under the concentrated conditions of the drying-lagoon or drying-beach model of prebiotic synthesis with yields as high as 50%. These compounds are therefore as prebiotic as adenine and guanine and could have played an important role in the RNA world by providing additional functional groups in ribozymes, especially for the construction of hydrophobic binding pockets.

  8. Coexpression of two closely linked avian genes for purine nucleotide synthesis from a bidirectional promoter.

    PubMed Central

    Gavalas, A; Dixon, J E; Brayton, K A; Zalkin, H

    1993-01-01

    Two avian genes encoding essential steps in the purine nucleotide biosynthetic pathway are transcribed divergently from a bidirectional promoter element. The bidirectional promoter, embedded in a CpG island, directs coexpression of GPAT and AIRC genes from distinct transcriptional start sites 229 bp apart. The bidirectional promoter can be divided in half, with each half retaining partial activity towards the cognate gene. GPAT and AIRC genes encode the enzymes that catalyze step 1 and steps 6 plus 7, respectively, in the de novo purine biosynthetic pathway. This is the first report of genes coding for structurally unrelated enzymes of the same pathway that are tightly linked and transcribed divergently from a bidirectional promoter. This arrangement has the potential to provide for regulated coexpression comparable to that in a prokaryotic operon. Images PMID:8336716

  9. Abiotic synthesis of purines and other heterocyclic compounds by the action of electrical discharges

    NASA Technical Reports Server (NTRS)

    Yuasa, S.; Flory, D.; Basile, B.; Oro, J.

    1984-01-01

    The synthesis of purines and pyrimidines using Oparin-Urey-type primitive earth atmospheres has been demonstrated by reacting methane, ethane, and ammonia in electrical discharges. Adenine, guaine, 4-aminoimidazole-5-carboxamide (AICA), and isocytosine have been identified by UV spectrometry and paper chromatography as the products of the reaction. The total yields of the identified heterocyclic compounds are 0.0023 percent. It is concluded that adenine synthesis occurs at a much lower concentration of hydrogen cyanide than has been shown by earlier studies. Pathways for the synthesis of purines from hydrogen cyanide are discussed, and a comparison of the heterocyclic compounds that have been identified in meteorites and in prebiotic reactions is presented.

  10. Purine Pathway Implicated in Mechanism of Resistance to Aspirin Therapy: Pharmacometabolomics-Informed-Pharmacogenomics

    PubMed Central

    Yerges-Armstrong, Laura M.; Ellero-Simatos, Sandrine; Georgiades, Anastasia; Zhu, Hongjie; Lewis, Joshua; Horenstein, Richard B.; Beitelshees, Amber L.; Dane, Adrie; Reijmers, Theo; Hankemeier, Thomas; Fiehn, Oliver; Shuldiner, Alan R.; Kaddurah-Daouk, Rima

    2014-01-01

    Though aspirin is a well-established antiplatelet agent, the mechanisms of aspirin resistance remain poorly understood. Metabolomics allows for measurement of hundreds of small molecules in biological samples enabling detailed mapping of pathways involved in drug response. We defined the metabolic signature of aspirin exposure in subjects from the Heredity and Phenotype Intervention (HAPI) Heart Study. Many metabolites, including known aspirin catabolites, changed upon exposure to aspirin and pathway enrichment analysis identified purine metabolism as significantly affected by drug exposure. Further, purines were associated with aspirin response and poor responders had higher post-aspirin adenosine and inosine than good responders (N=76;p<4×10-3 both). Using our established “pharmacometabolomics-informs-pharmacogenomics” approach we identified genetic variants in adenosine kinase (ADK) associated with aspirin response. Combining metabolomics and genomics allowed for more comprehensive interrogation of mechanisms of variation in aspirin response - an important step toward personalized treatment approaches for cardiovascular disease. PMID:23839601

  11. The prebiotic synthesis of modified purines and their potential role in the RNA world

    NASA Technical Reports Server (NTRS)

    Levy, M.; Miller, S. L.; Bada, J. L. (Principal Investigator)

    1999-01-01

    Modified purines are found in all organisms in the tRNA, rRNA, and even DNA, raising the possibility of an early role for these compounds in the evolution of life. These include N6-methyladenine, 1-methyladenine, N6,N6-dimethyladenine, 1-methylhypoxanthine, 1-methylguanine, and N2-methylguanine. We find that these bases as well as a number of nonbiological modified purines can be synthesized from adenine and guanine by the simple reaction of an amine or an amino group with adenine and guanine under the concentrated conditions of the drying-lagoon or drying-beach model of prebiotic synthesis with yields as high as 50%. These compounds are therefore as prebiotic as adenine and guanine and could have played an important role in the RNA world by providing additional functional groups in ribozymes, especially for the construction of hydrophobic binding pockets.

  12. Purification, crystallization, and preliminary X-ray diffraction study of purine nucleoside phosphorylase from E. coli

    SciTech Connect

    Abramchik, Yu. A. Timofeev, V. I. Zhukhlistova, N. E.; Muravieva, T. I.; Esipov, R. S.; Kuranova, I. P.

    2015-07-15

    Crystals of E. coli purine nucleoside phosphorylase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 0.99 Å resolution. The crystals belong to sp. gr. P2{sub 1} and have the following unit-cell parameters: a = 74.1 Å, b = 110.2 Å, c = 88.2 Å, α = γ = 90°, β = 111.08°. The crystal contains six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is the biological active form of E. coli. purine nucleoside phosphorylase.

  13. Purification, crystallization, and preliminary X-ray diffraction study of purine nucleoside phosphorylase from E. coli

    NASA Astrophysics Data System (ADS)

    Abramchik, Yu. A.; Timofeev, V. I.; Zhukhlistova, N. E.; Muravieva, T. I.; Esipov, R. S.; Kuranova, I. P.

    2015-07-01

    Crystals of E. coli purine nucleoside phosphorylase were grown in microgravity by the capillary counter-diffusion method through a gel layer. The X-ray diffraction data set suitable for the determination of the three-dimensional structure at atomic resolution was collected from one crystal at the Spring-8 synchrotron facility to 0.99 Å resolution. The crystals belong to sp. gr. P21 and have the following unit-cell parameters: a = 74.1 Å, b = 110.2 Å, c = 88.2 Å, α = γ = 90°, β = 111.08°. The crystal contains six subunits of the enzyme comprising a hexamer per asymmetric unit. The hexamer is the biological active form of E. coli. purine nucleoside phosphorylase.

  14. Structural characterization of purine nucleoside phosphorylase from human pathogen Helicobacter pylori.

    PubMed

    Štefanić, Zoran; Mikleušević, Goran; Luić, Marija; Bzowska, Agnieszka; Leščić Ašler, Ivana

    2017-08-01

    Microaerophilic bacterium Helicobacer pylori is a well known human pathogen involved in the development of many diseases. Due to the evergrowing infection rate and increase of H. pylori antibiotic resistence, it is of utmost importance to find a new way to attack and eradicate H. pylori. The purine metabolism in H. pylori is solely dependant on the salvage pathway and one of the key enzymes in this pathway is purine nucleoside phosphorylase (PNP). In this timely context, we report here the basic biochemical and structural characterization of recombinant PNP from the H. pylori clinical isolate expressed in Escherichia coli. Structure of H. pylori PNP is typical for high molecular mass PNPs. However, its activity towards adenosine is very low, thus resembling more that of low molecular mass PNPs. Understanding the molecular mechanism of this key enzyme may lead to the development of new drug strategies and help in the eradication of H. pylori. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Evidence for incorporation of intact dietary pyrimidine (but not purine) nucleosides into hepatic RNA.

    PubMed Central

    Berthold, H K; Crain, P F; Gouni, I; Reeds, P J; Klein, P D

    1995-01-01

    The absorption and metabolism of dietary nucleic acids have received less attention than those of other organic nutrients, largely because of methodological difficulties. We supplemented the rations of poultry and mice with the edible alga Spirulina platensis, which had been uniformly labeled with 13C by hydroponic culture in 13CO2. The rations were ingested by a hen for 4 wk and by four mice for 6 days; two mice were fed a normal diet and two were fed a nucleic acid-deficient diet. The animals were killed and nucleosides were isolated from hepatic RNA. The isotopic enrichment of all mass isotopomers of the nucleosides was analyzed by selected ion monitoring of the negative chemical ionization mass spectrum and the labeling pattern was deconvoluted by reference to the enrichment pattern of the tracer material. We found a distinct difference in the 13C enrichment pattern between pyrimidine and purine nucleosides; the isotopic enrichment of uniformly labeled [M + 9] isotopomers of pyrimidines exceeded that of purines [M + 10] by > 2 orders of magnitude in the avian nucleic acids and by 7- and 14-fold in the murine nucleic acids. The purines were more enriched in lower mass isotopomers, those less than [M + 3], than the pyrimidines. Our results suggest that large quantities of dietary pyrimidine nucleosides and almost no dietary purine nucleosides are incorporated into hepatic nucleic acids without hydrolytic removal of the ribose moiety. In addition, our results support a potential nutritional role for nucleosides and suggest that pyrimidines are conditionally essential organic nutrients. PMID:7479738

  16. Electronic and structural elements that regulate the excited-state dynamics in purine nucleobase derivatives.

    PubMed

    Crespo-Hernández, Carlos E; Martínez-Fernández, Lara; Rauer, Clemens; Reichardt, Christian; Mai, Sebastian; Pollum, Marvin; Marquetand, Philipp; González, Leticia; Corral, Inés

    2015-04-08

    The excited-state dynamics of the purine free base and 9-methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally excited (1)nπ* state. Following vibrational and conformational relaxation, the (1)nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments show an almost 2-fold increase in the intersystem crossing rate on going from polar aprotic to nonpolar solvents, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface-hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demonstrate that the accessibility of the nπ* states and the topology of the potential energy surfaces in the vicinity of conical intersections are key elements in controlling the excited-state dynamics of the purine derivatives. From a structural perspective, it is shown that the purine chromophore is not responsible for the ultrafast internal conversion in the adenine and guanine monomers. Instead, C6 functionalization plays an important role in regulating the rates of radiative and nonradiative relaxation. C6 functionalization inhibits access to the (1)nπ* state while simultaneously facilitating access to the (1)ππ*(La)/S0 conical intersection, such that population of the (1)nπ* state cannot compete with the relaxation pathways to the ground state involving ring puckering at the C2 position.

  17. [Glutathione redox system, immune status, antioxidant enzymes and metabolism of purine nucleotides in hypothyroidism].

    PubMed

    Tapbergenov, S O; Sovetov, B S; Bekbosynova, R B; Bolysbekova, S M

    2015-01-01

    The immune status, components of the glutathione redox system, the activity of antioxidant enzymes and metabolism of purine nucleotides have been investigated in animals with experimental hypothyroidism. On day 8 after an increase in the number of leukocytes, lymphocytes, T-helpers and T-suppressors as well as increased number of B-lymphocytes was found in blood of thyroidectomized rats. This was accompanied by decreased activity of adenosine deaminase (AD), AMP-deaminase (AMPD), and 5'-nucleotidase (5'N) in blood, but the ratio of enzyme activity AD/AMPD increased. These changes in the activity of enzymes, involved in purine catabolism can be regarded as increased functional relationships between T and B lymphocytes in hypothyroidism. The functional changes of immune system cells were accompanied by increased activity of glutathione peroxidase (GPx), a decrease in the activity of superoxide dismutase (SOD), glutathione reductase (GR) and the ratio GH/GPx. Thyroidectomized rats had increased amounts of total, oxidized (GSSG) and reduced glutathione (GSH), but the ratio GSH/GSSG decerased as compared with control animals. In the liver, hypothyroidism resulted in activation of SOD, GPx, decreased activity of GR and decreased ratio GR/GPx. At the same time, the levels of total, oxidized, and reduced glutathione increased, but the ratio GSH/GSSG as well as activities of enzymes involved in purine nucleotide metabolism ratio (and their ratio 5'N/AD + AMPD) decreased. All these data suggest a functional relationship of the glutathione redox system not only with antioxidant enzymes, but also activity of enzymes involved purine nucleotide metabolism and immune status.

  18. Electronic and Structural Elements That Regulate the Excited-State Dynamics in Purine Nucleobase Derivatives

    PubMed Central

    2015-01-01

    The excited-state dynamics of the purine free base and 9-methylpurine are investigated using experimental and theoretical methods. Femtosecond broadband transient absorption experiments reveal that excitation of these purine derivatives in aqueous solution at 266 nm results primarily in ultrafast conversion of the S2(ππ*) state to the vibrationally excited 1nπ* state. Following vibrational and conformational relaxation, the 1nπ* state acts as a doorway state in the efficient population of the triplet manifold with an intersystem crossing lifetime of hundreds of picoseconds. Experiments show an almost 2-fold increase in the intersystem crossing rate on going from polar aprotic to nonpolar solvents, suggesting that a solvent-dependent energy barrier must be surmounted to access the singlet-to-triplet crossing region. Ab initio static and surface-hopping dynamics simulations lend strong support to the proposed relaxation mechanism. Collectively, the experimental and computational results demonstrate that the accessibility of the nπ* states and the topology of the potential energy surfaces in the vicinity of conical intersections are key elements in controlling the excited-state dynamics of the purine derivatives. From a structural perspective, it is shown that the purine chromophore is not responsible for the ultrafast internal conversion in the adenine and guanine monomers. Instead, C6 functionalization plays an important role in regulating the rates of radiative and nonradiative relaxation. C6 functionalization inhibits access to the 1nπ* state while simultaneously facilitating access to the 1ππ*(La)/S0 conical intersection, such that population of the 1nπ* state cannot compete with the relaxation pathways to the ground state involving ring puckering at the C2 position. PMID:25763596

  19. [Measurement of purines and uric acid simultaneous in meat with high performance liquid chromatographys].

    PubMed

    Yang, Haibin; Zhang, Jialing; Liu, Guiying; Zhang, Ping

    2012-03-01

    To determinate adenine, guanine, hypoxanthine, xanthine and uric acid simultaneously in meat, a reversed-phase high performance liquid chromatography (HPLC) was developed. The meat were hydrolyzed with perchloric acid 10% (v/v) in boiling water for 60 mm. After the hydrolysate was adjusted to pH 4, centrifuge , and filtrated with a 0.45 mirom membrane, the supernatants were separated on an Agilent ZORBAX Eclipse XDB-C18 column (250 mm x 4.6 mm i.d., 5 microm) at 25 degrees C with a mobile phase of 7 x 10(-3) mol/L KH2PO4-H3P04(pH 4.0) ,a flow rate of 1.0 ml/ mm, and UV detection at 254 nm. Each component in the corresponding concentration range showed a good linear relation with its peak area, correlation coefficient r > 0.9999, recovery was 90.0%-107. 5%, RSD was 1.7%-13.3%. In addition to containing four kinds of purines, there was quite amount of uric acid (about 133.7 -86.2 pug/g) in the mentioned meat. The ratio of uric acid to total purine and uric acid was about 7%. The content of total purine in chicken was (1759.3 +/- 64.6) microg/g higher than in rabbit, mutton, pork and beef (1440-1000 microg/g). The validated method is simple, rapid, accurate and reliable to the determination of purines and uric acid in meat.

  20. Stacking of purines in water: the role of dipolar interactions in caffeine.

    PubMed

    Tavagnacco, L; Di Fonzo, S; D'Amico, F; Masciovecchio, C; Brady, J W; Cesàro, A

    2016-05-11

    During the last few decades it has been ascertained that base stacking is one of the major contributions stabilizing nucleic acid conformations. However, the understanding of the nature of the interactions involved in the stacking process remains under debate and it is a subject of theoretical and experimental studies. Structural similarity between purine bases (guanine and adenine) in DNA and the caffeine molecule makes caffeine an excellent model for the purine bases. The present study clearly shows that dipolar interactions play a fundamental role in determining stacking of purine molecules in solution. In order to reach this achievement, polarized ultraviolet Raman resonant scattering experiments have been carried out on caffeine aqueous solutions as a function of concentration and temperature. The investigation pointed out at the aggregation and solvation properties, particularly at elevated temperatures. Kubo-Anderson theory was used as a framework to investigate the non-coincidence effect (NCE) occurring in the totally symmetric breathing modes of the purine rings, and in the bending modes of the methyl groups of caffeine. The NCE concentration dependence shows that caffeine aggregation at 80 °C occurs by planar stacking of the hydrophobic faces. The data clearly indicate that dipolar interactions determine the reorientational motion of the molecules in solution and are the driving force for the stacking of caffeine. In parallel, the observed dephasing times imply a change in caffeine interactions as a function of temperature and concentration. A decrease, at low water content, of the dephasing time for the ring breathing vibration mode indicates that self-association alters the solvation structure that is detectable at low concentration. These results are in agreement with simulation predictions and serve as an important validation of the models used in those calculations.

  1. L-Enantiomers of Transition State Analogue Inhibitors Bound to Human Purine Nucleoside Phosphorylase

    SciTech Connect

    Rinaldo-Matthis,A.; Murkin, A.; Ramagopal, U.; Clinch, K.; Mee, S.; Evans, G.; Tyler, P.; Furneaux, R.; Almo, S.; Schramm, v.

    2008-01-01

    Human purine nucleoside phosphorylase (PNP) was crystallized with transition-state analogue inhibitors Immucillin-H and DADMe-Immucillin-H synthesized with ribosyl mimics of l-stereochemistry. The inhibitors demonstrate that major driving forces for tight binding of these analogues are the leaving group interaction and the cationic mimicry of the transition state, even though large geometric changes occur with d-Immucillins and l-Immucillins bound to human PNP.

  2. Proline metabolism in N2-fixing root nodules: energy transfer and regulation of purine synthesis.

    PubMed Central

    Kohl, D H; Schubert, K R; Carter, M B; Hagedorn, C H; Shearer, G

    1988-01-01

    N2-fixing root nodules of soybean (Glycine max L. Merr.) convert atmospheric N2 to ammonia(um) in an energy-intensive enzymatic reaction. These nodules synthesize large quantities of purines because nitrogen fixed by bacteria contained within this tissue is transferred to the shoots in the form of ureides, which are degradation products of purines. In animal systems, it has been proposed that proline biosynthesis by pyrroline-5-carboxylate reductase (P5CR) is used to generate the NADP+ required for the synthesis of the purine precursor ribose 5-phosphate. We have examined the levels, properties, and location of P5CR and proline dehydrogenase (ProDH) in soybean nodules. Nodule P5CR was found in the plant cytosol. Its activity was substantially higher than that reported for other animal and plant tissues and is 4-fold higher than in pea (Pisum sativum) nodules (which export amides). The Km for NADPH was lower by a factor of 25 than the Km for NADH, while the Vmax with NADPH was one-third of that with NADH. P5CR activity was diminished by NADP+ but not by proline. These characteristics are consistent with a role for P5CR in supporting nodule purine biosynthesis rather than in producing proline for incorporation into protein. ProDH activity was divided between the bacteroids and plant cytosol, but less than 2% was in the mitochondria-rich fractions. The specific activity of ProDH in soybean nodule bacteroids was comparable to that in rat liver mitochondria. In addition, we propose that some of the proline synthesized in the plant cytosol by P5CR is catabolized within the bacteroids by ProDH and that this represents a novel mechanism for transferring energy from the plant to its endosymbiont. PMID:3353366

  3. Purine nucleoside phosphorylase and xanthine oxidase activities in erythrocytes and plasma from marine, semiaquatic and terrestrial mammals.

    PubMed

    López-Cruz, Roberto I; Pérez-Milicua, Myrna Barjau; Crocker, Daniel E; Gaxiola-Robles, Ramón; Bernal-Vertiz, Jaime A; de la Rosa, Alejandro; Vázquez-Medina, José P; Zenteno-Savín, Tania

    2014-05-01

    Purine nucleoside phosphorylase (PNP) and xanthine oxidase (XO) are key enzymes involved in the purine salvage pathway. PNP metabolizes purine bases to synthetize purine nucleotides whereas XO catalyzes the oxidation of purines to uric acid. In humans, PNP activity is reported to be high in erythrocytes and XO activity to be low in plasma; however, XO activity increases after ischemic events. XO activity in plasma of northern elephant seals has been reported during prolonged fasting and rest and voluntary associated apneas. The objective of this study was to analyze circulating PNP and XO activities in marine mammals adapted to tolerate repeated cycles of ischemia/reperfusion associated with diving (bottlenose dolphin, northern elephant seal) in comparison with semiaquatic (river otter) and terrestrial mammals (human, pig). PNP activities in plasma and erythrocytes, as well as XO activity in plasma, from all species were quantified by spectrophotometry. No clear relationship in circulating PNP or XO activity could be established between marine, semiaquatic and terrestrial mammals. Erythrocytes from bottlenose dolphins and humans are highly permeable to nucleosides and glucose, intraerythrocyte PNP activity may be related to a release of purine nucleotides from the liver. High-energy costs will probably mean a higher ATP degradation rate in river otters, as compared to northern elephant seals or dolphins. Lower erythrocyte PNP activity and elevated plasma XO activity in northern elephant seal could be associated with fasting and/or sleep- and dive-associated apneas. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. The Formation of Nucleobases from the Irradiation of Purine in Astophysical Ices and Comparisons with Meteorites.

    NASA Technical Reports Server (NTRS)

    Sandford, S. A.; Materese, C. K.; Nuevo, M.

    2016-01-01

    N-heterocycles have been identified in meteorites and their extraterrestrial origins are suggested by isotopic ratio measurements. Although small N- heterocycles have not been detected in the interstellar medium (ISM), recent experiments in our lab have shown that the irradiation of the aromatic molecules like benzene (C6H6) and naphthalene (C10H8) in mixed molecular ices leads to the formation of O- and N-heterocyclic molecules. Among the class of N-heterocycles are the nucleobases, which are of astrobiological interest because they are the information bearing units of DNA and RNA. Nucleobases have been detected in meteorites [3-5], with isotopic signatures that are also consistent with an extraterrestrial origin. Three of the biologically relevant nucleobases (uracil, cytosine, and guanine) have a pyrimidine core structure while the remaining two (adenine and guanine) possess a purine core. Previous experiments in our lab have demonstrated that all of the bio-logical nucleobases (and numerous other molecules) with a pyrimidine core structure can be produced by irradiating pyrimidine in mixed molecular ices of several compositions [6-8]. In this work, we study the formation of purine-based molecules, including the nucleobases adenine, and guanine, from the ultraviolet (UV) irradiation of purine in ices consisting mixtures of H2O and NH3 at low temperature. The experiments are designed to simulate the astrophysical conditions under which these species may be formed in dense molecular clouds, protoplanetary disks, or on the surfaces of icy bodies in planetary systems.

  5. Purine and pyrimidine metabolism: Convergent evidence on chronic antidepressant treatment response in mice and humans

    PubMed Central

    Park, Dong Ik; Dournes, Carine; Sillaber, Inge; Uhr, Manfred; Asara, John M.; Gassen, Nils C.; Rein, Theo; Ising, Marcus; Webhofer, Christian; Filiou, Michaela D.; Müller, Marianne B.; Turck, Christoph W.

    2016-01-01

    Selective Serotonin Reuptake Inhibitors (SSRIs) are commonly used drugs for the treatment of psychiatric diseases including major depressive disorder (MDD). For unknown reasons a substantial number of patients do not show any improvement during or after SSRI treatment. We treated DBA/2J mice for 28 days with paroxetine and assessed their behavioral response with the forced swim test (FST). Paroxetine-treated long-time floating (PLF) and paroxetine-treated short-time floating (PSF) groups were stratified as proxies for drug non-responder and responder mice, respectively. Proteomics and metabolomics profiles of PLF and PSF groups were acquired for the hippocampus and plasma to identify molecular pathways and biosignatures that stratify paroxetine-treated mouse sub-groups. The critical role of purine and pyrimidine metabolisms for chronic paroxetine treatment response in the mouse was further corroborated by pathway protein expression differences in both mice and patients that underwent chronic antidepressant treatment. The integrated -omics data indicate purine and pyrimidine metabolism pathway activity differences between PLF and PSF mice. Furthermore, the pathway protein levels in peripheral specimens strongly correlated with the antidepressant treatment response in patients. Our results suggest that chronic SSRI treatment differentially affects purine and pyrimidine metabolisms, which may explain the heterogeneous antidepressant treatment response and represents a potential biosignature. PMID:27731396

  6. Purine molecules as hypnogenic factors role of adenosine, ATP, and caffeine.

    PubMed

    Díaz-Muñoz, M; Salín-Pascual, R

    2010-12-01

    Purines are ubiquitous molecules with important roles in the regulation of metabolic networks and signal transduction events. In the central nervous system, adenosine and ATP modulate the sleep-wake cycle, acting as ligands of specific transmembrane receptors and as allosteric effectors of key intracellular enzymes for brain energy expenditure. Two types of adenosine receptors seem to be relevant to the sleep function, A1 and A2A. Caffeine, an antagonist of adenosine receptors, has been used as a tool in some of the studies reviewed in the present chapter. Possible changes in adenosine functioning due to the aging process have been observed in animal models and abnormalities in the adenosine system could also explain primary insomnia or the reduced amount of delta sleep and increased sensitivity to caffeine in some subjects with sleep deficits. Caffeine is a methylated-derivate of xanthine with profound effects on the onset and quality of sleep episodes. This purine acts principally as an antagonist of the A2A receptors. Adenosine and ATP in the nervous system are the bridge between metabolic activity, recovery function, and purinergic transmission that underlies the daily wake-sleep cycle in mammals. Modulators of purine actions have the potential to alleviate insomnia and other sleep disorders based on their physiopathological role during the sleep process.

  7. GPCRs regulate the assembly of a multienzyme complex for purine biosynthesis

    PubMed Central

    Verrier, Florence; An, Songon; Ferrie, Ann M.; Sun, Haiyan; Kyoung, Minjoung; Deng, Huayun; Fang, Ye; Benkovic, Stephen J.

    2011-01-01

    G protein-coupled receptors (GPCRs) transmit exogenous signals to the nucleus, promoting a myriad of biological responses via multiple signaling pathways in both normal and cancer cells. However, little is known about the response in cytosolic metabolic pathways to GPCR-mediated signaling. Here, we applied fluorescent live-cell imaging and label-free dynamic mass redistribution assays to study whether purine metabolism is associated with GPCR signaling. By screening a library of GPCR ligands in conjunction with live-cell imaging of a metabolic multienzyme complex for de novo purine biosynthesis, the purinosome, we demonstrated that the activation of endogenous Gαi-coupled receptors correlates with purinosome assembly/disassembly in native HeLa cells. Given the implications of GPCRs in mitogenic signaling as well as the purinosome in controlling metabolic flux via de novo purine biosynthesis, we hypothesize that regulation of purinosome assembly/disassembly may represent one of downstream events of mitogenic GPCR signaling in human cancer cells. PMID:22020552

  8. GPCRs regulate the assembly of a multienzyme complex for purine biosynthesis.

    PubMed

    Verrier, Florence; An, Songon; Ferrie, Ann M; Sun, Haiyan; Kyoung, Minjoung; Deng, Huayun; Fang, Ye; Benkovic, Stephen J

    2011-10-23

    G protein-coupled receptors (GPCRs) transmit exogenous signals to the nucleus, promoting a myriad of biological responses via multiple signaling pathways in both healthy and cancerous cells. However, little is known about the response of cytosolic metabolic pathways to GPCR-mediated signaling. Here we applied fluorescent live-cell imaging and label-free dynamic mass redistribution assays to study whether purine metabolism is associated with GPCR signaling. Through a library screen of GPCR ligands in conjunction with live-cell imaging of a metabolic multienzyme complex for de novo purine biosynthesis, the purinosome, we demonstrated that the activation of endogenous Gα(i)-coupled receptors correlates with purinosome assembly and disassembly in native HeLa cells. Given the implications of GPCRs in mitogenic signaling and of the purinosome in controlling metabolic flux via de novo purine biosynthesis, we hypothesize that regulation of purinosome assembly and disassembly may be one of the downstream events of mitogenic GPCR signaling in human cancer cells.

  9. Purine biosynthetic genes are required for cadmium tolerance in Schizosaccharomyces pombe

    SciTech Connect

    Speiser, D.M.; Ortiz, D.F.; Kreppel, L.; Scheel, G.; McDonald, G.; Ow, D.W. Univ. of California, Berkeley )

    1992-12-01

    Phytochelatins (PCs) are metal-chelating peptides produced in plants and some fungi in response to heavy metal exposure. A Cd-sensitive mutant of the fission yeast Schizosaccharomyces pombe, defective in production of a PC-Cd-sulfide complex essential for metal tolerance, was found to harbor mutations in specific genes of the purine biosynthetic pathway. Genetic analysis of the link between metal complex accumulation and purine biosynthesis enzymes revealed that genetic lesions blocking two segments of the pathway, before and after the IMP branchpoint, are required to produce the Cd-sensitive phenotype. The biochemical functions of these two segments of the pathway are similar, and a model based on the alternate use of a sulfur analog substrate is presented. The novel participation of purine biosynthesis enzymes in the conversion of the PC-Cd complex to the PC-Cd-sulfide complex in the fission yeast raises an intriguing possibility that these same enzymes might have a role in sulfur metabolism in the fission yeast S. pombe, and perhaps in other biological systems. 41 refs., 8 figs., 2 tabs.

  10. Effects of allopurinol and oxipurinol on purine synthesis in cultured human cells

    PubMed Central

    Kelley, William N.; Wyngaarden, James B.

    1970-01-01

    In the present study we have examined the effects of allopurinol and oxipurinol on the de novo synthesis of purines in cultured human fibroblasts. Allopurinol inhibits de novo purine synthesis in the absence of xanthine oxidase. Inhibition at lower concentrations of the drug requires the presence of hypoxanthine-guanine phosphoribosyltransferase as it does in vivo. Although this suggests that the inhibitory effect of allopurinol at least at the lower concentrations tested is a consequence of its conversion to the ribonucleotide form in human cells, the nucleotide derivative could not be demonstrated. Several possible indirect consequences of such a conversion were also sought. There was no evidence that allopurinol was further utilized in the synthesis of nucleic acids in these cultured human cells and no effect of either allopurinol or oxipurinol on the long-term survival of human cells in vitro could be demonstrated. At higher concentrations, both allopurinol and oxipurinol inhibit the early steps of de novo purine synthesis in the absence of either xanthine oxidase or hypoxanthine-guanine phosphoribosyltransferase. This indicates that at higher drug concentrations, inhibition is occurring by some mechanism other than those previously postulated. PMID:5415686

  11. Chemical modification of the third strand: differential effects on purine and pyrimidine triple helix formation.

    PubMed

    Mills, Martin; Arimondo, Paola B; Lacroix, Laurent; Garestier, Thérèse; Klump, Horst; Mergny, Jean-Louis

    2002-01-08

    DNA triple helices offer exciting perspectives toward oligonucleotide-directed control of gene expression. Oligonucleotide analogues are routinely used with modifications in either the backbone or the bases to form more stable triple-helical structures or to prevent their degradation in cells. In this article, different chemical modifications are tested in a model system, which sets up a competition between the purine and pyrimidine motifs. For most modifications, the DeltaH degrees of purine triplex formation is close to zero, implying a nearly temperature-independent affinity constant. In contrast, the pyrimidine triplex is strongly favored at lower temperatures. The stabilization induced by modifications previously known to be favorable to the pyrimidine motif was quantified. Interestingly, modifications favorable to the GT motif (propynyl-U and dU replacing T) were also discovered. In a system where two third strands compete for triplex formation, replacement of the GA or GT strand by a pyrimidine strand may be observed at neutral pH upon lowering the temperature. This purine-to-pyrimidine triplex conversion depends on the chemical nature of the triplex-forming strands and the stability of the corresponding triplexes.

  12. Isolation of Purines and Pyrimidines from the Murchison Meteorite Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. L.

    2004-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The exogenous delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth s prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines. These compounds dominate terrestrial biochemistry and are integral components of proteins, DNA and RNA. Several purines including adenine, guanine, hypoxanthine, and xanthine, as well as the pyrimidine uracil, have previously been detected in water or formic acid extracts of Murchison using ion-exclusion chromatography and ultraviolet spectroscopy. However, even after purification of these extracts, the accurate identification and quantification of nucleobases is difficult due to interfering UV absorbing compounds. In order to reduce these effects, we have developed an extraction technique using sublimation to isolate purines and pyrimidines from other non-volatile organic compounds in Murchison acid extracts.

  13. Purine biosynthetic genes are required for cadmium tolerance in Schizosaccharomyces pombe.

    PubMed Central

    Speiser, D M; Ortiz, D F; Kreppel, L; Scheel, G; McDonald, G; Ow, D W

    1992-01-01

    Phytochelatins (PCs) are metal-chelating peptides produced in plants and some fungi in response to heavy metal exposure. A Cd-sensitive mutant of the fission yeast Schizosaccharomyces pombe, defective in production of a PC-Cd-sulfide complex essential for metal tolerance, was found to harbor mutations in specific genes of the purine biosynthetic pathway. Genetic analysis of the link between metal complex accumulation and purine biosynthesis enzymes revealed that genetic lesions blocking two segments of the pathway, before and after the IMP branchpoint, are required to produce the Cd-sensitive phenotype. The biochemical functions of these two segments of the pathway are similar, and a model based on the alternate use of a sulfur analog substrate is presented. The novel participation of purine biosynthesis enzymes in the conversion of the PC-Cd complex to the PC-Cd-sulfide complex in the fission yeast raises an intriguing possibility that these same enzymes might have a role in sulfur metabolism in the fission yeast S. pombe, and perhaps in other biological systems. Images PMID:1448066

  14. Isolation of Purines and Pyrimidines from the Murchison Meteorite Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. L.

    2004-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The exogenous delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth s prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines. These compounds dominate terrestrial biochemistry and are integral components of proteins, DNA and RNA. Several purines including adenine, guanine, hypoxanthine, and xanthine, as well as the pyrimidine uracil, have previously been detected in water or formic acid extracts of Murchison using ion-exclusion chromatography and ultraviolet spectroscopy. However, even after purification of these extracts, the accurate identification and quantification of nucleobases is difficult due to interfering UV absorbing compounds. In order to reduce these effects, we have developed an extraction technique using sublimation to isolate purines and pyrimidines from other non-volatile organic compounds in Murchison acid extracts.

  15. Levels of purine, kynurenine and lipid peroxidation products in patients with inflammatory bowel disease.

    PubMed

    Forrest, Caroline M; Gould, Stuart R; Darlington, L Gail; Stone, Trevor W

    2003-01-01

    The factors affecting gut activity in inflammatory bowel disease are unclear, but purines and kynurenines may be involved in the regulation of neuronal activity and therefore gut motility and secretion. We have measured the serum levels of these compounds in patients and in sex- and age-matched controls. Purines and kynurenines were analysed using HPLC. The levels of tryptophan and its metabolites 3-hydroxykynurenine, 3-hydroxyanthranilic acid and xanthurenic acid were unchanged in all patients. However, the levels of kynurenine and kynurenic acid were significantly elevated in patients with inflammatory bowel disease when compared to control subjects. There were no significant differences between patients and controls for any of the purines analysed or for neopterin. In the inflammatory bowel disease patients serum lipid peroxidation products were significantly elevated when compared to control subjects, suggesting the presence of increased oxidative stress consistent with inflammatory activity. The elevated level of kynurenic acid may represent either a compensatory response to elevated activation of enteric neurones, or a primary abnormality, which induces a compensatory increase in gut activity, but may indicate a role for kynurenine modulation of glutamate receptors in the symptoms of inflammatory bowel disease.

  16. Hypercrosslinked strong cation-exchange polymers for selective extraction of serum purine metabolites associated with gout.

    PubMed

    Xu, Yating; Liu, Ju; Zhang, Hongyang; Jiang, Min; Cao, Lingling; Zhang, Min; Sun, Wei; Ruan, Shengli; Hu, Ping

    2016-05-01

    In this study, hypercrosslinked strong cation-exchange polymer resins (HXLPP-SCX) were synthesized and employed as selective sorbents for the solid-phase extraction (SPE) of basic purine metabolites associated with gout. The HXLPP-SCX material was prepared based on hypercrosslinking reactions and sulfonated with concentrated H2SO4. This synthetic procedure is facile and efficient without using highly toxic reagent. The resulting resins were characterized in the form of monodisperse microspheres (mean diameters of 3‒5μm) with narrow pore size (2.1nm) and relatively high specific surface areas (801m(2)/g). The polymers also possess high ion-exchange capacity (IEC, 2.22mmol/g) and good adsorption and selectivity performances for basic compounds. The resins used as SPE sorbents permit the selective enrichment of three pivotal purine metabolites (hypoxanthine, xanthine and inosine) in human serum followed by HPLC analysis. Method validation including linearity range, sensitivity, accuracy and reproducibility were evaluated. This method was exemplarily applied in the analysis of serum purines in gout patients and healthy controls. The present results demonstrate a promising potential of this HXLPP-SCX material for the clinical sample pretreatment.

  17. [Purine and pyrimidine nucleoside phosphorylases - remarkable enzymes still not fully understood].

    PubMed

    Bzowska, Agnieszka

    2015-01-01

    Purine and pyrimidine nucleoside phosphorylases catalyze the reversible phosphorolytic cleavage of the glycosidic bond of purine and pyrimidine nucleosides, and are key enzymes of the nucleoside salvage pathway. This metabolic route is the less costly alternative to the de novo synthesis of nucleosides and nucleotides, supplying cells with these important building blocks. Interest in nucleoside phosphorylases is not only due to their important role in metabolism of nucleosides and nucleotides, but also due to the potential medical use of the enzymes (all phosphorylases in activating prodrugs - nucleoside and nucleic base analogs, high-molecular mass purine nucleoside phosphorylases in gene therapy of some solid tumors) and their inhibitors (as selective immunosuppressive, anticancer and antiparasitic agents, and preventing inactivation of other nucleoside drugs). Phosphorylases are also convenient tools for efficient enzymatic synthesis of otherwise inaccessible nucleoside analogues. In this paper the contribution of Professor David Shugar and some of his colleagues and coworkers in studies of these remarkable enzymes carried out over nearly 40 years is discussed on the background of global research in this field.

  18. Novel anomeric sugar phosphodiesters synthesis, hydrolytic mechanism, structure and interaction with purine nucleoside phosphorylase

    SciTech Connect

    Fathi, R.

    1988-01-01

    Some five-membered ring ribofuranosyl-1,2-cyclic phosphates were synthesized, purified, and characterized for the purpose of employing them as stereoselective electrophilic substrate analogs with a potential to trap enzymic nucleophiles on the purine salvage pathway. The purine salvage enzyme purine nucleoside phosphorylase from mammalian sources was irreversibly inactivated at its catalytic center by ..cap alpha..-D-ribofuranosyl-1,2-cyclic monophosphate. The product distribution and kinetics of hydronium and hydroxide catalyzed hydrolysis of cyclic phosphates were monitored by /sup 31/P NMR. Alkaline hydrolysis was demonstrated to proceed exclusively by O-P bond cleavage by employing a specifically /sup 18/O-labelled substrate. Acid hydrolysis proceeded by C-O bond cleavage. The high rates of alkaline hydrolysis were similar to those reported for ethylene phosphate, presumably due to the presence of a strained cyclic phosphate ring. Extensive NMR (/sup 1/H, /sup 13/C, and /sup 31/P) data on the cyclic phosphates were consistent with a C3-endo ribofuranosyl conformation.

  19. Computational design of donor-bridge-acceptor systems exhibiting pronounced quantum interference effects.

    PubMed

    Gorczak, Natalie; Renaud, Nicolas; Galan, Elena; Eelkema, Rienk; Siebbeles, Laurens D A; Grozema, Ferdinand C

    2016-03-07

    Quantum interference is a well-known phenomenon that dictates charge transport properties of single molecule junctions. However, reports on quantum interference in donor-bridge-acceptor molecules are scarce. This might be due to the difficulties in meeting the conditions for the presence of quantum interference in a donor-bridge-acceptor system. The electronic coupling between the donor, bridge, and acceptor moieties must be weak in order to ensure localised initial and final states for charge transfer. Yet, it must be strong enough to allow all bridge orbitals to mediate charge transfer. We present the computational route to the design of a donor-bridge-acceptor molecule that features the right balance between these contradicting requirements and exhibits pronounced interference effects.

  20. [Social inequalities in health less pronounced in women than in men: A question of measurements?].

    PubMed

    Cambois, E

    2016-04-01

    Social inequalities in mortality are generally less pronounced for women than for men. Are women's health risks and behaviours more homogeneous, or does this pattern arise from a measurement issue inducing an under-estimation of these inequalities? This article reviews a number of studies covering different dimensions of health and different dimensions of social status. Their findings show that there are large social inequalities in health among women. The focus on the working careers, family histories and conciliation of multiple activities provides evidence of major social determinants of health to which women are widely exposed. This article highlights the need to broaden the notion of social inequality and to redefine the social categories, notably by considering the distinct trajectories of men and women and their different spheres of activity. It highlights that gender differences in health are themselves partly socially constructed, as suggested by the gender approaches in the social sciences.

  1. LMTK3 deficiency causes pronounced locomotor hyperactivity and impairs endocytic trafficking.

    PubMed

    Inoue, Takeshi; Hoshina, Naosuke; Nakazawa, Takanobu; Kiyama, Yuji; Kobayashi, Shizuka; Abe, Takaya; Yamamoto, Toshifumi; Manabe, Toshiya; Yamamoto, Tadashi

    2014-04-23

    LMTK3 belongs to the LMTK family of protein kinases that are predominantly expressed in the brain. Physiological functions of LMTK3 and other members of the LMTK family in the CNS remain unknown. In this study, we performed a battery of behavioral analyses using Lmtk3(-/-) mice and showed that these mice exhibit abnormal behaviors, including pronounced locomotor hyperactivity, reduced anxiety behavior, and decreased depression-like behavior. Concurrently, the dopamine metabolite levels and dopamine turnover rate are increased in the striata of Lmtk3(-/-) mice compared with wild-type controls. In addition, using cultured primary neurons from Lmtk3(-/-) mice, we found that LMTK3 is involved in the endocytic trafficking of N-methyl-d-aspartate receptors, a type of ionotropic glutamate receptor. Altered membrane traffic of the receptor in Lmtk3(-/-) neurons may underlie behavioral abnormalities in the mutant animals. Together, our data suggest that LMTK3 plays an important role in regulating locomotor behavior in mice.

  2. Muscle carnosine loading by beta-alanine supplementation is more pronounced in trained vs. untrained muscles.

    PubMed

    Bex, T; Chung, W; Baguet, A; Stegen, S; Stautemas, J; Achten, E; Derave, W

    2014-01-15

    Carnosine occurs in high concentrations in human skeletal muscle and assists working capacity during high-intensity exercise. Chronic beta-alanine (BA) supplementation has consistently been shown to augment muscle carnosine concentration, but the effect of training on the carnosine loading efficiency is poorly understood. The aim of the present study was to compare muscle carnosine loading between trained and untrained arm and leg muscles. In a first study (n = 17), reliability of carnosine quantification by proton magnetic resonance spectroscopy ((1)H-MRS) was evaluated in deltoid and triceps brachii muscles. In a second study, participants (n = 35; 10 nonathletes, 10 cyclists, 10 swimmers, and 5 kayakers) were supplemented with 6.4 g/day of slow-release BA for 23 days. Carnosine content was evaluated in soleus, gastrocnemius medialis, and deltoid muscles by (1)H-MRS. All the results are reported as arbitrary units. In the nonathletes, BA supplementation increased carnosine content by 47% in the arm and 33% in the leg muscles (not significant). In kayakers, the increase was more pronounced in arm (deltoid) vs. leg (soleus + gastrocnemius) muscles (0.089 vs. 0.049), whereas the reverse pattern was observed in cyclists (0.065 vs. 0.084). Swimmers had significantly higher increase in carnosine in both deltoid (0.107 vs. 0.065) and gastrocnemius muscle (0.082 vs. 0.051) compared with nonathletes. We showed that 1) carnosine content can be reliably measured by (1)H-MRS in deltoid muscle, 2) carnosine loading is equally effective in arm vs. leg muscles of nonathletes, and 3) carnosine loading is more pronounced in trained vs. untrained muscles.

  3. Emergence of representations through repeated training on pronouncing novel letter combinations leads to efficient reading.

    PubMed

    Takashima, Atsuko; Hulzink, Iris; Wagensveld, Barbara; Verhoeven, Ludo

    2016-08-01

    Printed text can be decoded by utilizing different processing routes depending on the familiarity of the script. A predominant use of word-level decoding strategies can be expected in the case of a familiar script, and an almost exclusive use of letter-level decoding strategies for unfamiliar scripts. Behavioural studies have revealed that frequently occurring words are read more efficiently, suggesting that these words are read in a more holistic way at the word-level, than infrequent and unfamiliar words. To test whether repeated exposure to specific letter combinations leads to holistic reading, we monitored both behavioural and neural responses during novel script decoding and examined changes related to repeated exposure. We trained a group of Dutch university students to decode pseudowords written in an unfamiliar script, i.e., Korean Hangul characters. We compared behavioural and neural responses to pronouncing trained versus untrained two-character pseudowords (equivalent to two-syllable pseudowords). We tested once shortly after the initial training and again after a four days' delay that included another training session. We found that trained pseudowords were pronounced faster and more accurately than novel combinations of radicals (equivalent to letters). Imaging data revealed that pronunciation of trained pseudowords engaged the posterior temporo-parietal region, and engagement of this network was predictive of reading efficiency a month later. The results imply that repeated exposure to specific combinations of graphemes can lead to emergence of holistic representations that result in efficient reading. Furthermore, inter-individual differences revealed that good learners retained efficiency more than bad learners one month later. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Analysis of Intra- and Extracellular Levels of Purine Bases, Nucleosides, and Nucleotides in HepG2 Cells by High-performance Liquid Chromatography.

    PubMed

    Fukuuchi, Tomoko; Yamaoka, Noriko; Kaneko, Kiyoko

    2015-01-01

    To evaluate cellular uptake and purine transport, we developed a high-performance liquid chromatography method for intra- and extracellular purine quantification. Our aim was to develop an effective method for simultaneously quantifying the substrate and metabolites with high sensitivity. C18 columns from different manufacturers were tested for simultaneous quantification of 22 different purine bases, nucleosides, and nucleotides. We used a YMC-Triart C18 column. The analysis conditions, including extraction solutions for the cells and cell culture medium, were optimized to achieve good quantification. Linearity, accuracy, determination limits, and recovery were assessed and showed good performance. The developed HPLC method was successfully applied to the qualitative analysis of 22 different intra- and extracellular purines, demonstrating that it is useful for studying the overall pattern of purine metabolism. This method could also be useful for evaluating metabolic dynamics of purines under a variety of stimulatory conditions of culture cells.

  5. [Principles of the hydrolysis of bound purine and pyrimidine bases in foods and program-controlled calculation of nucleic acid content].

    PubMed

    Herbel, W; Montag, A

    1987-01-01

    In order to determine the amount of combined purine and pyrimidine bases in foods we investigated the chemical fundamentals of their hydrolytic digestion it was demonstrated that the digestion mixture used, containing trifluoracetic- and formic acids, protected the purine bases during hydrolysis from oxidative degradation due to carbon monoxide formation. Further, a time-saving computer-program was developed and presented. This program allows, depending on the purine composition, the calculation of the corresponding nucleic acids, the nucleotides and the purine-nitrogen-content of the food.

  6. Pronounced fixation, strong population differentiation and complex population history in the Canary Islands blue tit subspecies complex.

    PubMed

    Hansson, Bengt; Ljungqvist, Marcus; Illera, Juan-Carlos; Kvist, Laura

    2014-01-01

    Evolutionary molecular studies of island radiations may lead to insights in the role of vicariance, founder events, population size and drift in the processes of population differentiation. We evaluate the degree of population genetic differentiation and fixation of the Canary Islands blue tit subspecies complex using microsatellite markers and aim to get insights in the population history using coalescence based methods. The Canary Island populations were strongly genetically differentiated and had reduced diversity with pronounced fixation including many private alleles. In population structure models, the relationship between the central island populations (La Gomera, Tenerife and Gran Canaria) and El Hierro was difficult to disentangle whereas the two European populations showed consistent clustering, the two eastern islands (Fuerteventura and Lanzarote) and Morocco weak clustering, and La Palma a consistent unique lineage. Coalescence based models suggested that the European mainland forms an outgroup to the Afrocanarian population, a split between the western island group (La Palma and El Hierro) and the central island group, and recent splits between the three central islands, and between the two eastern islands and Morocco, respectively. It is clear that strong genetic drift and low level of concurrent gene flow among populations have shaped complex allelic patterns of fixation and skewed frequencies over the archipelago. However, understanding the population history remains challenging; in particular, the pattern of extreme divergence with low genetic diversity and yet unique genetic material in the Canary Island system requires an explanation. A potential scenario is population contractions of a historically large and genetically variable Afrocanarian population, with vicariance and drift following in the wake. The suggestion from sequence-based analyses of a Pleistocene extinction of a substantial part of North Africa and a Pleistocene/Holocene eastward

  7. Pronounced subsurface cooling of North Atlantic waters off Northwest Africa during Dansgaard-Oeschger interstadials

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hyun; Romero, Oscar E.; Lohmann, Gerrit; Donner, Barbara; Laepple, Thomas; Haam, Eddie; Sinninghe Damsté, Jaap S.

    2012-07-01

    Millennial-scale Atlantic meridional overturning circulation (AMOC) variability has often been invoked to explain the Dansgaard-Oeschger (DO) events. However, the underlying causes responsible for millennial-scale AMOC variability are still debated. High-resolution U37K' and TEX86H temperature records for the last 50 kyr obtained from the tropical Northeast (NE) Atlantic (core GeoB7926-2, 20°13'N, 18°27'W, 2500 m water depth) show that distinctive DO-type subsurface (i.e. below the mixed layer: >20 m water depth) temperature oscillations occurred with amplitudes of up to 8 °C in the tropical NE Atlantic during Marine Isotope Stage 3 (MIS3). Statistical analyses reveal a positive relationship between the reconstructed substantial cooling of subsurface waters and prominent surface warming over Greenland during DO interstadials. General circulation model (GCM) simulations without external freshwater forcing, the mechanism often invoked in explaining DO events, demonstrate similar anti-phase correlations between AMOC and pronounced NE Atlantic subsurface temperatures under glacial climate conditions. Together with our paleoproxy dataset, this suggests that the vertical temperature structure and associated changes in AMOC were key elements governing DO events during the last glacial.

  8. Pronounced reproductive skew in a natural population of green swordtails, Xiphophorus helleri.

    PubMed

    Tatarenkov, Andrey; Healey, Christiane I M; Grether, Gregory F; Avise, John C

    2008-10-01

    For many species in nature, a sire's progeny may be distributed among a few or many dams. This poses logistical challenges--typically much greater across males than across females--for assessing means and variances in mating success (number of mates) and reproductive success (number of progeny). Here we overcome these difficulties by exhaustively analyzing a population of green swordtail fish (Xiphophorus helleri) for genetic paternity (and maternity) using a suite of highly polymorphic microsatellite loci. Genetic analyses of 1476 progeny from 69 pregnant females and 158 candidate sires revealed pronounced skews in male reproductive success both within and among broods. These skews were statistically significant, greater than in females, and correlated in males but not in females with mating success. We also compare the standardized variances in swordtail reproductive success to the few such available estimates for other taxa, notably several mammal species with varied mating systems and degrees of sexual dimorphism. The comparison showed that the opportunity for selection on male X. helleri is among the highest yet reported in fishes, and it is intermediate compared to estimates available for mammals. This study is one of a few exhaustive genetic assessments of joint-sex parentage in a natural fish population, and results are relevant to the operation of sexual selection in this sexually dimorphic, high-fecundity species.

  9. A Source Area Approach Demonstrates Moderate Predictive Ability but Pronounced Variability of Invasive Species Traits

    PubMed Central

    Essl, Franz; Dullinger, Stefan

    2016-01-01

    The search for traits that make alien species invasive has mostly concentrated on comparing successful invaders and different comparison groups with respect to average trait values. By contrast, little attention has been paid to trait variability among invaders. Here, we combine an analysis of trait differences between invasive and non-invasive species with a comparison of multidimensional trait variability within these two species groups. We collected data on biological and distributional traits for 1402 species of the native, non-woody vascular plant flora of Austria. We then compared the subsets of species recorded and not recorded as invasive aliens anywhere in the world, respectively, first, with respect to the sampled traits using univariate and multiple regression models; and, second, with respect to their multidimensional trait diversity by calculating functional richness and dispersion metrics. Attributes related to competitiveness (strategy type, nitrogen indicator value), habitat use (agricultural and ruderal habitats, occurrence under the montane belt), and propagule pressure (frequency) were most closely associated with invasiveness. However, even the best multiple model, including interactions, only explained a moderate fraction of the differences in invasive success. In addition, multidimensional variability in trait space was even larger among invasive than among non-invasive species. This pronounced variability suggests that invasive success has a considerable idiosyncratic component and is probably highly context specific. We conclude that basing risk assessment protocols on species trait profiles will probably face hardly reducible uncertainties. PMID:27187616

  10. A Source Area Approach Demonstrates Moderate Predictive Ability but Pronounced Variability of Invasive Species Traits.

    PubMed

    Klonner, Günther; Fischer, Stefan; Essl, Franz; Dullinger, Stefan

    2016-01-01

    The search for traits that make alien species invasive has mostly concentrated on comparing successful invaders and different comparison groups with respect to average trait values. By contrast, little attention has been paid to trait variability among invaders. Here, we combine an analysis of trait differences between invasive and non-invasive species with a comparison of multidimensional trait variability within these two species groups. We collected data on biological and distributional traits for 1402 species of the native, non-woody vascular plant flora of Austria. We then compared the subsets of species recorded and not recorded as invasive aliens anywhere in the world, respectively, first, with respect to the sampled traits using univariate and multiple regression models; and, second, with respect to their multidimensional trait diversity by calculating functional richness and dispersion metrics. Attributes related to competitiveness (strategy type, nitrogen indicator value), habitat use (agricultural and ruderal habitats, occurrence under the montane belt), and propagule pressure (frequency) were most closely associated with invasiveness. However, even the best multiple model, including interactions, only explained a moderate fraction of the differences in invasive success. In addition, multidimensional variability in trait space was even larger among invasive than among non-invasive species. This pronounced variability suggests that invasive success has a considerable idiosyncratic component and is probably highly context specific. We conclude that basing risk assessment protocols on species trait profiles will probably face hardly reducible uncertainties.

  11. Objective analysis versus subjective assessment of vowels pronounced by deaf and normal-hearing children.

    PubMed

    Bakkum, M J; Plomp, R; Pols, L W

    1995-08-01

    Objective whole-spectrum and formant analyses have been performed on all 15 Dutch vowels pronounced in /C1VC2/ words by 24 deaf and 24 normal-hearing children, in order to develop a model of pronunciation quality for evaluating (deaf) speech; the results as obtained for adult males by Bakkum et al. [J. Acoust. Soc. Am. 94, 1989-2004 (1993)] have been verified and extended. Spectral representations of the vowels were created by determining the output levels of a bank of 16 filters (90-7200 Hz), with 1/3-oct bandwidths and logarithmic spacing of their center frequencies. Spectral differences agree well with subjective differences in pronunciation quality obtained from magnitude estimation and identification experiments. Spectral differences not related to pronunciation quality judgments arise as a consequence of physiological interspeaker differences and variation in fundamental frequency, but these differences can be compensated for by speaker-normalization and F0-compensation procedures. Using principal components analysis (PCA), the vowel spectra can be described by a limited number of dimensions, without losing much information; a description in a two-dimensional PCA subspace still agrees well with the subjective judgments and it also agrees with a description by the first two formants. The whole-spectrum approach provides a determinate, readily interpretable model of pronunciation quality for evaluating vowels. As a practical advantage, its computational requirements are modest and, in conjunction with PCA, the vowel dynamics can be visualized, which makes the approach suitable for vowel training and diagnostics.

  12. An endocannabinoid uptake inhibitor from black pepper exerts pronounced anti-inflammatory effects in mice.

    PubMed

    Reynoso Moreno, Inés; Najar-Guerrero, Israel; Escareno, Noe; Flores, Mario Eduardo; Gertsch, Jürg; Viveros-Paredes, Juan Manuel

    2017-09-24

    Guineensine is a dietary N-isobutylamide widely present in black and long pepper (Piper nigrum and P. longum) previously shown to inhibit cellular endocannabinoid uptake. Given the role of endocannabinoids in inflammation and pain reduction, here we evaluated guineensine in mouse models of acute and inflammatory pain and endotoxemia. Significant dose-dependent anti-inflammatory effects (95.6 ± 3.1 % inhibition of inflammatory pain at 2.5 mg/kg i.p. and 50.0 ± 15.9 % inhibition of edema formation at 5 mg/kg i.p.) and acute analgesia (66.1 ± 28.1 % inhibition at 5.0 mg/kg i.p.) were observed. Moreover, guineensine inhibited pro-inflammatory cytokine production in endotoxemia. Intriguingly, guineensine and LPS independently induced catalepsy but in combination this effect was abolished. Both hypothermia and analgesia were blocked by the CB1 receptor inverse agonist rimonabant but the pronounced hypolocomotion was CB1 receptor-independent. A subsequent screen of 45 CNS-related receptors, ion channels and transporters revealed apparent interactions of guineensine with the dopamine transporter DAT, 5HT2A and sigma receptors, uncovering its prospective polypharmacology. The described potent pharmacological effects of guineensine might relate to the reported anti-inflammatory effects of pepper.

  13. Pronounced interannual variability in tropical South Pacific temperatures during Heinrich Stadial 1.

    PubMed

    Felis, Thomas; Merkel, Ute; Asami, Ryuji; Deschamps, Pierre; Hathorne, Ed C; Kölling, Martin; Bard, Edouard; Cabioch, Guy; Durand, Nicolas; Prange, Matthias; Schulz, Michael; Cahyarini, Sri Yudawati; Pfeiffer, Miriam

    2012-07-24

    The early last glacial termination was characterized by intense North Atlantic cooling and weak overturning circulation. This interval between ~18,000 and 14,600 years ago, known as Heinrich Stadial 1, was accompanied by a disruption of global climate and has been suggested as a key factor for the termination. However, the response of interannual climate variability in the tropical Pacific (El Niño-Southern Oscillation) to Heinrich Stadial 1 is poorly understood. Here we use Sr/Ca in a fossil Tahiti coral to reconstruct tropical South Pacific sea surface temperature around 15,000 years ago at monthly resolution. Unlike today, interannual South Pacific sea surface temperature variability at typical El Niño-Southern Oscillation periods was pronounced at Tahiti. Our results indicate that the El Niño-Southern Oscillation was active during Heinrich Stadial 1, consistent with climate model simulations of enhanced El Niño-Southern Oscillation variability at that time. Furthermore, a greater El Niño-Southern Oscillation influence in the South Pacific during Heinrich Stadial 1 is suggested, resulting from a southward expansion or shift of El Niño-Southern Oscillation sea surface temperature anomalies.

  14. Pronounced differences between observed and CMIP5-simulated multidecadal climate variability in the twentieth century

    NASA Astrophysics Data System (ADS)

    Kravtsov, Sergey

    2017-06-01

    Identification and dynamical attribution of multidecadal climate undulations to either variations in external forcings or to internal sources is one of the most important topics of modern climate science, especially in conjunction with the issue of human-induced global warming. Here we utilize ensembles of twentieth century climate simulations to isolate the forced signal and residual internal variability in a network of observed and modeled climate indices. The observed internal variability so estimated exhibits a pronounced multidecadal mode with a distinctive spatiotemporal signature, which is altogether absent in model simulations. This single mode explains a major fraction of model-data differences over the entire climate index network considered; it may reflect either biases in the models' forced response or models' lack of requisite internal dynamics, or a combination of both.Plain Language SummaryGlobal and regional warming trends over the course of the twentieth century have been nonuniform, with decadal and longer periods of faster or slower warming, or even cooling. Here we show that state-of-the-art global models used to predict climate fail to adequately reproduce such multidecadal climate variations. In particular, the models underestimate the magnitude of the observed variability and misrepresent its spatial pattern. Therefore, our ability to interpret the observed climate change using these models is limited.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19841160','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19841160"><span>Specific and <span class="hlt">pronounced</span> impacts of lisinopril and lisinopril plus simvastatin on erythrocyte antioxidant enzymes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kaminsky, Yury; Suslikov, Alexander; Kosenko, Elena</p> <p>2010-02-01</p> <p>Angiotensin-converting enzyme inhibitors are effective at reducing blood pressure, whereas statins decrease plasma cholesterol impeding atherosclerosis. It is hypothesized that these medications may improve blood pressure and serum cholesterol by modifying the antioxidative status and energy metabolism of erythrocytes. In this study, the effects of 2 treatments are compared: lisinopril alone versus lisinopril + simvastatin, on erythrocyte antioxidant and energy metabolic enzymes. Patients with atherosclerosis and moderate hypertension are randomly assigned to receive lisinopril 10 to 20 mg/d or lisinopril 10 to 20 mg/d plus simvastatin 20 mg/d for 24 weeks. Higher catalase activity and lower glutathione peroxidase activity are observed in 94% to 100% patients from both groups after 12 and 24 weeks of treatment. Superoxide dismutase activity is increased significantly only after 24 weeks. No changes of glutathione reductase, lactate dehydrogenase, and phosphofructokinase activities are found under any conditions indicated. Both treatments decrease systolic and diastolic blood pressure equally. Only lisinopril + simvastatin treatment decreases plasma total cholesterol and low-density lipoprotein cholesterol. The results show for the first time that lisinopril monotherapy and combined lisinopril + simvastatin therapy exhibit specific and <span class="hlt">pronounced</span> effects on antioxidant and energy metabolic enzyme activities in erythrocytes of hypertensive patients.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1959505','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1959505"><span>Delay of Postnatal Maturation Sensitizes the Mouse Prostate to Testosterone-Induced <span class="hlt">Pronounced</span> Hyperplasia</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Savolainen, Saija; Pakarainen, Tomi; Huhtaniemi, Ilpo; Poutanen, Matti; Mäkelä, Sari</p> <p>2007-01-01</p> <p>The role of estrogens in the etiology of prostate cancer is controversial. To demonstrate the specific effects of estrogens and androgens on the development of the prostatic epithelial hyperplasia, we used luteinizing hormone receptor knockout mice (LuRKO), which are resistant to pituitary regulation mediated by luteinizing hormone, lack postnatal androgen production, and have rudimentary accessory sex glands, the growth of which can be induced with exogenous androgen replacement. This model is thus ideal for the investigation of direct hormonal effects on the prostate. Testosterone, but not 5α-dihydrotestosterone, replacement from 21 days of life for 8 weeks induced <span class="hlt">pronounced</span> hyperplasia and inflammation in the prostates of LuRKO mice. Interestingly, 5α-dihydrotestosterone combined with 17β-estradiol did not induce hyperplasia or inflammation, and treatments with inhibitors of estrogen action, aromatase inhibitor, and ICI 182780 further exacerbated testosterone-induced hyperplastic growth. However, the activation of estrogen receptor (ER)-β with a specific agonist, DPN [2,3-bis(4-hydroxyphenol)-propionitrile], prevented the development of prostatic hyperplasia and inflammation in testosterone-treated LuRKO mice. Thus, it seems that in the presence of sufficient androgenic stimulation, it is the balance between ER-α- and ER-β-mediated signaling that determines whether estrogens promote hyperplasia or protect the prostate against hyperplastic changes. PMID:17640960</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24990557','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24990557"><span>[High-sensitivity analysis of <span class="hlt">purines</span> in alcoholic beverages using hydrophilic interaction chromatography coupled with tandem mass spectrometry].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kakigi, Yasuhiro; Yoshioka, Toshiaki; Nagatomi, Yasushi; Uyama, Atsuo; Mochizuki, Naoki</p> <p>2014-01-01</p> <p>In this study, we established a high-sensitivity analytical method for <span class="hlt">purines</span> in alcoholic beverages using hydrophilic interaction chromatography coupled with tandem mass spectrometry. The alcoholic beverages were hydrolyzed with perchloric acid (60%) and subjected to strong cation exchange solid-phase extraction (Bond Elut SCX). The four <span class="hlt">purine</span> bases (hypoxanthine, adenine, xanthine, guanine) in the extracted solution were separated by hydrophilic interaction chromatography with TSKgel Amide-80 as a separation column, 10 mM ammonium formate (pH 2.0) as mobile phase A, and acetonitrile/100 mM ammonium formate (pH 2.0) (90/10) as mobile phase B. The detection of <span class="hlt">purine</span> bases was performed by tandem mass spectrometry with ESI. The linearity of this analytical method was not less than 0.996, and the repeatability was not more than 8.4% for each <span class="hlt">purine</span> base. The recovery was in the range of 60-105%, and the detection limit was not more than 0.005 mg/100 mL. This established method is expected to be useful for quality control and surveillance of <span class="hlt">purines</span> in alcoholic beverages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25105925','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25105925"><span>1,3,5-Triazine-based analogues of <span class="hlt">purine</span>: from isosteres to privileged scaffolds in medicinal chemistry.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lim, Felicia Phei Lin; Dolzhenko, Anton V</p> <p>2014-10-06</p> <p><span class="hlt">Purines</span> can be considered as the most ubiquitous and functional N-heterocyclic compounds in nature. Structural modifications of natural <span class="hlt">purines</span>, particularly using isosteric ring systems, have been in the focus of many drug discovery programs. Fusion of 1,3,5-triazine ring with pyrrole, pyrazole, imidazole, 1,2,3-triazole or 1,2,4-triazole results in seven bicyclic heterocyclic systems isosteric to <span class="hlt">purine</span>. Application of the isosterism concept for the development of new compounds with therapeutic potential in areas involving purinergic regulation or <span class="hlt">purine</span> metabolism led to significant advances in medicinal chemistry of the azolo[1,3,5]triazines. These 1,3,5-triazine-based <span class="hlt">purine</span>-like scaffolds significantly increase level of molecular diversity and allow covering chemical space in the important areas of medicinal chemistry. Some of these azolo[1,3,5]triazine systems have become privileged scaffolds in the development of inhibitors of various kinases, phosphodiesterase, xanthine oxidase, and thymidine phosphorylase, antagonists of adenosine and corticotropin-releasing hormone receptors, anticancer and antiviral agents.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4390545','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4390545"><span>Consequences of Impaired <span class="hlt">Purine</span> Recycling on the Proteome in a Cellular Model of Lesch-Nyhan Disease</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Duong, Duc M.; Hanfelt, John; Seyfried, Nicholas T.; Jinnah, H. A.</p> <p>2015-01-01</p> <p>The importance of specific pathways of <span class="hlt">purine</span> metabolism for normal brain function is highlighted by several inherited disorders, such as Lesch-Nyhan disease (LND). In this disorder, deficiency of the <span class="hlt">purine</span> recycling enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt), causes severe neurological and behavioral abnormalities. Despite many years of research, the mechanisms linking the defect in <span class="hlt">purine</span> recycling to the neurobehavioral abnormalities remain unclear. In the current studies, an unbiased approach to the identification of potential mechanisms was undertaken by examining changes in protein expression in a model of HGprt deficiency based on the dopaminergic rat PC6-3 line, before and after differentiation with nerve growth factor (NGF). Protein expression profiles of 5 mutant sublines carrying different mutations affecting HGprt enzyme activity were compared to the HGprt-competent parent line using the method of stable isotopic labeling by amino acids in cell culture (SILAC) followed by denaturing gel electrophoresis with liquid chromatography and tandem mass spectrometry (LC-MS/MS) of tryptic digests, and subsequent identification of affected biochemical pathways using the Database for Annotation, Visualization and Integrated Discovery (DAVID) functional annotation chart analysis. The results demonstrate that HGprt deficiency causes broad changes in protein expression that depend on whether the cells are differentiated or not. Several of the pathways identified reflect predictable consequences of defective <span class="hlt">purine</span> recycling. Other pathways were not anticipated, disclosing previously unknown connections with <span class="hlt">purine</span> metabolism and novel insights into the pathogenesis of LND. PMID:25769394</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25769394','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25769394"><span>Consequences of impaired <span class="hlt">purine</span> recycling on the proteome in a cellular model of Lesch-Nyhan disease.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dammer, Eric B; Göttle, Martin; Duong, Duc M; Hanfelt, John; Seyfried, Nicholas T; Jinnah, H A</p> <p>2015-04-01</p> <p>The importance of specific pathways of <span class="hlt">purine</span> metabolism for normal brain function is highlighted by several inherited disorders, such as Lesch-Nyhan disease (LND). In this disorder, deficiency of the <span class="hlt">purine</span> recycling enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt), causes severe neurological and behavioral abnormalities. Despite many years of research, the mechanisms linking the defect in <span class="hlt">purine</span> recycling to the neurobehavioral abnormalities remain unclear. In the current studies, an unbiased approach to the identification of potential mechanisms was undertaken by examining changes in protein expression in a model of HGprt deficiency based on the dopaminergic rat PC6-3 line, before and after differentiation with nerve growth factor (NGF). Protein expression profiles of 5 mutant sublines carrying different mutations affecting HGprt enzyme activity were compared to the HGprt-competent parent line using the method of stable isotopic labeling by amino acids in cell culture (SILAC) followed by denaturing gel electrophoresis with liquid chromatography and tandem mass spectrometry (LC-MS/MS) of tryptic digests, and subsequent identification of affected biochemical pathways using the Database for Annotation, Visualization and Integrated Discovery (DAVID) functional annotation chart analysis. The results demonstrate that HGprt deficiency causes broad changes in protein expression that depend on whether the cells are differentiated or not. Several of the pathways identified reflect predictable consequences of defective <span class="hlt">purine</span> recycling. Other pathways were not anticipated, disclosing previously unknown connections with <span class="hlt">purine</span> metabolism and novel insights into the pathogenesis of LND. Copyright © 2015 Elsevier Inc. All rights reserved.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24170203','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24170203"><span>Structure and function of nucleoside hydrolases from Physcomitrella patens and maize catalyzing the hydrolysis of <span class="hlt">purine</span>, pyrimidine, and cytokinin ribosides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kopecná, Martina; Blaschke, Hanna; Kopecny, David; Vigouroux, Armelle; Koncitíková, Radka; Novák, Ondrej; Kotland, Ondrej; Strnad, Miroslav; Moréra, Solange; von Schwartzenberg, Klaus</p> <p>2013-12-01</p> <p>We present a comprehensive characterization of the nucleoside N-ribohydrolase (NRH) family in two model plants, Physcomitrella patens (PpNRH) and maize (Zea mays; ZmNRH), using in vitro and in planta approaches. We identified two NRH subclasses in the plant kingdom; one preferentially targets the <span class="hlt">purine</span> ribosides inosine and xanthosine, while the other is more active toward uridine and xanthosine. Both subclasses can hydrolyze plant hormones such as cytokinin ribosides. We also solved the crystal structures of two <span class="hlt">purine</span> NRHs, PpNRH1 and ZmNRH3. Structural analyses, site-directed mutagenesis experiments, and phylogenetic studies were conducted to identify the residues responsible for the observed differences in substrate specificity between the NRH isoforms. The presence of a tyrosine at position 249 (PpNRH1 numbering) confers high hydrolase activity for <span class="hlt">purine</span> ribosides, while an aspartate residue in this position confers high activity for uridine. Bud formation is delayed by knocking out single NRH genes in P. patens, and under conditions of nitrogen shortage, PpNRH1-deficient plants cannot salvage adenosine-bound nitrogen. All PpNRH knockout plants display elevated levels of certain <span class="hlt">purine</span> and pyrimidine ribosides and cytokinins that reflect the substrate preferences of the knocked out enzymes. NRH enzymes thus have functions in cytokinin conversion and activation as well as in <span class="hlt">purine</span> and pyrimidine metabolism.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4550530','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4550530"><span>GMP synthase is essential for viability and infectivity of Trypanosoma brucei despite a redundant <span class="hlt">purine</span> salvage pathway</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Li, Qiong; Leija, Christopher; Rijo-Ferreira, Filipa; Chen, Jun; Cestari, Igor; Stuart, Kenneth; Tu, Benjamin P.; Phillips, Margaret A.</p> <p>2015-01-01</p> <p>Summary The causative agent of human African trypanosomiasis, Trypanosoma brucei, lacks de novo <span class="hlt">purine</span> biosynthesis and depends on <span class="hlt">purine</span> salvage from the host. The <span class="hlt">purine</span> salvage pathway is redundant and contains two routes to guanosine-5′-monophosphate (GMP) formation: conversion from xanthosine-5′-monophosphate (XMP) by GMP synthase (GMPS) or direct salvage of guanine by hypoxanthine-guanine phosphoribosyltransferase (HGPRT). We show recombinant T. brucei GMPS efficiently catalyzes GMP formation. Genetic knockout of GMPS in bloodstream parasites led to depletion of guanine nucleotide pools and was lethal. Growth of gmps null cells was only rescued by supraphysiological guanine concentrations (100 μM) or by expression of an extrachromosomal copy of GMPS. Hypoxanthine was a competitive inhibitor of guanine rescue, consistent with a common uptake/metabolic conversion mechanism. In mice, gmps null parasites were unable to establish an infection demonstrating that GMPS is essential for virulence and that plasma guanine is insufficient to support parasite <span class="hlt">purine</span> requirements. These data validate GMPS as a potential therapeutic target for treatment of HAT. The ability to strategically inhibit key metabolic enzymes in the <span class="hlt">purine</span> pathway unexpectedly bypasses its functional redundancy by exploiting both the nature of pathway flux and the limited nutrient environment of the parasite's extracellular niche. PMID:26043892</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/6441852','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/6441852"><span>[open quotes]Cryptic[close quotes] repeating triplets of <span class="hlt">purines</span> and pyrimidines (cRRY(i)) are frequent and polymorphic: Analysis of coding cRRY(i) in the proopiomelanocortin (POMC) and TATA-binding protein (TBP) genes</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Gostout, B.; Qiang Liu; Sommer, S.S. )</p> <p>1993-06-01</p> <p>Triplets of the form of <span class="hlt">purine</span>, <span class="hlt">purine</span>, pyrimidine (RRY(i)) are enhanced in frequency in the genomes of primates, rodents, and bacteria. Some RRY(i) are [open quotes]cryptic[close quotes] repeats (cRRY(i)) in which no one tandem run of a trinucleotide predominates. A search of human GenBank <span class="hlt">sequence</span> revealed that the <span class="hlt">sequences</span> of cRRY(i) are highly nonrandom. Three randomly chosen human cRRY(i) were <span class="hlt">sequenced</span> in search of polymorphic alleles. Multiple polymorphic alleles were found in cRRY(i) in the coding regions of the genes for proopiomelanocortin (POMC) and TATA-binding protein (TBP). The highly polymorphic TBP cRRY(i) was characterized in detail. Direct <span class="hlt">sequencing</span> of 157 unrelated human alleles demonstrated the presence of 20 different alleles which resulted in 29--40 consecutive glutamines in the amino-terminal region of TBP. These alleles are differently distributed among the races. PCR was used to screen 1,846 additional alleles in order to characterize more fully the range of variation in the population. Three additional alleles were discovered, but there was no example of a substantial <span class="hlt">sequence</span> amplification as is seen in the repeat <span class="hlt">sequences</span> associated with X-linked spinal and bulbar muscular atrophy, myotonic dystrophy, or the fragile-X syndrome. The structure of the TBP cRRY(i) is conserved in the five monkey species examined. In the chimpanzee, examination of four individuals revealed that the cRRY(i) was highly polymorphic, but the pattern of polymorphism differed from that in humans. The TBP cRRY(i) displays both similarities with and differences from the previously described RRY(i) in the coding <span class="hlt">sequence</span> of the androgen receptor. The data suggest how simple tandem repeats could evolve from cryptic repeats. 18 refs., 3 figs., 6 tabs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26986520','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26986520"><span>ATP and related <span class="hlt">purines</span> stimulate motility, spatial congregation, and coalescence in red algal spores.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huidobro-Toro, Juan P; Donoso, Verónica; Flores, Verónica; Santelices, Bernabé</p> <p>2015-04-01</p> <p>Adenosine 5'-triphosphate (ATP) is a versatile extracellular signal along the tree of life, whereas cAMP plays a major role in vertebrates as an intracellular messenger for hormones, transmitters, tastants, and odorants. Since red algal spore coalescence may be considered analogous to the congregation process of social amoeba, which is stimulated by cAMP, we ascertained whether exogenous applications of ATP, cAMP, adenine, or adenosine modified spore survival and motility, spore settlement and coalescence. Concentration-response studies were performed with carpospores of Mazzaella laminarioides (Gigartinales), incubated with and without added <span class="hlt">purines</span>. Stirring of algal blades released ADP/ATP to the cell media in a time-dependent manner. 10-300 μM ATP significantly increased spore survival; however, 1,500 μM ATP, cAMP or adenine induced 100% mortality within less than 24 h; the exception was adenosine, which up to 3,000 μM, did not alter spore survival. ATP exposure elicited spore movement with speeds of 2.2-2.5 μm · s(-1) . 14 d after 1,000 μM ATP addition, spore abundance in the central zone of the plaques was increased 2.7-fold as compared with parallel controls. Likewise, 1-10 μM cAMP or 30-100 μM adenine also increased central zone spore abundance, albeit these <span class="hlt">purines</span> were less efficacious than ATP; adenosine up to 3,000 μM did not influence settlement. Moreover, 1,000 μM ATP markedly accelerated coalescence, the other <span class="hlt">purines</span> caused a variable effect. We conclude that exogenous cAMP, adenine, but particularly ATP, markedly influence red algal spore physiology; effects are compatible with the expression of one or more membrane purinoceptor(s), discarding adenosine receptor participation. © 2015 Phycological Society of America.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27799897','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27799897"><span>Enhancement of Peripheral Nerve Regrowth by the <span class="hlt">Purine</span> Nucleoside Analog and Cell Cycle Inhibitor, Roscovitine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Law, Vincent; Dong, Sophie; Rosales, Jesusa L; Jeong, Myung-Yung; Zochodne, Douglas; Lee, Ki-Young</p> <p>2016-01-01</p> <p>Peripheral nerve regeneration is a slow process that can be associated with limited outcomes and thus a search for novel and effective therapy for peripheral nerve injury and disease is crucial. Here, we found that roscovitine, a synthetic <span class="hlt">purine</span> nucleoside analog, enhances neurite outgrowth in neuronal-like PC12 cells. Furthermore, ex vivo analysis of pre-injured adult rat dorsal root ganglion (DRG) neurons showed that roscovitine enhances neurite regrowth in these cells. Likewise, in vivo transected sciatic nerves in rats locally perfused with roscovitine had augmented repopulation of new myelinated axons beyond the transection zone. By mass spectrometry, we found that roscovitine interacts with tubulin and actin. It interacts directly with tubulin and causes a dose-dependent induction of tubulin polymerization as well as enhances Guanosine-5'-triphosphate (GTP)-dependent tubulin polymerization. Conversely, roscovitine interacts indirectly with actin and counteracts the inhibitory effect of cyclin-dependent kinases 5 (Cdk5) on Actin-Related Proteins 2/3 (Arp2/3)-dependent actin polymerization, and thus, causes actin polymerization. Moreover, in the presence of neurotrophic factors such as nerve growth factor (NGF), roscovitine-enhanced neurite outgrowth is mediated by increased activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) pathways. Since microtubule and F-actin dynamics are critical for axonal regrowth, the ability of roscovitine to activate the ERK1/2 and p38 MAPK pathways and support polymerization of tubulin and actin indicate a major role for this <span class="hlt">purine</span> nucleoside analog in the promotion of axonal regeneration. Together, our findings demonstrate a therapeutic potential for the <span class="hlt">purine</span> nucleoside analog, roscovitine, in peripheral nerve injury.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1539594','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1539594"><span>Construction and Characterization of an Attenuated <span class="hlt">Purine</span> Auxotroph in a Francisella tularensis Live Vaccine Strain</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Pechous, Roger; Celli, Jean; Penoske, Renee; Hayes, Stanley F.; Frank, Dara W.; Zahrt, Thomas C.</p> <p>2006-01-01</p> <p>Francisella tularensis is a facultative intracellular pathogen and is the etiological agent of tularemia. It is capable of escaping from the phagosome, replicating to high numbers in the cytosol, and inducing apoptosis in macrophages of a variety of hosts. F. tularensis has received significant attention recently due to its potential use as a bioweapon. Currently, there is no licensed vaccine against F. tularensis, although a partially protective live vaccine strain (LVS) that is attenuated in humans but remains fully virulent for mice was previously developed. An F. tularensis LVS mutant deleted in the purMCD <span class="hlt">purine</span> biosynthetic locus was constructed and partially characterized by using an allelic exchange strategy. The F. tularensis LVS ΔpurMCD mutant was auxotrophic for <span class="hlt">purines</span> when grown in defined medium and exhibited significant attenuation in virulence when assayed in murine macrophages in vitro or in BALB/c mice. Growth and virulence defects were complemented by the addition of the <span class="hlt">purine</span> precursor hypoxanthine or by introduction of purMCDN in trans. The F. tularensis LVS ΔpurMCD mutant escaped from the phagosome but failed to replicate in the cytosol or induce apoptotic and cytopathic responses in infected cells. Importantly, mice vaccinated with a low dose of the F. tularensis LVS ΔpurMCD mutant were fully protected against subsequent lethal challenge with the LVS parental strain. Collectively, these results suggest that F. tularensis mutants deleted in the purMCD biosynthetic locus exhibit characteristics that may warrant further investigation of their use as potential live vaccine candidates. PMID:16861631</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12151376','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12151376"><span>Effects of extracellular <span class="hlt">purines</span> on ion transport across the integument of Hirudo medicinalis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schnizler, Mikael; Buss, Mirjam; Clauss, Wolfgang</p> <p>2002-09-01</p> <p>Little is known about the long-term regulation of epithelial ion transport in invertebrates and the specific mediators involved. For some years, we have been investigating the short-term regulation of transepithelial ion transport across the dorsal integument of the leech Hirudo medicinalis, and we have established a model of Na+ uptake. In the present study, we investigated the effect of long-term acclimation on transintegumental ion transport by adapting leeches to high-salinity conditions. We dissected segments of dorsal integument and measured ion currents in Ussing chamber experiments. Electrophysiological variables, such as transepithelial potential (V(T)) and short-circuit-current (I(sc)), were profoundly affected by adaptation to high-salinity conditions. The total transepithelial Na+ current (I(Na)) decreased from 7.66+/-0.82 to 4.6+/-0.54 microA cm(-2) in preparations adapted to high salinity. The involvement of epithelial Na+ channels was determined as current inhibition (I(ami)) by apical application of amiloride; Na+ channels were equally active in control epithelia and epithelia from leeches adapted to high salinity. Removal of Ca2+ from the apical solutions, which is believed to reduce intracellular Ca2+ concentrations, equalized transepithelial variables between high-salt-adapted integuments and control integuments. Extracellular <span class="hlt">purines</span> regulate transepithelial Cl- secretion and Na+ absorption. In a variety of tissues we tested ATP and adenosine for their effects on epithelial transport. Examination of integuments from pondwater- and high-salinity-adapted leeches revealed different sensitivities for these <span class="hlt">purines</span>. Apical and basolateral application of ATP both stimulated transepithelial Na+ uptake and I(ami). Adenosine upregulated non-Na+ currents and acted from the basolateral side only. Apical Ca2+-free conditions attenuated these effects of <span class="hlt">purines</span> on transepithelial currents. Extracellular UTP had no effect on ion transport.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5066473','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5066473"><span>Enhancement of Peripheral Nerve Regrowth by the <span class="hlt">Purine</span> Nucleoside Analog and Cell Cycle Inhibitor, Roscovitine</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Law, Vincent; Dong, Sophie; Rosales, Jesusa L.; Jeong, Myung-Yung; Zochodne, Douglas; Lee, Ki-Young</p> <p>2016-01-01</p> <p>Peripheral nerve regeneration is a slow process that can be associated with limited outcomes and thus a search for novel and effective therapy for peripheral nerve injury and disease is crucial. Here, we found that roscovitine, a synthetic <span class="hlt">purine</span> nucleoside analog, enhances neurite outgrowth in neuronal-like PC12 cells. Furthermore, ex vivo analysis of pre-injured adult rat dorsal root ganglion (DRG) neurons showed that roscovitine enhances neurite regrowth in these cells. Likewise, in vivo transected sciatic nerves in rats locally perfused with roscovitine had augmented repopulation of new myelinated axons beyond the transection zone. By mass spectrometry, we found that roscovitine interacts with tubulin and actin. It interacts directly with tubulin and causes a dose-dependent induction of tubulin polymerization as well as enhances Guanosine-5′-triphosphate (GTP)-dependent tubulin polymerization. Conversely, roscovitine interacts indirectly with actin and counteracts the inhibitory effect of cyclin-dependent kinases 5 (Cdk5) on Actin-Related Proteins 2/3 (Arp2/3)-dependent actin polymerization, and thus, causes actin polymerization. Moreover, in the presence of neurotrophic factors such as nerve growth factor (NGF), roscovitine-enhanced neurite outgrowth is mediated by increased activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) pathways. Since microtubule and F-actin dynamics are critical for axonal regrowth, the ability of roscovitine to activate the ERK1/2 and p38 MAPK pathways and support polymerization of tubulin and actin indicate a major role for this <span class="hlt">purine</span> nucleoside analog in the promotion of axonal regeneration. Together, our findings demonstrate a therapeutic potential for the <span class="hlt">purine</span> nucleoside analog, roscovitine, in peripheral nerve injury. PMID:27799897</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22585795','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22585795"><span>Urinary excretion of <span class="hlt">purine</span> derivatives, microbial protein synthesis, nitrogen use, and ruminal fermentation in sheep and goats fed diets of different quality.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Carro, M D; Cantalapiedra-Hijar, G; Ranilla, M J; Molina-Alcaide, E</p> <p>2012-11-01</p> <p>The objective of this study was to compare N balance, microbial N flow (MNF) estimated from <span class="hlt">purine</span> derivatives (PD) urinary excretion, and its variation when estimated using <span class="hlt">purine</span> bases:N ratios in liquid associated bacteria (LAB) from models reported in the literature (MNF - response models) or measured ratios in liquid and solid-associated bacterial (SAB) pellets (MNF-LAB+SAB), diet digestibility, and rumen fermentation variables in sheep and goats fed 3 different practical, quality diets to study interspecies differences concerning N use as accurately as possible. Four mature female Merino sheep and 4 mature female Granadina goats, each fitted with a ruminal cannula, were used in 3 × 3 Latin square design with an extra animal. Two experimental diets had a forage-to-concentrate ratio of 70:30 (DM basis) with alfalfa hay (ALC) or grass hay (GRC) as forage, and the third diet contained 70% concentrate and 30% alfalfa hay (CAL). All animals were fed the diets at a daily rate of 56 g/kg BW(0.75) to minimize feed selection. Digestibility of nutrients was similar (P = 0.16 to 0.88) in the 2 species, but some animal species × diet interactions (P = 0.01 to 0.04) were detected. There were small differences between the fermentation patterns of both animal species. Goats showed decreased VFA concentrations (P = 0.005) and butyrate proportions (P = 0.04), and greater acetate proportions (P = 0.02) compared with sheep, whereas N intake and percentage of N intake excreted in feces were similar in both species (P = 0.58 and 0.15, respectively), the percentage excreted via the urine was greater in goats compared with sheep (P < 0.001). As a consequence, sheep had greater (P < 0.001) N retention than goats (averaged across diets, 32.6% and 16.1% of N intake, respectively). There were no differences (P = 0.95) between animal species in total PD excretion, but goats showed a greater excretion of allantoin (P = 0.01) and decreased excretion of xanthine (P = 0.008) and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11727978','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11727978"><span>Measurement of small scalar and dipolar couplings in <span class="hlt">purine</span> and pyrimidine bases.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zídek, L; Wu, H; Feigon, J; Sklenár, V</p> <p>2001-10-01</p> <p>A suite of spin-state-selective excitation (S3E) NMR experiments for the measurements of small one-bond (13C-13C, 15N-13C) and two-bond (1H-13C, 1H-15N) coupling constants in 13C,15N labeled <span class="hlt">purine</span> and pyrimidine bases is presented. The incorporation of band-selective shaped pulses, elimination of the cross talk between alpha and beta sub-spectra, and accuracy and precision of the proposed approach are discussed. Merits of using S3E rather than alpha/beta-half-filter are demonstrated using results obtained on isotopically labeled DNA oligonucleotides.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8017070','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8017070"><span>[Fitness by cold stimulation of various intensity: effects on metabolism of <span class="hlt">purines</span> and free radicals].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brenke, R; Siems, W; Maass, R</p> <p>1994-01-01</p> <p>Whole-body cold stimuli lead to a dosage-depended decrease of uric acid level in blood plasma. This could be observed in own studies on winter-swimming and cold shower application and in studies on patients treated by cold-chamber-therapy. This uric acid decrease is due to an accelerated oxygen radical formation during cold exposition rather than to an inhibition of <span class="hlt">purine</span> metabolism. The acute oxidative loading due to cold exposure and the long-term antioxidative adaptation may be interpreted as a new molecular mechanism resulting in body hardening.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790036251&hterms=Hydrocyanic+acid&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHydrocyanic%2Bacid','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790036251&hterms=Hydrocyanic+acid&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3DHydrocyanic%2Bacid"><span>HCN - A plausible source of <span class="hlt">purines</span>, pyrimidines and amino acids on the primitive earth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ferris, J.-P.; Joshi, P. C.; Edelson, E. H.; Lawless, J. G.</p> <p>1978-01-01</p> <p>Dilute (0.1 M) solutions of HCN condense to oligomers at pH 9.2, and hydrolysis of these oligomers yields 4,5-dihydroxypyrimidine, orotic acid, 5-hydroxyuracil, adenine, 4-aminoimidazole-5-carboxamide, and amino acids. It is suggested that the three main classes of nitrogen-containing biomolecules - <span class="hlt">purines</span>, pyrimidines, and amino acids may have originated from HCN on the primitive earth. It is also suggested that the presence of orotic acid and 4-aminoimidazole-5-carboxamide might indicate that contemporary biosynthetic pathways for nucleotides evolved from the compounds released on hydrolysis of HCN oligomers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3998501','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3998501"><span>9-Benzyl-6-benzyl­sulfanyl-9H-<span class="hlt">purin</span>-2-amine</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hariono, Maywan; Wahab, Habibah A.; Tan, Mei Lan; Rosli, Mohd Mustaqim; Razak, Ibrahim Abdul</p> <p>2014-01-01</p> <p>In the title compound, C19H17N5S, the dihedral angles between the <span class="hlt">purine</span> ring system (r.m.s. deviation = 0.009 Å) and the S-bound and methyl­ene-bound phenyl rings are 74.67 (8) and 71.28 (7)°, respectively. In the crystal, inversion dimers linked by pairs of N—H⋯N hydrogen bonds generate R 2 2(8) loops. C—H⋯N inter­actions link the dimers into (100) sheets. PMID:24764997</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19790036251&hterms=pyrimidine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dpyrimidine','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19790036251&hterms=pyrimidine&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3Dpyrimidine"><span>HCN - A plausible source of <span class="hlt">purines</span>, pyrimidines and amino acids on the primitive earth</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ferris, J.-P.; Joshi, P. C.; Edelson, E. H.; Lawless, J. G.</p> <p>1978-01-01</p> <p>Dilute (0.1 M) solutions of HCN condense to oligomers at pH 9.2, and hydrolysis of these oligomers yields 4,5-dihydroxypyrimidine, orotic acid, 5-hydroxyuracil, adenine, 4-aminoimidazole-5-carboxamide, and amino acids. It is suggested that the three main classes of nitrogen-containing biomolecules - <span class="hlt">purines</span>, pyrimidines, and amino acids may have originated from HCN on the primitive earth. It is also suggested that the presence of orotic acid and 4-aminoimidazole-5-carboxamide might indicate that contemporary biosynthetic pathways for nucleotides evolved from the compounds released on hydrolysis of HCN oligomers.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24378780','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24378780"><span>Synthesis and anticancer activity of novel C6-piperazine substituted <span class="hlt">purine</span> steroid-nucleosides analogues.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Huang, Li-Hua; Xu, Hong-De; Yang, Zhuo-Ya; Zheng, Yong-Fei; Liu, Hong-Min</p> <p>2014-04-01</p> <p>Novel C6-piperazine substituted <span class="hlt">purine</span> nucleoside analogues (2-9) bearing a modified pyranose-like D ring of the 4-azasteroid moiety were efficiently synthesized through nucleophilic substitution at C6 position of the steroid-nucleoside precursors (1) with versatile piperazines. All newly-synthesized compounds were evaluated for their anticancer activity in vitro against Hela, PC-3 and MCF-7 cell lines. Among them, compounds 8b and 9b exhibited significant cytotoxicity on PC-3 cell lines. Copyright © 2014 Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/3550441','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/3550441"><span>Transversion-specific <span class="hlt">purine</span> analogue mutagens and the mechanism of hydroxylaminopurine mutagenesis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Murray, V</p> <p>1987-04-01</p> <p>The tryptophan synthetase gene A series of mutants in E. coli has been used to examine the mutational specificity of over 80 <span class="hlt">purine</span> base analogues. 4 <span class="hlt">purine</span> analogues have been discovered that solely cause transversions. Evidence is presented that hydroxylaminopurine mutagenesis is caused by a covalent reaction of these compounds with DNA. The transversion-causing <span class="hlt">purine</span> analogues are derivatives of 2-aminopurine (2AP) and 2,6-diaminopurine (2,6DAP). They stimulate the full reversion frequency of those trp A which can revert through an AT----CG transversion. 8 <span class="hlt">purine</span> base analogues have been found that induce the AT----CG transversion at the trp A88 site; and 2-amino-6-methylaminopurine (2A6MAP) stimulates by 124-fold, 2-amino-6-ethylaminopurine by 20-fold, 2-methylaminopurine (2MAP) by 9.4-fold, 2,6-bismethylaminopurine by 25-fold, 2AP by 230-fold, 2,6DAP by 15-fold, 2.6-diaminopurine riboside by 5-fold, and 2-hydroxylaminopurine by 11-fold. The last 4 analogues also cause transitions. 2A6MAP, 2-amino-6-ethylaminopurine and 2,6-bismethylaminopurine stimulate only the AT----CG transversion while 2MAP additionally gives rise to AT----TA transversions. By testing other negative 2AP derivatives, the structural requirements necessary for AT----CG transversion mutagenesis have been determined. All 12 hydroxylaminopurine base analogues tested, 2,6-dimethoxyaminopurine and 2-hydrazinopurine were found to cause transition mutations. All of the compounds stimulated the AT----GC transition (by up to 1000-fold) and 11 of the 14 base analogues raised the GT----AT transition (by up to 450-fold). On increasing the hydroxylaminopurine concentration, the mutation frequency also increased concomitantly. Since 6-hydroxylamino-9-methylpurine and 6-methylhydroxylaminopurine cause transitions, the mechanism of hydroxylaminopurine mutagenesis cannot be entirely due to an alteration in tautomeric equilibria or "wobble" type base mispairing. It is proposed that a major mechanism for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18174994','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18174994"><span>Fluorescence and electrochemical detection of pyrimidine/<span class="hlt">purine</span> transversion by a ferrocenyl aminonaphthyridine derivative.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Morita, Kotaro; Sato, Yusuke; Seino, Takehiro; Nishizawa, Seiichi; Teramae, Norio</p> <p>2008-01-21</p> <p>A novel hydrogen bond-forming ligand for pyrimidine/<span class="hlt">purine</span> transversion, which contains both a fluorescent naphthyridine moiety and a ferrocenyl group as an electrochemical indicator, is described. Hydrogen bond-mediated recognition for a target nucleobase at an abasic site in a DNA duplex is confirmed by both fluorescence and electrochemical measurements. The analysis by fluorescence titration reveals that the ligand shows significant fluorescent quenching upon formation of a 1 : 1 complex with the target nucleobase opposite the abasic site, and the selectivity is in the order of cytosine > thymine > adenine, guanine, reflecting the stability of the hydrogen bond formation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17029630','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17029630"><span>Microarray analysis after RNA amplification can detect <span class="hlt">pronounced</span> differences in gene expression using limma.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Diboun, Ilhem; Wernisch, Lorenz; Orengo, Christine Anne; Koltzenburg, Martin</p> <p>2006-10-09</p> <p>RNA amplification is necessary for profiling gene expression from small tissue samples. Previous studies have shown that the T7 based amplification techniques are reproducible but may distort the true abundance of targets. However, the consequences of such distortions on the ability to detect biological variation in expression have not been explored sufficiently to define the true extent of usability and limitations of such amplification techniques. We show that expression ratios are occasionally distorted by amplification using the Affymetrix small sample protocol version 2 due to a disproportional shift in intensity across biological samples. This occurs when a shift in one sample cannot be reflected in the other sample because the intensity would lie outside the dynamic range of the scanner. Interestingly, such distortions most commonly result in smaller ratios with the consequence of reducing the statistical significance of the ratios. This becomes more critical for less <span class="hlt">pronounced</span> ratios where the evidence for differential expression is not strong. Indeed, statistical analysis by limma suggests that up to 87% of the genes with the largest and therefore most significant ratios (p < 10e(-20)) in the unamplified group have a p-value below 10e(-20) in the amplified group. On the other hand, only 69% of the more moderate ratios (10e(-20) < p < 10e(-10)) in the unamplified group have a p-value below 10e(-10) in the amplified group. Our analysis also suggests that, overall, limma shows better overlap of genes found to be significant in the amplified and unamplified groups than the Z-scores statistics. We conclude that microarray analysis of amplified samples performs best at detecting differences in gene expression, when these are large and when limma statistics are used.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23963224','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23963224"><span>Effects of riparian plant diversity loss on aquatic microbial decomposers become more <span class="hlt">pronounced</span> with increasing time.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fernandes, Isabel; Duarte, Sofia; Cássio, Fernanda; Pascoal, Cláudia</p> <p>2013-11-01</p> <p>We examined the potential long-term impacts of riparian plant diversity loss on diversity and activity of aquatic microbial decomposers. Microbial assemblages were obtained in a mixed-forest stream by immersion of mesh bags containing three leaf species (alder, oak and eucalyptus), commonly found in riparian corridors of Iberian streams. Simulation of species loss was done in microcosms by including a set of all leaf species, retrieved from the stream, and non-colonized leaves of three, two or one leaf species. Leaves were renewed every month throughout six months, and microbial inoculum was ensured by a set of colonized leaves from the previous month. Microbial diversity, leaf mass loss and fungal biomass were assessed at the second and sixth months after plant species loss. Molecular diversity of fungi and bacteria, as the total number of operational taxonomic units per leaf diversity treatment, decreased with leaf diversity loss. Fungal biomass tended to decrease linearly with leaf species loss on oak and eucalyptus, suggesting more <span class="hlt">pronounced</span> effects of leaf diversity on lower quality leaves. Decomposition of alder and eucalyptus leaves was affected by leaf species identity, mainly after longer times following diversity loss. Leaf decomposition of alder decreased when mixed with eucalyptus, while decomposition of eucalyptus decreased in mixtures with oak. Results suggest that the effects of leaf diversity on microbial decomposers depended on leaf species number and also on which species were lost from the system, especially after longer times. This may have implications for the management of riparian forests to maintain stream ecosystem functioning.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1618401','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1618401"><span>Microarray analysis after RNA amplification can detect <span class="hlt">pronounced</span> differences in gene expression using limma</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Diboun, Ilhem; Wernisch, Lorenz; Orengo, Christine Anne; Koltzenburg, Martin</p> <p>2006-01-01</p> <p>Background RNA amplification is necessary for profiling gene expression from small tissue samples. Previous studies have shown that the T7 based amplification techniques are reproducible but may distort the true abundance of targets. However, the consequences of such distortions on the ability to detect biological variation in expression have not been explored sufficiently to define the true extent of usability and limitations of such amplification techniques. Results We show that expression ratios are occasionally distorted by amplification using the Affymetrix small sample protocol version 2 due to a disproportional shift in intensity across biological samples. This occurs when a shift in one sample cannot be reflected in the other sample because the intensity would lie outside the dynamic range of the scanner. Interestingly, such distortions most commonly result in smaller ratios with the consequence of reducing the statistical significance of the ratios. This becomes more critical for less <span class="hlt">pronounced</span> ratios where the evidence for differential expression is not strong. Indeed, statistical analysis by limma suggests that up to 87% of the genes with the largest and therefore most significant ratios (p < 10e-20) in the unamplified group have a p-value below 10e-20 in the amplified group. On the other hand, only 69% of the more moderate ratios (10e-20 < p < 10e-10) in the unamplified group have a p-value below 10e-10 in the amplified group. Our analysis also suggests that, overall, limma shows better overlap of genes found to be significant in the amplified and unamplified groups than the Z-scores statistics. Conclusion We conclude that microarray analysis of amplified samples performs best at detecting differences in gene expression, when these are large and when limma statistics are used. PMID:17029630</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4327250','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4327250"><span><span class="hlt">Pronounced</span> and prevalent intersexuality does not impede the ‘Demon Shrimp’ invasion</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Green Etxabe, Amaia; Short, Stephen; Flood, Tim; Johns, Tim</p> <p>2015-01-01</p> <p>Crustacean intersexuality is widespread and often linked to infection by sex-distorting parasites. However, unlike vertebrate intersexuality, its association with sexual dysfunction is unclear and remains a matter of debate. The ‘Demon Shrimp,’ Dikerogammarus haemobaphes, an amphipod that has invaded continental waterways, has recently become widespread in Britain. Intersexuality has been noted in D. haemobaphes but not investigated further. We hypothesise that a successful invasive population should not display a high prevalence of intersexuality if this condition represents a truly dysfunctional phenotype. In addition, experiments have indicated that particular parasite burdens in amphipods may facilitate invasions. The rapid and ongoing invasion of British waterways represents an opportunity to determine whether these hypotheses are consistent with field observations. This study investigates the parasites and sexual phenotypes of D. haemobaphes in British waterways, characterising parasite burdens using molecular screening, and makes comparisons with the threatened Gammarus pulex natives. We reveal that invasive and native populations have distinct parasitic profiles, suggesting the loss of G. pulex may have parasite-mediated eco-system impacts. Furthermore, the parasite burdens are consistent with those previously proposed to facilitate biological invasions. Our study also indicates that while no intersexuality occurs in the native G. pulex, approximately 50% of D. haemobaphes males present <span class="hlt">pronounced</span> intersexuality associated with infection by the microsporidian Dictyocoela berillonum. This unambiguously successful invasive population presents, to our knowledge, the highest reported prevalence of male intersexuality. This is the clearest evidence to date that such intersexuality does not represent a form of debilitating sexual dysfunction that negatively impacts amphipod populations. PMID:25699206</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRD..121.6600H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRD..121.6600H"><span>On the origin of <span class="hlt">pronounced</span> O3 gradients in the thunderstorm outflow region during DC3</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Huntrieser, H.; Lichtenstern, M.; Scheibe, M.; Aufmhoff, H.; Schlager, H.; Pucik, T.; Minikin, A.; Weinzierl, B.; Heimerl, K.; Fütterer, D.; Rappenglück, B.; Ackermann, L.; Pickering, K. E.; Cummings, K. A.; Biggerstaff, M. I.; Betten, D. P.; Honomichl, S.; Barth, M. C.</p> <p>2016-06-01</p> <p>Unique in situ measurements of CO, O3, SO2, CH4, NO, NOx, NOy, VOC, CN, and rBC were carried out with the German Deutsches Zentrum für Luft- und Raumfahrt (DLR)-Falcon aircraft in the central U.S. thunderstorms during the Deep Convective Clouds and Chemistry experiment in summer 2012. Fresh and aged anvil outflow (9-12 km) from supercells, mesoscale convective systems, mesoscale convective complexes, and squall lines were probed over Oklahoma, Texas, Colorado, and Kansas. For three case studies (30 May and 8 and 12 June) a combination of trace species, radar, lightning, and satellite information, as well as model results, were used to analyze and design schematics of major trace gas transport pathways within and in the vicinity of the probed thunderstorms. The impact of thunderstorms on the O3 composition in the upper troposphere/lower stratosphere (LS) region was analyzed. Overshooting cloud tops injected high amounts of biomass burning and lightning-produced NOx emissions into the LS, in addition to low O3 mixing ratios from the lower troposphere. As a dynamical response, O3-rich air from the LS was transported downward into the anvil and also surrounded the outflow. The ΔO3/ΔCO ratio was determined in the anvil outflow region. A <span class="hlt">pronounced</span> in-mixing of O3-rich stratospheric air masses was observed in the outflow indicated by highly positive or even negative ΔO3/ΔCO ratios (+1.4 down to -3.9). Photochemical O3 production (ΔO3/ΔCO = +0.1) was found to be minor in the recently lofted pollution plumes. O3 mixing ratios within the aged anvil outflow were mainly enhanced due to dynamical processes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24753570','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24753570"><span><span class="hlt">Pronounced</span> zonal heterogeneity in Eocene southern high-latitude sea surface temperatures.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Douglas, Peter M J; Affek, Hagit P; Ivany, Linda C; Houben, Alexander J P; Sijp, Willem P; Sluijs, Appy; Schouten, Stefan; Pagani, Mark</p> <p>2014-05-06</p> <p>Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10-17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The <span class="hlt">pronounced</span> zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4020054','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4020054"><span><span class="hlt">Pronounced</span> zonal heterogeneity in Eocene southern high-latitude sea surface temperatures</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Douglas, Peter M. J.; Affek, Hagit P.; Ivany, Linda C.; Houben, Alexander J. P.; Sijp, Willem P.; Sluijs, Appy; Schouten, Stefan; Pagani, Mark</p> <p>2014-01-01</p> <p>Paleoclimate studies suggest that increased global warmth during the Eocene epoch was greatly amplified at high latitudes, a state that climate models cannot fully reproduce. However, proxy estimates of Eocene near-Antarctic sea surface temperatures (SSTs) have produced widely divergent results at similar latitudes, with SSTs above 20 °C in the southwest Pacific contrasting with SSTs between 5 and 15 °C in the South Atlantic. Validation of this zonal temperature difference has been impeded by uncertainties inherent to the individual paleotemperature proxies applied at these sites. Here, we present multiproxy data from Seymour Island, near the Antarctic Peninsula, that provides well-constrained evidence for annual SSTs of 10–17 °C (1σ SD) during the middle and late Eocene. Comparison of the same paleotemperature proxy at Seymour Island and at the East Tasman Plateau indicate the presence of a large and consistent middle-to-late Eocene SST gradient of ∼7 °C between these two sites located at similar paleolatitudes. Intermediate-complexity climate model simulations suggest that enhanced oceanic heat transport in the South Pacific, driven by deep-water formation in the Ross Sea, was largely responsible for the observed SST gradient. These results indicate that very warm SSTs, in excess of 18 °C, did not extend uniformly across the Eocene southern high latitudes, and suggest that thermohaline circulation may partially control the distribution of high-latitude ocean temperatures in greenhouse climates. The <span class="hlt">pronounced</span> zonal SST heterogeneity evident in the Eocene cautions against inferring past meridional temperature gradients using spatially limited data within given latitudinal bands. PMID:24753570</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017JaJAP..56hLB02T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017JaJAP..56hLB02T"><span><span class="hlt">Sequencing</span> of adenine in DNA by scanning tunneling microscopy</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tanaka, Hiroyuki; Taniguchi, Masateru</p> <p>2017-08-01</p> <p>The development of DNA <span class="hlt">sequencing</span> technology utilizing the detection of a tunnel current is important for next-generation <span class="hlt">sequencer</span> technologies based on single-molecule analysis technology. Using a scanning tunneling microscope, we previously reported that dI/dV measurements and dI/dV mapping revealed that the guanine base (<span class="hlt">purine</span> base) of DNA adsorbed onto the Cu(111) surface has a characteristic peak at V s = -1.6 V. If, in addition to guanine, the other <span class="hlt">purine</span> base of DNA, namely, adenine, can be distinguished, then by reading all the <span class="hlt">purine</span> bases of each single strand of a DNA double helix, the entire base <span class="hlt">sequence</span> of the original double helix can be determined due to the complementarity of the DNA base pair. Therefore, the ability to read adenine is important from the viewpoint of <span class="hlt">sequencing</span>. Here, we report on the identification of adenine by STM topographic and spectroscopic measurements using a synthetic DNA oligomer and viral DNA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1218491','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1218491"><span>Validation and steady-state analysis of a power-law model of <span class="hlt">purine</span> metabolism in man.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Curto, R; Voit, E O; Sorribas, A; Cascante, M</p> <p>1997-01-01</p> <p>The paper introduces a model of human <span class="hlt">purine</span> metabolism in situ. Chosen from among several alternative system descriptions, the model is formulated as a Generalized Mass Action system within Biochemical Systems Theory and validated with analyses of steady-state and dynamic characteristics. Eigenvalue and sensitivity analyses indicate that the model has a stable and robust steady-state. The model quite accurately reproduces numerous biochemical and clinical observations in healthy subjects as well as in patients with disorders of <span class="hlt">purine</span> metabolism. These results suggest that the model can be used to assess biochemical and clinical aspects of human <span class="hlt">purine</span> metabolism. It provides a means of exploring effects of enzyme deficiencies and is a potential tool for identifying steps of the pathway that could be the target of therapeutical intervention. Numerous quantitative comparisons with data are given. The model can be used for biomathematical exploration of relationships between enzymic deficiencies and clinically manifested diseases. PMID:9210399</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22448670','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22448670"><span><span class="hlt">Pronounced</span> microheterogeneity in a sorbitol-water mixture observed through variable temperature neutron scattering.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chou, Shin G; Soper, Alan K; Khodadadi, Sheila; Curtis, Joseph E; Krueger, Susan; Cicerone, Marcus T; Fitch, Andrew N; Shalaev, Evgenyi Y</p> <p>2012-04-19</p> <p>In this study, the structure of concentrated d-sorbitol-water mixtures is studied by wide- and small-angle neutron scattering (WANS and SANS) as a function of temperature. The mixtures are prepared using both deuterated and regular sorbitol and water at a molar fraction of sorbitol of 0.19 (equivalent to 70% by weight of regular sorbitol in water). Retention of an amorphous structure (i.e., absence of crystallinity) is confirmed for this system over the entire temperature range, 100-298 K. The glass transition temperature, Tg, is found from differential scanning calorimetry to be approximately 200 K. WANS data are analyzed using empirical potential structure refinement, to obtain the site-site radial distribution functions (RDFs) and coordination numbers. This analysis reveals the presence of nanoscaled water clusters surrounded by (and interacting with) sorbitol molecules. The water clusters appear more structured compared to bulk water and, especially at the lowest temperatures, resemble the structure of low-density amorphous ice (LDA). Upon cooling to 100 K the peaks in the water RDFs become markedly sharper, with increased coordination number, indicating enhanced local (nanometer-scale) ordering, with changes taking place both above and well below the Tg. On the mesoscopic (submicrometer) scale, although there are no changes between 298 and 213 K, cooling the sample to 100 K results in a significant increase in the SANS signal, which is indicative of <span class="hlt">pronounced</span> inhomogeneities. This increase in the scattering is partly reversed during heating, although some hysteresis is observed. Furthermore, a power law analysis of the SANS data indicates the existence of domains with well-defined interfaces on the submicrometer length scale, probably as a result of the appearance and growth of microscopic voids in the glassy matrix. Because of the unusual combination of small and wide scattering data used here, the present results provide new physical insight into the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25684787','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25684787"><span>Fertility and Pregnancy Outcome after Myoma Enucleation by Minilaparotomy under Microsurgical Conditions in <span class="hlt">Pronounced</span> Uterus Myomatosus.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Floss, K; Garcia-Rocha, G-J; Kundu, S; von Kaisenberg, C S; Hillemanns, P; Schippert, C</p> <p>2015-01-01</p> <p>Introduction: Besides the typical complaints and symptoms, myomas can cause sterility, infertility and complications during pregnancy. Laparoscopic interventions reach their limits with regard to organ preservation and the simultaneous desire to have children in the removal of multiple and larger intramural myoma nodes. The aim of this study is to examine fertility status and pregnancy outcome after myoma removal by minilaparotomy (skin incision maximal 8 cm) in women with <span class="hlt">pronounced</span> uterus myomatosus. Materials and Methods: This retrospective study makes use of the data from 160 patients with an average age of 34.6 years. Factors analysed include number, size and localisation of the myomas, complaints due to the myoma, pre- and postoperative gravidity, mode of delivery, and complications of birth. Results: Indications for organ-sparing myoma enucleation were the desire to have children (72.5 %), bleeding disorders (60 %) and pressure discomfort (36.5 %). On average 4.95 (SD ± 0.41), maximally 46 myomas were removed. The largest myoma had a diameter of 6.64 cm (SD ± 2.74). 82.5 % of the patients had transmural myomas, in 17.5 % the uterine cavity was inadvertently opened. On average the operating time was 163 minutes (SD ± 45.47), the blood loss 1.59 g/dL (SD ± 0.955). 60.3 % of the patients with the desire to have children became pregnant postoperatively. 75.3 % of the pregnancies were on average carried through to the 38th week (28.4 % vaginal deliveries, 71.6 % Caesarean sections). In the postoperative period there was one case of uterine rupture in the vicinity of a previous scar. Discussion: By means of the microsurgical "mini-laparotomy" even extensive myomatous uterine changes can, in the majority of cases, be operated in an organ-sparing manner with retention of the ability to conceive and to carry a pregnancy through to maturity of the infant. The risk for a postoperative uterine rupture in a subsequent pregnancy and</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=525616','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=525616"><span>Importance of specific <span class="hlt">purine</span> amino and hydroxyl groups for efficient cleavage by a hammerhead ribozyme.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Fu, D J; McLaughlin, L W</p> <p>1992-01-01</p> <p>Eight modified ribozymes of 19 residues have been prepared with individual <span class="hlt">purine</span> amino or hydroxyl groups excised. The modified ribozymes were chemically synthesized with the substitution of a single 2'-deoxyadenosine, 2'-deoxyguanosine, inosine, or <span class="hlt">purine</span> riboside for residues G10, A11, G13, or A14. Five of the modified ribozymes cleaved the 24-mer substrate with little change in rate as monitored by simple first-order kinetics. However, deletion of the 2-amino group at G10 (replacement with inosine) or deletion of either of the 2'-hydroxyls at G10 or G13 (replacement with 2'-deoxyguanosine) resulted in ribozymes with a drastic decrease in cleavage efficiency. Increasing the concentration of the Mg2+ cofactor from 10 mM to 50 mM significantly enhanced cleavage efficiency by these three derivatives. Steady-state kinetic assays for these three ribozymes indicated that the modifications result in both an increase in Km and a decrease in kcat. These results suggest that the exocyclic amino group at-G10 and the hydroxyls at G10 and G13 are important both for ribozyme-substrate binding and for the Mg(2+)-catalyzed cleavage reaction. PMID:1570323</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4538711','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4538711"><span>An Ancient Riboswitch Class in Bacteria Regulates <span class="hlt">Purine</span> Biosynthesis and One-carbon Metabolism</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kim, Peter B.; Nelson, James W.; Breaker, Ronald R.</p> <p>2015-01-01</p> <p>SUMMARY Over thirty years ago, ZTP (5-amino-4-imidazole carboxamide riboside 5'-triphosphate), a modified <span class="hlt">purine</span> biosynthetic intermediate, was proposed to signal 10-formyl-tetrahydrofolate (10f-THF) deficiency in bacteria. However, the mechanisms by which this putative alarmone or its precursor ZMP (5-aminoimidazole-4-carboxamide ribonucleotide, also known as AICAR) brings about any metabolic changes remain unexplained. Herein we report the existence of a widespread riboswitch class that is most commonly associated with genes related to de novo <span class="hlt">purine</span> biosynthesis and one carbon metabolism. Biochemical data confirms that members of this riboswitch class selectively bind ZMP and ZTP with nanomolar affinity, while strongly rejecting numerous natural analogs. Indeed, increases in the ZMP/ZTP pool, caused by folate stress in bacterial cells, trigger changes in the expression of a reporter gene fused to representative ZTP riboswitches in vivo. The wide distribution of this riboswitch class suggests that ZMP/ZTP signaling is important for species in numerous bacterial lineages. PMID:25616067</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23615735','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23615735"><span>Single tryptophan of disordered loop from Plasmodium falciparum <span class="hlt">purine</span> nucleoside phosphorylase: involvement in catalysis and microenvironment.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Suthar, Manish Kumar; Verma, Anita; Doharey, Pawan Kumar; Singh, Shiv Vardan; Saxena, Jitendra Kumar</p> <p>2013-06-01</p> <p>Among various tropical diseases, malaria is a major life-threatening disease caused by Plasmodium parasite. Plasmodium falciparum is responsible for the deadliest form of malaria, so-called cerebral malaria. <span class="hlt">Purine</span> nucleoside phosphorylase from P. falciparum is a homohexamer containing single tryptophan residue per subunit that accepts inosine and guanosine but not adenosine for its activity. This enzyme has been exploited as drug target against malaria disease. It is important to draw together significant knowledge about inherent properties of this enzyme which will be helpful in better understanding of this drug target. The enzyme shows disorder to order transition during catalysis. The single tryptophan residue residing in conserved region of transition loop is present in <span class="hlt">purine</span> nucleoside phosphorylases throughout the Plasmodium genus. This active site loop motif is conserved among nucleoside phosphorylases from apicomplexan parasites. Modification of tryptophan residue by N-bromosuccinamide resulted in complete loss of activity showing its importance in catalysis. Inosine was not able to protect enzyme against N-bromosuccinamide modification. Extrinsic fluorescence studies revealed that tryptophan might not be involved in substrate binding. The tryptophan residue localised in electronegative environment showed collisional and static quenching in the presence of quenchers of different polarities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24604285','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24604285"><span>Microwave-assisted synthesis of novel <span class="hlt">purine</span> nucleosides as selective cholinesterase inhibitors.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Schwarz, S; Csuk, R; Rauter, A P</p> <p>2014-04-21</p> <p>Alzheimer's disease (AD), the most common form of senile dementia, is characterized by high butyrylcholinesterase (BChE) levels in the brain in later AD stages, for which no treatment is available. Pursuing our studies on selective BChE inhibitors, that may contribute to understand the role of this enzyme in disease progression, we present now microwave-assisted synthesis and anticholinesterase activity of a new nucleoside series embodying 6-chloropurine or 2-acetamido-6-chloropurine linked to D-glucosyl, D-galactosyl and D-mannosyl residues. It was designed to assess the contribution of sugar stereochemistry, <span class="hlt">purine</span> structure and linkage to the sugar for cholinesterase inhibition efficiency and selectivity. Compounds were subjected to Ellman's assay and their inhibition constants determined. The α-anomers were the most active compounds, while selectivity for BChE or acetylcholinesterase (AChE) inhibition could be tuned by the <span class="hlt">purine</span> base, by the glycosyl moiety and by N(7)-ligation. Some of the nucleosides were far more potent than the drug galantamine, and the most promising competitive and selective BChE inhibitor, the N(7)-linked 2-acetamido-α-D-mannosylpurine, showed a Ki of 50 nM and a selectivity factor of 340 fold for BChE over AChE.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4494960','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4494960"><span>Myc-dependent <span class="hlt">purine</span> biosynthesis affects nucleolar stress and therapy response in prostate cancer</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Barfeld, Stefan J.; Fazli, Ladan; Persson, Margareta; Marjavaara, Lisette; Urbanucci, Alfonso; Kaukoniemi, Kirsi M.; Rennie, Paul S.; Ceder, Yvonne; Chabes, Andrei; Visakorpi, Tapio; Mills, Ian G.</p> <p>2015-01-01</p> <p>The androgen receptor is a key transcription factor contributing to the development of all stages of prostate cancer (PCa). In addition, other transcription factors have been associated with poor prognosis in PCa, amongst which c-Myc (MYC) is a well-established oncogene in many other cancers. We have previously reported that the AR promotes glycolysis and anabolic metabolism; many of these metabolic pathways are also MYC-regulated in other cancers. In this study, we report that in PCa cells de novo <span class="hlt">purine</span> biosynthesis and the subsequent conversion to XMP is tightly regulated by MYC and independent of AR activity. We characterized two enzymes, PAICS and IMPDH2, within the pathway as PCa biomarkers in tissue samples and report increased efficacy of established anti-androgens in combination with a clinically approved IMPDH inhibitor, mycophenolic acid (MPA). Treatment with MPA led to a significant reduction in cellular guanosine triphosphate (GTP) levels accompanied by nucleolar stress and p53 stabilization. In conclusion, targeting <span class="hlt">purine</span> biosynthesis provides an opportunity to perturb PCa metabolism and enhance tumour suppressive stress responses. PMID:25869206</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17166630','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17166630"><span>New bis-N9-(methylphenylmethyl)<span class="hlt">purine</span> derivatives: synthesis and antitumor activity.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kode, Nageswara; Chen, Liying; Murthy, Devangachinta; Adewumi, Dare; Phadtare, Shashikant</p> <p>2007-03-01</p> <p>A series of ortho-, meta- and para-bis-N9-(methylphenylmethyl)<span class="hlt">purine</span> derivatives 4-15 were obtained by two-step synthesis from various substituted chloropurines with alpha,alpha'-dichloroxylenes. These bis-N9-(methylphenylmethyl)<span class="hlt">purines</span> 4-15 were evaluated for the primary cytotoxic activity against a panel of NCI-H460 (lung), MCF-7 (breast) and SF-268 (CNS) cancer cell lines. The 'active' compounds which reduced growth of cancer cells to ca. 32% or less, have been evaluated in a full panel of 60 human cancer cell lines over a 5-log dose range at the National Cancer Institute, Bethesda, MD. In this series, the most activity is correlated to the compounds derived from the 2,6-dichloropurines such as bis-9-[o-(methylphenylmethyl)]2,6-dichloropurine (5), bis-9-[m-(methylphenylmethyl)]2,6-dichloropurine (8), and bis-9-[p-(methylphenylmethyl)]2,6-dichloropurine (11). In particular compound 8 exhibited high sensitivity in leukemia cell lines and compounds 5, 8 and 11 exhibited consistent high sensitivity in many breast cancer cell lines. Compound 11 was the most potent in this series and exhibited GI(50)<0.01 microM sensitivity against non-small lung cancer EKVX, colon cancer HT-29, melanoma SK-MEL-28, renal cancer RXF 393, prostate cancer DU-145 and several breast cancer HS 578T and BT-549 cell lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20222071','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20222071"><span>Separation of <span class="hlt">purine</span> and pyrimidine bases and nucleosides by hydrophilic interaction chromatography.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Marrubini, Giorgio; Mendoza, Bolivar Enrique Castillo; Massolini, Gabriella</p> <p>2010-03-01</p> <p>The separation of 12 model compounds chosen among <span class="hlt">purine</span> and pyrimidine bases and nucleosides was studied by using hydrophilic interaction chromatography (HILIC). The compounds investigated were small molecules with relevant properties for biomedical and pharmaceutical studies. The mixture of pyrimidines and <span class="hlt">purines</span> was applied on a ZIC-HILIC 150 x 2.1 mm, 5 microm, and two TSKgel Amide-80 150 x 2.0 mm, 5 microm and 3 microm particle size columns. The retention of the analytes was studied by varying ACN%, ammonium formate concentration, pH, and column temperature. The results obtained confirmed the elution order of nucleobases, nucleosides, and nucleotides based on their hydrophobicity. The retention mechanism of the columns was studied considering the models used for describing partitioning and surface adsorption. The influence on retention of chromatographic conditions (ACN%, salt concentration, pH, and temperature) was described and discussed for both columns. The optimization of the conditions studied allowed to assess a gradient method for the separation of the 12 analytes. The developed method is a valuable alternative to existing methods for the separation of the compounds concerned.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/2538926','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/2538926"><span>Imbalance of <span class="hlt">purine</span> nucleotides in alanosine-resistant baby hamster kidney cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pang, J C; Du, R P; Bingham, H; Juranka, P; Chan, V L</p> <p>1989-03-01</p> <p>Human DNA was used to transform adenosine kinase (AK)-deficient BHK cells followed by selection of AK+ cells in medium containing alanosine, adenosine, and uridine (AAU medium). Twenty AAUr isolates were analyzed, and none of them contained AK activity. Several <span class="hlt">purine</span> salvage enzymes were, however, found to be affected in these cells. The levels of hypoxanthine-guanine phosphoribosyltransferase and adenylosuccinate synthetase activities were elevated, while the adenylosuccinase activity was reduced. AAU-resistance may be explained by elevated activity of adenylosuccinate synthetase to overcome the alanosine block; thus AAUr cells were able to convert exogenous adenosine----inosine----hypoxanthine----IMP----AMPS----AMP. Moreover, these AAUr cells required exogenous <span class="hlt">purines</span> for growth. HPLC analyses of endogenous nucleotide pools of AAUr cells showed that the levels of adenine nucleotides have diminished to less than 10% of the parental levels. These results suggest that the AAU-resistant mutation, which elicits pleiotropic phenotypes in BHK cells, affects an important component in the regulation of adenine nucleotide synthesis. By including erthyro-9-(2-hydroxy-3-nonyl)adenine in the AAU medium (renamed as AAUE medium) to block deamination of adenosine, AK+ BHK cells were isolated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005OLEB...35...79B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005OLEB...35...79B"><span>An Investigation of Prebiotic <span class="hlt">Purine</span> Synthesis from the Hydrolysis of HCN Polymers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Borquez, Eduardo; Cleaves, H. James; Lazcano, Antonio; Miller, Stanley L.</p> <p>2005-04-01</p> <p>The polymerization of concentrated NH4CN solutions has been studied at various temperatures and ammonia concentrations. The products of the oligomerization of ammonium cyanide include adenine and guanine, as well as trace amounts of 2,6-diaminopurine. Our results indicate that the adenine yield is not strongly dependent on temperature. Guanine is produced in lower yield. The original studies by Oró and Kimball (1961) showed that the 6 N HCl hydrolysis of the NH4CN polymerization supernatant greatly increased the adenine yield. However, this hydrolysis also decomposes adenine and other <span class="hlt">purines</span>. Therefore, we have measured the yields from an NH4CN polymerization as a function of hydrolysis time, and found that shorter hydrolytic periods give higher yields of adenine.We have also investigated the hydrolysis of the supernatant at pH 8, which is a more reasonable model of primitive oceanic conditions, and found that the adenine yield is comparable to that obtained with acid hydrolysis (approximately 0.1%). The yield of adenine does not decline at longer hydrolysis times because of the greater stability of adenine at pH 8. The insoluble black polymer formed from NH4CN has been analyzed by both acid and neutral hydrolysis. In both cases adenine yields of approximately 0.05% were obtained. This suggests that the polymer may have been as important a prebiotic source of <span class="hlt">purines</span> as the usually analyzed supernatant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22890959','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22890959"><span>Sustainable synthesis and automated deposition: an accessible discovery screening library of fragment-like <span class="hlt">purines</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kamper, Christoph; Korpis, Katharina; Specker, Edgar; Anger, Lennart; Neuenschwander, Martin; Bednarski, Patrick J; Link, Andreas</p> <p>2012-08-01</p> <p>A sub-library of 88 information-rich lead-like <span class="hlt">purine</span> derivatives were prepared and deposited in an open access academic screening facility. The rationale for the synthesis of these rigid low complexity structures was the privileged character of the <span class="hlt">purine</span> heterocycle associated with its inherent probability of interactions with multiple adenine-related targets. Although generally expected to be weak binders in many assays, such fragment-like compounds are estimated to match diverse binding sites. It is suggested that heterocycles with many anchor points for hydrogen bonds can be anticipated to undergo very specific interactions to produce more negative enthalpies and thus provide superior starting points for lead optimization than compounds that owe their activity to entropic effects. The in vitro cytotoxicity of the small compounds on a panel of human cancer cell lines has been investigated and some of them showed marked unselective or selective toxicity. This data may be useful if these fragments are to be incorporated into drug-like structures via metabolically cleavable connections. The sub-library will be implemented as part of the ChemBioNet ( www.chembionet.info ) library, and it is open to screening campaigns of academic research groups striving for a fragment-based approach in their biological assays.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25728022','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25728022"><span><span class="hlt">Purine</span>-benzimidazole hybrids: synthesis, single crystal determination and in vitro evaluation of antitumor activities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Sharma, Alka; Luxami, Vijay; Paul, Kamaldeep</p> <p>2015-03-26</p> <p>In an effort to identify novel compounds for the treatment of cancer, a diverse array of potential bioactive hybrid, <span class="hlt">purine</span>-benzimidazole was synthesized in good yields through nucleophilic substitution at C6 position of <span class="hlt">purine</span> ring with versatile cyclic amines at C2 position. The structures of newly prepared compounds were confirmed by IR, (1)H, (13)C NMR, mass spectroscopy and, in case of 19, by single crystal X-ray diffraction analysis. The newly synthesized compounds were evaluated against 60 human tumour cell lines at one dose concentration level. Compound 6 exhibited significant growth inhibition and was evaluated as 60 cell panel at five dose concentration levels. Compound 6 proved to be 1.25 fold more active than the positive control 5-FU, with GI50 value of 18.12 μM (MG-MID). Interaction of the compounds with Aurora-A enzyme involved in the process of propagation of cancer, has also been investigated. Compound 6 showed selectivity towards Aurora-A kinase inhibition with IC50 value of 0.0l μM. Molecular docking studies in the active binding site provided theoretical support for the experimental biological data acquired.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4790316','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4790316"><span>Genetic Screen Reveals the Role of <span class="hlt">Purine</span> Metabolism in Staphylococcus aureus Persistence to Rifampicin</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Yee, Rebecca; Cui, Peng; Shi, Wanliang; Feng, Jie; Zhang, Ying</p> <p>2015-01-01</p> <p>Chronic infections with Staphylococcus aureus such as septicemia, osteomyelitis, endocarditis, and biofilm infections are difficult to treat because of persisters. Despite many efforts in understanding bacterial persistence, the mechanisms of persister formation in S. aureus remain elusive. Here, we performed a genome-wide screen of a transposon mutant library to study the molecular mechanisms involved in persistence of community-acquired S. aureus. Screening of the library for mutants defective in persistence or tolerance to rifampicin revealed many genes involved in metabolic pathways that are important for antibiotic persistence. In particular, the identified mutants belonged to metabolic pathways involved in carbohydrate, amino acid, lipid, vitamin and <span class="hlt">purine</span> biosynthesis. Five mutants played a role in <span class="hlt">purine</span> biosynthesis and two mutants, purB, an adenylosuccinate lyase, and purM, a phosphoribosylaminoimidazole synthetase, were selected for further confirmation. Mutants purB and purM showed defective persistence compared to the parental strain USA300 in multiple stress conditions including various antibiotics, low pH, and heat stress. The defect in persistence was restored by complementation with the wildtype purB and purM gene in the respective mutants. These findings provide new insights into the mechanisms of persistence in S. aureus and provide novel therapeutic targets for developing more effective treatment for persistent infections due to S. aureus. PMID:27025643</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18571422','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18571422"><span>N-Arylmethyl substituted iminoribitol derivatives as inhibitors of a <span class="hlt">purine</span> specific nucleoside hydrolase.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Goeminne, Annelies; Berg, Maya; McNaughton, Michael; Bal, Gunther; Surpateanu, Georgiana; Van der Veken, Pieter; De Prol, Stijn; Versées, Wim; Steyaert, Jan; Haemers, Achiel; Augustyns, Koen</p> <p>2008-07-15</p> <p>A key enzyme within the <span class="hlt">purine</span> salvage pathway of parasites, nucleoside hydrolase, is proposed as a good target for new antiparasitic drugs. We have developed N-arylmethyl-iminoribitol derivatives as a novel class of inhibitors against a <span class="hlt">purine</span> specific nucleoside hydrolase from Trypanosoma vivax. Several of our inhibitors exhibited low nanomolar activity, with 1,4-dideoxy-1,4-imino-N-(8-quinolinyl)methyl-d-ribitol (UAMC-00115, K(i) 10.8nM), N-(9-deaza-adenin-9-yl)methyl-1,4-dideoxy-1,4-imino-d-ribitol (K(i) 4.1nM), and N-(9-deazahypoxanthin-9-yl)methyl-1,4-dideoxy-1,4-imino-d-ribitol (K(i) 4.4nM) being the three most active compounds. Docking studies of the most active inhibitors revealed several important interactions with the enzyme. Among these interactions are aromatic stacking of the nucleobase mimic with two Trp-residues, and hydrogen bonds between the hydroxyl groups of the inhibitors and amino acid residues in the active site. During the course of these docking studies we also identified a strong interaction between the Asp40 residue from the enzyme and the inhibitor. This is an interaction which has not previously been considered as being important.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3355689','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3355689"><span>An expanding role for <span class="hlt">purine</span> uptake permease-like transporters in plant secondary metabolism</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Jelesko, John G.</p> <p>2012-01-01</p> <p>For the past decade, our understanding of the plant <span class="hlt">purine</span> uptake permease (PUP) transporter family was primarily oriented on <span class="hlt">purine</span> nucleobase substrates and their tissue-specific expression patterns in Arabidopsis. However, a tobacco PUP-like homolog demonstrating nicotine uptake permease activity was recently shown to affect both nicotine metabolism and root cell growth. These new findings expand the physiological role for PUP-like transporters to include plant secondary metabolism. Molecular evolution analyses of PUP-like transporters indicate they are distinct group within an ancient super family of drug and metabolite transporters (DMTs). The PUP-like family originated during terrestrial plant evolution sometime between the bryophytes and the lycophytes. A phylogenetic analysis indicates that the PUP-like transporters were likely derived from a pre-existing nucleotide-sugar transporter family within the DMT super family. Within the lycophyte Selaginella, there are three paralogous groups of PUP-like transporters. One of the three PUP-like paralogous groups showed an extensive pattern of gene duplication and diversification within the angiosperm lineage, whereas the more ancestral PUP-like paralogous groups did not. Biochemical characterization of four closely related PUP-like paralogs together with model-based phylogenetic analyses indicate both subfunctionalization and neofunctionalization during the molecular evolution of angiosperm PUP-like transporters. These findings suggest that members of the PUP-like family of DMT transporters are likely involved in diverse primary and secondary plant metabolic pathways. PMID:22639664</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016RaPC..128...75C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016RaPC..128...75C"><span><span class="hlt">Purine</span> 5‧,8-cyclo-2‧-deoxynucleoside lesions in irradiated DNA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chatgilialoglu, Chryssostomos; Krokidis, Marios G.; Papadopoulos, Kyriakos; Terzidis, Michael A.</p> <p>2016-11-01</p> <p>Having their position gained among the smallest bulky DNA lesions recognized by the nucleotide excision repair (NER) enzyme, <span class="hlt">purine</span> 5‧,8-cyclo-2‧-deoxynucleosides (5‧,8-cPu) are increasingly attracting the interest in the field of genome integrity in health and diseases. Exclusively generated by one of the most harmful of the reactive oxygen species, the hydroxyl radical, 5‧,8-cPu can be utilized also for highly valuable information regarding the oxidative status nearby the area where the genetic information is stored. Herein, we have collected the most recently reported biological studies, focusing on the repair mechanism of these lesions and their biological significance particularly in transcription. The LC-MS/MS quantification protocols that appeared in the literature are discussed in details, along with the reported values for the four 5‧,8-cPu produced by in vitro γ-radiolysis experiments with calf thymus DNA. Mechanistic insights in the formation of the <span class="hlt">purine</span> 5‧,8-cyclo-2‧-deoxynucleosides and their chemical stability are also given in the light of their potential to be utilized as DNA biomarkers of oxidative stress.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3596326','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3596326"><span>Structural Phylogenomics Reveals Gradual Evolutionary Replacement of Abiotic Chemistries by Protein Enzymes in <span class="hlt">Purine</span> Metabolism</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Caetano-Anollés, Kelsey; Caetano-Anollés, Gustavo</p> <p>2013-01-01</p> <p>The origin of metabolism has been linked to abiotic chemistries that existed in our planet at the beginning of life. While plausible chemical pathways have been proposed, including the synthesis of nucleobases, ribose and ribonucleotides, the cooption of these reactions by modern enzymes remains shrouded in mystery. Here we study the emergence of <span class="hlt">purine</span> metabolism. The ages of protein domains derived from a census of fold family structure in hundreds of genomes were mapped onto enzymes in metabolic diagrams. We find that the origin of the nucleotide interconversion pathway benefited most parsimoniously from the prebiotic formation of adenine nucleosides. In turn, pathways of nucleotide biosynthesis, catabolism and salvage originated ∼300 million years later by concerted enzymatic recruitments and gradual replacement of abiotic chemistries. Remarkably, this process led to the emergence of the fully enzymatic biosynthetic pathway ∼3 billion years ago, concurrently with the appearance of a functional ribosome. The simultaneous appearance of <span class="hlt">purine</span> biosynthesis and the ribosome probably fulfilled the expanding matter-energy and processing needs of genomic information. PMID:23516625</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8306068','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8306068"><span>Action of <span class="hlt">purine</span> and pyrimidine nucleotides on the rat superior cervical ganglion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Connolly, G P; Harrison, P J; Stone, T W</p> <p>1993-12-01</p> <p>1. Using a grease-gap technique, we have investigated the effects of <span class="hlt">purine</span> and pyrimidine nucleotides on the d.c. potential of the rat isolated superior cervical ganglion (SCG). 2. Of the <span class="hlt">purines</span> tested, adenosine, adenosine 5'-triphosphate (ATP), beta,gamma-methylene-adenosine 5'-triphosphate (beta,gamma-MeATP) at up to 300 microM produced concentration-dependent hyperpolarizations, whereas 2-methyl-thio-ATP (2-Me.S.ATP) and alpha,beta-methylene-ATP (alpha,beta-MeATP) depolarized ganglia. Of the pyrimidines tested, uridine 5'-triphosphate (UTP) produced concentration-dependent depolarizations and cytosine 5'-triphosphate (CTP) at 1000 microM produced considerably smaller but significant depolarizations. In contrast uridine 5'-monophosphate (UMP) at 1000 microM hyperpolarized ganglia. The relative order of potency of <span class="hlt">purines</span> and pyrimidines to depolarize ganglia was: UTP > alpha,beta-MeATP > CTP > 2-Me.S.ATP and to hyperpolarize ganglia was: adenosine = beta,gamma-MeATP > ATP > UMP. 3. The ability of <span class="hlt">purines</span> and pyrimidines to alter the depolarizing response caused by muscarine and of <span class="hlt">purines</span> to alter depolarization induced by gamma-aminobutyric acid (GABA) was determined. The relative order of potency of nucleotides in depressing submaximal depolarization caused by muscarine (100 nM) was: adenosine = ATP > beta,gamma-MeATP whereas 2-Me.S.ATP, alpha,beta-MeATP and UTP did not significantly alter depolarization caused by muscarine. At 100 microM beta,gamma-MeATP and adenosine but not ATP potentiated GABA-induced depolarizations. 4. Hyperpolarizations caused by adenosine, ATP, beta,gamma-MeATP and UMP and depolarizations caused by alpha,beta-MeATP were enhanced in medium containing reduced concentrations of calcium (0.1 mM) and potassium (2 mM). In this medium 8-phenyltheophylline abolished hyperpolarizations caused by adenosine and reversed hyperpolarizations caused by ATP into depolarizations. Suramin (300 microM), a P2-purinoceptor antagonist, significantly</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26466447','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26466447"><span>[THE DIAGNOSTICS OF HEREDITARY DISORDERS OF METABOLISM OF <span class="hlt">PURINES</span> AND PYRIMIDINES IN CHILDREN USING HIGH PERFORMANCE LIQUID CHROMATOGRAPHY OF ELECTRO-SPRAY TANDEM MASS-SPECTROMETRY].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mamedov, I S; Zolkina, I V; Sukhorukov, V S</p> <p>2015-06-01</p> <p>The article presents data concerning new technique of diagnostic of diseases of metabolism of <span class="hlt">purines</span> and pyrimidines using high performance liquid chromatography combined with electro-spray mass-spectrometry. The procedure of analysis is described in detail: from pre-analytical stage to interpretation of data of liquid chromatography mass-spectrometry, control of quality of data analysis, mass-spectrometry parameters and chromatographic conditions of analysis of <span class="hlt">purines</span>, pyrimidines and their metabolites. The reference values are presented for <span class="hlt">purine</span> and pyrimidine nucleosides and bases in urine of healthy individuals. The chemical structure of <span class="hlt">purines</span>, pyrimidines and their metabolites and examples of chromato-mass-spectrograms under various hereditary disorders of metabolism of <span class="hlt">purines</span> and pyrimidines are presented as well. The article is targeted to pediatricians of all profiles, medical geneticists and physicians of laboratory diagnostic.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25760070','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25760070"><span>Osmylated DNA, a novel concept for <span class="hlt">sequencing</span> DNA using nanopores.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kanavarioti, Anastassia</p> <p>2015-03-27</p> <p>Saenger <span class="hlt">sequencing</span> has led the advances in molecular biology, while faster and cheaper next generation technologies are urgently needed. A newer approach exploits nanopores, natural or solid-state, set in an electrical field, and obtains base <span class="hlt">sequence</span> information from current variations due to the passage of a ssDNA molecule through the pore. A hurdle in this approach is the fact that the four bases are chemically comparable to each other which leads to small differences in current obstruction. 'Base calling' becomes even more challenging because most nanopores sense a short <span class="hlt">sequence</span> and not individual bases. Perhaps <span class="hlt">sequencing</span> DNA via nanopores would be more manageable, if only the bases were two, and chemically very different from each other; a <span class="hlt">sequence</span> of 1s and 0s comes to mind. Osmylated DNA comes close to such a <span class="hlt">sequence</span> of 1s and 0s. Osmylation is the addition of osmium tetroxide bipyridine across the C5-C6 double bond of the pyrimidines. Osmylation adds almost 400% mass to the reactive base, creates a sterically and electronically notably different molecule, labeled 1, compared to the unreactive <span class="hlt">purines</span>, labeled 0. If osmylated DNA were successfully <span class="hlt">sequenced</span>, the result would be a <span class="hlt">sequence</span> of osmylated pyrimidines (1), and <span class="hlt">purines</span> (0), and not of the actual nucleobases. To solve this problem we studied the osmylation reaction with short oligos and with M13mp18, a long ssDNA, developed a UV-vis assay to measure extent of osmylation, and designed two protocols. Protocol A uses mild conditions and yields osmylated thymidines (1), while leaving the other three bases (0) practically intact. Protocol B uses harsher conditions and effectively osmylates both pyrimidines, but not the <span class="hlt">purines</span>. Applying these two protocols also to the complementary of the target polynucleotide yields a total of four osmylated strands that collectively could define the actual base <span class="hlt">sequence</span> of the target DNA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015Nanot..26m4003K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015Nanot..26m4003K"><span>Osmylated DNA, a novel concept for <span class="hlt">sequencing</span> DNA using nanopores</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kanavarioti, Anastassia</p> <p>2015-03-01</p> <p>Saenger <span class="hlt">sequencing</span> has led the advances in molecular biology, while faster and cheaper next generation technologies are urgently needed. A newer approach exploits nanopores, natural or solid-state, set in an electrical field, and obtains base <span class="hlt">sequence</span> information from current variations due to the passage of a ssDNA molecule through the pore. A hurdle in this approach is the fact that the four bases are chemically comparable to each other which leads to small differences in current obstruction. ‘Base calling’ becomes even more challenging because most nanopores sense a short <span class="hlt">sequence</span> and not individual bases. Perhaps <span class="hlt">sequencing</span> DNA via nanopores would be more manageable, if only the bases were two, and chemically very different from each other; a <span class="hlt">sequence</span> of 1s and 0s comes to mind. Osmylated DNA comes close to such a <span class="hlt">sequence</span> of 1s and 0s. Osmylation is the addition of osmium tetroxide bipyridine across the C5-C6 double bond of the pyrimidines. Osmylation adds almost 400% mass to the reactive base, creates a sterically and electronically notably different molecule, labeled 1, compared to the unreactive <span class="hlt">purines</span>, labeled 0. If osmylated DNA were successfully <span class="hlt">sequenced</span>, the result would be a <span class="hlt">sequence</span> of osmylated pyrimidines (1), and <span class="hlt">purines</span> (0), and not of the actual nucleobases. To solve this problem we studied the osmylation reaction with short oligos and with M13mp18, a long ssDNA, developed a UV-vis assay to measure extent of osmylation, and designed two protocols. Protocol A uses mild conditions and yields osmylated thymidines (1), while leaving the other three bases (0) practically intact. Protocol B uses harsher conditions and effectively osmylates both pyrimidines, but not the <span class="hlt">purines</span>. Applying these two protocols also to the complementary of the target polynucleotide yields a total of four osmylated strands that collectively could define the actual base <span class="hlt">sequence</span> of the target DNA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4251298','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4251298"><span>Does <span class="hlt">pronounceability</span> modulate the letter string deficit of children with dyslexia? A study with the rate and amount model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Marinelli, Chiara V.; Traficante, Daniela; Zoccolotti, Pierluigi</p> <p>2014-01-01</p> <p>The locus of the deficit of children with dyslexia in dealing with strings of letters may be a deficit at a pre-lexical graphemic level or an inability to bind orthographic and phonological information. We evaluate these alternative hypotheses in two experiments by examining the role of stimulus <span class="hlt">pronounceability</span> in a lexical decision task (LDT) and in a forced-choice letter discrimination task (Reicher–Wheeler paradigm). Seventeen fourth grade children with dyslexia and 24 peer control readers participated to two experiments. In the LDT children were presented with high-, low-frequency words, <span class="hlt">pronounceable</span> pseudowords (such as DASU) and unpronounceable non-words (such as RNGM) of 4-, 5-, or 6- letters. No sign of group by <span class="hlt">pronounceability</span> interaction was found when over-additivity was taken into account. Children with dyslexia were impaired when they had to process strings, not only of <span class="hlt">pronounceable</span> stimuli but also of unpronounceable stimuli, a deficit well accounted for by a single global factor. Complementary results were obtained with the Reicher–Wheeler paradigm: both groups of children gained in accuracy in letter discrimination in the context of <span class="hlt">pronounceable</span> primes (words and pseudowords) compared to unpronounceable primes (non-words). No global factor was detected in this task which requires the discrimination between a target letter and a competitor but does not involve simultaneous letter string processing. Overall, children with dyslexia show a selective difficulty in simultaneously processing a letter string as a whole, independent of its <span class="hlt">pronounceability</span>; however, when the task involves isolated letter processing, also these children can make use of the ortho-phono-tactic information derived from a previously seen letter string. This pattern of findings is in keeping with the idea that an impairment in pre-lexical graphemic analysis may be a core deficit in developmental dyslexia. PMID:25520680</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.ars.usda.gov/research/publications/publication/?seqNo115=340011','TEKTRAN'); return false;" href="http://www.ars.usda.gov/research/publications/publication/?seqNo115=340011"><span>Urinary <span class="hlt">purine</span> derivatives as a tool to estimate dry matter intake in cattle: a meta-analysis</span></a></p> <p><a target="_blank" href="https://www.ars.usda.gov/research/publications/find-a-publication/">USDA-ARS?s Scientific Manuscript database</a></p> <p></p> <p></p> <p>The objectives of this study were: 1) to investigate the relationship between dry matter intake (DMI) and urinary <span class="hlt">purine</span> derivatives (PD) excretion in order to develop equations to predict DMI, and 2) to determine the endogenous excretion of PD for beef and dairy cattle using a meta-analytic approac...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25648759','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25648759"><span>TD-DFT investigation of the magnetic circular dichroism spectra of some <span class="hlt">purine</span> and pyrimidine bases of nucleic acids.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fahleson, Tobias; Kauczor, Joanna; Norman, Patrick; Santoro, Fabrizio; Improta, Roberto; Coriani, Sonia</p> <p>2015-05-28</p> <p>We present a computational study of the magnetic circular dichroism (MCD) spectra in the 200-300 nm wavelength region of <span class="hlt">purine</span> and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil, thymine, and cytosine, using the B3LYP and CAM-B3LYP functionals. Solvent effects are investigated within the polarizable continuum model and by inclusion of explicit water molecules. In general, the computed spectra are found to be in good agreement with the experimental ones, apart from some overall blue shifts. Both the pseudo-A term shape of the MCD spectra of the <span class="hlt">purines</span> and the B term shape of the spectra of pyrimidine bases are reproduced. Our calculations also correctly reproduce the reversed phase of the MCD bands in <span class="hlt">purine</span> compared to that of its derivatives present in nucleic acids. Solvent effects are sizable and system specific, but they do not in general alter the qualitative shape of the spectra. The bands are dominated by the bright π → π* transitions, and our calculations in solution nicely reproduce their energy differences, improving the estimates obtained in the gas phase. Shoulders are predicted for <span class="hlt">purine</span> and uracil due to n → π* excitations, but they are too weak to be observed in the experiment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23651393','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23651393"><span>Involvement of the ribose operon repressor RbsR in regulation of <span class="hlt">purine</span> nucleotide synthesis in Escherichia coli.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shimada, Tomohiro; Kori, Ayako; Ishihama, Akira</p> <p>2013-07-01</p> <p>Escherichia coli is able to utilize d-ribose as its sole carbon source. The genes for the transport and initial-step metabolism of d-ribose form a single rbsDACBK operon. RbsABC forms the ABC-type high-affinity d-ribose transporter, while RbsD and RbsK are involved in the conversion of d-ribose into d-ribose 5-phosphate. In the absence of inducer d-ribose, the ribose operon is repressed by a LacI-type transcription factor RbsR, which is encoded by a gene located downstream of this ribose operon. At present, the rbs operon is believed to be the only target of regulation by RbsR. After Genomic SELEX screening, however, we have identified that RbsR binds not only to the rbs promoter but also to the promoters of a set of genes involved in <span class="hlt">purine</span> nucleotide metabolism. Northern blotting analysis indicated that RbsR represses the purHD operon for de novo synthesis of <span class="hlt">purine</span> nucleotide but activates the add and udk genes involved in the salvage pathway of <span class="hlt">purine</span> nucleotide synthesis. Taken together, we propose that RbsR is a global regulator for switch control between the de novo synthesis of <span class="hlt">purine</span> nucleotides and its salvage pathway.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3214022','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3214022"><span>Plasmodium falciparum Parasites Are Killed by a Transition State Analogue of <span class="hlt">Purine</span> Nucleoside Phosphorylase in a Primate Animal Model</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cassera, María B.; Hazleton, Keith Z.; Merino, Emilio F.; Obaldia, Nicanor; Ho, Meng-Chiao; Murkin, Andrew S.; DePinto, Richard; Gutierrez, Jemy A.; Almo, Steven C.; Evans, Gary B.; Babu, Yarlagadda S.; Schramm, Vern L.</p> <p>2011-01-01</p> <p>Plasmodium falciparum causes most of the one million annual deaths from malaria. Drug resistance is widespread and novel agents against new targets are needed to support combination-therapy approaches promoted by the World Health Organization. Plasmodium species are <span class="hlt">purine</span> auxotrophs. Blocking <span class="hlt">purine</span> nucleoside phosphorylase (PNP) kills cultured parasites by <span class="hlt">purine</span> starvation. DADMe-Immucillin-G (BCX4945) is a transition state analogue of human and Plasmodium PNPs, binding with picomolar affinity. Here, we test BCX4945 in Aotus primates, an animal model for Plasmodium falciparum infections. Oral administration of BCX4945 for seven days results in parasite clearance and recrudescence in otherwise lethal infections of P. falciparum in Aotus monkeys. The molecular action of BCX4945 is demonstrated in crystal structures of human and P. falciparum PNPs. Metabolite analysis demonstrates that PNP blockade inhibits <span class="hlt">purine</span> salvage and polyamine synthesis in the parasites. The efficacy, oral availability, chemical stability, unique mechanism of action and low toxicity of BCX4945 demonstrate potential for combination therapies with this novel antimalarial agent. PMID:22096507</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28228507','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28228507"><span>Alcohol Dehydrogenase 5 Is a Source of Formate for De Novo <span class="hlt">Purine</span> Biosynthesis in HepG2 Cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bae, Sajin; Chon, James; Field, Martha S; Stover, Patrick J</p> <p>2017-04-01</p> <p>Background: Formate provides one-carbon units for de novo <span class="hlt">purine</span> and thymidylate (dTMP) synthesis and is produced via both folate-dependent and folate-independent pathways. Folate-independent pathways are mediated by cytosolic alcohol dehydrogenase 5 (ADH5) and mitochondrial aldehyde dehydrogenase 2 (ALDH2), which generate formate by oxidizing formaldehyde. Formate is a potential biomarker of B-vitamin-dependent one-carbon metabolism.Objective: This study investigated the contributions of ADH5 and ALDH2 to formate production and folate-dependent de novo <span class="hlt">purine</span> and dTMP synthesis in HepG2 cells.Methods:ADH5 knockout and ALDH2 knockdown HepG2 cells were cultured in folate-deficient [0 nM (6S) 5-formyltetrahydrofolate] or folate-sufficient [25 nM (6S) 5-formyltetrahydrofolate] medium. <span class="hlt">Purine</span> biosynthesis was quantified as the ratio of [(14)C]-formate to [(3)H]-hypoxanthine incorporated into genomic DNA, which indicates the contribution of the de novo <span class="hlt">purine</span> synthesis pathway relative to salvage synthesis. dTMP synthesis was quantified as the ratio of [(14)C]-deoxyuridine to [(3)H]-thymidine incorporation into genomic DNA, which indicates the capacity of de novo dTMP synthesis relative to salvage synthesis.Results: The [(14)C]-formate-to-[(3)H]-hypoxanthine ratio was greater in ADH5 knockout than in wild-type HepG2 cells, under conditions of both folate deficiency (+30%; P < 0.001) and folate sufficiency (+22%; P = 0.02). These data indicate that ADH5 deficiency increases the use of exogenous formate for de novo <span class="hlt">purine</span> biosynthesis. The [(14)C]-deoxyuridine-to-[(3)H]-thymidine ratio did not differ between ADH5 knockout and wild-type cells, indicating that ADH5 deficiency does not affect de novo dTMP synthesis capacity relative to salvage synthesis. Under folate deficiency, ALDH2 knockdown cells exhibited a 37% lower ratio of [(14)C]-formate to [(3)H]-hypoxanthine (P < 0.001) compared with wild-type HepG2 cells, indicating decreased use of exogenous formate, or</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5722359','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5722359"><span>Determination of the recognition site for adenine-specific methylase of Shigella sonnei 47 by hydazinolysis of DNA, followed by separation of the <span class="hlt">purine</span> oligonucleotides by thin-layer chromatography on DEAE-cellulose</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Lopatina, N.G.; Kirnos, M.D.; Suchkov, S.V.; Vanyushin, B.F.; Nikol'skaya, I.I.; Debov, S.S.</p> <p>1985-09-20</p> <p>A method has been developed for the separation of oligopurine units according to length and composition by two-dimensional thin-layer chromatography on plates with DEAE-cellulose, permitting a comparative analysis of the content of various <span class="hlt">purine</span> isopliths in DNA of different origin. In the case of the analysis of methylated DNA, the method permits a comparison of the substrate specificity of various enzymes of methylation of the adenine residues in DNA. In conjunction with enzymatic treatment of labeled methylated isopliths, the method permits determination of the methylatable <span class="hlt">sequence</span> and in a number of cases an ascertainment of the recognition site for adenine-specific methylase as a whole. The proposed method was used to establish the fact that the methylase Ssol recognizes the <span class="hlt">sequence</span> 5'...G-A-A-T-T-C...3' and methylates the adenine residue closest to its 5'-end.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=306349','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=306349"><span>An analysis of 5'-noncoding <span class="hlt">sequences</span> from 699 vertebrate messenger RNAs.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kozak, M</p> <p>1987-01-01</p> <p>5'-Noncoding <span class="hlt">sequences</span> have been compiled from 699 vertebrate mRNAs. (GCC) GCCA/GCCATGG emerges as the consensus <span class="hlt">sequence</span> for initiation of translation in vertebrates. The most highly conserved position in that motif is the <span class="hlt">purine</span> in position -3 (three nucleotides upstream from the ATG codon); 97% of vertebrate mRNAs have a <span class="hlt">purine</span>, most often A, in that position. The periodical occurrence of G (in positions -3, -6, -9) is discussed. Upstream ATG codons occur in fewer than 10% of vertebrate mRNAs-at-large; a notable exception are oncogene transcripts, two-thirds of which have ATG codons preceding the start of the major open reading frame. The leader <span class="hlt">sequences</span> of most vertebrate mRNAs fall in the size range of 20 to 100 nucleotides. The significance of shorter and longer 5'-noncoding <span class="hlt">sequences</span> is discussed. PMID:3313277</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.gpo.gov/fdsys/pkg/CFR-2010-title39-vol1/pdf/CFR-2010-title39-vol1-sec211-3.pdf','CFR'); return false;" href="https://www.gpo.gov/fdsys/pkg/CFR-2010-title39-vol1/pdf/CFR-2010-title39-vol1-sec211-3.pdf"><span>39 CFR 211.3 - Executive orders and other executive <span class="hlt">pronouncements</span>; circulars, bulletins, and other issuances of...</span></a></p> <p><a target="_blank" href="http://www.gpo.gov/fdsys/browse/collectionCfr.action?selectedYearFrom=2010&page.go=Go">Code of Federal Regulations, 2010 CFR</a></p> <p></p> <p>2010-07-01</p> <p>... which it has previously complied, unless a management decision by an appropriate department head is made... <span class="hlt">pronouncements</span>; circulars, bulletins, and other issuances of the Office of Management and Budget. 211.3 Section... issuances of the Office of Management and Budget. (a) By virtue of the Postal Reorganization Act, certain...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16965822','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16965822"><span>HPLC separation of some <span class="hlt">purine</span> and pyrimidine derivatives on Chromolith Performance Si monolithic column.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kazoka, H</p> <p>2007-02-23</p> <p>The chromatographic behavior of some <span class="hlt">purines</span> and pyrimidines on a monolithic Chromolith Performance Si column under normal-phase high-performance liquid chromatography mode has been studied. Column pressure, column efficiency and selectivity of Chromolith Performance Si column were compared to those of conventional spherical 5 microm silica packed columns Econosphere Silica and Zorbax Rx-SIL. The investigation has shown that application of Chromolith Performance Si column for analysis of polar solutes can reduce the separation time without sacrificing column efficiency and selectivity. Improvement of the monolithic silica column efficiency for polar solutes is observed when ternary mobile phases (mixtures of hexane-isopropanol with ethylene glycol, water or acetonitrile) are applied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/930356','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/930356"><span>Inhibition and Structure of Trichomonas vaginalis <span class="hlt">Purine</span> Nucleoside Phosphorylase with Picomolar Transition State Analogues</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rinaldo-Matthis,A.; Wing, C.; Ghanem, M.; Deng, H.; Wu, P.; Gupta, A.; Tyler, P.; Evans, G.; Furneaux, R.; et al.</p> <p>2007-01-01</p> <p>Trichomonas vaginalis is a parasitic protozoan <span class="hlt">purine</span> auxotroph possessing a unique <span class="hlt">purine</span> salvage pathway consisting of a bacterial type <span class="hlt">purine</span> nucleoside phosphorylase (PNP) and a <span class="hlt">purine</span> nucleoside kinase. Thus, T. vaginalis PNP (TvPNP) functions in the reverse direction relative to the PNPs in other organisms. Immucillin-A (ImmA) and DADMe-Immucillin-A (DADMe-ImmA) are transition stte mimics of adenosine with geometric and electrostatic features that resemble early and late transition states of adenosine at the transition state stabilized by TvPNP. ImmA demonstrates slow-onset tight-binding inhibition with TvPNP, to give an equilibrium dissociation constant of 87 pM, an inhibitor release half-time of 17.2 min, and a K{sub m}/K{sub d} ratio of 70,100. DADMe-ImmA resembles a late ribooxacarbenium ion transition state for TvPNP to give a dissociation constant of 30 pM, an inhibitor release half-time of 64 min, and a K{sub m}/K{sub d} ratio of 203,300. The tight binding of DADMe-ImmA supports a late S{sub N}1 transition state. Despite their tight binding to TvPNP, ImmA and DADMe-ImmA are weak inhibitors of human and P. falciparum PNPs. The crystal structures of the TvPNP-ImmA{center_dot}PO{sub 4} and TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4} ternary complexes differ from previous structures with substrate anologues. The tight binding with DADMe-ImmA is in part due to a 2.7 {angstrom} ionic interaction between a PO{sub 4} oxygen and the N1 cation of the hydroxypyrrolidine and is weaker in the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure at 3.5 {angstrom}. However, the TvPNP{center_dot}ImmA{center_dot}PO{sub 4} structure includes hydrogen bonds between the 2'-hydroxyl and the protein that are not present in TvPNP{center_dot}DADMe-ImmA{center_dot}PO{sub 4}. These structures explain why DADMe-ImmA binds tighter than ImmA. Immucillin-H is a 12 nM inhibitor of TvPNP but a 56 pM inhibitor of human PNP. And this difference is explained by isotope</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20227468','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20227468"><span>Theacrine, a <span class="hlt">purine</span> alkaloid with anti-inflammatory and analgesic activities.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Yuanyuan; Yang, Xiaorong; Zheng, Xinqiang; Li, Jing; Ye, Chuangxing; Song, Xiaohong</p> <p>2010-09-01</p> <p>The anti-inflammatory and analgesic effects of theacrine (1, 3, 7, 9-tetramethyluric acid), a <span class="hlt">purine</span> alkaloid which is abundantly present in Camellia kucha, were investigated. Xylene-induced ear edema, acetic acid-induced vascular permeability and lambda-carrageenan-induced paw edema were used to investigate anti-inflammatory activity, and acetic acid-induced writhing and hot-plate tests were used to determine analgesic effect. Oral administration of theacrine (8-32 mg/kg) induced dose-related anti-inflammatory and analgesic effects. On the other hand, oral caffeine administration (8-32 mg/kg) did not show an inhibitory effect on the inhibition of inflammatory response or cause analgesia. Additionally, the result of the acute toxicity test showed that the LD(50) of theacrine was 810.6 mg/kg (769.5-858.0mg/kg). The data obtained suggest theacrine possessed analgesic and anti-inflammatory activities.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24630982','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24630982"><span>Evaluation of capillary chromatographic supports for immobilized human <span class="hlt">purine</span> nucleoside phosphorylase in frontal affinity chromatography studies.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Moraes, Marcela Cristina; Temporini, Caterina; Calleri, Enrica; Bruni, Giovanna; Ducati, Rodrigo Gay; Santos, Diógenes Santiago; Cardoso, Carmen Lucia; Cass, Quezia Bezerra; Massolini, Gabriella</p> <p>2014-04-18</p> <p>The aim of this work was to optimize the preparation of a capillary human <span class="hlt">purine</span> nucleoside phosphorylase (HsPNP) immobilized enzyme reactor (IMER) for characterization and affinity screening studies of new inhibitors by frontal affinity chromatography coupled to mass spectrometry (FAC-MS). For this purpose two monolithic supports, a Chromolith Speed Rod (0.1mm I.D.×5cm) and a methacrylate-based monolithic epoxy polymeric capillary column (0.25mm I.D.×5cm) with epoxy reactive groups were considered and compared to an IMER previously developed using an open fused silica capillary. Each HsPNP-IMER was characterized in terms of catalytic activity using Inosine as standard substrate. Furthermore, they were also explored for affinity ranking experiments. Kd determination was carried out with the based fused silica HsPNP-IMER and the results are herein discussed. Copyright © 2014 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/5278674','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/5278674"><span>De novo synthesis of <span class="hlt">purine</span> nucleotides in different fiber types of rat skeletal muscle</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Tullson, P.C.; John-Alder, H.; Hood, D.A.; Terjung, R.L.</p> <p>1986-03-01</p> <p>The contribution of de novo <span class="hlt">purine</span> nucleotide synthesis to nucleotide metabolism in skeletal muscles is not known. The authors have determined rates of de novo synthesis in soleus (slow-twitch red), red gastrocnemius (fast-twitch red), and white gastrocnemius (fast-twitch white) using the perfused rat hindquarter. /sup 14/C glycine incorporation into ATP was linear after 1 and 2 hours of perfusion with 0.2 mM added glycine. The intracellular (I) and extracellular (E) specific activity of /sup 14/C glycine was determined by HPLC of phenylisothiocyanate derivatives of neutralized PCA extracts. The rates of de novo synthesis when expressed relative to muscle ATP content show slow and fast-twitch red muscles to be similar and about twice as great as fast-twitch white muscles. This could represent a greater turnover of the adenine nucleotide pool in more oxidative red muscle types.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2945287','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2945287"><span>Antifolate-Induced Depletion of Intracellular Glycine and <span class="hlt">Purines</span> Inhibits Thymineless Death in E. coli</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kwon, Yun Kyung; Higgins, Meytal B.; Rabinowitz, Joshua D.</p> <p>2010-01-01</p> <p>Despite the therapeutic importance of antifolates, the links between their direct antimetabolite activity and downstream consequences remain incompletely understood. Here we employ metabolomics to examine the complete metabolic effects of the antibiotic trimethoprim in E. coli. In rich media, trimethoprim treatment causes thymineless death. In minimal media, in contrast, trimethoprim addition results in rapid stoppage of cell growth and stable cell stasis. We show that initial impairment of cell growth is due to rapid depletion of glycine and associated activation of the stringent response. Long-term stasis is due to <span class="hlt">purine</span> insufficiency. Thus, E. coli has dual systems for surviving folate depletion and avoiding thymineless death: a short-term response based on sensing of amino acids and a long-term response based on sensing of nucleotides. PMID:20553049</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3119931','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3119931"><span>Novel Ligands for a <span class="hlt">Purine</span> Riboswitch Discovered by RNA-Ligand Docking</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Daldrop, Peter; Reyes, Francis E.; Robinson, David A.; Hammond, Colin M.; Lilley, David M.; Batey, Robert T.; Brenk, Ruth</p> <p>2011-01-01</p> <p>Summary The increasing number of RNA crystal structures enables a structure-based approach to the discovery of new RNA-binding ligands. To develop the poorly explored area of RNA-ligand docking, we have conducted a virtual screening exercise for a <span class="hlt">purine</span> riboswitch to probe the strengths and weaknesses of RNA-ligand docking. Using a standard protein-ligand docking program with only minor modifications, four new ligands with binding affinities in the micromolar range were identified, including two compounds based on molecular scaffolds not resembling known ligands. RNA-ligand docking performed comparably to protein-ligand docking indicating that this approach is a promising option to explore the wealth of RNA structures for structure-based ligand design. PMID:21439477</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22057319','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22057319"><span>Release of extracellular <span class="hlt">purines</span> from plant roots and effect on ion fluxes.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dark, Adeeba; Demidchik, Vadim; Richards, Siân L; Shabala, Sergey; Davies, Julia M</p> <p>2011-11-01</p> <p>Extracellular <span class="hlt">purine</span> nucleotides appear capable of regulating plant development, defence and stress responses by acting in part as agonists of plasma membrane calcium channels. Factors stimulating ATP release include wounding, osmotic stress and elicitors. Here we show that exogenous abscisic acid and L-glutamate can also cause ATP accumulation around Arabidopsis thaliana roots. Release of ADP from root epidermis would trigger ionotropic receptor-like activity in the plasma membrane, resulting in transient elevation of cytosolic free calcium. Root epidermal protoplasts (expressing aequorin as a cytosolic free calcium reporter) can support an extracellular ADP-induced cytosolic calcium elevation in the presence of an extracellular reductant. This confirms that ADP could elicit calcium-based responses distinct to those of ATP, which have been shown previously to involve production of extracellular reactive oxygen species.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=425074','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=425074"><span>Myoadenylate deaminase deficiency. Functional and metabolic abnormalities associated with disruption of the <span class="hlt">purine</span> nucleotide cycle.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sabina, R L; Swain, J L; Olanow, C W; Bradley, W G; Fishbein, W N; DiMauro, S; Holmes, E W</p> <p>1984-01-01</p> <p>To assess the role of the <span class="hlt">purine</span> nucleotide cycle in human skeletal muscle function, we evaluated 10 patients with AMP deaminase deficiency (myoadenylate deaminase deficiency; MDD). 4 MDD and 19 non-MDD controls participated in an exercise protocol. The latter group was composed of a patient cohort (n = 8) exhibiting a constellation of symptoms similar to those of the MDD patients, i.e., postexertional aches, cramps, and pains; as well as a cohort of normal, unconditioned volunteers (n = 11). The individuals with MDD fatigued after performing only 28% as much work as their non-MDD counterparts. Muscle biopsies were obtained from the four MDD patients and the eight non-MDD patients at rest and following exercise to the point of fatigue. Creatine phosphate content fell to a comparable extent in the MDD (69%) and non-MDD (52%) patients at the onset of fatigue. Following exercise the 34% decrease in ATP content of muscle from the non-MDD subjects was significantly greater than the 6% decrease in ATP noted in muscle from the MDD patients (P = 0.048). Only one of four MDD patients had a measurable drop in ATP compared with seven of eight non-MDD patients. At end-exercise the muscle content of inosine 5'-monophosphate (IMP), a product of AMP deaminase, was 13-fold greater in the non-MDD patients than that observed in the MDD group (P = 0.008). Adenosine content of muscle from the MDD patients increased 16-fold following exercise, while there was only a twofold increase in adenosine content of muscle from the non-MDD patients (P = 0.028). Those non-MDD patients in whom the decrease in ATP content following exercise was measurable exhibited a stoichiometric increase in IMP, and total <span class="hlt">purine</span> content of the muscle did not change significantly. The one MDD patient in whom the decrease in ATP was measurable, did not exhibit a stoichiometric increase in IMP. Although the adenosine content increased 13-fold in this patient, only 48% of the ATP catabolized could be accounted for</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10455109','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10455109"><span>Identification of amino acid residues responsible for the pyrimidine and <span class="hlt">purine</span> nucleoside specificities of human concentrative Na(+) nucleoside cotransporters hCNT1 and hCNT2.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Loewen, S K; Ng, A M; Yao, S Y; Cass, C E; Baldwin, S A; Young, J D</p> <p>1999-08-27</p> <p>hCNT1 and hCNT2 mediate concentrative (Na(+)-linked) cellular uptake of nucleosides and nucleoside drugs by human cells and tissues. The two proteins (650 and 658 residues, 71 kDa) are 72% identical in <span class="hlt">sequence</span> and contain 13 putative transmembrane helices (TMs). When produced in Xenopus oocytes, recombinant hCNT1 is selective for pyrimidine nucleosides (system cit), whereas hCNT2 is selective for <span class="hlt">purine</span> nucleosides (system cif). Both transport uridine. We have used (i) chimeric constructs between hCNT1 and hCNT2, (ii) <span class="hlt">sequence</span> comparisons with a newly identified broad specificity concentrative nucleoside transporter (system cib) from Eptatretus stouti, the Pacific hagfish (hfCNT), and (iii) site-directed mutagenesis of hCNT1 to identify two sets of adjacent residues in TMs 7 and 8 of hCNT1 (Ser(319)/Gln(320) and Ser(353)/Leu(354)) that, when converted to the corresponding residues in hCNT2 (Gly(313)/Met(314) and Thr(347)/Val(348)), changed the specificity of the transporter from cit to cif. Mutation of Ser(319) in TM 7 of hCNT1 to Gly enabled transport of <span class="hlt">purine</span> nucleosides, whereas concurrent mutation of Gln(320) to Met (which had no effect on its own) augmented this transport. The additional mutation of Ser(353) to Thr in TM 8 converted hCNT1/S319G/Q320M, from cib to cif, but with relatively low adenosine transport activity. Additional mutation of Leu(354) to Val (which had no effect on its own) increased the adenosine transport capability of hCNT1/S319G/Q320M/S353T, producing a full cif-type transporter phenotype. On its own, the S353T mutation converted hCNT1 into a transporter with novel uridine-selective transport properties. Helix modeling of hCNT1 placed Ser(319) (TM 7) and Ser(353) (TM 8) within the putative substrate translocation channel, whereas Gln(320) (TM 7) and Leu(354) (TM 8) may exert their effects through altered helix packing.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/16899691','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/16899691"><span>Effects of dairy cow diet forage proportion on duodenal nutrient supply and urinary <span class="hlt">purine</span> derivative excretion.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Moorby, J M; Dewhurst, R J; Evans, R T; Danelón, J L</p> <p>2006-09-01</p> <p>Four mature Holstein-Friesian dairy cows were used in a 4 x 4 Latin square change-over design experiment made up of four 4-wk periods to investigate the relationship between microbial protein flow to the duodenum and excretion of <span class="hlt">purine</span> derivatives (PD) in the urine. Four dietary treatments based on ad libitum access to ryegrass silage were offered, with a standard dairy concentrate included at different forage:concentrate (F:C) ratios, calculated on a dry matter basis: 80:20, 65:35, 50:50, and 35:65. Feed intakes increased as the proportion of concentrate in the diet increased, despite a concurrent decrease in silage intake. Increased feed intake led to increased nutrient flow to the duodenum. Milk yields increased as the diet F:C ratio decreased, with cows offered the 35:65 diet yielding nearly 8 kg/d more milk than cows offered the 80:20 diet; the concentrations of milk fat decreased and milk protein increased with a decreasing F:C ratio. <span class="hlt">Purine</span> derivative excretion in the urine increased with an increasing proportion of concentrate in the diet, and there was a strong linear relationship between total PD excretion (allantoin and uric acid) and microbial N flow to the duodenum: microbial N (g/d) = 19.9 + 0.689 x total PD (mmol/d); R = 0.887. This strengthens the case for using PD excretion as a noninvasive marker of microbial protein flow from the rumen in dairy cows.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4047668','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4047668"><span>One-electron oxidation reactions of <span class="hlt">purine</span> and pyrimidine bases in cellular DNA</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Cadet, Jean; Wagner, J. Richard; Shafirovich, Vladimir; Geacintov, Nicholas E.</p> <p>2014-01-01</p> <p>Purpose The aim of this survey is to critically review the available information on one-electron oxidation reactions of nucleobases in cellular DNA with emphasis on damage induced through the transient generation of <span class="hlt">purine</span> and pyrimidine radical cations. Since the indirect effect of ionizing radiation mediated by hydroxyl radical is predominant in cells, efforts have been made to selectively ionize bases using suitable one-electron oxidants that consist among others of high intensity UVC laser pulses. Thus, the main oxidation product in cellular DNA was found to be 8-oxo-7,8-dihydroguanine as a result of direct bi-photonic ionization of guanine bases and indirect formation of guanine radical cations through hole transfer reactions from other base radical cations. The formation of 8-oxo-7,8-dihydroguanine and other <span class="hlt">purine</span> and pyrimidine degradation products was rationalized in terms of the initial generation of related radical cations followed by either hydration or deprotonation reactions in agreement with mechanistic pathways inferred from detailed mechanistic studies. The guanine radical cation has been shown to be implicated in three other nucleophilic additions that give rise to DNA-protein and DNA-DNA cross-links in model systems. Evidence was recently provided for the occurrence of these three reactions in cellular DNA. Conclusion There is growing evidence that one-electron oxidation reactions of nucleobases whose mechanisms have been characterized in model studies involving aqueous solutions take place in a similar way in cells. It may also be pointed out that the above cross-linked lesions are only produced from the guanine radical cation and may be considered as diagnostic products of the direct effect of ionizing radiation. PMID:24369822</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17224163','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17224163"><span>Octameric structure of the human bifunctional enzyme PAICS in <span class="hlt">purine</span> biosynthesis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Shu-Xing; Tong, Yong-Ping; Xie, Xiao-Cong; Wang, Qi-Hai; Zhou, Hui-Na; Han, Yi; Zhang, Zhan-Yu; Gao, Wei; Li, Sheng-Guang; Zhang, Xuejun C; Bi, Ru-Chang</p> <p>2007-03-09</p> <p>Phosphoribosylaminoimidazole carboxylase/phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS) is an important bifunctional enzyme in de novo <span class="hlt">purine</span> biosynthesis in vertebrate with both 5-aminoimidazole ribonucleotide carboxylase (AIRc) and 4-(N-succinylcarboxamide)-5-aminoimidazole ribonucleotide synthetase (SAICARs) activities. It becomes an attractive target for rational anticancer drug design, since rapidly dividing cancer cells rely heavily on the <span class="hlt">purine</span> de novo pathway for synthesis of adenine and guanine, whereas normal cells favor the salvage pathway. Here, we report the crystal structure of human PAICS, the first in the entire PAICS family, at 2.8 A resolution. It revealed that eight PAICS subunits, each composed of distinct AIRc and SAICARs domains, assemble a compact homo-octamer with an octameric-carboxylase core and four symmetric periphery dimers formed by synthetase domains. Based on structural comparison and functional complementation analyses, the active sites of SAICARs and AIRc were identified, including a putative substrate CO(2)-binding site. Furthermore, four symmetry-related, separate tunnel systems in the PAICS octamer were found that connect the active sites of AIRc and SAICARs. This study illustrated the octameric nature of the bifunctional enzyme. Each carboxylase active site is formed by structural elements from three AIRc domains, demonstrating that the octamer structure is essential for the carboxylation activity. Furthermore, the existence of the tunnel system implies a mechanism of intermediate channeling and suggests that the quaternary structure arrangement is crucial for effectively executing the sequential reactions. In addition, this study provides essential structural information for designing PAICS-specific inhibitors for use in cancer chemotherapy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22486543','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22486543"><span>On the accessibility to conical intersections in <span class="hlt">purines</span>: hypoxanthine and its singly protonated and deprotonated forms.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Villabona-Monsalve, Juan P; Noria, Raquel; Matsika, Spiridoula; Peón, Jorge</p> <p>2012-05-09</p> <p>The dynamics following electronic excitation of hypoxanthine and its nucleoside inosine were studied by femtosecond fluorescence up-conversion. Our objective was to explore variants of the <span class="hlt">purinic</span> DNA bases in order to determine the molecular parameters that increase or reduce the accessibility to ground state conical intersections. From experiments in water and methanol solution we conclude that both dominant neutral tautomers of hypoxanthine exhibit ultrashort excited state lifetimes (τ < 0.2 ps), which are significantly shorter than in the related nucleobase guanine. This points to a more accessible conical intersection for the fluorescent state upon removal of the amino group, present in guanine but absent in hypoxanthine. The excited state dynamics of singly protonated hypoxanthine were also studied, showing biexponential decays with a 1.1 ps component (5%) besides a sub-0.2 ps ultrafast component. On the other hand, the S(1) lifetimes of the singly deprotonated forms of hypoxanthine and inosine show drastic differences, where the latter remains ultrafast but the singly deprotonated hypoxanthine shows a much longer lifetime of 19 ps. This significant variation is related to the different deprotonation sites in hypoxanthine versus inosine, which gives rise to significantly different resonance structures. In our study we also include multireference perturbation theory (MRMP2) excited state calculations in order to determine the nature of the initial electronic excitation in our experiments and clarify the ordering of the states in the singlet manifold at the ground state geometry. In addition, we performed multireference configuration interaction calculations (MR-CIS) that identify the presence of low-lying conical intersections for both prominent neutral tautomers of hypoxanthine. In both cases, the surface crossings occur at geometries reached by out of plane opposite motions of C2 and N3. The study of this simpler <span class="hlt">purine</span> gives several insights into how small</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5386672','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5386672"><span>Structure-guided design of <span class="hlt">purine</span>-based probes for selective Nek2 inhibition</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Coxon, Christopher R.; Wong, Christopher; Bayliss, Richard; Boxall, Kathy; Carr, Katherine H.; Fry, Andrew M.; Hardcastle, Ian R.; Matheson, Christopher J.; Newell, David R.; Sivaprakasam, Mangaleswaran; Thomas, Huw; Turner, David; Yeoh, Sharon; Wang, Lan Z.; Golding, Bernard T.; Cano, Céline</p> <p>2017-01-01</p> <p>Nek2 (NIMA-related kinase 2) is a cell cycle-dependent serine/threonine protein kinase that regulates centrosome separation at the onset of mitosis. Overexpression of Nek2 is common in human cancers and suppression can restrict tumor cell growth and promote apoptosis. Nek2 inhibition with small molecules, therefore, offers the prospect of a new therapy for cancer. To achieve this goal, a better understanding of the requirements for selective-inhibition of Nek2 is required. 6-Alkoxypurines were identified as ATP-competitive inhibitors of Nek2 and CDK2. Comparison with CDK2-inhibitor structures indicated that judicious modification of the 6-alkoxy and 2-arylamino substituents could achieve discrimination between Nek2 and CDK2. In this study, a library of 6-cyclohexylmethoxy-2-arylaminopurines bearing carboxamide, sulfonamide and urea substituents on the 2-arylamino ring was synthesized. Few of these compounds were selective for Nek2 over CDK2, with the best result being obtained for 3-((6-(cyclohexylmethoxy)-9H-<span class="hlt">purin</span>-2-yl)amino)-N,N-dimethylbenzamide (CDK2 IC50 = 7.0 μM; Nek2 IC50 = 0.62 μM) with >10-fold selectivity. Deletion of the 6-substituent abrogated activity against both Nek2 and CDK2. Nine compounds containing an (E)-dialkylaminovinyl substituent at C-6, all showed selectivity for Nek2, e.g. (E)-6-(2-(azepan-1-yl)vinyl)-N-phenyl-9H-<span class="hlt">purin</span>-2-amine (CDK2 IC50 = 2.70 μM; Nek2 IC50 = 0.27 μM). Structural biology of selected compounds enabled a partial rationalization of the observed structure activity relationships and mechanism of Nek2 activation. This showed that carboxamide 11 is the first reported inhibitor of Nek2 in the DFG-in conformation. PMID:27833088</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2916491','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2916491"><span>Requirement of <span class="hlt">Purine</span> and Pyrimidine Synthesis for Colonization of the Mouse Intestine by Escherichia coli▿</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Vogel-Scheel, Jacqueline; Alpert, Carl; Engst, Wolfram; Loh, Gunnar; Blaut, Michael</p> <p>2010-01-01</p> <p>To study the adaptation of an intestinal bacterium to its natural environment, germfree mice were associated with commensal Escherichia coli MG1655. Two-dimensional gel electrophoresis was used to identify proteins differentially expressed in E. coli MG1655 collected from either cecal contents or anaerobic in vitro cultures. Fourteen differentially expressed proteins (>3-fold; P < 0.05) were identified, nine of which were upregulated in cecal versus in vitro-grown E. coli. Four of these proteins were investigated further for their role in gut colonization. After deletion of the corresponding genes, the resulting E. coli mutants were tested for their ability to colonize the intestines of gnotobiotic mice in competition with the wild-type strain. A mutant devoid of ydjG, which encodes a putative NADH-dependent methylglyoxal reductase, reached a 1.2-log-lower cecal concentration than the wild type. Deletion of the nanA gene encoding N-acetylneuraminate lyase affected the colonization and persistence of E. coli in the intestines of the gnotobiotic mice only slightly. A mutant devoid of 5′-phosphoribosyl 4-(N-succinocarboxamide)-5-aminoimidazole synthase, a key enzyme of <span class="hlt">purine</span> synthesis, displayed intestinal cell counts >4 logs lower than those of the wild type. Deletion of the gene encoding aspartate carbamoyltransferase, a key enzyme of pyrimidine synthesis, even resulted in the washout of the corresponding mutant from the mouse intestinal tract. These findings indicate that E. coli needs to synthesize <span class="hlt">purines</span> and pyrimidines to successfully colonize the mouse intestine. PMID:20562286</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21277179','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21277179"><span><span class="hlt">Purine</span>-rich foods, protein intake, and the prevalence of hyperuricemia: the Shanghai Men's Health Study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Villegas, R; Xiang, Y-B; Elasy, T; Xu, W H; Cai, H; Cai, Q; Linton, M F; Fazio, S; Zheng, W; Shu, X-O</p> <p>2012-05-01</p> <p>Diet may play an important role in the development of hyperuricemia and gout. However, the association between dietary factors and hyperuricemia remains unclear, and few studies have investigated direct links between food intake and hyperuricemia. The aim of this study was to investigate associations between high <span class="hlt">purine</span>-content foods and protein intake with the prevalence of hyperuricemia by using data from a cross-sectional study of 3978 men aged 40-74 yrs living in Shanghai, China. Hyperuricemia was defined as blood uric acid level >7.0 mg/dl. One quarter of this population had hyperuricemia. Dietary information was collected by using a food frequency questionnaire. We collected information on anthropometric measurements and lifestyle factors and other potential confounding factors and disease history via interviews. Total protein consumption was not associated with hyperuricemia. We found a positive association between protein from animal sources and prevalence of hyperuricemia and an inverse association between protein from plant sources and hyperuricemia. However, these associations failed to reach significance in mutually adjusted analysis. Seafood intake was associated with higher prevalence of hyperuricemia. The ORs for quintiles of seafood intake (including fish and shellfish) were 1.00, 1.49, 1.35, 1.34, and 1.56 (p for trend: 0.01). An inverse association approaching significance between soy food consumption and hyperuricemia was observed (ORs: 1.00, 0.90, 0.70, 0.89, and 0.77 for quintiles of intake; p for trend: 0.07). No associations between consumption of <span class="hlt">purine</span>-rich vegetables or meat and prevalence of hyperuricemia were observed. Our data suggest a direct association between seafood consumption and hyperuricemia and an inverse association between consumption of soy food and hyperuricemia among middle-aged, Chinese men. Copyright © 2010 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26506131','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26506131"><span><span class="hlt">Purine</span> metabolism in response to hypoxic conditions associated with breath-hold diving and exercise in erythrocytes and plasma from bottlenose dolphins (Tursiops truncatus).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>del Castillo Velasco-Martínez, Iris; Hernández-Camacho, Claudia J; Méndez-Rodríguez, Lía C; Zenteno-Savín, Tania</p> <p>2016-01-01</p> <p>In mammalian tissues under hypoxic conditions, ATP degradation results in accumulation of <span class="hlt">purine</span> metabolites. During exercise, muscle energetic demand increases and oxygen consumption can exceed its supply. During breath-hold diving, oxygen supply is reduced and, although oxygen utilization is regulated by bradycardia (low heart rate) and peripheral vasoconstriction, tissues with low blood flow (ischemia) may become hypoxic. The goal of this study was to evaluate potential differences in the circulating levels of <span class="hlt">purine</span> metabolism components between diving and exercise in bottlenose dolphins (Tursiops truncatus). Blood samples were taken from captive dolphins following a swimming routine (n=8) and after a 2min dive (n=8). Activity of enzymes involved in <span class="hlt">purine</span> metabolism (hypoxanthine guanine phosphoribosyl transferase (HGPRT), inosine monophosphate deshydrogenase (IMPDH), xanthine oxidase (XO), <span class="hlt">purine</span> nucleoside phosphorylase (PNP)), and <span class="hlt">purine</span> metabolite (hypoxanthine (HX), xanthine (X), uric acid (UA), inosine monophosphate (IMP), inosine, nicotinamide adenine dinucleotide (NAD(+)), adenosine, adenosine monophosphate (AMP), adenosine diphosphate (ADP), ATP, guanosine diphosphate (GDP), guanosine triphosphate (GTP)) concentrations were quantified in erythrocyte and plasma samples. Enzymatic activity and <span class="hlt">purine</span> metabolite concentrations involved in <span class="hlt">purine</span> synthesis and degradation, were not significantly different between diving and exercise. Plasma adenosine concentration was higher after diving than exercise (p=0.03); this may be related to dive-induced ischemia. In erythrocytes, HGPRT activity was higher after diving than exercise (p=0.007), suggesting an increased capacity for <span class="hlt">purine</span> recycling and ATP synthesis from IMP in ischemic tissues of bottlenose dolphins during diving. <span class="hlt">Purine</span> recycling and physiological adaptations may maintain the ATP concentrations in bottlenose dolphins after diving and exercise. Copyright © 2015 Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28887269','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28887269"><span>Which physicians' behaviors on death <span class="hlt">pronouncement</span> affect family-perceived physician compassion? A randomized, scripted, video-vignette study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mori, Masanori; Fujimori, Maiko; Hamano, Jun; Naito, Akemi Shirado; Morita, Tatsuya</p> <p>2017-09-05</p> <p>Although the death of a loved one is a devastating family event, little is known about which behaviors positively affect families' perceptions on death <span class="hlt">pronouncements</span>. To evaluate the effect of a compassionate death <span class="hlt">pronouncement</span> on participant-perceived physician compassion, trust in physicians, and emotions. In this randomized, video-vignette study, 92 people (≥50 years) in Tokyo metropolitan area viewed two videos of death <span class="hlt">pronouncements</span> by an on-call physician with or without compassion-enhanced behaviors, including 5 components: waiting until the families calm themselves down; explaining that the physician has received a sign-out about information of the patient's condition; performing examination respectfully; ascertaining the time of death with a wristwatch (vs. smartphone); and reassuring the families that the patient did not experience pain. Main outcomes were physician compassion score, trust in physician, and emotions. After viewing the video with compassion-enhanced behaviors as compared with the video without them, participants assigned significantly lower compassion scores (reflecting higher physician compassion) (mean, 26.2 vs. 36.4, F=33.1, p<0.001); higher trust in physician (5.10 vs. 3.00, F=39.7, p<0.001); and lower scores for anger (2.49 vs. 3.78, F=18.0, p<0.001), sadness (3.42 vs. 3.85, F=11.8, p=0.001), fear (1.93 vs. 2.55, F=15.8, p<0.001), and disgust (2.45 vs. 3.71, F=19.4, p<0.001). To convey compassion on death <span class="hlt">pronouncement</span>, we recommend that physicians initiate prompt examination; explain that the physician has received a sign-out; perform examination respectfully; ascertain the time of death with a wristwatch; and reassure the families that the patient did not experience pain. Copyright © 2017 American Academy of Hospice and Palliative Medicine. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15058383','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15058383"><span>Identification of a <span class="hlt">purine</span>-rich intronic enhancer element in the mouse eosinophil-associated ribonuclease 2 (mEar 2) gene.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dyer, Kimberly D; Nitto, Takeaki; Moreau, Joanne M; McDevitt, Amanda L; Rosenberg, Helene F</p> <p>2004-02-01</p> <p>The Mus musculus eosinophil-associated ribonuclease (mEar) gene cluster includes multiple distinct coding <span class="hlt">sequences</span> that are highly divergent orthologs of the human eosinophil ribonucleases, eosinophil-derived neurotoxin (EDN/RNase 2) and eosinophil cationic protein (ECP/RNase 3). We present a transcriptional analysis of the gene encoding mEar 2, the only member of this cluster with a well-defined expression profile. In this work, we demonstrate that the presence of non-coding exon 1 and the intron in tandem with a 361-bp 5' promoter of mEar 2 results in enhanced reporter gene expression, as much as 6-to 10-fold over the activity observed with the 5' promoter alone. We have identified a conserved <span class="hlt">purine</span>-rich element in the intron of the mEar 2 gene that is necessary for maximum transcription and that interacts specifically with NFAT-binding proteins in nuclear extracts derived from the mouse LA4 epithelial cell line. Similar intronic enhancers have been described as regulating transcription of the human EDN gene, suggesting an overall conservation of an important regulatory strategy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22832875','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22832875"><span>Synthesis of 9,9'-[1,2-ethanediylbis(oxymethylene)]bis-2-amino-1,9-dihydro-6H-<span class="hlt">purin</span>-6-one, an impurity of acyclovir.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Suárez, Rosa M; Matía, Maria Paz; Novella, José Luis; Molina, Andres; Cosme, Antonio; Vaquero, Juan José; Alvarez-Builla, Julio</p> <p>2012-07-25</p> <p>The synthesis of 9,9'-[1,2-ethanediylbis(oxymethylene)]bis-2-amino-1,9-dihydro-6H-<span class="hlt">purin</span>-6-one, a minor impurity of acyclovir, is described. Starting with commercial N-(9-acetyl-6-oxo-1H-<span class="hlt">purin</span>-2-yl)acetamide, the process uses an acid catalysed phase transfer catalysis (PTC) process to produce the selective alkylation at the 9 position of the guanine ring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/17943563','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/17943563"><span>Theacrine, a special <span class="hlt">purine</span> alkaloid with sedative and hypnotic properties from Cammelia assamica var. kucha in mice.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Xu, Jie-Kun; Kurihara, Hiroshi; Zhao, Liang; Yao, Xin-Sheng</p> <p>2007-01-01</p> <p>The central nervous system activities of theacrine (1,3,7,9-tetramethyluric acid), a <span class="hlt">purine</span> alkaloid which is abundantly present in Camellia assamica var. kucha, were investigated in ambulatory activity, pentobarbital-induced sleep and forced swimming test in mice, compared with two other <span class="hlt">purine</span> alkaloids, caffeine and theobromine. Caffeine treatment led to a marked increase in the ambulatory activity accompanied with decreasing of the immobility time in forced swimming test at both 10 and 30 mg/kg. Under the same conditions, neither theacrine nor theobromine showed obvious excited efficacy. Both doses of theacrine could significantly prolong the sleeping time induced by pentobarbital, while caffeine and theobromine exhibited an inverted effect. These results indicated that theacrine possessed potent sedative and hypnotic properties and its central nervous system effects were different from those of caffeine and theobromine.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8425270','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8425270"><span>Radical oxidation reactions of the <span class="hlt">purine</span> moiety of 2'-deoxyribonucleosides and DNA by iron-containing minerals.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Berger, M; de Hazen, M; Nejjari, A; Fournier, J; Guignard, J; Pezerat, H; Cadet, J</p> <p>1993-01-01</p> <p>The radical oxidation capability of several classes of iron minerals, including biotite, hematite, magnetite, minette, nemalite, pyrite, vivianite and two chrysotiles (asbestos), was investigated by using a double experimental approach. One involved the electron spin resonance spin-trapping measurement of organic radicals obtained by the reaction of activated oxygen species, released upon incubation of the minerals in phosphate buffered solutions with formate used as the target molecule. In addition, the formation of mineral-mediated oxidation <span class="hlt">purine</span> decomposition products, including 7,8-dihydro-8-oxo-2'-deoxyguanosine and 7,8-dihydro-8-oxo-2'-deoxyadenosine, was searched within nucleosides and DNA by using specific and sensitive HPLC electrochemical assays. Emphasis was placed on the mechanistic aspects of the radical oxidation reactions involved in the formation of the two C(8) hydroxylated <span class="hlt">purine</span> decomposition products.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=92806','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=92806"><span>Isolation and Characterization of a Slowly Milk-Coagulating Variant of Lactobacillus helveticus Deficient in <span class="hlt">Purine</span> Biosynthesis</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hebert, Elvira M.; De Giori, Graciela S.; Raya, Raul R.</p> <p>2001-01-01</p> <p>A slowly milk-coagulating variant (Fmc−) of Lactobacillus helveticus CRL 1062, designated S1, was isolated and characterized. Strain S1 possessed all the known essential components required to utilize casein as a nitrogen source, which include functional proteinase and peptidase activities as well as functional amino acid, di- and tripeptide, and oligopeptide transport systems. The amino acid requirements of strain S1 were similar to those of the parental strain. However, on a <span class="hlt">purine</span>-free, chemically defined medium, the growth rate of the Fmc− strain was threefold lower than that of the wild-type strain. L. helveticus S1 was found to be defective in IMP dehydrogenase activity and therefore was deficient in the ability to synthesize XMP and GMP. This conclusion was further supported by the observation that the addition of guanine or xanthine to milk, a substrate poor in <span class="hlt">purine</span> compounds, restored the Fmc+ phenotype of L. helveticus S1. PMID:11282642</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26854276','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26854276"><span>Effects of different lipid sources on intake, digestibility and <span class="hlt">purine</span> derivatives in hair lambs.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pereira, E S; Pereira, M W F; Arruda, P C L; Cabral, L S; Oliveira, R L; Mizubuti, I Y; Pinto, A P; Campos, A C N; Gadelha, C R F; Carneiro, M S S</p> <p>2016-08-01</p> <p>An experiment was conducted to evaluate the effects of different lipid sources on the nutrient intake, digestibility and <span class="hlt">purine</span> derivative excretion of lambs. Thirty-five 60-day-old, male, non-castrated Santa Ines lambs with an initial average body weight (BW) of 13.00 ± 1.80 kg were used in a randomized complete block design with seven blocks and five treatments. The experimental treatments consisted of a control diet without supplemental lipids and four test diets with different lipid supplements, selected according to the degree of ruminal protection from hydrogenation: supplementation, being supplementation with whole cottonseed (WC), supplementation with cashew nut meal (CNM), supplementation with both cottonseed and cashew nut meal (WC-CNM) and supplementation with calcium salts of long-chain fatty acids (Ca-LCFA). The lambs were slaughtered after reaching 28 kg average BW for each treatment. The ether extract intake (EEI) was higher (p < 0.01) for the lipid supplemented compared to control diet lambs. Supplementation with WC decreased the digestibility of dry matter (DM), organic matter (OM), neutral detergent fibre (NDF) and total carbohydrate (TC) (p < 0.01), whereas supplementation with CNM, WC-CNM and Ca-LCFA reduced non-fibrous carbohydrate (NFC) digestibility (p < 0.01). The ether extract (EE) digestibility coefficient was higher with CNM, followed by Ca-LCFA and WC, when compared to WC-CNM and control diets. Nitrogen balance (NB) was not influenced (p > 0.05) by the different lipid sources. A lower <span class="hlt">purine</span> derivative (PD) excretion and thus lower microbial protein supply (MPS) was observed for animals supplemented with Ca-LCFA (p < 0.01) compared to the WC-CNM and control diets. In conclusion, WC, CNM and WC-CNM supplementation did not have negative effects on MPS, although negative effects have been observed on nutrient digestibility. Journal of Animal Physiology and Animal Nutrition © 2016 Blackwell Verlag GmbH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012RJPCA..86.1826K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012RJPCA..86.1826K"><span>Distribution coefficients of <span class="hlt">purine</span> alkaloids in water-ammonium sulfate-alkyl acetate-dialkyl phthalate systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Korenman, Ya. I.; Krivosheeva, O. A.; Mokshina, N. Ya.</p> <p>2012-12-01</p> <p>The distribution of <span class="hlt">purine</span> alkaloids (caffeine, theobromine, theophylline) was studied in the systems: alkyl acetates-dialkyl phtalate-salting-out agent (ammonium sulfate). The quantitative characteristics of the extraction-distribution coefficients ( D) and the degree of extraction ( R, %) are calculated. The relationships between the distribution coefficients of alkaloids and the length of the hydrocarbon radical in the molecule of alkyl acetate (dialkyl phtalate) are determined. The possibility of predicting the distribution coefficients is demonstrated.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26720700','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26720700"><span>Development of a new HPLC method using fluorescence detection without derivatization for determining <span class="hlt">purine</span> nucleoside phosphorylase activity in human plasma.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Giuliani, Patricia; Zuccarini, Mariachiara; Buccella, Silvana; Rossini, Margherita; D'Alimonte, Iolanda; Ciccarelli, Renata; Marzo, Matteo; Marzo, Antonio; Di Iorio, Patrizia; Caciagli, Francesco</p> <p>2016-01-15</p> <p><span class="hlt">Purine</span> nucleoside phosphorylase (PNP) activity is involved in cell survival and function, since PNP is a key enzyme in the <span class="hlt">purine</span> metabolic pathway where it catalyzes the phosphorolysis of the nucleosides to the corresponding nucleobases. Its dysfunction has been found in relevant pathological conditions (such as inflammation and cancer), so the detection of PNP activity in plasma could represent an attractive marker for early diagnosis or assessment of disease progression. Thus the aim of this study was to develop a simple, fast and sensitive HPLC method for the determination of PNP activity in plasma. The separation was achieved on a Phenomenex Kinetex PFP column using 0.1% formic acid in water and methanol as mobile phases in gradient elution mode at a flow rate of 1ml/min and <span class="hlt">purine</span> compounds were detected using UV absorption and fluorescence. The analysis was fast since the run was achieved within 13min. This method improved the separation of the different <span class="hlt">purines</span>, allowing the UV-based quantification of the natural PNP substrates (inosine and guanosine) or products (hypoxanthine and guanine) and its subsequent metabolic products (xanthine and uric acid) with a good precision and accuracy. The most interesting innovation is the simultaneous use of a fluorescence detector (excitation/emission wavelength of 260/375nm) that allowed the quantification of guanosine and guanine without derivatization. Compared with UV, the fluorescence detection improved the sensitivity for guanine detection by about 10-fold and abolished almost completely the baseline noise due to the presence of plasma in the enzymatic reaction mixture. Thus, the validated method allowed an excellent evaluation of PNP activity in plasma which could be useful as an indicator of several pathological conditions. Copyright © 2015 Elsevier B.V. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18511280','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18511280"><span>Pleuromutilin derivatives having a <span class="hlt">purine</span> ring. Part 1: new compounds with promising antibacterial activity against resistant Gram-positive pathogens.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Hirokawa, Yoshimi; Kinoshita, Hironori; Tanaka, Tomoyuki; Nakamura, Takanori; Fujimoto, Koichi; Kashimoto, Shigeki; Kojima, Tsuyoshi; Kato, Shiro</p> <p>2008-06-15</p> <p>In the course of our research aimed at the discovery of metabolic stable pleuromutilin derivatives with more potent antibacterial activity against Gram-positive pathogens than previous analogues, a series of compounds bearing a <span class="hlt">purine</span> ring were prepared and evaluated. From SAR studies, we identified two promising compounds 85 and 87, which have excellent in vitro activity against a number of Gram-positive pathogens, including existing drug-resistant strains, and potent in vivo efficacy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=148060','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=148060"><span>Two Nucleoside Uptake Systems in Lactococcus lactis: Competition between <span class="hlt">Purine</span> Nucleosides and Cytidine Allows for Modulation of Intracellular Nucleotide Pools</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Martinussen, Jan; Wadskov-Hansen, Steen L. L.; Hammer, Karin</p> <p>2003-01-01</p> <p>A method for measuring internal nucleoside triphosphate pools of lactococci was optimized and validated. This method is based on extraction of 33P-labeled nucleotides with formic acid and evaluation by two-dimensional chromatography with a phosphate buffer system for the first dimension and with an H3BO3-LiOH buffer for separation in the second dimension. We report here the sizes of the ribo- and deoxyribonucleotide pools in laboratory strain MG1363 during growth in a defined medium. We found that <span class="hlt">purine</span>- and pyrimidine-requiring strains may be used to establish physiological conditions in batch fermentations with altered nucleotide pools and growth rates by addition of nucleosides in different combinations. Addition of cytidine together with inosine to a <span class="hlt">purine</span>-requiring strain leads to a reduction in the internal <span class="hlt">purine</span> nucleotide pools and a decreased growth rate. This effect was not seen if cytidine was replaced by uridine. A similar effect was observed if cytidine and inosine were added to a pyrimidine-requiring strain; the UTP pool size was significantly decreased, and the growth rate was reduced. To explain the observed inhibition, the nucleoside transport systems in Lactococcus lactis were investigated by measuring the uptake of radioactively labeled nucleosides. The Km for for inosine, cytidine, and uridine was determined to be in the micromolar range. Furthermore, it was found that cytidine and inosine are competitive inhibitors of each other, whereas no competition was found between uridine and either cytidine or inosine. These findings suggest that there are two different high-affinity nucleoside transporters, one system responsible for uridine uptake and another system responsible for the uptake of all <span class="hlt">purine</span> nucleosides and cytidine. PMID:12591866</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3681135','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3681135"><span>Study of Copper and <span class="hlt">Purine</span>-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Trnkova, Libuse; Zerzankova, Lenka; Dycka, Filip; Mikelova, Radka; Jelen, Frantisek</p> <p>2008-01-01</p> <p>Using a paraffin impregnated graphite electrode (PIGE) and mercury-modified pyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNA <span class="hlt">purine</span> base solutions have been studied by cyclic (CV) and linear sweep voltammetry (LSV) in connection with elimination voltammetry with linear scan (EVLS). In chloride and bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with two cathodic and two anodic potentially separated signals. According to the elimination function E4, the first cathodic peak corresponds to the reduction Cu(II) + e- → Cu(I) with the possibility of fast disproportionation 2Cu(I) → Cu(II)+ Cu(0). The E4 of the second cathodic peak signalized an electrode process controlled by a surface reaction. The electrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by one cathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodic stripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where the reduction of copper ions took place and Cu(I)-<span class="hlt">purine</span> complexes were formed. By using ASV and CSV in combination with EVLS, the sensitivity of Cu(I)-<span class="hlt">purine</span> complex detection was enhanced relative to either ASV or CSV alone, resulting in higher peak currents of more than one order of magnitude. The statistical treatment of CE data was used to determine the reproducibility of measurements. Our results show that EVLS in connection with the stripping procedure is useful for both qualitative and quantitative microanalysis of <span class="hlt">purine</span> derivatives and can also reveal details of studied electrode processes. PMID:27879715</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/6521743','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/6521743"><span>[Anisotropic flexibility of DNA depends on the base <span class="hlt">sequence</span>. Conformation calculations of double-stranded tetranucleotides AAAA:TTTT, (AATT)2, (TTAA)2, GGGG:CCCC, (GGCC)2, (CCGG)2].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ul'ianov, N B; Zhurkin, V B</p> <p>1984-01-01</p> <p>The bending flexibility of six tetramers was studied in an assumption that they were extended in the both directions by regular double helices. The bends of B-DNA in different directions were considered. The stiffness of the B-DNA double helix when bent into the both grooves proved to be less <span class="hlt">pronounced</span> than in the perpendicular direction by the order of magnitude. Such an anisotropy is a feature of the sugar-phosphate backbone structure. The calculated fluctuations of the DNA bending along the dyad axis, 5-7 degrees, are in agreement with the experimental value of DNA persistence length. Anisotropy of the double helix is <span class="hlt">sequence</span>-dependent: most easily bent into the minor groove are the tetramers with <span class="hlt">purine</span>-pyrimidine dimer (RY) in the middle. In contrast, YR dinucleotides prefer bending into the major groove, moreover, they have an equilibrium bend of 6-12 degrees into this groove. The above inequality is caused by the stacking interaction of the bases. The bend in the central dimers is distributed to some extent between the adjacent links, though the main fraction of the bend remains within the central link. Variation of the sugar-phosphate geometry in the bent helix is unessential, so that DNA remains within the limits of the B-family of forms: namely, when the helical axis is bent by 20 degrees the backbone dihedral angles vary by no more than 15 degrees. The obtained results are in accord with the X-ray structure of B-DNA dodecamer; they further substantiate our earlier model of DNA wrapping in the nucleosome by means of "mini-kinks" separated by a half-pitch of the double helix, i.e. by 5-6 b. p. <span class="hlt">Sequence</span>-dependent anisotropy of DNA presumably dictates the three-dimensional structure of DNA in solution as well. We have found that nonrandom allocation of YR dimers leads to the systematic bends in the equilibrium structure of certain DNA fragments. To the four "Calladine rules" two more can be added: the minor-groove steric clash of <span class="hlt">purines</span> in the YR</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27297670','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27297670"><span>Altered Mitochondria, Protein Synthesis Machinery, and <span class="hlt">Purine</span> Metabolism Are Molecular Contributors to the Pathogenesis of Creutzfeldt-Jakob Disease.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ansoleaga, Belén; Garcia-Esparcia, Paula; Llorens, Franc; Hernández-Ortega, Karina; Carmona Tech, Margarita; Antonio Del Rio, José; Zerr, Inga; Ferrer, Isidro</p> <p>2016-06-12</p> <p>Neuron loss, synaptic decline, and spongiform change are the hallmarks of sporadic Creutzfeldt-Jakob disease (sCJD), and may be related to deficiencies in mitochondria, energy metabolism, and protein synthesis. To investigate these relationships, we determined the expression levels of genes encoding subunits of the 5 protein complexes of the electron transport chain, proteins involved in energy metabolism, nucleolar and ribosomal proteins, and enzymes of <span class="hlt">purine</span> metabolism in frontal cortex samples from 15 cases of sCJD MM1 and age-matched controls. We also assessed the protein expression levels of subunits of the respiratory chain, initiation and elongation translation factors of protein synthesis, and localization of selected mitochondrial components. We identified marked, generalized alterations of mRNA and protein expression of most subunits of all 5 mitochondrial respiratory chain complexes in sCJD cases. Expression of molecules involved in protein synthesis and <span class="hlt">purine</span> metabolism were also altered in sCJD. These findings point to altered mRNA and protein expression of components of mitochondria, protein synthesis machinery, and <span class="hlt">purine</span> metabolism as components of the pathogenesis of CJD. © 2016 American Association of Neuropathologists, Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23215441','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23215441"><span>Profiles of phenolic compounds and <span class="hlt">purine</span> alkaloids during the development of seeds of Theobroma cacao cv. Trinitario.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pereira-Caro, Gema; Borges, Gina; Nagai, Chifumi; Jackson, Mel C; Yokota, Takao; Crozier, Alan; Ashihara, Hiroshi</p> <p>2013-01-16</p> <p>Changes occurring in phenolic compounds and <span class="hlt">purine</span> alkaloids, during the growth of seeds of cacao (Theobroma cacao) cv. Trinitario, were investigated using HPLC-MS/MS. Extracts of seeds with a fresh weight of 125, 700, 1550, and 2050 mg (stages 1-4, respectively) were analyzed. The phenolic compounds present in highest concentrations in developing and mature seeds (stages 3 and 4) were flavonols and flavan-3-ols. Flavan-3-ols existed as monomers of epicatechin and catechin and as procyanidins. Type B procyanidins were major components and varied from dimers to pentadecamer. Two anthocyanins, cyanidin-3-O-arabinoside and cyanidin-3-O-galactoside, along with the N-phenylpropernoyl-l-amino acids, N-caffeoyl-l-aspartate, N-coumaroyl-l-aspartate, N-coumaroyl-3-hydroxytyrosine (clovamide), and N-coumaroyltyrosine (deoxyclovamide), and the <span class="hlt">purine</span> alkaloids theobromine and caffeine, were present in stage 3 and 4 seeds. Other <span class="hlt">purine</span> alkaloids, such as theophylline and additional methylxanthines, did not occur in detectable quantities. Flavan-3-ols were the only components to accumulate in detectable quantities in young seeds at developmental stages 1 and 2.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3538647','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3538647"><span>Metabolic engineering of the <span class="hlt">purine</span> biosynthetic pathway in Corynebacterium glutamicum results in increased intracellular pool sizes of IMP and hypoxanthine</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p></p> <p>2012-01-01</p> <p>Background <span class="hlt">Purine</span> nucleotides exhibit various functions in cellular metabolism. Besides serving as building blocks for nucleic acid synthesis, they participate in signaling pathways and energy metabolism. Further, IMP and GMP represent industrially relevant biotechnological products used as flavor enhancing additives in food industry. Therefore, this work aimed towards the accumulation of IMP applying targeted genetic engineering of Corynebacterium glutamicum. Results Blocking of the degrading reactions towards AMP and GMP lead to a 45-fold increased intracellular IMP pool of 22 μmol gCDW-1. Deletion of the pgi gene encoding glucose 6-phosphate isomerase in combination with the deactivated AMP and GMP generating reactions, however, resulted in significantly decreased IMP pools (13 μmol gCDW-1). Targeted metabolite profiling of the <span class="hlt">purine</span> biosynthetic pathway further revealed a metabolite shift towards the formation of the corresponding nucleobase hypoxanthine (102 μmol gCDW-1) derived from IMP degradation. Conclusions The <span class="hlt">purine</span> biosynthetic pathway is strongly interconnected with various parts of the central metabolism and therefore tightly controlled. However, deleting degrading reactions from IMP to AMP and GMP significantly increased intracellular IMP levels. Due to the complexity of this pathway further degradation from IMP to the corresponding nucleobase drastically increased suggesting additional targets for future strain optimization. PMID:23092390</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2841989','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2841989"><span>Regio- and Enantioselective N-Allylations of Imidazole, Benzimidazole, and <span class="hlt">Purine</span> Heterocycles Catalyzed by Single-Component Metallacyclic Iridium Complexes</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stanley, Levi M.</p> <p>2010-01-01</p> <p>Highly regio- and enantioselective iridium-catalyzed N-allylations of benzimidazoles, imidazoles, and <span class="hlt">purines</span> have been developed. N-Allylated benzimidazoles and imidazoles were isolated in high yields (up to 97%) with high branched-to-linear selectivity (up to 99:1) and enantioselectivity (up to 98% ee) from the reactions of benzimidazole and imidazole nucleophiles with unsymmetrical allylic carbonates in the presence of single component, ethylene-bound, metallacyclic iridium catalysts. N-Allylated <span class="hlt">purines</span> were also obtained in high yields (up to 91%) with high N9:N7 selectivity (up to 96:4), high branched-to-linear selectivity (98:2), and high enantioselectivity (up to 98% ee) under similar conditions. The reactions encompass a range of benzimidazole, imidazole, and <span class="hlt">purine</span> nucleophiles, as well as a variety of unsymmetrical aryl, heteroaryl, and aliphatic allylic carbonates. Competition experiments between common amine nucleophiles and the heterocyclic nitrogen nucleophiles studied in this work illustrate the effect of nucleophile pKa on the rate of iridium-catalyzed N-allylation reactions. Kinetic studies on the allylation of benzimidazole catalyzed by metallacyclic iridium-phosphoramidite complexes, in combination with studies on the deactivation of these catalysts in the presence of heterocyclic nucleophiles, provide insight into the effects of the structure of the phosphoramidite ligands on the stability of the metallacyclic catalysts. The data obtained from these studies has led to the development of N-allylations of benzimidazoles and imidazoles in the absence of an exogenous base. PMID:19480431</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19514135','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19514135"><span>[Genetic control of metabolism of mutagenic <span class="hlt">purine</span> base analogs 6-hydroxylaminopurine and 2-amino-6-hydroxylaminopurine in yeast Saccharomyces cerevisiae].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stepchenkova, E I; Koz'min, S G; Alenin, V V; Pavlov, Iu I</p> <p>2009-04-01</p> <p>The influence of inactivation of genes, which control biosynthesis of inosine monophosphate (IMP) de novo and the <span class="hlt">purine</span> utilization and interconversion pathway, on sensitivity of yeast Saccharomyces cerevisiae cells to the mutagenic and toxic action of 6-hydroxylaminopurine (HAP) and 2-amino-6-hydroxylaminopurine (AHA) was studied. It was shown that the manifestation of HAP and AHA mutagenic properties involves the action of enzyme adenine phosphoribosyltransferase encoded in yeast by APT1 gene. A blockade of each stage of IMP biosynthesis, with the exception of the block mediated by inactivation of genes ADE16 and ADE17 leading to the accumulation of 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR), was shown to enhance yeast cell sensitivity to the HAP mutagenic effect; however, it does not affect the sensitivity to AHA. A blockade of conversion of IMP into adenosine monophosphate (AMP) causes hypersensitivity of yeast cells to the mutagenic action of HAP and to the toxic effect of HAP, AHA, and hypoxanthine. It is fully probable that this enhancement of sensitivity to HAP and AHA is conditioned by changes in the pool of <span class="hlt">purines</span>. This indicates that genes ADE12, ADE13, AAH1, and HAM1 controlling processes of <span class="hlt">purine</span> utilization and interconversion in yeast make the greatest contribution to the system of protection against the toxic and mutagenic action of the examined analogs. Possible mechanisms of HAP detoxication in bacteria, yeast, and humans are considered.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23092390','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23092390"><span>Metabolic engineering of the <span class="hlt">purine</span> biosynthetic pathway in Corynebacterium glutamicum results in increased intracellular pool sizes of IMP and hypoxanthine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Peifer, Susanne; Barduhn, Tobias; Zimmet, Sarah; Volmer, Dietrich A; Heinzle, Elmar; Schneider, Konstantin</p> <p>2012-10-24</p> <p><span class="hlt">Purine</span> nucleotides exhibit various functions in cellular metabolism. Besides serving as building blocks for nucleic acid synthesis, they participate in signaling pathways and energy metabolism. Further, IMP and GMP represent industrially relevant biotechnological products used as flavor enhancing additives in food industry. Therefore, this work aimed towards the accumulation of IMP applying targeted genetic engineering of Corynebacterium glutamicum. Blocking of the degrading reactions towards AMP and GMP lead to a 45-fold increased intracellular IMP pool of 22 μmol g(CDW)⁻¹. Deletion of the pgi gene encoding glucose 6-phosphate isomerase in combination with the deactivated AMP and GMP generating reactions, however, resulted in significantly decreased IMP pools (13 μmol g(CDW)⁻¹). Targeted metabolite profiling of the <span class="hlt">purine</span> biosynthetic pathway further revealed a metabolite shift towards the formation of the corresponding nucleobase hypoxanthine (102 μmol g(CDW)⁻¹) derived from IMP degradation. The <span class="hlt">purine</span> biosynthetic pathway is strongly interconnected with various parts of the central metabolism and therefore tightly controlled. However, deleting degrading reactions from IMP to AMP and GMP significantly increased intracellular IMP levels. Due to the complexity of this pathway further degradation from IMP to the corresponding nucleobase drastically increased suggesting additional targets for future strain optimization.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8045862','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8045862"><span>Influence of sprint training on human skeletal muscle <span class="hlt">purine</span> nucleotide metabolism.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Stathis, C G; Febbraio, M A; Carey, M F; Snow, R J</p> <p>1994-04-01</p> <p>To examine the effect of sprint training on human skeletal muscle <span class="hlt">purine</span> nucleotide metabolism, eight active untrained subjects completed a maximal 30-s sprint bout on a cycle ergometer before and after 7 wk of sprint training. Resting muscle ATP and total adenine nucleotide content were reduced (P < 0.05) by 19 and 18%, respectively, after training. Training resulted in a 52% attenuation (P < 0.05) in the magnitude of ATP depletion after exercise and a similar reduction (P < 0.05) in the accumulation of inosine 5'-monophosphate and ammonia. During recovery, muscle inosine 5'-monophosphate (P < 0.05) and inosine (P < 0.01) content were reduced after training, as was the accumulation of inosine (P < 0.05). Plasma ammonia was higher (P < 0.05) after training early in recovery; in contrast, plasma hypoxanthine concentrations were reduced (P < 0.05) during the latter stages of recovery. The attenuated resting ATP and total adenine nucleotide contents after training probably result from the acute effects of prior training sessions. The reduction in the magnitude of ATP depletion during a 30-s sprint bout after training must reflect an improved balance between ATP hydrolysis and resynthesis. It is unclear which mechanism(s) is responsible for the reduction in the magnitude of ATP degradation after training.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/14529388','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/14529388"><span>Development of <span class="hlt">purine</span>-scaffold small molecule inhibitors of Hsp90.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chiosis, Gabriela; Lucas, Brian; Huezo, Henri; Solit, David; Basso, Andrea; Rosen, Neal</p> <p>2003-10-01</p> <p>The Hsp90 chaperones play a key role in regulating the physiology of cells exposed to environmental stress and in maintaining the malignant phenotype in tumor cells. Agents that interfere with the function of the chaperone may thus be beneficial in the treatment of cancers. The ansamycins (geldanamycin and herbimycin) and the unrelated natural product radicicol were found to bind to the N-terminal pocket of Hsp90 and inhibit its function. However, translation of these compounds to the clinic was impeded by stability and hepatoxicity issues. 17AAG, a derivative of geldanamycin, was found to be less hepatotoxic and is currently undergoing Phase I clinical trial. Unfortunately, 17AAG is insoluble, difficult to formulate and it is not yet clear if therapeutically effective doses can be administered without escalating non-Hsp90 associated toxicities. Additionally, for reasons not yet completely understood, a subset of tumor cells are insensitive to the action of the drug. The development of novel agents that lack the drawbacks of the natural products is thus necessary. Here we present an overview of such efforts with focus on a new class of <span class="hlt">purine</span>-scaffold Hsp90 inhibitors developed by rational design.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15936302','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15936302"><span>Effect of ethanol on metabolism of <span class="hlt">purine</span> bases (hypoxanthine, xanthine, and uric acid).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yamamoto, Tetsuya; Moriwaki, Yuji; Takahashi, Sumio</p> <p>2005-06-01</p> <p>There are many factors that contribute to hyperuricemia, including obesity, insulin resistance, alcohol consumption, diuretic use, hypertension, renal insufficiency, genetic makeup, etc. Of these, alcohol (ethanol) is the most important. Ethanol enhances adenine nucleotide degradation and increases lactic acid level in blood, leading to hyperuricemia. In beer, <span class="hlt">purines</span> also contribute to an increase in plasma uric acid. Although rare, dehydration and ketoacidosis (due to ethanol ingestion) are associated with the ethanol-induced increase in serum uric acid levels. Ethanol also increases the plasma concentrations and urinary excretion of hypoxanthine and xanthine via the acceleration of adenine nucleotide degradation and a possible weak inhibition of xanthine dehydrogenase activity. Since many factors such as the ALDH2*1 gene and ADH2*2 gene, daily drinking habits, exercise, and dehydration enhance the increase in plasma concentration of uric acid induced by ethanol, it is important to pay attention to these factors, as well as ingested ethanol volume, type of alcoholic beverage, and the administration of anti-hyperuricemic agents, to prevent and treat ethanol-induced hyperuricemia.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26295691','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26295691"><span>The antibacterial activity and toxicity of enrofloxacin are decreased by nanocellulose conjugated with aminobenzyl <span class="hlt">purin</span>.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yasini, Seyed Ali; Zadeh, Mohammad Hossein Balal; Shahdadi, Hossein</p> <p>2015-11-01</p> <p>The first aim of this study was to synthesize nanocellulose conjugated with aminobenzyl <span class="hlt">purin</span> (NCABP), and the second aim was to evaluate the effect of NCABP on both toxicity and antibacterial activity of enrofloxacin. Here, the adsorption of enrofloxacin by NCABP was first modeled by molecular dynamic (MD) simulation. In the next step, NCABP was synthesized, and was exposed to enrofloxacin, 1000 μg mL(-1), at various conditions. Then, the quantity of adsorption and release was separately measured. Furthermore, both toxicity and antibacterial activity of NCABP, enrofloxacin, and (NCABP+enrofloxacin) were separately evaluated. In this study, MD simulation clearly showed the adsorption after 50 picoseconds. The adsorption tests revealed that the increase of incubation time and NCABP concentration, at range of 50-200 μg mL(-1), led to increase of adsorption. Moreover, the decrease of pH led to increase of adsorption. Interestingly, NCABP could adsorb enrofloxacin, up to 1000 μg mL(-1), in different types of meat. Moreover, the increase of incubation time and temperature did not release enrofloxacin, but the increase of pH increased release. This study showed that both toxicity and antibacterial activity of enrofloxacin were decreased when exposed together with NCABP.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5011229','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5011229"><span>A 90-Day Oral Toxicological Evaluation of the Methylurate <span class="hlt">Purine</span> Alkaloid Theacrine</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hirka, Gábor; Glávits, Róbert; Palmer, Philip A.; Endres, John R.; Pasics Szakonyiné, Ilona</p> <p>2016-01-01</p> <p>A 90-day repeated-dose oral toxicological evaluation was conducted according to GLP and OECD guidelines on the methylurate <span class="hlt">purine</span> alkaloid theacrine, which is found naturally in certain plants. Four groups of Hsd.Brl.Han Wistar rats (ten/sex/group) were administered theacrine by gavage doses of 0 (vehicle only), 180, 300, and 375 mg/kg bw/day. Two females and one male in the 300 and 375 mg/kg bw/day groups, respectively, died during the study. Histological examination revealed centrilobular hepatocellular necrosis as the probable cause of death. In 375 mg/kg bw/day males, slight reductions in body weight development, food consumption, and feed efficiency, decreased weight of the testes and epididymides and decreased intensity of spermatogenesis in the testes, lack or decreased amount of mature spermatozoa in the epididymides, and decreased amount of prostatic secretions were detected at the end of the three months. At 300 mg/kg bw/day, slight decreases in the weights of the testes and epididymides, along with decreased intensity of spermatogenesis in the testes, and lack or decreased amount of mature spermatozoa in the epididymides were detected in male animals. The NOAEL was considered to be 180 mg/kg bw/day, as at this dose there were no toxicologically relevant treatment-related findings in male or female animals. PMID:27635133</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27635133','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27635133"><span>A 90-Day Oral Toxicological Evaluation of the Methylurate <span class="hlt">Purine</span> Alkaloid Theacrine.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Clewell, Amy; Hirka, Gábor; Glávits, Róbert; Palmer, Philip A; Endres, John R; Murbach, Timothy S; Marx, Tennille; Pasics Szakonyiné, Ilona</p> <p>2016-01-01</p> <p>A 90-day repeated-dose oral toxicological evaluation was conducted according to GLP and OECD guidelines on the methylurate <span class="hlt">purine</span> alkaloid theacrine, which is found naturally in certain plants. Four groups of Hsd.Brl.Han Wistar rats (ten/sex/group) were administered theacrine by gavage doses of 0 (vehicle only), 180, 300, and 375 mg/kg bw/day. Two females and one male in the 300 and 375 mg/kg bw/day groups, respectively, died during the study. Histological examination revealed centrilobular hepatocellular necrosis as the probable cause of death. In 375 mg/kg bw/day males, slight reductions in body weight development, food consumption, and feed efficiency, decreased weight of the testes and epididymides and decreased intensity of spermatogenesis in the testes, lack or decreased amount of mature spermatozoa in the epididymides, and decreased amount of prostatic secretions were detected at the end of the three months. At 300 mg/kg bw/day, slight decreases in the weights of the testes and epididymides, along with decreased intensity of spermatogenesis in the testes, and lack or decreased amount of mature spermatozoa in the epididymides were detected in male animals. The NOAEL was considered to be 180 mg/kg bw/day, as at this dose there were no toxicologically relevant treatment-related findings in male or female animals.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26411681','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26411681"><span>Adenylosuccinate Is an Insulin Secretagogue Derived from Glucose-Induced <span class="hlt">Purine</span> Metabolism.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gooding, Jessica R; Jensen, Mette V; Dai, Xiaoqing; Wenner, Brett R; Lu, Danhong; Arumugam, Ramamani; Ferdaoussi, Mourad; MacDonald, Patrick E; Newgard, Christopher B</p> <p>2015-10-06</p> <p>Pancreatic islet failure, involving loss of glucose-stimulated insulin secretion (GSIS) from islet β cells, heralds the onset of type 2 diabetes (T2D). To search for mediators of GSIS, we performed metabolomics profiling of the insulinoma cell line 832/13 and uncovered significant glucose-induced changes in <span class="hlt">purine</span> pathway intermediates, including a decrease in inosine monophosphate (IMP) and an increase in adenylosuccinate (S-AMP), suggesting a regulatory role for the enzyme that links the two metabolites, adenylosuccinate synthase (ADSS). Inhibition of ADSS or a more proximal enzyme in the S-AMP biosynthesis pathway, adenylosuccinate lyase, lowers S-AMP levels and impairs GSIS. Addition of S-AMP to the interior of patch-clamped human β cells amplifies exocytosis, an effect dependent upon expression of sentrin/SUMO-specific protease 1 (SENP1). S-AMP also overcomes the defect in glucose-induced exocytosis in β cells from a human donor with T2D. S-AMP is, thus, an insulin secretagogue capable of reversing β cell dysfunction in T2D. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24933643','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24933643"><span>Solution-phase parallel synthesis of acyclic nucleoside libraries of <span class="hlt">purine</span>, pyrimidine, and triazole acetamides.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Pathak, Ashish K; Pathak, Vibha; Reynolds, Robert C</p> <p>2014-09-08</p> <p>Molecular diversity plays a pivotal role in modern drug discovery against phenotypic or enzyme-based targets using high throughput screening technology. Under the auspices of the Pilot Scale Library Program of the NIH Roadmap Initiative, we produced and report herein a diverse library of 181 <span class="hlt">purine</span>, pyrimidine, and 1,2,4-triazole-N-acetamide analogues which were prepared in a parallel high throughput solution-phase reaction format. A set of assorted amines were reacted with several nucleic acid N-acetic acids utilizing HATU as the coupling reagent to produce diverse acyclic nucleoside N-acetamide analogues. These reactions were performed using 24 well reaction blocks and an automatic reagent-dispensing platform under inert atmosphere. The targeted compounds were purified on an automated purification system using solid sample loading prepacked cartridges and prepacked silica gel columns. All compounds were characterized by NMR and HRMS, and were analyzed for purity by HPLC before submission to the Molecular Libraries Small Molecule Repository (MLSMR) at NIH. Initial screening through the Molecular Libraries Probe Production Centers Network (MLPCN) program, indicates that several analogues showed diverse and interesting biological activities.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1219067','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1219067"><span>Analysis of abnormalities in <span class="hlt">purine</span> metabolism leading to gout and to neurological dysfunctions in man.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Curto, R; Voit, E O; Cascante, M</p> <p>1998-01-01</p> <p>A modelling approach is used to analyse diseases associated with <span class="hlt">purine</span> metabolism in man. The specific focus is on deficiencies in two enzymes, hypoxanthine:guanine phosphoribosyltransferase and adenylosuccinate lyase. These deficiencies can lead to a number of symptoms, including neurological dysfunctions and mental retardation. Although the biochemical mechanisms of dysfunctions associated with adenylosuccinate lyase deficiency are not completely understood, there is at least general agreement in the literature about possible causes. Simulations with our model confirm that accumulation of the two substrates of the enzyme can lead to significant biochemical imbalance. In hypoxanthine:guanine phosphoribosyltransferase deficiency the biochemical mechanisms associated with neurological dysfunctions are less clear. Model analyses support some old hypotheses but also suggest new indicators for possible causes of neurological dysfunctions associated with this deficiency. Hypoxanthine:guanine phosphoribosyltransferase deficiency is known to cause hyperuricaemia and gout. We compare the relative importance of this deficiency with other known causes of gout in humans. The analysis suggests that defects in the excretion of uric acid are more consequential than defects in uric acid synthesis such as hypoxanthine:guanine phosphoribosyltransferase deficiency. PMID:9445373</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/8793014','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/8793014"><span>Cytogenetic genotoxicity of antiherpes virostatics in Chinese hamster V79-E cells. I. <span class="hlt">Purine</span> nucleoside analogues.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Thust, R; Schacke, M; Wutzler, P</p> <p>1996-06-01</p> <p>The antiherpes virostatics acyclovir (ACV), valaciclovir (VACV), penciclovir (PCV), famciclovir (FCV) and ganciclovir (GCV), which belong to the group of <span class="hlt">purine</span> acyclic nucleoside analogues, were tested for clastogenic and sister chromatid exchange (SCE)-inducing activity in Chinese hamster V79-E cells upon chronic application with and without a recovery period. ACV induced borderline effects in both cytogenetic assays, a dose-dependent reduction of the mitotic index and an increasing cell cycle delay. With VACV and PCV only a decrease of the mitotic index and an increase of cell cycle delay were observed. FCV was negative with respect to the four parameters studied, presumably due to the incapacity of the target cells of metabolizing FCV to PCV. GCV was a very potent genotoxin in both assays. It induced a statistically significant SCE response even in the range of the cytomegalovirus IC50 of < 10 microM. By variation of the experimental protocol it was shown that SCEs are induced in the second cell cycle following exposure to GCV but not in the first one. It is assumed that the drugs under study are metabolized to their respective triphosphates and then inhibit DNA replication as detected by decreasing mitotic index and increasing cell cycle delay. In the case of GCV it is suggested that GCV-TP is incorporated into the target cell DNA and that chromosomal aberrations and SCEs are secondary lesions due to repair processes at the substituted template.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18451042','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18451042"><span>The role of a <span class="hlt">purine</span>-specific nucleoside hydrolase in spore germination of Bacillus thuringiensis.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Liang, Liang; He, Xihong; Liu, Gang; Tan, Huarong</p> <p>2008-05-01</p> <p>A homologous gene (iunH) of a putative nucleoside hydrolase (NH), which had been identified from the exosporia of Bacillus cereus and Bacillus anthracis spores, was cloned from Bacillus thuringiensis subsp. kurstaki. Disruption of iunH did not affect the vegetative growth and sporulation of Bacillus thuringiensis, but promoted both inosine- and adenosine-induced spore germination. The inosine- or adenosine-induced germination rate decreased when the wild-type iunH gene was overexpressed in Bacillus thuringiensis. The iunH gene product was characterized as a <span class="hlt">purine</span>-specific NH. The kinetic parameters of IunH with inosine as substrate were K(m)=399+/-115 microM, k(cat)=48.9+/-8.5 s(-1) and k(cat)/K(m)=1.23 x 10(5) M(-1) s(-1). The optimal pH and temperature for IunH were found to be pH 6 and 80 degrees C. Meanwhile, the specific activity of inosine hydrolase in intact spores of the wild-type strain with inosine as substrate was 2.89+/-0.23x10(-2) micromol min(-1) (mg dry wt)(-1). These results indicate that IunH is important in moderating inosine- or adenosine-induced germination of Bacillus thuringiensis spores.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/12218359','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/12218359"><span><span class="hlt">Purine</span>, kynurenine, neopterin and lipid peroxidation levels in inflammatory bowel disease.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Forrest, Caroline M; Youd, Philippa; Kennedy, Alan; Gould, Stuart R; Darlington, L Gail; Stone, Trevor W</p> <p>2002-01-01</p> <p>The kynurenine metabolites of tryptophan may be involved in the regulation of neuronal activity and thus gut motility and secretion. We have now performed a pilot study to measure serum concentrations of <span class="hlt">purines</span> and kynurenines in patients with mild inflammatory bowel disease, as well as in sex- and age-matched control subjects. For some analyses, the patients were subdivided into subgroups of those with Crohn's disease and those with ulcerative colitis. The analyses indicated an increased activity in one branch of the kynurenine pathway. While there was no demonstrable difference in neopterin levels in either of the patient groups compared with controls, indicating that the disorders were in an inactive quiescent phase, both groups showed significantly higher levels of lipid peroxidation products. This suggests the presence of increased oxidative stress even during relative disease inactivity. The increased level of kynurenic acid may represent either a compensatory response to elevated activation of enteric neurones or a primary abnormality which induces a compensatory increase in gut activity. In either case, the data may indicate a role for kynurenine modulation of glutamate receptors in the symptoms of inflammatory bowel disease. Copyright 2002 National Science Council, ROC and S. Karger AG, Basel</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28111097','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28111097"><span>An Unusual Protector-Protégé Strategy for the Biosynthesis of <span class="hlt">Purine</span> Nucleoside Antibiotics.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wu, Pan; Wan, Dan; Xu, Gudan; Wang, Gui; Ma, Hongmin; Wang, Tingting; Gao, Yaojie; Qi, Jianzhao; Chen, Xiaoxia; Zhu, Jian; Li, Yong-Quan; Deng, Zixin; Chen, Wenqing</p> <p>2017-02-16</p> <p>Pentostatin (PTN, deoxycoformycin) and arabinofuranosyladenine (Ara-A, vidarabine) are <span class="hlt">purine</span> nucleoside antibiotics used clinically to treat hematological cancers and human DNA virus infections, respectively. PTN has a 1,3-diazepine ring, and Ara-A is an adenosine analog with an intriguing epimerization at the C-2' hydroxyl group. However, the logic underlying the biosynthesis of these interesting molecules has long remained elusive. Here, we report that the biosynthesis of PTN and Ara-A employs an unusual protector-protégé strategy. To our surprise, we determined that a single gene cluster governs PTN and Ara-A biosynthesis via two independent pathways. Moreover, we verified that PenB functions as a reversible oxidoreductase for the final step of PTN. Remarkably, we provided the first direct biochemical evidence that PTN can protect Ara-A from deamination by selective inhibition of the host adenosine deaminase. These findings expand our knowledge of natural product biosynthesis and open the way for target-directed genome mining of Ara-A/PTN-related antibiotics.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22615034','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22615034"><span>The synthetic <span class="hlt">purine</span> reversine selectively induces cell death of cancer cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Piccoli, Marco; Palazzolo, Giacomo; Conforti, Erika; Lamorte, Giuseppe; Papini, Nadia; Creo, Pasquale; Fania, Chiara; Scaringi, Raffaella; Bergante, Sonia; Tringali, Cristina; Roncoroni, Leda; Mazzoleni, Stefania; Doneda, Luisa; Galli, Rossella; Venerando, Bruno; Tettamanti, Guido; Gelfi, Cecilia; Anastasia, Luigi</p> <p>2012-10-01</p> <p>The synthetic <span class="hlt">purine</span> reversine has been shown to possess a dual activity as it promotes the de-differentiation of adult cells, including fibroblasts, into stem-cell-like progenitors, but it also induces cell growth arrest and ultimately cell death of cancer cells, suggesting its possible application as an anti-cancer agent. Aim of this study was to investigate the mechanism underneath reversine selectivity in inducing cell death of cancer cells by a comparative analysis of its effects on several tumor cells and normal dermal fibroblasts. We found that reversine is lethal for all cancer cells studied as it induces cell endoreplication, a process that malignant cells cannot effectively oppose due to aberrations in cell cycle checkpoints. On the other hand, normal cells, like dermal fibroblasts, can control reversine activity by blocking the cell cycle, entering a reversible quiescent state. However, they can be induced to become sensitive to the molecule when key cell cycle proteins, e.g., p53, are silenced. Copyright © 2012 Wiley Periodicals, Inc.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1006745','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1006745"><span>Elucidation of Different Binding Modes of <span class="hlt">Purine</span> Nucleosides to Human Deoxycytidine Kinase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sabini, Elisabetta; Hazra, Saugata; Konrad, Manfred; Lavie, Arnon</p> <p>2008-07-30</p> <p><span class="hlt">Purine</span> nucleoside analogues of medicinal importance, such as cladribine, require phosphorylation by deoxycytidine kinase (dCK) for pharmacological activity. Structural studies of ternary complexes of human dCK show that the enzyme conformation adjusts to the different hydrogen-bonding properties between dA and dG and to the presence of substituent at the 2-position present in dG and cladribine. Specifically, the carbonyl group in dG elicits a previously unseen conformational adjustment of the active site residues Arg104 and Asp133. In addition, dG and cladribine adopt the anti conformation, in contrast to the syn conformation observed with dA. Kinetic analysis reveals that cladribine is phosphorylated at the highest efficiency with UTP as donor. We attribute this to the ability of cladribine to combine advantageous properties from dA (favorable hydrogen-bonding pattern) and dG (propensity to bind to the enzyme in its anti conformation), suggesting that dA analogues with a substituent at the 2-position are likely to be better activated by human dCK.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/24520464','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/24520464"><span>Effect of <span class="hlt">purine</span> nucleoside analogue-acyclovir on the sperm parameters and testosterone production in rats.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Movahed, Elham; Sadrkhanlou, Rajabali; Ahmadi, Abbas; Nejati, Vahid; Zamani, Zahra</p> <p>2013-04-01</p> <p>Acyclovir (ACV), a synthetic <span class="hlt">purine</span> nucleoside analogue derived from guanosine, is known to be toxic to gonads and the aim of this study was to evaluate the effect of ACV on the sperm parameters and testosterone production in rat. In this experimental study, forty adult male Wistar rats (220 ± 20 g) were randomly divided into five groups (n=8 for each group). One group served as control and one group served as sham control [distilled water was intraperitoneally (i.p.) injected]. ACV was administered intraperitoneally in the drug treatment groups (4, 16 and 48 mg/kg/day) for 15 days. Eighteen days after the last injection, rats were sacrificed by CO2 inhalation. After that, cauda epididymides were removed surgically. At the end, sperm concentrations in the cauda epididymis, sperm motility, morphology, viability, chromatin quality and DNA integrity were analyzed. Serum testosterone concentrations were determined. The results showed that ACV did not affect sperm count, but decreased sperm motility and sperm viability at 16 and 48 mg/kg dose-levels. Sperm abnormalities increased at 48 mg/kg dose-level of ACV. Further, ACV significantly increases DNA damage at 16 and 48 mg/kg dose-levels and chromatin abnormality at all doses. Besides, a significant decrease in serum testosterone concentrations was observed at 16 and 48 mg/ kg doses. The present results highly support the idea that ACV induces testicular toxicity by adverse effects on the sperm parameters and serum level of testosterone in male rats.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2714976','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2714976"><span>Recognizing <span class="hlt">Sequences</span> of <span class="hlt">Sequences</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kiebel, Stefan J.; von Kriegstein, Katharina; Daunizeau, Jean; Friston, Karl J.</p> <p>2009-01-01</p> <p>The brain's decoding of fast sensory streams is currently impossible to emulate, even approximately, with artificial agents. For example, robust speech recognition is relatively easy for humans but exceptionally difficult for artificial speech recognition systems. In this paper, we propose that recognition can be simplified with an internal model of how sensory input is generated, when formulated in a Bayesian framework. We show that a plausible candidate for an internal or generative model is a hierarchy of ‘stable heteroclinic channels’. This model describes continuous dynamics in the environment as a hierarchy of <span class="hlt">sequences</span>, where slower <span class="hlt">sequences</span> cause faster <span class="hlt">sequences</span>. Under this model, online recognition corresponds to the dynamic decoding of causal <span class="hlt">sequences</span>, giving a representation of the environment with predictive power on several timescales. We illustrate the ensuing decoding or recognition scheme using synthetic <span class="hlt">sequences</span> of syllables, where syllables are <span class="hlt">sequences</span> of phonemes and phonemes are <span class="hlt">sequences</span> of sound-wave modulations. By presenting anomalous stimuli, we find that the resulting recognition dynamics disclose inference at multiple time scales and are reminiscent of neuronal dynamics seen in the real brain. PMID:19680429</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/20209081','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/20209081"><span>Homeostatic imbalance of <span class="hlt">purine</span> catabolism in first-episode neuroleptic-naïve patients with schizophrenia.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Yao, Jeffrey K; Dougherty, George G; Reddy, Ravinder D; Keshavan, Matcheri S; Montrose, Debra M; Matson, Wayne R; McEvoy, Joseph; Kaddurah-Daouk, Rima</p> <p>2010-03-03</p> <p><span class="hlt">Purine</span> catabolism may be an unappreciated, but important component of the homeostatic response of mitochondria to oxidant stress. Accumulating evidence suggests a pivotal role of oxidative stress in schizophrenia pathology. Using high-pressure liquid chromatography coupled with a coulometric multi-electrode array system, we compared 6 <span class="hlt">purine</span> metabolites simultaneously in plasma between first-episode neuroleptic-naïve patients with schizophrenia (FENNS, n = 25) and healthy controls (HC, n = 30), as well as between FENNS at baseline (BL) and 4 weeks (4w) after antipsychotic treatment. Significantly higher levels of xanthosine (Xant) and lower levels of guanine (G) were seen in both patient groups compared to HC subjects. Moreover, the ratios of G/guanosine (Gr), uric acid (UA)/Gr, and UA/Xant were significantly lower, whereas the ratio of Xant/G was significantly higher in FENNS-BL than in HC. Such changes remained in FENNS-4w with exception that the ratio of UA/Gr was normalized. All 3 groups had significant correlations between G and UA, and Xan and hypoxanthine (Hx). By contrast, correlations of UA with each of Xan and Hx, and the correlation of Xan with Gr were all quite significant for the HC but not for the FENNS. Finally, correlations of Gr with each of UA and G were significant for both HC and FENNS-BL but not for the FENNS-4w. During <span class="hlt">purine</span> catabolism, both conversions of Gr to G and of Xant to Xan are reversible. Decreased ratios of product to precursor suggested a shift favorable to Xant production from Xan, resulting in decreased UA levels in the FENNS. Specifically, the reduced UA/Gr ratio was nearly normalized after 4 weeks of antipsychotic treatment. In addition, there are tightly correlated precursor and product relationships within <span class="hlt">purine</span> pathways; although some of these correlations persist across disease or medication status, others appear to be lost among FENNS. Taken together, these results suggest that the potential for steady formation of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/15571394','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/15571394"><span>Promoting vibrations in human <span class="hlt">purine</span> nucleoside phosphorylase. A molecular dynamics and hybrid quantum mechanical/molecular mechanical study.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Núñez, Sara; Antoniou, Dimitri; Schramm, Vern L; Schwartz, Steven D</p> <p>2004-12-08</p> <p>Crystallographic studies of human <span class="hlt">purine</span> nucleoside phosphorylase (hPNP) with several transition-state (TS) analogues in the immucillin family showed an unusual geometric arrangement of the atoms O-5', O-4', and O(P), the nucleophilic phosphate oxygen, lying in a close three-oxygen stack. These observations were corroborated by extensive experimental kinetic isotope effect analysis. We propose that protein-facilitated dynamic modes in hPNP cause this stack, centered on the ribosyl O-4' oxygen, to squeeze together and push electrons toward the <span class="hlt">purine</span> ring, stabilizing the oxacarbenium character of the TS. As the N-ribosidic bond is cleaved during the reaction, the pK(a) values of N-7 and O-6 increase by the electron density expelled by the oxygen-stack compression toward the <span class="hlt">purine</span> ring. Increased electron density in the <span class="hlt">purine</span> ring improves electrostatic interactions with nearby residues and facilitates the abstraction of a proton from a solvent proton or an unidentified general acid, making the <span class="hlt">purine</span> a better leaving group, and accelerating catalysis. Classical and mixed quantum/classical molecular dynamics (MD) simulations of the Michaelis complex of hPNP with the substrates guanosine and phosphate were performed to assess the existence of protein-promoting vibrations (PPVs). Analogous simulations were performed for the substrates in aqueous solution. In the catalytic site, the O-5', O-4', and O(P) oxygens vibrate at frequencies of ca. 125 and 465 cm(-1), as opposed to 285 cm(-1) in the absence of hPNP. The hybrid quantum mechanical/molecular mechanical method was used to assess whether this enzymatic vibration pushing the oxygens together is coupled to the reaction coordinate, and thus has a direct positive impact on catalysis. The potential energy surface for the phosphorolysis reaction for several snapshots taken from the classical MD simulation showed substantial differences in oxygen compression. Our calculations showed the existence of PPVs coupled to the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/6327016','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/6327016"><span>Enzymic capacities of <span class="hlt">purine</span> de Novo and salvage pathways for nucleotide synthesis in normal and neoplastic tissues.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Natsumeda, Y; Prajda, N; Donohue, J P; Glover, J L; Weber, G</p> <p>1984-06-01</p> <p>The enzymic capacities of the de novo and the salvage pathways for <span class="hlt">purine</span> nucleotide synthesis were compared in rat in normal, differentiating, and regenerating liver, and in three hepatomas of widely different growth rates. The activities of the key de novo and salvage enzymes were also determined in mouse lung and Lewis lung carcinoma, in human kidney and liver, and in renal cell carcinoma and hepatocellular carcinomas. A precise and reproducible assay was worked out for measuring the activities of adenine phosphoribosyltransferase (EC 2.4.2.7) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8) in crude liver and hepatoma systems. Kinetic studies on the salvage enzymes were carried out in the crude 100,000 X g supernatant fluid from normal liver and rapidly growing hepatoma 3924A. In both tissue extracts, Michaelis-Menten kinetics was observed for adenine phosphoribosyltransferase and HGPRT. The reciprocal plots for 5-phosphoribosyl-1-pyrophosphate (PRPP) of liver and hepatoma enzymes gave apparent KmS of 2 microM for adenine phosphoribosyltransferase and 4 microM for HGPRT, showing two orders of magnitude higher affinities for PRPP than that of the rate-limiting enzyme of de novo <span class="hlt">purine</span> synthesis, amidophosphoribosyltransferase (EC 2.4.2.14) (Km = 400 to 900 microM). The apparent Km values for adenine of liver and hepatoma adenine phosphoribosyltransferase were 0.6 to 0.9 microM, respectively. For both liver and hepatoma HGPRT, the reciprocal plots for hypoxanthine and guanine yielded the same Km of 3 microM. The specific activities of <span class="hlt">purine</span> phosphoribosyltransferases were markedly higher than that of amidophosphoribosyltransferase in rat thymus, spleen, testis, bone marrow, colon, liver, kidney cortex, lung, heart, brain, and skeletal muscle, but were lower in the small intestine. In hepatomas and regenerating and differentiating liver, the activities of the salvage enzymes were 2.1- to 32-fold higher than that of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1262711','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1262711"><span>Mitochondrial-encoded membrane protein transcripts are pyrimidine-rich while soluble protein transcripts and ribosomal RNA are <span class="hlt">purine</span>-rich</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bradshaw, Patrick C; Rathi, Anand; Samuels, David C</p> <p>2005-01-01</p> <p>Background Eukaryotic organisms contain mitochondria, organelles capable of producing large amounts of ATP by oxidative phosphorylation. Each cell contains many mitochondria with many copies of mitochondrial DNA in each organelle. The mitochondrial DNA encodes a small but functionally critical portion of the oxidative phosphorylation machinery, a few other species-specific proteins, and the rRNA and tRNA used for the translation of these transcripts. Because the microenvironment of the mitochondrion is unique, mitochondrial genes may be subject to different selectional pressures than those affecting nuclear genes. Results From an analysis of the mitochondrial genomes of a wide range of eukaryotic species we show that there are three simple rules for the pyrimidine and <span class="hlt">purine</span> abundances in mitochondrial DNA transcripts. Mitochondrial membrane protein transcripts are pyrimidine rich, rRNA transcripts are <span class="hlt">purine</span>-rich and the soluble protein transcripts are <span class="hlt">purine</span>-rich. The transitions between pyrimidine and <span class="hlt">purine</span>-rich regions of the genomes are rapid and are easily visible on a pyrimidine-<span class="hlt">purine</span> walk graph. These rules are followed, with few exceptions, independent of which strand encodes the gene. Despite the robustness of these rules across a diverse set of species, the magnitude of the differences between the pyrimidine and <span class="hlt">purine</span> content is fairly small. Typically, the mitochondrial membrane protein transcripts have a pyrimidine richness of 56%, the rRNA transcripts are 55% <span class="hlt">purine</span>, and the soluble protein transcripts are only 53% <span class="hlt">purine</span>. Conclusion The pyrimidine richness of mitochondrial-encoded membrane protein transcripts is partly driven by U nucleotides in the second codon position in all species, which yields hydrophobic amino acids. The <span class="hlt">purine</span>-richness of soluble protein transcripts is mainly driven by A nucleotides in the first codon position. The <span class="hlt">purine</span>-richness of rRNA is also due to an abundance of A nucleotides. Possible mechanisms as to how these</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27976868','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27976868"><span>Thermodynamics of the <span class="hlt">Purine</span> Nucleoside Phosphorylase Reaction Revealed by Computer Simulations.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Isaksen, Geir Villy; Åqvist, Johan; Brandsdal, Bjørn Olav</p> <p>2017-01-10</p> <p>Enzymes are able to catalyze chemical reactions by reducing the activation free energy, yielding significant increases in the reaction rates. This can thermodynamically be accomplished by either reducing the activation enthalpy or increasing the activation entropy. The effect of remote mutations on the thermodynamic activation parameters of human <span class="hlt">purine</span> nucleoside phosphorylase is examined using extensive molecular dynamics and free energy simulations. More than 2700 independent reaction free energy profiles for six different temperatures have been calculated to obtain high-precision computational Arrhenius plots. On the basis of these, the activation enthalpies and entropies were computed from linear regression of the plots with ΔG(⧧) as a function of 1/T, and the obtained thermodynamic activation parameters are in very good agreement with those from experiments. The Arrhenius plots immediately show that the 6-oxopurines (INO and GUO) have identical slopes, whereas the 6-aminopurine (ADO) has a significantly different slope, indicating that the substrate specificity is related to the difference in thermodynamic activation parameters. Furthermore, the calculations show that the human PNP specificity for 6-oxopurines over 6-aminopurines originates from significant differences in electrostatic preorganization. The effect of the remote double mutation, K22E and H104R (E:R), has also been examined, as it alters human PNP toward the bovine PNP. These residues are situated on the protein surface, 28-35 Å from the active site, and the mutation alters the enthalpy-entropy balance with little effect on the catalytic rates. It is thus quite remarkable that the empirical valence bond method can reproduce the enthalpies and entropies induced by these long-range mutations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2877996','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2877996"><span>The Evolutionary Fate of the Genes Encoding the <span class="hlt">Purine</span> Catabolic Enzymes in Hominoids, Birds, and Reptiles</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Keebaugh, Alaine C.; Thomas, James W.</p> <p>2010-01-01</p> <p>Gene loss has been proposed to play a major role in adaptive evolution, and recent studies are beginning to reveal its importance in human evolution. However, the potential consequence of a single gene-loss event upon the fates of functionally interrelated genes is poorly understood. Here, we use the <span class="hlt">purine</span> metabolic pathway as a model system in which to explore this important question. The loss of urate oxidase (UOX) activity, a necessary step in this pathway, has occurred independently in the hominoid and bird/reptile lineages. Because the loss of UOX would have removed the functional constraint upon downstream genes in this pathway, these downstream genes are generally assumed to have subsequently deteriorated. In this study, we used a comparative genomics approach to empirically determine the fate of UOX itself and the downstream genes in five hominoids, two birds, and a reptile. Although we found that the loss of UOX likely triggered the genetic deterioration of the immediate downstream genes in the hominoids, surprisingly in the birds and reptiles, the UOX locus itself and some of the downstream genes were present in the genome and predicted to encode proteins. To account for the variable pattern of gene retention and loss after the inactivation of UOX, we hypothesize that although gene loss is a common fate for genes that have been rendered obsolete due to the upstream loss of an enzyme a metabolic pathway, it is also possible that same lack of constraint will foster the evolution of new functions or allow the optimization of preexisting alternative functions in the downstream genes, thereby resulting in gene retention. Thus, adaptive single-gene losses have the potential to influence the long-term evolutionary fate of functionally interrelated genes. PMID:20106906</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9030766','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9030766"><span>Nicotinamide riboside, an unusual, non-typical, substrate of purified <span class="hlt">purine</span>-nucleoside phosphorylases.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wielgus-Kutrowska, B; Kulikowska, E; Wierzchowski, J; Bzowska, A; Shugar, D</p> <p>1997-01-15</p> <p>Nicotinamide 1-beta-D-riboside (Nir), the cationic, reducible moiety of the coenzyme NAD+, has been confirmed as an unusual substrate for purified <span class="hlt">purine</span>-nucleoside phosphorylase (PNP) from a mammalian source (calf spleen). It is also a substrate of the enzyme from Escherichia coli. The Km values at pH 7, 1.48 mM and 0.62 mM, respectively, were 1-2 orders of magnitude higher than for the natural substrate inosine, but the Vmax values were comparable, 96% and 35% that for Ino. The pseudo first-order rate constants, Vmax/Km, were 1.1% and 2.5% for the calf spleen and E. coli enzymes. The aglycon, nicotinamide, was neither a substrate nor an inhibitor of PNP. Nir was a weak inhibitor of inosine phosphorolysis catalyzed by both enzymes, with Ki values close to the Km for its phosphorolysis, consistent with simple competitive inhibition; this was further confirmed by Dixon plots. Phosphorolysis of the fluorescent positively charged substrate 7-methylguanosine was also inhibited in a competitive manner by both Ino and Nir. Phosphorolysis of Nir by both enzymes was inhibited competitively by several specific inhibitors of calf spleen and E. coli PNP, with Ki values similar to those for inhibition of other natural substrates. The pH dependence of the kinetic constants for the phosphorolysis of Nir and of a variety of other substrates, was extensively investigated, particularly in the alkaline pH range, where Nir exhibited abnormally high substrate activity relative to the reduced reaction rates of both enzymes towards other anionic or neutral substrates. The overall results are discussed in relation to present concepts regarding binding and phosphorolysis of substrates by PNP based on crystallographic data of enzyme-inhibitor complexes, and current studies on enzymatic and nonenzymatic mechanisms of the cleavage of the Nir glycosidic bond.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23815368','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23815368"><span>Hydrogen bond donors accelerate vibrational cooling of hot <span class="hlt">purine</span> derivatives in heavy water.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Zhang, Yuyuan; Chen, Jinquan; Kohler, Bern</p> <p>2013-08-08</p> <p>Natural nucleobases and many of their derivatives have ultrashort excited state lifetimes that make them excellent model systems for studying intermolecular energy flow from a hot solute molecule to the solvent. UV-pump/broadband-mid-IR-probe transient absorption spectra of canonical <span class="hlt">purine</span> nucleobases and several xanthine derivatives were acquired in D2O and acetonitrile in the probe frequency range of 1500-1750 cm(-1). The spectra reveal that vibrationally hot ground state molecules created by ultrafast internal conversion return to thermal equilibrium in several picoseconds by dissipating their excess energy to solvent molecules. In acetonitrile solution, where hydrogen bonding is minimal, vibrational cooling (VC) occurs with the same time constant of 10 ± 3 ps for paraxanthine, theophylline, and caffeine within experimental uncertainty. In D2O, VC by these molecules occurs more rapidly and at different rates that are correlated with the number of N-D bonds. Hypoxanthine has a VC time constant of 3 ± 1 ps, while similar lifetimes of 2.3 ± 0.8 ps and 3.1 ± 0.3 ps are seen for 5'-adenosine monophosphate and 5'-guanosine monophosphate, respectively. All three molecules have at least two N-D bonds. Slightly slower VC time constants are measured for paraxanthine (4 ± 1 ps) and theophylline (5.1 ± 0.8 ps), dimethylated xanthines that have only one N-D bond. Caffeine, a trimethylated xanthine with no N-D bonds, has a VC time constant of 7.7 ± 0.9 ps, the longest ever observed for any nucleobase in aqueous solution. Hydrogen bond donation by solute molecules is proposed to enable rapid energy disposal to water via direct coupling of high frequency solute-solvent modes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1019610','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1019610"><span>Four Generations of Transition State Analogues for Human <span class="hlt">Purine</span> Nucleoside Phosphorylase</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Ho, M.; Shi, W; Rinaldo-Mathis, A; Tyler, P; Evans, G; Almo, S; Schramm, V</p> <p>2010-01-01</p> <p>Inhibition of human <span class="hlt">purine</span> nucleoside phosphorylase (PNP) stops growth of activated T-cells and the formation of 6-oxypurine bases, making it a target for leukemia, autoimmune disorders, and gout. Four generations of ribocation transition-state mimics bound to PNP are structurally characterized. Immucillin-H (K*{sub i} = 58 pM, first-generation) contains an iminoribitol cation with four asymmetric carbons. DADMe-Immucillin-H (K*{sub i} = 9 pM, second-generation), uses a methylene-bridged dihydroxypyrrolidine cation with two asymmetric centers. DATMe-Immucillin-H (K*{sub i} = 9 pM, third-generation) contains an open-chain amino alcohol cation with two asymmetric carbons. SerMe-ImmH (K*{sub i} = 5 pM, fourth-generation) uses achiral dihydroxyaminoalcohol seramide as the ribocation mimic. Crystal structures of PNPs establish features of tight binding to be; (1) ion-pair formation between bound phosphate (or its mimic) and inhibitor cation, (2) leaving-group interactions to N1, O6, and N7 of 9-deazahypoxanthine, (3) interaction between phosphate and inhibitor hydroxyl groups, and (4) His257 interacting with the 5{prime}-hydroxyl group. The first generation analogue is an imperfect fit to the catalytic site with a long ion pair distance between the iminoribitol and bound phosphate and weaker interactions to the leaving group. Increasing the ribocation to leaving-group distance in the second- to fourth-generation analogues provides powerful binding interactions and a facile synthetic route to powerful inhibitors. Despite chemical diversity in the four generations of transition-state analogues, the catalytic site geometry is almost the same for all analogues. Multiple solutions in transition-state analogue design are available to convert the energy of catalytic rate enhancement to binding energy in human PNP.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4175147','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4175147"><span><span class="hlt">Purines</span> in the eye: recent evidence for the physiological and pathological role of <span class="hlt">purines</span> in the RPE, retinal neurons, astrocytes, Müller cells, lens, trabecular meshwork, cornea and lacrimal gland</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Sanderson, Julie; Dartt, Darlene A.; Trinkaus-Randall, Vickery; Pintor, Jesus; Civan, Mortimer M.; Delamere, Nicholas A.; Fletcher, Erica L.; Salt, Thomas E.; Grosche, Antje; Mitchell, Claire H.</p> <p>2014-01-01</p> <p>This review highlights recent findings that describe how <span class="hlt">purines</span> modulate the physiological and pathophysiological responses of ocular tissues. For example, in lacrimal glands the cross-talk between P2X7 receptors and both M3 muscarinic receptors and α1D-adrenergic receptors can influence tear secretion. In the cornea, <span class="hlt">purines</span> lead to post-translational modification of EGFR and structural proteins that participate in wound repair in the epithelium and influence the expression of matrix proteins in the stroma. <span class="hlt">Purines</span> act at receptors on both the trabecular meshwork and ciliary epithelium to modulate intraocular pressure (IOP); ATP-release pathways of inflow and outflow cells differ, possibly permitting differential modulation of adenosine delivery. Modulators of trabecular meshwork cell ATP release include cell volume, stretch, extracellular Ca2+ concentration, oxidation state, actin remodeling and possibly endogenous cardiotonic steroids. In the lens, osmotic stress leads to ATP release following TRPV4 activation upstream of hemichannel opening. In the anterior eye, diadenosine polyphosphates such as Ap4A act at P2 receptors to modulate the rate and composition of tear secretion, impact corneal wound healing and lower IOP. The Gq11-coupled P2Y1-receptor contributes to volume control in Müller cells and thus the retina. P2X receptors are expressed in neurons in the inner and outer retina and contribute to visual processing as well as the demise of retinal ganglion cells. In RPE cells, the balance between extracellular ATP and adenosine may modulate lysosomal pH and the rate of lipofuscin formation. In optic nerve head astrocytes, mechanosensitive ATP release via pannexin hemichannels, coupled with stretch-dependent upregulation of pannexins, provides a mechanism for ATP signaling in chronic glaucoma. With so many receptors linked to divergent functions throughout the eye, ensuring the transmitters remain local and stimulation is restricted to the intended target</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830057389&hterms=negative+DNA&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnegative%2BDNA','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830057389&hterms=negative+DNA&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Dnegative%2BDNA"><span>Negatively supercoiled simian virus 40 DNA contains Z-DNA segments within transcriptional enhancer <span class="hlt">sequences</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nordheim, A.; Rich, A.</p> <p>1983-01-01</p> <p>Three 8-base pair (bp) segments of alternating <span class="hlt">purine</span>-pyrimidine from the simian virus 40 enhancer region form Z-DNA on negative supercoiling; minichromosome DNase I-hypersensitive sites determined by others bracket these three segments. A survey of transcriptional enhancer <span class="hlt">sequences</span> reveals a pattern of potential Z-DNA-forming regions which occur in pairs 50-80 bp apart. This may influence local chromatin structure and may be related to transcriptional activation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19830057389&hterms=kidney+cancer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dkidney%2Bcancer','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19830057389&hterms=kidney+cancer&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dkidney%2Bcancer"><span>Negatively supercoiled simian virus 40 DNA contains Z-DNA segments within transcriptional enhancer <span class="hlt">sequences</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Nordheim, A.; Rich, A.</p> <p>1983-01-01</p> <p>Three 8-base pair (bp) segments of alternating <span class="hlt">purine</span>-pyrimidine from the simian virus 40 enhancer region form Z-DNA on negative supercoiling; minichromosome DNase I-hypersensitive sites determined by others bracket these three segments. A survey of transcriptional enhancer <span class="hlt">sequences</span> reveals a pattern of potential Z-DNA-forming regions which occur in pairs 50-80 bp apart. This may influence local chromatin structure and may be related to transcriptional activation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28662952','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28662952"><span>Vaccination against histomonosis limits <span class="hlt">pronounced</span> changes of B cells and T-cell subsets in turkeys and chickens.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Mitra, Taniya; Gerner, Wilhelm; Kidane, Fana Alem; Wernsdorf, Patricia; Hess, Michael; Saalmüller, Armin; Liebhart, Dieter</p> <p>2017-07-24</p> <p>The protozoan parasite Histomonas meleagridis is the causative agent of histomonosis in gallinaceous birds. In turkeys, the disease can result in high mortality due to severe inflammation and necrosis in caecum and liver, whereas in chickens the disease is less severe. Recently, experimental vaccination was shown to protect chickens and turkeys against histomonosis but dynamics in the cellular immune response are not yet demonstrated. In the present work, different groups of birds of both species were vaccinated with attenuated, and/or infected with virulent histomonads. Flow cytometry was applied at different days post inoculation to analyse the absolute number of T-cell subsets and B cells in caecum, liver, spleen and blood, in order to monitor changes in these major lymphocyte subsets. In addition, in chicken samples total white blood cells were investigated. Infected turkeys showed a significant decrease of T cells in the caecum within one week post infection compared to control birds, whereas vaccination showed delayed changes. The challenge of vaccinated turkeys led to a significant increase of all investigated lymphocytes in the blood already at 4 DPI, indicating an effective and fast recall response of the primed immune system. In the caecum of chickens, changes of B cells, CD4(+) and CD8α(+) T cells were much less <span class="hlt">pronounced</span> than in turkeys, however, mostly caused by virulent histomonads. Analyses of whole blood in non-vaccinated but infected chickens revealed increasing numbers of monocytes/macrophages on all sampling days, whereas a decrease of heterophils was observed directly after challenge, suggesting recruitment of this cell population to the local site of infection. Our results showed that virulent histomonads caused more severe changes in the distribution of lymphocyte subsets in turkeys compared to chickens. Moreover, vaccination with attenuated histomonads resulted in less <span class="hlt">pronounced</span> alterations in both species, even after challenge. Copyright</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMPP51B1132C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMPP51B1132C"><span><span class="hlt">Pronounced</span> Climatic and Environmental Changes in the South West Pacific Ocean Following the End-Cretaceous Extinction Event</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Crouch, E. M.; Taylor, K. W.; Willumsen, P. S.; Hollis, C. J.; Pancost, R. D.</p> <p>2014-12-01</p> <p>Dinoflagellate cyst assemblages from Cretaceous/Paleogene (K/Pg) boundary sections in eastern New Zealand record an alternating succession of <span class="hlt">pronounced</span> abundance changes in two peridinioid (primarily heterotrophic) genera following the K/Pg boundary event. In Canterbury and East Coast Basin sections, two phases of abundant Trithyrodinium evittii, the first immediately following the K/Pg boundary, are interposed by two acme intervals of Palaeoperidinium pyrophorum. While several lines of evidence suggest T. evittii was a warm-water species and P. pyrophorum flourished in cooler oceanic conditions, robust temperature records have not been available from these K/Pg boundary sections. We have completed sea surface temperature (SST) reconstructions, based on glycerol dialkyl glycerol tetraether (GDGT) distributions, at mid-Waipara River, North Canterbury, from ~1 m below to 20 m above the K/Pg boundary. Changes in GDGT distribution across the K/Pg boundary indicates warming of 2-3°C, regardless of which TEX86-based proxy is used, coincident with the interval of abundant T. evittii. Detailed climatic records at the K/Pg boundary layer are hampered by intense bioturbation. Above an unconformity (at 23 cm) notable shifts in GDGT distribution indicates <span class="hlt">pronounced</span> cooling, yielding SST estimates that are 7°C lower than the uppermost Cretaceous. The acme of P. pyrophorum corresponds with these cooler SSTs, and an unusual increase in the proportion of GDGT-2 in this interval can be attributed to cool water upwelling. The P. pyrophorum acme is also documented in distal diatom-rich siliceous sediments in Marlborough, where siliceous microfossils and element geochemistry indicate cool-water upwelling in the basal Paleocene. The second phase of abundant T. evittii, at ~2 m in Waipara, coincides with an interval of more stable SSTs that are comparable to the uppermost Cretaceous. Further discussion of the TEX86-based SST proxy and GDGT distributions will be provided in the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21127361','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21127361"><span>More <span class="hlt">pronounced</span> diastolic left ventricular dysfunction in patients with accelerated idioventricular rhythm after reperfusion by primary percutaneous coronary intervention.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Remmelink, Maurice; Delewi, Ronak; Yong, Ze Yie; Piek, Jan J; Baan, Jan</p> <p>2010-12-01</p> <p>Reperfusion-induced accelerated idioventricular rhythm (AIVR) during primary percutaneous coronary intervention (pPCI) may be a sign of left ventricular (LV) dysfunction. We compared LV dynamic effects of reperfusion between patients with and without reperfusion-induced AIVR during pPCI for ST-elevation myocardial infarction (STEMI). We studied 15 consecutive patients, who presented with their first acute anterior STEMI within 6 hours after onset of symptoms, and in whom LV pressure-volume (PV) loops were directly obtained during pPCI. Immediate effects of pPCI on LV function were compared between patients with (n = 5) and without (n = 10) occurrence of AIVR after reperfusion, as well as the direct effects of AIVR on LV function compared to sinus rhythm. Patients with reperfusion-induced AIVR showed more <span class="hlt">pronounced</span> diastolic LV dysfunction before the onset of the arrhythmia, i.e., a delayed active relaxation expressed by Tau (53 ± 15 vs. 39 ± 6 ms; p = 0.03), a worse compliance curve (p = 0.01), and a higher end-diastolic stiffness (p = 0.07). At the end of the procedure, AIVR patients showed less improvement in diastolic LV function, indicated by a downward shift of the compliance curve (-3.1 ± 2.3 vs. -7.5 ± 1.4 mmHg; p = 0.001), a decrease in end-diastolic stiffness (13 ± 18 vs. 34 ± 15%; p = 0.03) and end-diastolic pressure (12 ± 8 vs. 29 ± 19%; p = 0.07). STEMI patients with reperfusion-induced AIVR after pPCI showed more <span class="hlt">pronounced</span> diastolic LV dysfunction before and after AIVR than patients without AIVR, which suggests that diastolic LV dysfunction contributes to the occurrence of AIVR and that AIVR is a sign of diastolic LV dysfunction.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/9951733','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/9951733"><span><span class="hlt">Pronounced</span> differences between the native K+ channels and KAT1 and KST1 alpha-subunit homomers of guard cells.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brüggemann, L; Dietrich, P; Dreyer, I; Hedrich, R</p> <p>1999-01-01</p> <p>Stomatal opening is the result of K(+)-salt accumulation in guard cells. Potassium uptake in these motor cells is mediated by voltage-dependent, K(+)-selective ion channels. Here we compare the invitro properties of two guard-cell K(+)-channel alpha-subunits from Arabidopsis thaliana (L.) Heynh. (KAT1) and Solanum tuberosum L. (KST1) after heterologous expression with the respective K(+)-transport characteristics in their mother cell. The KAT1 and KST1 subunits when expressed in Xenopus oocytes shared the basic features of the K(+)-uptake channels in the corresponding guard cells, including voltage dependence and single-channel conductance. Besides these similarities, the electrophysiological comparison of K+ channels in the homologous and the heterologous expression systems revealed <span class="hlt">pronounced</span> differences with respect to modulation and block by extracellular cations. In the presence of 1 mM Cs+, 50% of the guard-cell K(+)-uptake channels (GCKClin) in A. thaliana and S. tuberosum, were inhibited upon hyperpolarization to -90 mV. For a similar effect on KAT1 and KST1 in oocytes, voltages as negative as -155 mV were required. In contrast, compared to the K+ channels in vivo the functional alpha-subunit homomers almost lacked a voltage-dependent block by extracellular Ca2+. Similar to the block by Cs+ and Ca2+, the acid activation of the alpha-homomers was less <span class="hlt">pronounced</span> in oocytes. Upon acidification the voltage-dependence shifted by 82 and 90 mV for GCKCLin in A. thaliana and S. tuberosum, respectively, but only by 25 mV for KAT1 and KST1. From the differences in K(+)-channel modulation in vivo and after heterologous expression we conclude that the properties of functional guard-cell K(+)-uptake channels result either from the heterometric assembly of different alpha-subunits or evolve from cell-type specific posttranslational modification.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/10567244','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/10567244"><span>Design of an adenosine phosphorylase by active-site modification of murine <span class="hlt">purine</span> nucleoside phosphorylase. Enzyme kinetics and molecular dynamics simulation of Asn-243 and Lys-244 substitutions of <span class="hlt">purine</span> nucleoside phosphorylase.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Maynes, J T; Yam, W; Jenuth, J P; Gang Yuan, R; Litster, S A; Phipps, B M; Snyder, F F</p> <p>1999-12-01</p> <p>Our objective was to alter the substrate specificity of <span class="hlt">purine</span> nucleoside phosphorylase such that it would catalyse the phosphorolysis of 6-aminopurine nucleosides. We modified both Asn-243 and Lys-244 in order to promote the acceptance of the C6-amino group of adenosine. The Asn-243-Asp substitution resulted in an 8-fold increase in K(m) for inosine from 58 to 484 microM and a 1000-fold decrease in k(cat)/K(m). The Asn-243-Asp construct catalysed the phosphorolysis of adenosine with a K(m) of 45 microM and a k(cat)/K(m) 8-fold that with inosine. The Lys-244-Gln construct showed only marginal reduction in k(cat)/K(m), 83% of wild type, but had no activity with adenosine. The Asn-243-Asp;Lys-244-Gln construct had a 14-fold increase in K(m) with inosine and 7-fold decrease in k(cat)/K(m) as compared to wild type. This double substitution catalysed the phosphorolysis of adenosine with a K(m) of 42 microM and a k(cat)/K(m) twice that of the single Asn-243-Asp substitution. Molecular dynamics simulation of the engineered proteins with adenine as substrate revealed favourable hydrogen bond distances between N7 of the <span class="hlt">purine</span> ring and the Asp-243 carboxylate at 2.93 and 2.88 A, for Asn-243-Asp and the Asn-243-Asp;Lys-244-Gln constructs respectively. Simulation also supported a favourable hydrogen bond distance between the <span class="hlt">purine</span> C6-amino group and Asp-243 at 2.83 and 2.88 A for each construct respectively. The Asn-243-Thr substitution did not yield activity with adenosine and simulation gave unfavourable hydrogen bond distances between Thr-243 and both the C6-amino group and N7 of the <span class="hlt">purine</span> ring. The substitutions were not in the region of phosphate binding and the apparent S(0.5) for phosphate with wild type and the Asn-243-Asp enzymes were 1.35+/-0.01 and 1.84+/-0.06 mM, respectively. Both proteins exhibited positive co-operativity with phosphate giving Hill coefficients of 7.9 and 3.8 respectively.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1220679','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1220679"><span>Design of an adenosine phosphorylase by active-site modification of murine <span class="hlt">purine</span> nucleoside phosphorylase. Enzyme kinetics and molecular dynamics simulation of Asn-243 and Lys-244 substitutions of <span class="hlt">purine</span> nucleoside phosphorylase.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Maynes, J T; Yam, W; Jenuth, J P; Gang Yuan, R; Litster, S A; Phipps, B M; Snyder, F F</p> <p>1999-01-01</p> <p>Our objective was to alter the substrate specificity of <span class="hlt">purine</span> nucleoside phosphorylase such that it would catalyse the phosphorolysis of 6-aminopurine nucleosides. We modified both Asn-243 and Lys-244 in order to promote the acceptance of the C6-amino group of adenosine. The Asn-243-Asp substitution resulted in an 8-fold increase in K(m) for inosine from 58 to 484 microM and a 1000-fold decrease in k(cat)/K(m). The Asn-243-Asp construct catalysed the phosphorolysis of adenosine with a K(m) of 45 microM and a k(cat)/K(m) 8-fold that with inosine. The Lys-244-Gln construct showed only marginal reduction in k(cat)/K(m), 83% of wild type, but had no activity with adenosine. The Asn-243-Asp;Lys-244-Gln construct had a 14-fold increase in K(m) with inosine and 7-fold decrease in k(cat)/K(m) as compared to wild type. This double substitution catalysed the phosphorolysis of adenosine with a K(m) of 42 microM and a k(cat)/K(m) twice that of the single Asn-243-Asp substitution. Molecular dynamics simulation of the engineered proteins with adenine as substrate revealed favourable hydrogen bond distances between N7 of the <span class="hlt">purine</span> ring and the Asp-243 carboxylate at 2.93 and 2.88 A, for Asn-243-Asp and the Asn-243-Asp;Lys-244-Gln constructs respectively. Simulation also supported a favourable hydrogen bond distance between the <span class="hlt">purine</span> C6-amino group and Asp-243 at 2.83 and 2.88 A for each construct respectively. The Asn-243-Thr substitution did not yield activity with adenosine and simulation gave unfavourable hydrogen bond distances between Thr-243 and both the C6-amino group and N7 of the <span class="hlt">purine</span> ring. The substitutions were not in the region of phosphate binding and the apparent S(0.5) for phosphate with wild type and the Asn-243-Asp enzymes were 1.35+/-0.01 and 1.84+/-0.06 mM, respectively. Both proteins exhibited positive co-operativity with phosphate giving Hill coefficients of 7.9 and 3.8 respectively. PMID:10567244</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3367216','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3367216"><span><span class="hlt">Sequence</span> dependence of isothermal DNA amplification via EXPAR</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Qian, Jifeng; Ferguson, Tanya M.; Shinde, Deepali N.; Ramírez-Borrero, Alissa J.; Hintze, Arend; Adami, Christoph; Niemz, Angelika</p> <p>2012-01-01</p> <p>Isothermal nucleic acid amplification is becoming increasingly important for molecular diagnostics. Therefore, new computational tools are needed to facilitate assay design. In the isothermal EXPonential Amplification Reaction (EXPAR), template <span class="hlt">sequences</span> with similar thermodynamic characteristics perform very differently. To understand what causes this variability, we characterized the performance of 384 template <span class="hlt">sequences</span>, and used this data to develop two computational methods to predict EXPAR template performance based on <span class="hlt">sequence</span>: a position weight matrix approach with support vector machine classifier, and RELIEF attribute evaluation with Naïve Bayes classification. The methods identified well and poorly performing EXPAR templates with 67–70% sensitivity and 77–80% specificity. We combined these methods into a computational tool that can accelerate new assay design by ruling out likely poor performers. Furthermore, our data suggest that variability in template performance is linked to specific <span class="hlt">sequence</span> motifs. Cytidine, a pyrimidine base, is over-represented in certain positions of well-performing templates. Guanosine and adenosine, both <span class="hlt">purine</span> bases, are over-represented in similar regions of poorly performing templates, frequently as GA or AG dimers. Since polymerases have a higher affinity for <span class="hlt">purine</span> oligonucleotides, polymerase binding to GA-rich regions of a single-stranded DNA template may promote non-specific amplification in EXPAR and other nucleic acid amplification reactions. PMID:22416064</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AsBio..17..771B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AsBio..17..771B"><span>Mechanisms of the Formation of Adenine, Guanine, and Their Analogues in UV-Irradiated Mixed NH3:H2O Molecular Ices Containing <span class="hlt">Purine</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bera, Partha P.; Stein, Tamar; Head-Gordon, Martin; Lee, Timothy J.</p> <p>2017-08-01</p> <p>We investigated the formation mechanisms of the nucleobases adenine and guanine and the nucleobase analogues hypoxanthine, xanthine, isoguanine, and 2,6-diaminopurine in a UV-irradiated mixed 10:1 H2O:NH3 ice seeded with precursor <span class="hlt">purine</span> by using ab initio and density functional theory computations. Our quantum chemical investigations suggest that a multistep reaction mechanism involving <span class="hlt">purine</span> cation, hydroxyl and amino radicals, together with water and ammonia, explains the experimentally obtained products in an independent study. The relative abundances of these products appear to largely follow from relative thermodynamic stabilities. The key role of the <span class="hlt">purine</span> cation is likely to be the reason why <span class="hlt">purine</span> is not functionalized in pure ammonia ice, where cations are promptly neutralized by free electrons from NH3 ionization. Amine group addition to <span class="hlt">purine</span> is slightly favored over hydroxyl group attachment based on energetics, but hydroxyl is much more abundant due to higher abundance of H2O. The amino group is preferentially attached to the 6 position, giving 6-aminopurine, that is, adenine, while the hydroxyl group is preferentially attached to the 2 position, leading to 2-hydroxypurine. A second substitution by hydroxyl or amino group occurs at either the 6 or the 2 position depending on the first substitution. Given that H2O is far more abundant than NH3 in the experimentally studied ices (as well as based on interstellar abundances), xanthine and isoguanine are expected to be the most abundant bi-substituted photoproducts.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2071872','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=2071872"><span>The effects of morphine and methionine-enkephalin on the release of <span class="hlt">purines</span> from cerebral cortex slices of rats and mice.</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Stone, T. W.</p> <p>1981-01-01</p> <p>1 Slices of cerebral cortex from Wistar rats, TO mice or C57 mice were preincubated with [3H]-adenosine, and labelled <span class="hlt">purines</span> were subsequently releases by electrical stimulation or by perfusing with ouabain, 100 micro M. 2 Electrically-evoked <span class="hlt">purine</span> release was substantially reduced when the Ca2+ concentration in the medium was lowered from 2.4 to 0.1 mM. In both rats and mice, the electrically-evoked release was increased by morphine and methionine-enkephalin (Met-enkephalin), 10 micro M, and in rats and TO mice by morphine 1 micro M, both drug effects being prevented by naloxone. 3 <span class="hlt">Purine</span> release evoked by ouabain was also increased by morphine 1 and 10 micro M, though not by Met-enkephalin, from slices of rat cortex. Ouabain-induced release from TO mice was reduced by morphine, and from C57 mice was unchanged. 4 The enhancement by morphine of electrically-evoked <span class="hlt">purine</span> release may indicate that <span class="hlt">purines</span> mediate some effects of morphine in the CNS. PMID:7272599</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3850210','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3850210"><span>Structure and Function of Nucleoside Hydrolases from Physcomitrella patens and Maize Catalyzing the Hydrolysis of <span class="hlt">Purine</span>, Pyrimidine, and Cytokinin Ribosides1[W</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kopečná, Martina; Blaschke, Hanna; Kopečný, David; Vigouroux, Armelle; Končitíková, Radka; Novák, Ondřej; Kotland, Ondřej; Strnad, Miroslav; Moréra, Solange; von Schwartzenberg, Klaus</p> <p>2013-01-01</p> <p>We present a comprehensive characterization of the nucleoside N-ribohydrolase (NRH) family in two model plants, Physcomitrella patens (PpNRH) and maize (Zea mays; ZmNRH), using in vitro and in planta approaches. We identified two NRH subclasses in the plant kingdom; one preferentially targets the <span class="hlt">purine</span> ribosides inosine and xanthosine, while the other is more active toward uridine and xanthosine. Both subclasses can hydrolyze plant hormones such as cytokinin ribosides. We also solved the crystal structures of two <span class="hlt">purine</span> NRHs, PpNRH1 and ZmNRH3. Structural analyses, site-directed mutagenesis experiments, and phylogenetic studies were conducted to identify the residues responsible for the observed differences in substrate specificity between the NRH isoforms. The presence of a tyrosine at position 249 (PpNRH1 numbering) confers high hydrolase activity for <span class="hlt">purine</span> ribosides, while an aspartate residue in this position confers high activity for uridine. Bud formation is delayed by knocking out single NRH genes in P. patens, and under conditions of nitrogen shortage, PpNRH1-deficient plants cannot salvage adenosine-bound nitrogen. All PpNRH knockout plants display elevated levels of certain <span class="hlt">purine</span> and pyrimidine ribosides and cytokinins that reflect the substrate preferences of the knocked out enzymes. NRH enzymes thus have functions in cytokinin conversion and activation as well as in <span class="hlt">purine</span> and pyrimidine metabolism. PMID:24170203</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19570845','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19570845"><span>Zebrafish mutations in gart and paics identify crucial roles for de novo <span class="hlt">purine</span> synthesis in vertebrate pigmentation and ocular development.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ng, Anthony; Uribe, Rosa A; Yieh, Leah; Nuckels, Richard; Gross, Jeffrey M</p> <p>2009-08-01</p> <p>Although <span class="hlt">purines</span> and purinergic signaling are crucial for numerous biochemical and cellular processes, their functions during vertebrate embryonic development have not been well characterized. We analyze two recessive zebrafish mutations that affect de novo <span class="hlt">purine</span> synthesis, gart and paics. gart encodes phosphoribosylglycinamide formyltransferase, phosphoribosylglycinamide synthetase, phosphoribosylaminoimidazole synthetase, a trifunctional enzyme that catalyzes steps 2, 3 and 5 of inosine monophosphate (IMP) synthesis. paics encodes phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase, a bifunctional enzyme that catalyzes steps 6 and 7 of this process. Zygotic gart and paics mutants have pigmentation defects in which xanthophore and iridophore pigmentation is almost completely absent, and melanin-derived pigmentation is significantly decreased, even though pigment cells are present in normal amounts and distributions. Zygotic gart and paics mutants are also microphthalmic, resulting from defects in cell cycle exit of proliferative retinoblasts within the developing eye. Maternal-zygotic and maternal-effect mutants demonstrate a crucial requirement for maternally derived gart and paics; these mutants show more severe developmental defects than their zygotic counterparts. Pigmentation and eye growth phenotypes in zygotic gart and paics mutants can be ascribed to separable biosynthetic pathways: pigmentation defects and microphthalmia result from deficiencies in a GTP synthesis pathway and an ATP synthesis pathway, respectively. In the absence of ATP pathway activity, S phase of proliferative retinoblasts is prolonged and cell cycle exit is compromised, which results in microphthalmia. These results demonstrate crucial maternal and zygotic requirements for de novo <span class="hlt">purine</span> synthesis during vertebrate embryonic development, and identify independent functions for ATP and GTP pathways in mediating eye growth and pigmentation</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23383496','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23383496"><span>[Separation of <span class="hlt">purines</span>, pyrimidines, pterins and flavonoids on magnolol-bonded silica gel stationary phase by high performance liquid chromatography].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Chen, Hong; Li, Laishen; Zhang, Yang; Zhou, Rendan</p> <p>2012-10-01</p> <p>A new magnolol-bonded silica gel stationary phase (MSP) was used to separate the basic drugs including four <span class="hlt">purines</span>, eight pyrimidines, four pterins and five flavonoids as polar representative samples by high performance liquid chromatography (HPLC). To clarify the separation mechanism, a commercial ODS column was also tested under the same chromatographic conditions. The high selectivities and fast baseline separations of the above drugs were achieved by using simple mobile phases on MSP. Although there is no end-caped treatment, the peak shapes of basic drugs containing nitrogen such as <span class="hlt">purines</span>, pyrimidines and pterins were rather symmetrical on MSP, which indicated the the magnolol as ligand with multi-sites could shield the side effect of residual silanol groups on the surface of silica gel. Although somewhat different in the separation resolution, it was found that the elution orders of some drugs were generally similar on both MSP and ODS. The hydrophobic interaction should play a significant role in the separations of the above basic drugs, which was attributed to their reversed-phase property in the nature. However, MSP could provide the additional sites for many polar solutes, which was a rational explanation for the high selectivity of MSP. For example, in the separation of <span class="hlt">purines</span>, pyrimidines and pterins on MSP, hydrogen-bonding and dipole-dipole interactions played leading roles besides hydrophobic interaction. Some solute molecules (such as mercaptopurine, vitexicarpin) and MSP can form the strong pi-pi stacking in the separation process. All enhanced the retention and improved the separation selectivity of MSP, which facilitated the separation of the basic drugs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27879715','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27879715"><span>Study of Copper and <span class="hlt">Purine</span>-Copper Complexes on Modified Carbon Electrodes by Cyclic and Elimination Voltammetry.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Trnkova, Libuse; Zerzankova, Lenka; Dycka, Filip; Mikelova, Radka; Jelen, Frantisek</p> <p>2008-01-24</p> <p>Using a paraffin impregnated graphite electrode (PIGE) and mercury-modifiedpyrolytic graphite electrode with basal orientation (Hg-PGEb) copper(II) and Cu(II)-DNApurine base solutions have been studied by cyclic (CV) and linear sweep voltammetry(LSV) in connection with elimination voltammetry with linear scan (EVLS). In chlorideand bromide solutions (pH 6), the redox process of Cu(II) proceeded on PIGE with twocathodic and two anodic potentially separated signals. According to the eliminationfunction E4, the first cathodic peak corresponds to the reduction Cu(II) e⁻ → Cu(I) withthe possibility of fast disproportionation 2Cu(I) → Cu(II) Cu(0). The E4 of the secondcathodic peak signalized an electrode process controlled by a surface reaction. Theelectrode system of Cu(II) on Hg-PGEb in borate buffer (pH 9.2) was characterized by onecathodic and one anodic peak. Anodic stripping voltammetry (ASV) on PIGE and cathodicstripping voltammetry (CSV) on Hg-PGEb were carried out at potentials where thereduction of copper ions took place and Cu(I)-<span class="hlt">purine</span> complexes were formed. By usingASV and CSV in combination with EVLS, the sensitivity of Cu(I)-<span class="hlt">purine</span> complexdetection was enhanced relative to either ASV or CSV alone, resulting in higher peakcurrents of more than one order of magnitude. The statistical treatment of CE data wasused to determine the reproducibility of measurements. Our results show that EVLS inconnection with the stripping procedure is useful for both qualitative and quantitativemicroanalysis of <span class="hlt">purine</span> derivatives and can also reveal details of studied electrodeprocesses.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23665623','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23665623"><span>A simple HPLC method for determining the <span class="hlt">purine</span> content of beer and beer-like alcoholic beverages.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fukuuchi, Tomoko; Yasuda, Makoto; Inazawa, Katsunori; Ota, Tatsuhiro; Yamaoka, Noriko; Mawatari, Ken-ichi; Nakagomi, Kazuya; Kaneko, Kiyoko</p> <p>2013-01-01</p> <p>Several methods for quantifying the <span class="hlt">purine</span> content in food and drink have been described using high-performance liquid chromatography (HPLC). We have developed an improved HPLC method that is based on a method reported by Kaneko et al. and that is more sensitive yet simple, and suitable for determining the <span class="hlt">purine</span> content of beer and beer-like alcoholic beverages. Quantitative HPLC separation was performed on a Shodex Asahi Pak GS-320HQ column with an isocratic elution of 150 mmol/L sodium phosphate buffer (H(3)PO(4)/NaH(2)PO(4) = 20:100 (v/v)). The retention times for the four analytes, namely, adenine, guanine, hypoxanthine and xanthine, were 19.9, 25.0, 29.3 and 43.0 min, respectively. The resolution was good, and there was no excessive interference from the other compounds in the beverages at these retention times. Furthermore, the detection limit for all the analytes was improved to less than 0.0075 mg/L, and all the calibration curves showed good linearity (r(2) > 0.999) between 0.013 and 10 mg/L for adenine and guanine, and between 0.025 and 10 mg/L for hypoxanthine and xanthine. The pretreatment was simplified by removing some procedures and optimizing the perchloric acid hydrolysis and the enzymatic peak-shift assay. We reduced the sample dilution rate by almost 50%, and the time spent on pretreatment from 4 days to only 180 min. The recovery of the analytes from spiked samples was 94.8 - 103.8%. This method may be useful for evaluating quantitative and qualitative differences in the <span class="hlt">purine</span> content of beer and beer-like alcoholic beverages.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/11032837','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/11032837"><span>Molecular identification and characterization of novel human and mouse concentrative Na+-nucleoside cotransporter proteins (hCNT3 and mCNT3) broadly selective for <span class="hlt">purine</span> and pyrimidine nucleosides (system cib).</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Ritzel, M W; Ng, A M; Yao, S Y; Graham, K; Loewen, S K; Smith, K M; Ritzel, R G; Mowles, D A; Carpenter, P; Chen, X Z; Karpinski, E; Hyde, R J; Baldwin, S A; Cass, C E; Young, J D</p> <p>2001-01-26</p> <p>The human concentrative (Na(+)-linked) plasma membrane transport proteins hCNT1 and hCNT2 are selective for pyrimidine nucleosides (system cit) and <span class="hlt">purine</span> nucleosides (system cif), respectively. Both have homologs in other mammalian species and belong to a gene family (CNT) that also includes hfCNT, a newly identified broad specificity pyrimidine and <span class="hlt">purine</span> Na(+)-nucleoside symporter (system cib) from the ancient marine vertebrate, the Pacific hagfish (Eptatretus stouti). We now report the cDNA cloning and characterization of cib homologs of hfCNT from human mammary gland, differentiated human myeloid HL-60 cells, and mouse liver. The 691- and 703-residue human and mouse proteins, designated hCNT3 and mCNT3, respectively, were 79% identical in amino acid <span class="hlt">sequence</span> and contained 13 putative transmembrane helices. hCNT3 was 48, 47, and 57% identical to hCNT1, hCNT2, and hfCNT, respectively. When produced in Xenopus oocytes, both proteins exhibited Na(+)-dependent cib-type functional activities. hCNT3 was electrogenic, and a sigmoidal dependence of uridine influx on Na(+) concentration indicated a Na(+):uridine coupling ratio of at least 2:1 for both hCNT3 and mCNT3 (cf 1:1 for hCNT1/2). Phorbol myristate acetate-induced differentiation of HL-60 cells led to the parallel appearance of cib-type activity and hCNT3 mRNA. Tissues containing hCNT3 transcripts included pancreas, bone marrow, trachea, mammary gland, liver, prostate, and regions of intestine, brain, and heart. The hCNT3 gene mapped to chromosome 9q22.2 and included an upstream phorbol myristate acetate response element.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014CPL...597...69Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014CPL...597...69Z"><span>Hetero-ring-expansion design for <span class="hlt">purine</span> analogs: A theoretical study on the structural, electronic, and excited-state properties</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zhang, Laibin; Zhou, Liuzhu; Tian, Jianxiang; Li, Xiaoming</p> <p>2014-03-01</p> <p>A series of hetero-ring-expanded <span class="hlt">purine</span> analogs are designed and their structural, electronic and excited-state properties are investigated by DFT calculations. The results indicate that the designed analogs can form stable base pairs with natural counterparts. Compared with natural ones, these size-expanded analogs and corresponding base pairs have smaller ionization potentials and HOMO-LUMO gaps. Furthermore, the A-analogs have ionization potentials even lower than natural G. Finally, the electronic absorption spectra are calculated and the nature of the low-lying excited states is discussed. These observations imply their promising applications as molecular wires and new DNA motifs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4493925','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4493925"><span>Methanocarba ring as a ribose modification in ligands of G protein-coupled <span class="hlt">purine</span> and pyrimidine receptors: synthetic approaches</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Tosh, Dilip K.</p> <p>2015-01-01</p> <p>Adenosine receptors (ARs) and P2Y receptors for <span class="hlt">purine</span> and pyrimidine nucleotides have widespread distribution and regulate countless physiological processes. Various synthetic ligands are in clinical trials for treatment of inflammatory diseases, pain, cancer, thrombosis, ischemia, and other conditions. The methanocarba (bicyclo[3.1.0]hexane) ring system as a rigid substitution for ribose, which maintains either a North (N) or South (S) conformation, tends to preserve or enhance the potency and/or selectivity for certain receptor subtypes. This review summarizes recent developments in the synthetic approaches to these biologically important nucleoside and nucleotide analogues. PMID:26161251</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_23 --> <div id="page_24" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li class="active"><span>24</span></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="461"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3150417','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3150417"><span><span class="hlt">Purine</span>-rich foods, protein intake, and the prevalence of hyperuricemia: The Shanghai Men’s Health Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Villegas, Raquel; Xiang, Yong-Bang; Elasy, Tom; Xu, Wang-Hong; Cai, Hui; Cai, Qiuyin; Linton, MacRae; Fazio, Sergio; Zheng, Wei; Shu, Xiao-Ou</p> <p>2011-01-01</p> <p>Background and Aims Diet may play an important role in the development of hyperuricemia and gout. However, the association between dietary factors and hyperuricemia remains unclear, and few studies have investigated direct links between food intake and hyperuricemia. The aim of this study was to investigate associations between high <span class="hlt">purine</span>-content foods and protein intake with the prevalence of hyperuricemia by using data from a cross-sectional study of 3,978 men aged 40–74 yrs living in Shanghai, China. PMID:21277179</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3481282','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3481282"><span>Modeling, Substrate Docking, and Mutational Analysis Identify Residues Essential for the Function and Specificity of a Eukaryotic <span class="hlt">Purine</span>-Cytosine NCS1 Transporter*</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Krypotou, Emilia; Kosti, Vasiliki; Amillis, Sotiris; Myrianthopoulos, Vassilios; Mikros, Emmanuel; Diallinas, George</p> <p>2012-01-01</p> <p>The recent elucidation of crystal structures of a bacterial member of the NCS1 family, the Mhp1 benzyl-hydantoin permease from Microbacterium liquefaciens, allowed us to construct and validate a three-dimensional model of the Aspergillus nidulans <span class="hlt">purine</span>-cytosine/H+ FcyB symporter. The model consists of 12 transmembrane α-helical, segments (TMSs) and cytoplasmic N- and C-tails. A distinct core of 10 TMSs is made of two intertwined inverted repeats (TMS1–5 and TMS6–10) that are followed by two additional TMSs. TMS1, TMS3, TMS6, and TMS8 form an open cavity that is predicted to host the substrate binding site. Based on primary <span class="hlt">sequence</span> alignment, three-dimensional topology, and substrate docking, we identified five residues as potentially essential for substrate binding in FcyB; Ser-85 (TMS1), Trp-159, Asn-163 (TMS3), Trp-259 (TMS6), and Asn-354 (TMS8). To validate the role of these and other putatively critical residues, we performed a systematic functional analysis of relevant mutants. We show that the proposed substrate binding residues, plus Asn-350, Asn-351, and Pro-353 are irreplaceable for FcyB function. Among these residues, Ser-85, Asn-163, Asn-350, Asn-351, and Asn-354 are critical for determining the substrate binding affinity and/or the specificity of FcyB. Our results suggest that Ser-85, Asn-163, and Asn-354 directly interact with substrates, Trp-159 and Trp-259 stabilize binding through π-π stacking interactions, and Pro-353 affects the local architecture of substrate binding site, whereas Asn-350 and Asn-351 probably affect substrate binding indirectly. Our work is the first systematic approach to address structure-function-specificity relationships in a eukaryotic member of NCS1 family by combining genetic and computational approaches. PMID:22969088</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1807K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1807K"><span>Unexpected <span class="hlt">pronounced</span> heating in the uppermost layer of the Dead Sea after a sharp drop in noon surface solar radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kishcha, Pavel; Starobinets, Boris; Gertman, Isaac; Ozer, Tal; Alpert, Pinhas</p> <p>2016-04-01</p> <p>A passage of frontal cloudiness accompanied by dust pollution over the Judean Mountains and the Dead Sea valley, which occurred on March 22, 2013, led to a sharp drop in noon solar radiation under weak winds (from 860 W m-2 to 50 W m-2). Solar radiation measurements showed that the transition from clear-sky to overcast conditions was sharper over the Dead Sea than over the Israel Mediterranean coast. The maximal rate of decrease in noon solar radiation at the Dead Sea almost doubled that near the Mediterranean coast (17 W m-2 min-1 vs. 10 W m-2 min-1). The temperature stratification was observed in the uppermost layer of the Dead Sea before the aforementioned drop in noon solar radiation. This temperature stratification was evidence that the weak winds were incapable of producing significant mixing in the Dead Sea. Buoy measurements showed that, unexpectedly, a sharp decrease in noon solar radiation caused <span class="hlt">pronounced</span> heating in the uppermost layer of the Dead Sea. Evaporation from the Dead Sea surface leads to an increase in salinity in the surface layer. In the presence of significant solar radiation, this increased salinity in the surface layer did not lead to an increase in water density. The gravitational stability and temperature stratification in the uppermost layer were observed. By contrast, after the drop in solar radiation, the increased salinity in the surface layer led to an increase in water density and, consequently, to gravitational instability, because of higher density of surface seawater compared to the density in the layers below. The gravitational instability switched on a <span class="hlt">pronounced</span> heating process in the 2-m uppermost layer of the Dead Sea. This temperature increase took place under weak winds, which were incapable of creating significant mechanical mixing in the Dead Sea. The heating of seawater in the 2-m uppermost layer was switched off later by the sharp influx of hot foehn winds up to 20 m/s from the lee side of the Judean Mts. into the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25106615','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25106615"><span>Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of <span class="hlt">purine</span>-containing nucleotides in aqueous solution.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji</p> <p>2014-08-07</p> <p>The N K-edge X-ray absorption near edge structure (XANES) spectra of the <span class="hlt">purine</span>-containing nucleotide, guanosine 5'-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other <span class="hlt">purine</span>-containing nucleotides, adenosine 5'-monophosphate, and adenosine 5'-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the <span class="hlt">purine</span> moiety.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4761651','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4761651"><span>Complex coordinated extracellular metabolism: Acid phosphatases activate diluted human leukocyte proteins to generate energy flow as NADPH from <span class="hlt">purine</span> nucleotide ribose</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Hibbs, John B.; Vavrin, Zdenek; Cox, James E.</p> <p>2016-01-01</p> <p>Complex metabolism is thought to occur exclusively in the crowded intracellular environment. Here we report that diluted enzymes from lysed human leukocytes produce extracellular energy. Our findings involve two pathways: the <span class="hlt">purine</span> nucleotide catabolic pathway and the pentose phosphate pathway, which function together to generate energy as NADPH. Glucose6P fuel for NADPH production is generated from structural ribose of <span class="hlt">purine</span> ribonucleoside monophosphates, ADP, and ADP-ribose. NADPH drives glutathione reductase to reduce an oxidized glutathione disulfide-glutathione redox couple. Acid phosphatases initiate ribose5P salvage from <span class="hlt">purine</span> ribonucleoside monophosphates, and transaldolase controls the direction of carbon chain flow through the nonoxidative branch of the pentose phosphate pathway. These metabolic control points are regulated by pH. Biologically, this energy conserving metabolism could function in perturbed extracellular spaces. PMID:26895212</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141625&hterms=acids+bases&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dacids%2Bbases','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141625&hterms=acids+bases&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dacids%2Bbases"><span>Nanopores and nucleic acids: prospects for ultrarapid <span class="hlt">sequencing</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deamer, D. W.; Akeson, M.</p> <p>2000-01-01</p> <p>DNA and RNA molecules can be detected as they are driven through a nanopore by an applied electric field at rates ranging from several hundred microseconds to a few milliseconds per molecule. The nanopore can rapidly discriminate between pyrimidine and <span class="hlt">purine</span> segments along a single-stranded nucleic acid molecule. Nanopore detection and characterization of single molecules represents a new method for directly reading information encoded in linear polymers. If single-nucleotide resolution can be achieved, it is possible that nucleic acid <span class="hlt">sequences</span> can be determined at rates exceeding a thousand bases per second.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040141625&hterms=Nucleic+acids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DNucleic%2Bacids','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040141625&hterms=Nucleic+acids&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DNucleic%2Bacids"><span>Nanopores and nucleic acids: prospects for ultrarapid <span class="hlt">sequencing</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Deamer, D. W.; Akeson, M.</p> <p>2000-01-01</p> <p>DNA and RNA molecules can be detected as they are driven through a nanopore by an applied electric field at rates ranging from several hundred microseconds to a few milliseconds per molecule. The nanopore can rapidly discriminate between pyrimidine and <span class="hlt">purine</span> segments along a single-stranded nucleic acid molecule. Nanopore detection and characterization of single molecules represents a new method for directly reading information encoded in linear polymers. If single-nucleotide resolution can be achieved, it is possible that nucleic acid <span class="hlt">sequences</span> can be determined at rates exceeding a thousand bases per second.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25690435','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25690435"><span>Response of urinary <span class="hlt">purine</span> derivatives excretion to different levels of ruminal glucose infusion in heifers.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Dickhoefer, Uta; Ahnert, Sandra; Schoof, Hartwig; Moritz, Niels; Susenbeth, Andreas</p> <p>2015-01-01</p> <p>This study investigated the response of urinary <span class="hlt">purine</span> derivatives (PD) excretion to increasing levels of intraruminal glucose infusion to evaluate how well this indicator reflects induced changes in microbial crude protein flow. Four rumen-cannulated heifers (482 ± 25 kg body weight) were fed at maintenance energy level with a basal diet (on fresh matter basis) of 4 kg/d hay, 1.5 kg/d concentrate and 60 g/d minerals in two equal meals. The trial comprised a control period (Control I) without glucose infusion followed by four consecutive periods in which all animals received 125 g, 250 g, 500 g or 1000 g/d of glucose, respectively. For this, daily dosages of glucose and urea (90 g/d during all periods) were divided into three portions that were dissolved in water and directly administered into the rumen during morning and afternoon feedings and once during noon. After the highest glucose dosage, a second control period was carried out (Control II). Urinary PD excretion increased with glucose infusion of 125 g/d (71.4 mmol/d) and 1000 g/d (74.2 mmol/d) over the level at Control I (53.9 mmol/d (standard error of the mean (SEM) 3.4; p = 0.012). After withdrawing glucose infusion, PD excretion (79.0 mmol/d) did not return to Control I level (p = 0.001). In contrast, faecal nitrogen (N) excretions linearly increased with incremental glucose infusion (p < 0.001) from 33.9 g/d at Control I to 39.7 g/d (SEM 0.5) at 1000 g/d of glucose and were similar in Control I and II (p = 0.086). The contradicting responses in the excretions of faecal N and urinary PD to increasing glucose infusions highlight the limited accuracy of the PD excretion as a non-invasive indicator when incremental dosages of rapidly fermentable carbohydrates are supplied.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3318484','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3318484"><span>Novel, Highly Specific N-Demethylases Enable Bacteria To Live on Caffeine and Related <span class="hlt">Purine</span> Alkaloids</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Summers, Ryan M.; Louie, Tai Man; Yu, Chi-Li; Gakhar, Lokesh; Louie, Kailin C.</p> <p>2012-01-01</p> <p>The molecular basis for the ability of bacteria to live on caffeine as a sole carbon and nitrogen source is unknown. Pseudomonas putida CBB5, which grows on several <span class="hlt">purine</span> alkaloids, metabolizes caffeine and related methylxanthines via sequential N-demethylation to xanthine. Metabolism of caffeine by CBB5 was previously attributed to one broad-specificity methylxanthine N-demethylase composed of two subunits, NdmA and NdmB. Here, we report that NdmA and NdmB are actually two independent Rieske nonheme iron monooxygenases with N1- and N3-specific N-demethylation activity, respectively. Activity for both enzymes is dependent on electron transfer from NADH via a redox-center-dense Rieske reductase, NdmD. NdmD itself is a novel protein with one Rieske [2Fe-2S] cluster, one plant-type [2Fe-2S] cluster, and one flavin mononucleotide (FMN) per enzyme. All ndm genes are located in a 13.2-kb genomic DNA fragment which also contained a formaldehyde dehydrogenase. ndmA, ndmB, and ndmD were cloned as His6 fusion genes, expressed in Escherichia coli, and purified using a Ni-NTA column. NdmA-His6 plus His6-NdmD catalyzed N1-demethylation of caffeine, theophylline, paraxanthine, and 1-methylxanthine to theobromine, 3-methylxanthine, 7-methylxanthine, and xanthine, respectively. NdmB-His6 plus His6-NdmD catalyzed N3-demethylation of theobromine, 3-methylxanthine, caffeine, and theophylline to 7-methylxanthine, xanthine, paraxanthine, and 1-methylxanthine, respectively. One formaldehyde was produced from each methyl group removed. Activity of an N7-specific N-demethylase, NdmC, has been confirmed biochemically. This is the first report of bacterial N-demethylase genes that enable bacteria to live on caffeine. These genes represent a new class of Rieske oxygenases and have the potential to produce biofuels, animal feed, and pharmaceuticals from coffee and tea waste. PMID:22328667</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22328667','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22328667"><span>Novel, highly specific N-demethylases enable bacteria to live on caffeine and related <span class="hlt">purine</span> alkaloids.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Summers, Ryan M; Louie, Tai Man; Yu, Chi-Li; Gakhar, Lokesh; Louie, Kailin C; Subramanian, Mani</p> <p>2012-04-01</p> <p>The molecular basis for the ability of bacteria to live on caffeine as a sole carbon and nitrogen source is unknown. Pseudomonas putida CBB5, which grows on several <span class="hlt">purine</span> alkaloids, metabolizes caffeine and related methylxanthines via sequential N-demethylation to xanthine. Metabolism of caffeine by CBB5 was previously attributed to one broad-specificity methylxanthine N-demethylase composed of two subunits, NdmA and NdmB. Here, we report that NdmA and NdmB are actually two independent Rieske nonheme iron monooxygenases with N(1)- and N(3)-specific N-demethylation activity, respectively. Activity for both enzymes is dependent on electron transfer from NADH via a redox-center-dense Rieske reductase, NdmD. NdmD itself is a novel protein with one Rieske [2Fe-2S] cluster, one plant-type [2Fe-2S] cluster, and one flavin mononucleotide (FMN) per enzyme. All ndm genes are located in a 13.2-kb genomic DNA fragment which also contained a formaldehyde dehydrogenase. ndmA, ndmB, and ndmD were cloned as His(6) fusion genes, expressed in Escherichia coli, and purified using a Ni-NTA column. NdmA-His(6) plus His(6)-NdmD catalyzed N(1)-demethylation of caffeine, theophylline, paraxanthine, and 1-methylxanthine to theobromine, 3-methylxanthine, 7-methylxanthine, and xanthine, respectively. NdmB-His(6) plus His(6)-NdmD catalyzed N(3)-demethylation of theobromine, 3-methylxanthine, caffeine, and theophylline to 7-methylxanthine, xanthine, paraxanthine, and 1-methylxanthine, respectively. One formaldehyde was produced from each methyl group removed. Activity of an N(7)-specific N-demethylase, NdmC, has been confirmed biochemically. This is the first report of bacterial N-demethylase genes that enable bacteria to live on caffeine. These genes represent a new class of Rieske oxygenases and have the potential to produce biofuels, animal feed, and pharmaceuticals from coffee and tea waste.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28450711','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28450711"><span><span class="hlt">Pronounced</span> Plasticity Caused by Phase Separation and β-relaxation Synergistically in Zr-Cu-Al-Mo Bulk Metallic Glasses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Wang, Tuo; Wang, Lu; Wang, Qinjia; Liu, Yanhui; Hui, Xidong</p> <p>2017-04-27</p> <p>Bulk metallic glasses (BMGs) are known to have extraordinary merits such as ultrahigh strength and dynamic toughness etc. but tied to the detrimental brittleness, which has become a critical issue to the engineering application and understanding the glass nature. In this article, we report a new class of Zr-Cu-Al-Mo BMGs with extraordinary plastic strain above 20%. "Work-hardening" effect after yielding in a wide range of plastic deformation process has been detected for this kind of BMGs. Compositional heterogeneity, which can be classified into ZrMo- and Cu-rich zones, was differentiated in this kind of BMG. <span class="hlt">Pronounced</span> humps have been observed on the high frequency kinetic spectrum in Mo containing BMGs, which is the indicator of β-relaxation transition. The underlying mechanism for the excellent plastic deforming ability of this class of BMGs is ascribed to the synergistic effects of soft ZrMo-rich glass formed through phase separation and abundant flow units which related to β-relaxation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/26257746','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/26257746"><span>Functional traits variation explains the distribution of Aextoxicon punctatum (Aextoxicaceae) in <span class="hlt">pronounced</span> moisture gradients within fog-dependent forest fragments.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Salgado-Negret, Beatriz; Canessa, Rafaella; Valladares, Fernando; Armesto, Juan J; Pérez, Fernanda</p> <p>2015-01-01</p> <p>Climate change and fragmentation are major threats to world forests. Understanding how functional traits related to drought tolerance change across small-scale, <span class="hlt">pronounced</span> moisture gradients in fragmented forests is important to predict species' responses to these threats. In the case of Aextoxicon punctatum, a dominant canopy tree in fog-dependent rain forest patches in semiarid Chile, we explored how the magnitude, variability and correlation patterns of leaf and xylem vessel traits and hydraulic conductivity varied across soil moisture (SM) gradients established within and among forest patches of different size, which are associated with differences in tree establishment and mortality patterns. Leaf traits varied across soil-moisture gradients produced by fog interception. Trees growing at drier leeward edges showed higher leaf mass per area, trichome and stomatal density than trees from the wetter core and windward zones. In contrast, xylem vessel traits (vessels diameter and density) did not vary producing loss of hydraulic conductivity at drier leeward edges. We also detected higher levels of phenotypic integration and variability at leeward edges. The ability of A. punctatum to modify leaf traits in response to differences in SM availability established over short distances (<500 m) facilitates its persistence in contrasting microhabitats within forest patches. However, xylem anatomy showed limited plasticity, which increases cavitation risk at leeward edges. Greater patch fragmentation, together with fluctuations in irradiance and SM in small patches, could result in higher risk of drought-related tree mortality, with profound impacts on hydrological balances at the ecosystem scale.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1357001','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1357001"><span><span class="hlt">Pronounced</span> Size Dependence in Structure and Morphology of Gas-Phase Produced, Partially Oxidized Cobalt Nanoparticles under Catalytic Reaction Conditions</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bartling, Stephan; Yin, Chunrong; Barke, Ingo; Oldenburg, Kevin; Hartmann, Hannes; von Oeynhausen, Viola; Pohl, Marga-Martina; Houben, Kelly; Tyo, Eric C.; Seifert, Sönke; Lievens, Peter; Meiwes-Broer, Karl-Heinz; Vajda, Stefan</p> <p>2015-06-23</p> <p>It is generally accepted that optimal particle sizes are key for efficient nanocatalysis. Much less attention is paid to the role of morphology and atomic arrangement during catalytic reactions. Here we unravel the structural, stoichiometric, and morphological evolution of gas-phase produced cobalt nanoparticles in a broad size range. Particles with diameters between 1.4 nm and 22nm generated in cluster sources are size selected and deposited on amorphous alumina (Al2O3) and ultrananocrystalline diamond (UNCD) films. A combination of different techniques is employed to monitor particle properties at the stages of production, exposure to ambient conditions, and catalytic reaction, in this case the oxidative dehydrogenation of cyclohexane at elevated temperatures. A <span class="hlt">pronounced</span> size dependence is found, naturally classifying the particles into three size regimes. While small and intermediate clusters essentially retain their compact morphology, large particles transform into hollow spheres due to the nanoscale Kirkendall effect. Depending on the substrate an isotropic (Al2O3) or anisotropic (UNCD) Kirkendall effect is observed. The latter results in dramatic lateral size changes. Our results shed light on the interplay between chemical reactions and the catalyst's structure and provide an approach to tailor the cobalt oxide phase composition required for specific catalytic schemes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28401414','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28401414"><span>Getting to the Heart of Masculinity Stressors: Masculinity Threats Induce <span class="hlt">Pronounced</span> Vagal Withdrawal During a Speaking Task.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Kramer, Brandon L; Himmelstein, Mary S; Springer, Kristen W</p> <p>2017-04-11</p> <p>Previous work has found that traditional masculinity ideals and behaviors play a crucial role in higher rates of morbidity and mortality for men. Some studies also suggest that threatening men's masculinity can be stressful. Over time, this stress can weigh on men's cardiovascular and metabolic systems, which may contribute to men's higher rates of cardiometabolic health issues. The purpose of this study is to explore how masculinity threats affect men's heart rate and heart rate variability reactivity (i.e., vagal withdrawal) to masculinity feedback on a social speaking task. Two hundred and eighty-five undergraduate males were randomly assigned to one of six conditions during a laboratory-based speech task. They received one of two feedback types (masculinity or control) and one of three feedback levels (low, high, or dropping) in order to assess whether masculinity threats influence heart rate reactivity and vagal withdrawal patterns during the speech task. Men who receive low masculinity feedback during the speech task experienced more <span class="hlt">pronounced</span> vagal withdrawal relative to those who received the control. Masculinity threats can induce vagal withdrawal that may accumulate over the life course to contribute to men's relatively worse cardiometabolic health.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4511825','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4511825"><span>Functional traits variation explains the distribution of Aextoxicon punctatum (Aextoxicaceae) in <span class="hlt">pronounced</span> moisture gradients within fog-dependent forest fragments</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Salgado-Negret, Beatriz; Canessa, Rafaella; Valladares, Fernando; Armesto, Juan J.; Pérez, Fernanda</p> <p>2015-01-01</p> <p>Climate change and fragmentation are major threats to world forests. Understanding how functional traits related to drought tolerance change across small-scale, <span class="hlt">pronounced</span> moisture gradients in fragmented forests is important to predict species’ responses to these threats. In the case of Aextoxicon punctatum, a dominant canopy tree in fog-dependent rain forest patches in semiarid Chile, we explored how the magnitude, variability and correlation patterns of leaf and xylem vessel traits and hydraulic conductivity varied across soil moisture (SM) gradients established within and among forest patches of different size, which are associated with differences in tree establishment and mortality patterns. Leaf traits varied across soil-moisture gradients produced by fog interception. Trees growing at drier leeward edges showed higher leaf mass per area, trichome and stomatal density than trees from the wetter core and windward zones. In contrast, xylem vessel traits (vessels diameter and density) did not vary producing loss of hydraulic conductivity at drier leeward edges. We also detected higher levels of phenotypic integration and variability at leeward edges. The ability of A. punctatum to modify leaf traits in response to differences in SM availability established over short distances (<500 m) facilitates its persistence in contrasting microhabitats within forest patches. However, xylem anatomy showed limited plasticity, which increases cavitation risk at leeward edges. Greater patch fragmentation, together with fluctuations in irradiance and SM in small patches, could result in higher risk of drought-related tree mortality, with profound impacts on hydrological balances at the ecosystem scale. PMID:26257746</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/7617593','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/7617593"><span>[Differentiation of arousal in sleep before and after CPAP therapy in patients with <span class="hlt">pronounced</span> sleep apnea syndrome].</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Fietze, I; Warmuth, R; Waschke, K; Witt, C; Baumann, G</p> <p>1995-03-01</p> <p>The sleep apnea syndrome is often associated with the syndromes of daytime exhaustion and involuntary daytime sleeping fits. The cause is assumed to be fragmentary sleep resulting from night-time arousal. The central nervous activation reactions caused by apnea or hypopnea, respectively, and not the movement arousal determine the sleep structure. We have examined 10 male patients in the age range 40-55 years (48 +/- 6 SD) before and during the first 3 nights of CPAP therapy. Cardiorespiratory polysomnography was performed in all four nights. Sleep way analyzed visually and differentiation was made between respiratory (RA) and movement arousal (MA). All 10 patients had a <span class="hlt">pronounced</span> sleep apnea syndrome. Deep and dream sleep were reduced, significantly more respiratory arousals occurred than movement arousals. The SWS latency was shortened in the first therapy night, the deep and dream sleep proportions increased and the RA decreased significantly. No further significant changes in the sleep parameters occurred during the second and third nights. We found that the number of apnea/hypopnea was not equal to the number of RA. When less arousal was recognized it was suggestive of a deficit of the diversion function while more RA was indicative of additional respiratory events, e.g. pharyngeal obstructions and hyperventilations which were not recognized as apnea or hypopnea. In addition to its role in the differential diagnosis of sleeping disorders, in particular sleep apnea, arousal differentiation is also an important criterion for estimating the efficiency of CPAP therapy.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27380895','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27380895"><span><span class="hlt">Pronounced</span> genetic differentiation and recent secondary contact in the mangrove tree Lumnitzera racemosa revealed by population genomic analyses.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Li, Jianfang; Yang, Yuchen; Chen, Qipian; Fang, Lu; He, Ziwen; Guo, Wuxia; Qiao, Sitan; Wang, Zhengzhen; Guo, Miaomiao; Zhong, Cairong; Zhou, Renchao; Shi,