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Sample records for guanosine analogue 2-amino-6-mercapto-7-methylpurine

  1. Alkylation of guanosine and 4-(p-nitrobenzyl)-pyridine by styrene oxide analogues in vitro.

    PubMed

    Hemminki, K; Heinonen, T; Vainio, H

    1981-11-01

    In vitro alkylation activity of styrene oxide (SO) and three of its analogues, 4-vinyltoluene oxide (VTO), 3,5-dimethylstyrene oxide (DMSO), and 4-nitrostyrene oxide (NSO) was assayed using 4-(p-nitrobenzyl)pyridine (NBP) and guanosine as nucleophiles. Hydrolysis rates were also determined. The half-lives of VTO, DMSO, SO, and NSO were 8, 11, 40, and 60 h, respectively in aqueous solution. The rate of NBP alkylation correlated with the rate of hydrolysis. By contrast, the rates of guanosine alkylation were quite different: SO greater than VTO greater than DMSO. NSO did not react with guanosine. Fluorescence an ultraviolet spectroscopic data on the guanosine adducts indicated that SO, VTO, and DMSO formed main alkyl products at N-7. PMID:7325798

  2. Structural Basis for Recognition of Guanosine by a Synthetic Tricyclic Cytosine Analogue: Guanidinium G-Clamp

    SciTech Connect

    Wilds, C.J.; Maier, M.A.; Manoharan, M.; Egli, M.

    2010-03-08

    An oligonucleotide analogue containing a novel heterocyclic analogue, the guanidinium G-clamp, was designed to allow formation of five H-bonds to guanosine. The guanidinium group was introduced postsynthetically by treatment of the deprotected oligonucleotide containing a free amino group with a solution of 1H-pyrazole-1-carboxamidine and purified by a combination of size-exclusion chromatography and reversed-phase HPLC. A single incorporation of this modification into an oligodeoxynucleotide sequence was found to increase duplex stability by 13{sup o} and 16{sup o} per modification to RNA and DNA, respectively. Crystals of a self-complementary decamer sequence containing this modification were grown and diffracted to 1-{angstrom} resolution. The structure was solved by molecular replacement and revealed that the modification forms additional H-bonds to O(6) and N(7) of guanosine through the amino and imino N-atoms, respectively. The origins of enhanced duplex stability are also attributed to increased stacking interactions mediated by the phenoxazine moiety of the G-clamp and formation of H-bond networks between the positively charged guanidinium group, H{sub 2}O molecules, and negatively charged O-atoms from phosphates on the adjacent strand.

  3. Phosphonylated Acyclic Guanosine Analogues with the 1,2,3-Triazole Linker.

    PubMed

    Głowacka, Iwona E; Andrei, Graciela; Schols, Dominique; Snoeck, Robert; Piotrowska, Dorota G

    2015-01-01

    A novel series of {4-[(2-amino-6-chloro-9H-purin-9-yl)methyl]-1H-1,2,3-triazol-1-yl}alkylphosphonates and {4-[(2-amino-6-oxo-1,6-dihydro-9H-purin-9-yl)methyl]-1H-1,2,3-triazol-1-yl}alkylphosphonates as acyclic analogues of guanosine were synthesized and assessed for antiviral activity against a broad range of DNA and RNA viruses and for their cytostatic activity toward three cancerous cell lines (HeLa, L1210 and CEM). They were devoid of antiviral activity; however, several phosphonates were found slightly cytostatic against HeLa cells at an IC50 in the 80-210 µM range. Compounds (1R,2S)-17k and (1S,2S)-17k showed the highest inhibitory effects (IC50=15-30 µM) against the proliferation of murine leukemia (L1210) and human T-lymphocyte (CEM) cell lines. PMID:26501246

  4. An industrial process for selective synthesis of 7-methyl guanosine 5'-diphosphate: versatile synthon for synthesis of mRNA cap analogues.

    PubMed

    Kore, Anilkumar R; Parmar, Gaurang

    2006-03-01

    We report an industrial scale facile synthesis of 7-methyl guanosine 5'-diphosphate, which plays an important role in synthesis of various mRNA cap analogs. An efficient and selective methylation at position 7 of guanosine 5'-diphosphate was achieved by dissolving guanosine 5'-diphosphate in water and drops wise addition of dimethyl sulfate over a period of 1 h at room temperature. The reaction was completed within 2 h and resulted in more than a 96% yield. The desired product, 7-methyl GDP was purified by using BPG column on AKTA Purifier 100. Certainly, this method has advantages over the known methylation method, in terms of yield, economy, safety, and environmental concerns. PMID:16629126

  5. A new nonhydrolyzable reactive cGMP analogue, (Rp)-Guanosine-3′, 5′-cyclic-S-(4-bromo-2, 3-dioxobutyl)monophosphorothioate, which targets the cGMP binding site of human platelet PDE3A

    PubMed Central

    Hung, Su H.; Liu, Andy H.; Pixley, Robin A.; Francis, Penelope; Williams, LaTeeka D.; Matsko, Christopher M.; Barnes, Karine D.; Sivendran, Sharmila; Colman, Roberta F.; Colman, Robert W.

    2008-01-01

    The amino acids involved in substrate (cAMP) binding to human platelet cGMP-inhibited cAMP phosphodiesterase (PDE3A) are identified. Less is known about the inhibitor (cGMP) binding site. We have now synthesized a nonhydrolyzable reactive cGMP analog, Rp-guanosine-3′, 5′-cyclic-S-(4-bromo-2, 3-dioxobutyl)monophosphorothioate (Rp-cGMPS-BDB). Rp-cGMPS-BDB irreversibly inactivates PDE3A (KI = 43.4 ± 7.2 μM and kcart = 0.007 ± 0.0006 min−1). The effectiveness of protectants in decreasing the rate of inactivation by Rp-cGMPS-BDB is: Rp-cGMPS (Kd = 72 μM) > Sp-cGMPS (124), Sp-cAMPS (182) > GMP (1517), Rp-cAMPS (3762), AMP (4370 μM). NAD+, neither a substrate nor an inhibitor of PDE3A, does not protect. Nonhydrolyzable cGMP analogs exhibit greater affinity than the cAMP analogs. These results indicate that Rp-cGMPS-BDB targets favorably the cGMP binding site consistent with a docking model of PDE3A-Rp-cGMPS-BDB active site. We conclude that Rp-cGMPS-BDB is an effective active site-directed affinity label for PDE3A with potential for other cGMP-dependent enzymes. PMID:18394675

  6. Extracellular guanosine regulates extracellular adenosine levels

    PubMed Central

    Cheng, Dongmei; Jackson, Travis C.; Verrier, Jonathan D.; Gillespie, Delbert G.

    2013-01-01

    The aim of this investigation was to test the hypothesis that extracellular guanosine regulates extracellular adenosine levels. Rat preglomerular vascular smooth muscle cells were incubated with adenosine, guanosine, or both. Guanosine (30 μmol/l) per se had little effect on extracellular adenosine levels. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) were 0.125 ± 0.020 μmol/l, indicating rapid disposition of extracellular adenosine. Extracellular adenosine levels 1 h after addition of adenosine (3 μmol/l) plus guanosine (30 μmol/l) were 1.173 ± 0.061 μmol/l, indicating slow disposition of extracellular adenosine. Cell injury increased extracellular levels of endogenous adenosine and guanosine, and the effects of cell injury on endogenous extracellular adenosine were modulated by altering the levels of endogenous extracellular guanosine with exogenous purine nucleoside phosphorylase (converts guanosine to guanine) or 8-aminoguanosine (inhibits purine nucleoside phosphorylase). Extracellular guanosine also slowed the disposition of extracellular adenosine in rat preglomerular vascular endothelial cells, mesangial cells, cardiac fibroblasts, and kidney epithelial cells and in human aortic and coronary artery vascular smooth muscle cells and coronary artery endothelial cells. The effects of guanosine on adenosine levels were not mimicked or attenuated by 5-iodotubericidin (adenosine kinase inhibitor), erythro-9-(2-hydroxy-3-nonyl)-adenine (adenosine deaminase inhibitor), 5-aminoimidazole-4-carboxamide (guanine deaminase inhibitor), aristeromycin (S-adenosylhomocysteine hydrolase inhibitor), low sodium (inhibits concentrative nucleoside transporters), S-(4-nitrobenzyl)−6-thioinosine [inhibits equilibrative nucleoside transporter (ENT) type 1], zidovudine (inhibits ENT type 2), or acadesine (known modulator of adenosine levels). Guanosine also increases extracellular inosine, uridine, thymidine, and cytidine, yet decreases

  7. Guanosine nucleotide precursor for flavinogenesis of Eremothecium Ashbyii.

    PubMed

    Mitsuda, H; Nakajima, K

    1975-01-01

    The purine precursor in the riboflavin biosynthetic pathway in Eremothecium ashbyii was examined using a guanine analogue, 8-azaguanine, with non-growing cell systems. 1. Riboflavin formation in the culture filtrate was determined at 0, 5, 10 and 20 hr after start of the incubation of the non-growing cells in the presence of xanthine or 8-azaguanine (1 mM, respectively). At 20 hr of incubation, the addition of xanthine stimulated riboflavin formation by 36% and the addition of 8-azaguanine inhibited the formation by 57%. 2. Acid soluble nucleotide pools in the cells were followed at 0, 5, 10 and 20 hr of the incubation period in the presence of xanthine or 8-azaguanine by means of anion exchange column chromatography. The result showed that the GTP pool changed markedly despite the fact that the adenosine nucleotide pool was almost constant irrespective of the presence or absence of these purines till 10 hr of incubation. But, the decrease of the former was overcome in part by the addition of flavinogenic xanthine. Furthermore, the total amounts of GTP and guanosine accumulated in cells in the presence of 8-azaguanine reached the maximum already at 5 hr, attaining a level twice as much as the GTP contents of the control. 3. The role of guanosine nucleotide pool in riboflavin formation was further examined using 8-azaguanine. In this experiment the drug was added to the suspension of non-growing cells at 3 hr or 6 hr after the incubation was started and the reaction was continued till the 12th hr. A more clear-cut correlationship between riboflavin formation and guanosine nucleotide pool was oberved by this experiment. The guanosine nucleotide pool (consisting of GMP, GDP and GTP) increased simultaneously with the inhibition of riboflavin formation. Of the guanosine nucleotides pools, the GMP pool increased 2.7 times above normal upon the addition of 8-azaguanine during the incubation for 6 hr and 5.3 fold for 9 hr. While, the GTP pool increased 1.9 fold above

  8. Affinity of guanosine derivatives for polycytidylate revisited

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Hurley, T. B.; Baird, E. E.

    1995-01-01

    Evidence is presented for complexation of guanosine 5'-monophosphate 2-methylimidazolide (2-MeImpG) with polycytidylate (poly(C)) at pH 8.0 and 23 degrees C in the presence of 1.0 M NaCl2 and 0.2 M MgCl2 in water. The association of 2-MeImpG with poly(C) was investigated using UV-vis spectroscopy as well as by monitoring the kinetics of the nucleophilic substitution reaction of the imidazole moiety by amines. The results of both methods are consistent with moderately strong poly(C) 2-MeImpG complexation and the spectrophotometric measurements allowed the construction of a binding isotherm with a concentration of 2-MeImpG equal to 5.55 +/- 0.15 mM at half occupancy. UV spectroscopy was employed to establish the binding of other guanosine derivatives on poly(C). These derivatives are guanosine 5'-monophosphate (5'GMP), guanosine 5'-monophosphate imidazolide (ImpG), and guanosine 5'-monophosphate morpholidate (morpG). Within experimental error these guanosine derivatives exhibit the same affinity for poly(C) as 2-MeImpG.

  9. A broadly applicable continuous spectrophotometric assay for measuring aminoacyl-tRNA synthetase activity.

    PubMed Central

    Lloyd, A J; Thomann, H U; Ibba, M; Söll, D

    1995-01-01

    We describe a convenient, simple and novel continuous spectrophotometric method for the determination of aminoacyl-tRNA synthetase activity. The assay relies upon the measurement of inorganic pyrophosphate generated in the first step of the aminoacylation of a tRNA. Pyrophosphate release is coupled to inorganic pyrophosphatase, to generate phosphate, which in turn is used as the substrate of purine nucleoside phosphorylase to catalyze the N-glycosidic cleavage of 2-amino 6-mercapto 7-methylpurine ribonucleoside. Of the reaction products, ribose 1-phosphate and 2-amino 6-mercapto 7-methylpurine, the latter has a high absorbance at 360 nm relative to the nucleoside and hence provides a spectrophotometric signal that can be continuously followed. The non-destructive nature of the spectrophotometric assay allowed the re-use of the tRNAs in question in successive experiments. The usefulness of this method was demonstrated for glutaminyl-tRNA synthetase (GlnRS) and tryptophanyl-tRNA synthetase. Initial velocities measured using this assay correlate closely with those assayed by quantitation of [3H]Gln-tRNA or [14C]Trp-tRNA formation respectively. In both cases amino acid transfer from the aminoacyl adenylate to the tRNA represents the rate determining step. In addition, aminoacyl adenylate formation by aspartyl-tRNA synthetase was followed and provided a more sensitive means of active site titration than existing techniques. Finally, this novel method was used to provide direct evidence for the cooperativity of tRNA and ATP binding to GlnRS. PMID:7659511

  10. 2'-Modified Guanosine Analogs for the Treatment of HCV.

    PubMed

    Girijavallabhan, Vinay; Arasappan, Ashok; Bennett, Frank; Chen, Kevin; Dang, Qun; Huang, Ying; Kerekes, Angela; Nair, Latha; Pissarnitski, Dmitri; Verma, Vishal; Alvarez, Carmen; Chen, Ping; Cole, David; Esposite, Sara; Huang, Yuhua; Hong, Qingmei; Liu, Zhidan; Pan, Weidong; Pu, Haiyan; Rossman, Randall; Truong, Quang; Vibulbhan, Bancha; Wang, Jun; Zhao, Zhiqiang; Olsen, David; Stamford, Andrew; Bogen, Stephane; Njoroge, F George

    2016-06-01

    Novel 2'-modified guanosine nucleosides were synthesized from inexpensive starting materials in 7-10 steps via hydroazidation or hydrocyanation reactions of the corresponding 2'-olefin. The antiviral effectiveness of the guanosine nucleosides was evaluated by converting them to the corresponding 5'-O-triphosphates (compounds 38-44) and testing their biochemical inhibitory activity against the wild-type NS5B polymerase. PMID:27104963

  11. Injection of guanosine and adenosine nucleotides into Limulus ventral photoreceptor cells

    PubMed Central

    Bolsover, S. R.; Brown, J. E.

    1982-01-01

    1. Several nucleotide and nucleotide analogues had striking effects when pressure-injected into Limulus ventral photoreceptor cells. The poorly hydrolysable GTP analogues guanosine 5′-0-(3-thiotriphosphate) (GTPγS), guanylyl imidodiphosphate (Gpp[NH]p) and guanylyl (β, γ methylene) diphosphonate (Gpp[CH2]p) produced large increases in the frequency of `discrete events' that were recorded from photoreceptors in darkness. This effect was only observed after the injected cell was exposed to light. Injection of the ATP analogue ATPγS had effects similar to those of the GTP analogues. 2. We conclude that GTPγS, Gpp[NH]p, Gpp[CH2]p and ATPγS act at a common site to cause a light-dependent, long-term activation of the excitation mechanism of the photoreceptor. 3. Injection of GTP or GDP at pH 4.8 was followed by a smooth, transient depolarization that was observed neither when GTP at pH 7.5 was injected nor when ATP, 5′GMP or 2-[N-morpholino] ethane sulphonic acid (MES) were injected at pH 4.8. The reversal potential of the current induced by GTP injection was significantly more positive than the reversal potential of the light-induced current. 4. We conclude that GTP injection induces changes of membrane conductance either in addition to, or different from, the light-induced change of membrane conductance. 5. Injection of the ATP analogue adenylyl imidodiphosphate (App[NH]p), and the pyrophosphate analogue imidodiphosphate (p[NH]p) produced a drastic decrease in the sensitivity of photoreceptors to light. This decrease in sensitivity was partially reversed when the concentration of calcium ions in the bathing medium was reduced. 6. We suggest that App[NH]p and p[NH]p injections act by increasing the cytoplasmic concentration of calcium ions. PMID:7153930

  12. The roles of initiation factor 2 and guanosine triphosphate in initiation of protein synthesis

    PubMed Central

    Antoun, Ayman; Pavlov, Michael Y.; Andersson, Kerstin; Tenson, Tanel; Ehrenberg, Måns

    2003-01-01

    The role of IF2 from Escherichia coli was studied in vitro using a system for protein synthesis with purified components. Stopped flow experiments with light scattering show that IF2 in complex with guanosine triphosphate (GTP) or a non-cleavable GTP analogue (GDPNP), but not with guanosine diphosphate (GDP), promotes fast association of ribosomal subunits during initiation. Biochemical experiments show that IF2 promotes fast formation of the first peptide bond in the presence of GTP, but not GDPNP or GDP, and that IF2–GDPNP binds strongly to post-initiation ribosomes. We conclude that the GTP form of IF2 accelerates formation of the 70S ribosome from subunits and that GTP hydrolysis accelerates release of IF2 from the 70S ribosome. The results of a recent report, suggesting that GTP and GDP promote initiation equally fast, have been addressed. Our data, indicating that eIF5B and IF2 have similar functions, are used to rationalize the phenotypes of GTPase-deficient mutants of eIF5B and IF2. PMID:14532131

  13. Recognition of guanosine by dissimilar tRNA methyltransferases.

    PubMed

    Sakaguchi, Reiko; Giessing, Anders; Dai, Qing; Lahoud, Georges; Liutkeviciute, Zita; Klimasauskas, Saulius; Piccirilli, Joseph; Kirpekar, Finn; Hou, Ya-Ming

    2012-09-01

    Guanosines are important for biological activities through their specific functional groups that are recognized for RNA or protein interactions. One example is recognition of N(1) of G37 in tRNA by S-adenosyl-methionine (AdoMet)-dependent tRNA methyltransferases to synthesize m(1)G37-tRNA, which is essential for translational fidelity in all biological domains. Synthesis of m(1)G37-tRNA is catalyzed by TrmD in bacteria and by Trm5 in eukarya and archaea, using unrelated and dissimilar structural folds. This raises the question of how dissimilar proteins recognize the same guanosine. Here we probe the mechanism of discrimination among functional groups of guanosine by TrmD and Trm5. Guanosine analogs were systematically introduced into tRNA through a combination of chemical and enzymatic synthesis. Single turnover kinetic assays and thermodynamic analysis of the effect of each analog on m(1)G37-tRNA synthesis reveal that TrmD and Trm5 discriminate functional groups differently. While both recognize N(1) and O(6) of G37, TrmD places a much stronger emphasis on these functional groups than Trm5. While the exocyclic 2-amino group of G37 is important for TrmD, it is dispensable for Trm5. In addition, while an adjacent G36 is obligatory for TrmD, it is nonessential for Trm5. These results depict a more rigid requirement of guanosine functional groups for TrmD than for Trm5. However, the sensitivity of both enzymes to analog substitutions, together with an experimental revelation of their low cellular concentrations relative to tRNA substrates, suggests a model in which these enzymes rapidly screen tRNA by direct recognition of G37 in order to monitor the global state of m(1)G37-tRNA. PMID:22847817

  14. Guanosine Protects Against Cortical Focal Ischemia. Involvement of Inflammatory Response.

    PubMed

    Hansel, Gisele; Tonon, André Comiran; Guella, Felipe Lhywinskh; Pettenuzzo, Letícia Ferreira; Duarte, Thiago; Duarte, Marta Maria Medeiros Frescura; Oses, Jean Pierre; Achaval, Matilde; Souza, Diogo Onofre

    2015-12-01

    Stroke is the major cause of death and the most frequent cause of disability in the adult population worldwide. Guanosine plays an important neuroprotective role in several cerebral ischemic models and is involved in the modulation of oxidative responses and glutamatergic parameters. Because the excessive reactive oxygen species produced during an ischemic event can trigger an inflammatory response, the purpose of this study was to evaluate the hypothesis that guanosine is neuroprotective against focal cerebral ischemia, inhibits microglia/macrophages activation, and mediates an inflammatory response ameliorating the neural damage. Permanent focal cerebral ischemia was induced in adult rats, and guanosine was administered immediately, 1, 3, and 6 h after surgery. Twenty-four hours after ischemia, the asymmetry scores were evaluated by the cylinder test; neuronal damage was evaluated by Fluoro-Jade C (FJC) staining and propidium iodide (PI) incorporation; microglia and immune cells were evaluated by anti-Iba-1 antibody; and inflammatory parameters such as interleukins (IL): IL-1, IL-6, IL-10; tumor necrosis factors alpha (TNF-α); and interferon-gamma (INF-γ) were evaluated in the brain tissue and cerebrospinal fluid. The ischemic event increased the levels of Iba-1-positive cells and pro-inflammatory cytokines and decreased IL-10 levels (an anti-inflammatory cytokine) in the lesion periphery. The guanosine treatment attenuated the changes in these inflammatory parameters and also reduced the infarct volume, PI incorporation, and number of FJC-positive cells, improving the functional recovery. Thus, guanosine may have been a promising therapeutic agent for the treatment of ischemic brain injury by reduction of inflammatory process triggered in an ischemic event. PMID:25394382

  15. Regulation of Phospholipid Synthesis in Escherichia coli by Guanosine Tetraphosphate

    PubMed Central

    Merlie, John P.; Pizer, Lewis I.

    1973-01-01

    Phospholipid synthesis has been reported to be subject to stringent control in Escherichia coli. We present evidence that demonstrates a strict correlation between guanosine tetraphosphate accumulation and inhibition of phospholipid synthesis. In vivo experiments designed to examine the pattern of phospholipid labeling with 32P-inorganic phosphate and 32P-sn-glycerol-3-phosphate suggest that regulation must occur at the glycerol-3-phosphate acyltransferase step. Assay of phospholipid synthesis by cell-free extracts and semipurified preparations revealed that guanosine tetraphosphate inhibits at least two enzymes specific for the biosynthetic pathway, sn-glycerol-3-phosphate acyltransferase as well as sn-glycerol-3-phosphate phosphatidyl transferase. These findings provide a biochemical basis for the stringent control of lipid synthesis as well as regulation of steady-state levels of phospholipid in growing cells. Images PMID:4583220

  16. The role of surface energy in guanosine nucleotide alignment: an intriguing scenario.

    PubMed

    Tone, Caterina M; De Santo, Maria P; Ciuchi, Federica

    2014-07-01

    In this paper we report how the confining surfaces and the ionic effects of different concentration of guanosine solution can be used to vary the alignment of liquid crystal phases of guanosine nucleotides. Liquid crystal phases of guanosine 5'-monophosphate ammonium salt and guanosine 5'-monophosphate free acid in pure water, with and without silver sulphate, were studied by polarized optical microscope. A periodic modulation of the texture was observed. This modulation depends on both on the concentration and on the presence of silver ions in the liquid crystal phase. We demonstrate that, according to the surface energy of the alignment layers, it is possible to homeotropically align the guanosine chromonic phase without applying any external magnetic field. Finally, we report the formation of spherical, vesicle-like guanosine 5'-monophosphate aggregates, when the solution was confined between two hydrophobic surfaces containing exposed Si groups. PMID:24832053

  17. PRODUCTION OF EXTRACELLULAR GUANOSINE-5'-MONOPHOSPHATE BY BACILLUS SUBTILIS

    PubMed Central

    Demain, A. L.; Miller, I. M.; Hendlin, D.

    1964-01-01

    Demain, A. L. (Merck Sharp & Dohme Research Laboratories, Rahway, N.J.), I. M. Miller, and D. Hendlin. Production of extracellular guanosine-5'-monophosphate by Bacillus subtilis. J. Bacteriol. 88:991–995. 1964.—Wild-type Bacillus subtilis colonies were found to feed purineless mutants. A strain with high feeding capacity was selected for study, with a guanineless mutant of B. subtilis used as the assay organism. The factor was excreted during its growth phase in a complex medium containing starch and soybean meal extract. Nutritional studies led to the development of a defined medium to be used for biochemical studies and to aid in the isolation of the factor. Starch was replaced by maltose and the soybean meal extract by Mn++. Production of the factor was sensitive to the pH of the medium during growth. Practically its entire extracellular accumulation occurred before visible lysis. The factor was identified as guanosine-5'-monophosphate derived by extracellular enzymatic hydrolysis of excreted ribonucleic acid. PMID:14219064

  18. Mechanisms involved in the antinociception induced by systemic administration of guanosine in mice

    PubMed Central

    Schmidt, AP; Böhmer, AE; Schallenberger, C; Antunes, C; Tavares, RG; Wofchuk, ST; Elisabetsky, E; Souza, DO

    2010-01-01

    Background and purpose: It is well known that adenine-based purines exert multiple effects on pain transmission. However, less attention has been given to the potential effects of guanine-based purines on pain transmission. The aim of this study was to investigate the effects of intraperitoneal (i.p.) and oral (p.o.) administration of guanosine on mice pain models. Additionally, investigation into the mechanisms of action of guanosine, its potential toxicity and cerebrospinal fluid (CSF) purine levels were also assessed. Experimental approach: Mice received an i.p. or p.o. administration of vehicle (0.1 mM NaOH) or guanosine (up to 240 mg·kg−1) and were evaluated in several pain models. Key results: Guanosine produced dose-dependent antinociceptive effects in the hot-plate, glutamate, capsaicin, formalin and acetic acid models, but it was ineffective in the tail-flick test. Additionally, guanosine produced a significant inhibition of biting behaviour induced by i.t. injection of glutamate, AMPA, kainate and trans-ACPD, but not against NMDA, substance P or capsaicin. The antinociceptive effects of guanosine were prevented by selective and non-selective adenosine receptor antagonists. Systemic administration of guanosine (120 mg·kg−1) induced an approximately sevenfold increase on CSF guanosine levels. Guanosine prevented the increase on spinal cord glutamate uptake induced by intraplantar capsaicin. Conclusions and implications: This study provides new evidence on the mechanism of action of the antinociceptive effects after systemic administration of guanosine. These effects seem to be related to the modulation of adenosine A1 and A2A receptors and non-NMDA glutamate receptors. PMID:20132210

  19. DNAzyme-mediated catalysis with only guanosine and cytidine nucleotides

    PubMed Central

    Schlosser, Kenny; Li, Yingfu

    2009-01-01

    Single-stranded DNA molecules have the capacity to adopt catalytically active structures known as DNAzymes, although the fundamental limits of this ability have not been determined. Starting with a parent DNAzyme composed of all four types of standard nucleotides, we conducted a search of the surrounding sequence space to identify functional derivatives with catalytic cores composed of only three, and subsequently only two types of nucleotides. We provide the first report of a DNAzyme that contains only guanosine and cytidine deoxyribonucleotides in its catalytic domain, which consists of just 13 nucleotides. This DNAzyme catalyzes the Mn2+-dependent cleavage of an RNA phosphodiester bond ∼5300-fold faster than the corresponding uncatalyzed reaction, but ∼10 000-fold slower than the parent. The demonstration of a catalytic DNA molecule made from a binary nucleotide alphabet broadens our understanding of the fundamental limits of nucleic-acid-mediated catalysis. PMID:19050014

  20. Kinetics of the hydrolysis of guanosine 5'-phospho-2-methylimidazolide

    NASA Technical Reports Server (NTRS)

    Kanavarioti, Anastassia

    1986-01-01

    The hydrolysis kinetics of guanosine 5'-phospho-2-methylimidazolide (2-MeImpG) in aqueous buffered solutions of various pH's was studied at 75 and 37 C, using spectrophotometric and HPLC techniques. The hydrolysis was found to be very slow even at low pH. At 75 C and pH at or below l.0, two kinetic processes were observed: the more rapid one was attributed to the hydrolysis of the phosphoimidazolide P-N bond; the second, much slower one, was attributed to the cleavage of the glycosidic bond. It is noted that the P-N hydrolysis in phosphoimidazolides is very slow compared to other phosphoramidates, and that this might be one of the reasons why the phosphoimidazolides showed an extraordinary ability to form long oligomers under template-directed conditions.

  1. Nucleotides as nucleophiles: reactions of nucleotides with phosphoimidazolide activated guanosine

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Rosenbach, M. T.; Hurley, T. B.

    1991-01-01

    An earlier study of the reaction of phosphoimidazolide activated nucleosides (ImpN) in aqueous phosphate buffers indicated two modes of reaction of the phosphate monoanion and dianion. The first mode is catalysis of the hydrolysis of the P-N bond in ImpN's which leads to imidazole and nucleoside 5'-monophosphate. The second represents a nucleophilic substitution of the imidazole to yield the nucleoside 5'-diphosphate. This earlier study thus served as a model for the reaction of ImpN with nucleoside monophosphates (pN) because the latter can be regarded as phosphate derivatives. In the present study we investigated the reaction of guanosine 5'-phosphate-2-methylimidazolide, 2-MeImpG, in the presence of pN (N = guanosine, adenosine and uridine) in the range 6.9 less than or equal to pH less than or equal to 7.7. We observed that pN's do act as nucleophiles to form NppG, and as general base to enhance the hydrolysis of the P-N bond in 2-MeImpG, i.e. pN show the same behavior as inorganic phosphate. The kinetic analysis yields the following rate constants for the dianion pN2-: knpN = 0.17 +/- 0.02 M-1 h-1 for nucleophilic attack and khpN = 0.11 +/- 0.07 M-1 h-1 for general base catalysis of the hydrolysis. These rate constants which are independent of the nucleobase compare with kp.2 = 0.415 M-1 h-1 and khp2. = 0.217 M-1 h-1 for the reactions of HPO4(2-). In addition, this study shows that under conditions where pN presumably form stacks, the reaction mechanism remains unchanged although in quantitative terms stacked pN are somewhat less reactive. Attack by the 2'-OH and 3'-OH groups of the ribose moiety in amounts greater than or equal to 1% is not observed; this is attributed to the large difference in nucleophilicity in the neutral pH range between the phosphate group and the ribose hydroxyls. This nucleophilicity rank is not altered by stacking.

  2. Nitric oxide and cyclic guanosine monophosphate signaling in the eye.

    PubMed

    Murad, Ferid

    2008-06-01

    This brief review describes the components and pathways utilized in nitric oxide (NO) and cyclic guanosine monophosphate (cGMP) signaling. Since the discovery of the effects of NO and cGMP on smooth muscle relaxation about 30 years ago, the field has expanded in many directions such that many, but not all, biochemical and biological effects seem to be regulated by these unique signaling molecules. While many of the effects of NO are due to activation of soluble guanylyl cyclase (sGC) that can be considered the receptor for NO, cGMP, in turn, can activate a cGMP-dependent protein kinase (PKG) to phosphorylate an array of proteins. Some of the effects of cGMP can be independent of PKG and are due to effects on ion channels or cyclic nucleotide phosphodiesterases. Also, some of the effects of NO can be independent of sGC activation. The isoenzymes and macromolecules that participate in these signaling pathways can serve as molecular targets to identify compounds that increase or decrease their activation and thus serve as chemical leads for discovering novel drugs for a variety of diseases. Some examples are given. However, with about 90,000 publications in the field since our first reports in 1977, this brief review can only give the readers a sample of the excitement and opportunities we have found in this cell signaling system. PMID:18443613

  3. Ag(+)-mediated assembly of 5'-guanosine monophosphate.

    PubMed

    Loo, Kristine; Degtyareva, Natalya; Park, Jihae; Sengupta, Bidisha; Reddish, Michaeal; Rogers, Christopher C; Bryant, Andrea; Petty, Jeffrey T

    2010-04-01

    Polymorphic forms of nucleic acids provide platforms for new nanomaterials, and transition metal cations give access to alternative arrangements of nucleobases by coordinating with electron-rich functional groups. Interaction of Ag(+) with 5'-guanosine monophosphate (5'-GMP) is considered in this work. Ag(+) promotes nucleotide stacking and aggregation, as indicated by the increased viscosity of 5'-GMP solutions with Ag(+), magnification of the circular dichroism response of guanine by Ag(+), and exothermic reactions between Ag(+) and guanine derivatives. Isothermal titration calorimetry studies show that the reaction is favored starting at 10 microM 5'-GMP. Utilizing the exothermic heat change associated with reaction of Ag(+) with 5'-GMP, local structure within the aggregate was assessed. On the basis of the salt dependence of the reaction and comparison with the corresponding nucleoside, the dianionic phosphate of 5'-GMP is one binding site for Ag(+), although this electrostatic interaction is not a dominant contribution to the overall heat change. Another binding site is the N7 on the nucleobase, as determined via studies with 7-deazaguanosine. Besides this binding site, Ag(+) also associates with the O6, as earlier studies deduced from the shift in the carbonyl stretching frequency associated with adduct formation. With these two binding sites on the nucleobase, the empirical stoichiometry of approximately 1 Ag(+):nucleobase derived from the calorimetry studies indicates that Ag(+) coordinates two nucleobases. The proposed structural model is a Ag(+)-mediated guanine dimer within a base stacked aggregate. PMID:20205377

  4. Guanosine potentiates the antiproliferative effect of cytosine-beta-D-arabinofuranoside in melanoma cell lines.

    PubMed

    Sidi, Y; Panet, C; Cyjon, A; Fenig, E; Beery, E; Nordenberg, J

    1993-01-01

    Guanosine is shown to potentiate markedly the antiproliferative effect of cytosine-beta-D-arabinoside (ara-C) on B16 F10 mouse and SKMEL-28 human melanoma cell lines. Several metabolic consequences of the synergistic interaction between ara-C and guanosine on cell growth were determined in B16 F10 mouse melanoma cells. Treatment of the cells with guanosine for 24 hr resulted in an increase in the percentage of cells in the S phase of the cell cycle, a threefold increase in intracellular GTP concentration, and an increase in the incorporation of ara-C into acid-insoluble material and phosphorylated metabolites. These findings suggest that guanosine potentiates the growth-inhibitory effect of ara-C in B16 F10 melanoma cells by increasing the intracellular concentration of its active metabolites. PMID:8402221

  5. Tissue distribution and metabolism of guanosine in rats following intraperitoneal injection.

    PubMed

    Giuliani, P; Ballerini, P; Ciccarelli, R; Buccella, S; Romano, S; D'Alimonte, I; D' Alimonte, I; Poli, A; Beraudi, A; Peña, E; Jiang, S; Rathbone, M P; Caciagli, F; Di Iorio, P

    2012-01-01

    Guanosine has long been known as an endogenous purine nucleoside deeply involved in the modulation of several intracellular processes, especially G-protein activity. More recently, it has been reported to act as an extracellular signaling molecule released from neurons and, more markedly, from astrocytes either in basal conditions or after different kinds of stimulation including hypoxia. Moreover, in vivo studies have shown that guanosine plays an important role as both a neuroprotective and neurotrophic agent in the central nervous system. Specific high-affinity binding sites for this nucleoside have been found on membrane preparations from rat brain. The present study was undertaken to investigate the distribution and metabolic profiles of guanosine after administering the nucleoside to gain a better understanding of the biological effects of this potential drug candidate. Rats were given an intraperitonal (i.p.) injection of 2, 4, 8 or 16 mg/kg of guanosine combined with 0.05% of [3H]guanosine. Plasma samples were collected 7.5, 15, 30, 60 and 90 min after the guanosine-mixture administration and analyzed by either a liquid scintillation counter or by HPLC connected to a UV and to an on-line radiochemical detector to measure the levels of guanosine and its metabolic products guanine, xanthine and uric acid. The levels of guanosine, guanine and xanthine were also measured in brain, lung, heart, kidney and liver tissue homogenates at the defined time points after the injection of 8 mg/kg of the guanosine-mixture. We found that the levels of radioactivity in plasma increased linearly in a dose- and time-dependent manner. Guanosine was widely distributed in all tissues examined in the present study, at almost twice its usual levels. In addition, guanine levels dramatically increased in all the organs. Interestingly, enzymatic analysis of the plasma samples showed the presence of a soluble purine nucleoside phosphorylase, a key enzyme in the purine salvage pathway

  6. Determination of phosphate in soil extracts in the field: A green chemistry enzymatic method

    PubMed Central

    Campbell, Ellen R.; Warsko, Kayla; Davidson, Anna-Marie; (Bill) Campbell, Wilbur H.

    2015-01-01

    Measurement of ortho-phosphate in soil extracts usually involves sending dried samples of soil to a laboratory for analysis and waiting several weeks for the results. Phosphate determination methods often involve use of strong acids, heavy metals, and organic dyes. To overcome limitations of this approach, we have developed a phosphate determination method which can be carried out in the field to obtain results on the spot. This new method uses: • Small volumes. • An enzymatic reaction. • Green chemistry. First, the soil sample is extracted with deionized water and filtered. Next, an aliquot of the soil extract (0.5 mL) is transferred to a disposable cuvette, containing 0.5 mL of reaction mixture [200 mM HEPES, pH 7.6, 20 mM MgCl2, with 80 nmol 2-amino-6-mercapto-7-methylpurine ribonucleoside (MESG) and 1 unit of recombinant purine nucleoside phosphorylase (PNP; EC 2.4.2.1)], mixed, and incubated for 10 min at field temperature. Absorbance of the completed reaction is measured at 360 nm in open-source, portable photometer linked by bluetooth to a smartphone. The phosphate and phosphorus content of the soil is determined by comparison of its absorbance at 360 nm to a previously prepared standard phosphate curve, which is stored in the smartphone app. PMID:26150991

  7. Determination of phosphate in soil extracts in the field: A green chemistry enzymatic method.

    PubMed

    Campbell, Ellen R; Warsko, Kayla; Davidson, Anna-Marie; Bill Campbell, Wilbur H

    2015-01-01

    Measurement of ortho-phosphate in soil extracts usually involves sending dried samples of soil to a laboratory for analysis and waiting several weeks for the results. Phosphate determination methods often involve use of strong acids, heavy metals, and organic dyes. To overcome limitations of this approach, we have developed a phosphate determination method which can be carried out in the field to obtain results on the spot. This new method uses: •Small volumes.•An enzymatic reaction.•Green chemistry. First, the soil sample is extracted with deionized water and filtered. Next, an aliquot of the soil extract (0.5 mL) is transferred to a disposable cuvette, containing 0.5 mL of reaction mixture [200 mM HEPES, pH 7.6, 20 mM MgCl2, with 80 nmol 2-amino-6-mercapto-7-methylpurine ribonucleoside (MESG) and 1 unit of recombinant purine nucleoside phosphorylase (PNP; EC 2.4.2.1)], mixed, and incubated for 10 min at field temperature. Absorbance of the completed reaction is measured at 360 nm in open-source, portable photometer linked by bluetooth to a smartphone. The phosphate and phosphorus content of the soil is determined by comparison of its absorbance at 360 nm to a previously prepared standard phosphate curve, which is stored in the smartphone app. PMID:26150991

  8. Guanosine protects glial cells against 6-hydroxydopamine toxicity.

    PubMed

    Giuliani, Patricia; Ballerini, Patrizia; Buccella, Silvana; Ciccarelli, Renata; Rathbone, Michel P; Romano, Silvia; D'Alimonte, Iolanda; Caciagli, Francesco; Di Iorio, Patrizia; Pokorski, Mieczyslaw

    2015-01-01

    Increasing body of evidence indicates that neuron-neuroglia interaction may play a key role in determining the progression of neurodegenerative diseases including Parkinson's disease (PD), a chronic pathological condition characterized by selective loss of dopaminergic (DA) neurons in the substantia nigra. We have previously reported that guanosine (GUO) antagonizes MPP(+)-induced cytotoxicity in neuroblastoma cells and exerts neuroprotective effects against 6-hydroxydopamine (6-OHDA) and beta-amyloid-induced apoptosis of SH-SY5Y cells. In the present study we demonstrate that GUO protected C6 glioma cells, taken as a model system for astrocytes, from 6-OHDA-induced neurotoxicity. We show that GUO, either alone or in combination with 6-OHDA activated the cell survival pathways ERK and PI3K/Akt. The involvement of these signaling systems in the mechanism of the nucleoside action was strengthened by a reduction of the protective effect when glial cells were pretreated with U0126 or LY294002, the specific inhibitors of MEK1/2 and PI3K, respectively. Since the protective effect on glial cell death of GUO was not affected by pretreatment with a cocktail of nucleoside transporter blockers, GUO transport and its intracellular accumulation were not at play in our in vitro model of PD. This fits well with our data which pointed to the presence of specific binding sites for GUO on rat brain membranes. On the whole, the results described in the present study, along with our recent evidence showing that GUO when administered to rats via intraperitoneal injection is able to reach the brain and with previous data indicating that it stimulates the release of neurotrophic factors, suggest that GUO, a natural compound, by acting at the glial level could be a promising agent to be tested against neurodegeneration. PMID:25310956

  9. Indolyl-3-butyric acid-induced Arabidopsis stomatal opening mediated by 3',5'-cyclic guanosine-monophosphate.

    PubMed

    Cousson, A

    2010-12-01

    It has been pharmacologically suggested that 3',5'-cyclic guanosine-monophosphate (cGMP) mediates indolyl-3-butyric acid (IBA)-induced stomatal opening. In Arabidopsis thaliana (L.) Heynh., such investigations compared the wild type (Columbia and Ws ecotypes) to mutants knockout for either GTP-binding protein (G protein) α subunit 1 (gpa1-4), putative G protein-coupled receptor 1 (gcr1-5), calcineurin B-like isoform 1 (cbl1) or 9 (cbl9), or the NADPH oxidases AtrbohD and AtrbohF (atrbohD/F). Stomatal opening to IBA or the permeant cGMP analogue, 8-bromo-cGMP (8-Br-cGMP) was abolished in the atrbohD/F mutant. The IBA response was fully or partially suppressed, respectively, in the gcr1-5 mutant, or the gpa1-4 and cbl1 mutants. In the cbl9 mutant, the response to IBA or 8-Br-cGMP, respectively, was partially or fully suppressed. Phenylarsine oxide (PAO) affected the IBA response, which the cbl1 mutant overlapped or the gpa1-4 and cbl9 mutants increased up to 100% inhibition. 6-anilino-5,8-quinolinedione, mas17, the (Rp)-diastereomer of 8-bromo-3',5'-cyclic guanosine monophosphorothioate (Rp-8-Br-cGMPS), nicotinamide, ruthenium red (RRed), 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), cyclosporine A (CsA) and FK506 converged to affect the IBA response, which the gpa1-4 and cbl9 mutants overlapped or the cbl1 mutant and PAO increased up to 100% inhibition. Rp-8-Br-cGMPS, nicotinamide, RRed, BAPTA, CsA or FK506 paralled the cbl9 and atrbohD/F mutants to abolish the 8-Br-cGMP response. Based on so far revealed features of these mutants and pharmacological compounds, these results confirmed cGMP as a Ca(2+)-mobilizing second messenger for apoplastic auxin whose perception and transduction would implicate a seven-transmembrane receptor - G protein - guanylyl cyclase unit at the guard cell plasma membrane. PMID:20951600

  10. Nonenzymatic template-directed synthesis on hairpin oligonucleotides. II - Templates containing cytidine and guanosine residues

    NASA Technical Reports Server (NTRS)

    Wu, Taifeng; Orgel, Leslie E.

    1992-01-01

    Hairpin oligonucleotides were prepared with 5-prime-terminal single-stranded sequments containing cytidylate (C) and guanylate (G) residues. It was found that incubation of these hairpin oligonucleotides with a mixutre of cytidine and guanosine 5-prime-phosphoro (2-methyl)imidazolides results in sequence-specific addition of C and G residues to the 3-prime terminus of the hairpin.

  11. Voltammetric determination of adenosine and guanosine using fullerene-C(60)-modified glassy carbon electrode.

    PubMed

    Goyal, Rajendra N; Gupta, Vinod K; Oyama, Munetaka; Bachheti, Neeta

    2007-02-28

    A fullerene-C(60)-modified glassy carbon electrode (GCE) is used for the simultaneous determination of adenosine and guanosine by differential pulse voltammetry. Compared to a bare glassy carbon electrode, the modified electrode exhibits an apparent shift of the oxidation potentials in the cathodic direction and a marked enhancement in the voltammetric peak current response for both the biomolecules. Linear calibration curves are obtained over the concentration range 0.5muM-1.0mM in 0.1M phosphate buffer solution at pH 7.2 with a detection limit of 3.02x10(-7)M and 1.45x10(-7)M for individual determination of adenosine and guanosine, respectively. The interference studies showed that the fullerene-C(60)-modified glassy carbon electrode exhibited excellent selectivity in the presence of hypoxanthine, xanthine, uric acid and ascorbic acid. The proposed procedure was successfully applied to detect adenosine and guanosine in human blood plasma and urine, without any preliminary pre-treatment. PMID:19071420

  12. Novel bimodular DNA aptamers with guanosine quadruplexes inhibit phylogenetically diverse HIV-1 reverse transcriptases

    PubMed Central

    Michalowski, Daniel; Chitima-Matsiga, Rebecca; Held, Daniel M.; Burke, Donald H.

    2008-01-01

    DNA aptamers RT5, RT6 and RT47 form a group of related sequences that inhibit HIV-1 reverse transcriptase (RT). The essential inhibitory structure is identified here as bimodular, with a 5′ stem–loop module physically connected to a 3′-guanosine quadruplex module. The stem–loop tolerates considerable sequence plasticity. Connections between the guanosine triplets in the quadruplex could be simplified to a single nucleotide or a nonnucleic acid linker, such as hexaethylene glycol. All 12 quadruplex guanosines are required in an aptamer retaining most of the original loop sequence from RT6; only 11 are required for aptamer R1T (single T residue in intra-quadruplex loops). Circular dichroism (CD) spectroscopy gave ellipticity minima and maxima at 240 nm and 264 nm, indicating a parallel arrangement of the quadruplex strands. The simplified aptamers displayed increased overall stability. An aptamer carrying the original intra-quadruplex loops from RT6 inhibited RT in K+ buffers but not in Na+ buffers and displayed significant CD spectral broadening in Na+ buffers, while R1T inhibited RT in both buffers and displayed less broadening in Na+ buffers. The bimodular ssDNA aptamers inhibited RT from diverse primate lentiviruses with low nM IC50 values. These data provide insight into the requirements for broad-spectrum RT inhibition by nucleic acid aptamers. PMID:18996899

  13. Guanosine effect on cholesterol efflux and apolipoprotein E expression in astrocytes.

    PubMed

    Ballerini, Patrizia; Ciccarelli, Renata; Di Iorio, Patrizia; Buccella, Silvana; D'Alimonte, Iolanda; Giuliani, Patricia; Masciulli, Arianna; Nargi, Eleonora; Beraudi, Alina; Rathbone, Michel P; Caciagli, Francesco

    2006-11-01

    The main source of cholesterol in the central nervous system (CNS) is represented by glial cells, mainly astrocytes, which also synthesise and secrete apolipoproteins, in particular apolipoprotein E (ApoE), the major apolipoprotein in the brain, thus generating cholesterol-rich high density lipoproteins (HDLs). This cholesterol trafficking, even though still poorly known, is considered to play a key role in different aspects of neuronal plasticity and in the stabilisation of synaptic transmission. Moreover, cell cholesterol depletion has recently been linked to a reduction in amyloid beta formation. Here we demonstrate that guanosine, which we previously reported to exert several neuroprotective effects, was able to increase cholesterol efflux from astrocytes and C6 rat glioma cells in the absence of exogenously added acceptors. In this effect the phosphoinositide 3 kinase/extracellular signal-regulated kinase 1/2 (PI3K/ERK1/2) pathway seems to play a pivotal role. Guanosine was also able to increase the expression of ApoE in astrocytes, whereas it did not modify the levels of ATP-binding cassette protein A1 (ABCA1), considered the main cholesterol transporter in the CNS. Given the emerging role of cholesterol balance in neuronal repair, these effects provide evidence for a role of guanosine as a potential pharmacological tool in the modulation of cholesterol homeostasis in the brain. PMID:18404467

  14. Remyelination after chronic spinal cord injury is associated with proliferation of endogenous adult progenitor cells after systemic administration of guanosine.

    PubMed

    Jiang, Shucui; Ballerini, Patrizia; Buccella, Silvana; Giuliani, Patricia; Jiang, Cai; Huang, Xinjie; Rathbone, Michel P

    2008-03-01

    Axonal demyelination is a consistent pathological sequel to chronic brain and spinal cord injuries and disorders that slows or disrupts impulse conduction, causing further functional loss. Since oligodendroglial progenitors are present in the demyelinated areas, failure of remyelination may be due to lack of sufficient proliferation and differentiation of oligodendroglial progenitors. Guanosine stimulates proliferation and differentiation of many types of cells in vitro and exerts neuroprotective effects in the central nervous system (CNS). Five weeks after chronic traumatic spinal cord injury (SCI), when there is no ongoing recovery of function, intraperitoneal administration of guanosine daily for 2 weeks enhanced functional improvement correlated with the increase in myelination in the injured cord. Emphasis was placed on analysis of oligodendrocytes and NG2-positive (NG2+) cells, an endogenous cell population that may be involved in oligodendrocyte replacement. There was an increase in cell proliferation (measured by bromodeoxyuridine staining) that was attributable to an intensification in progenitor cells (NG2+ cells) associated with an increase in mature oligodendrocytes (determined by Rip+ staining). The numbers of astroglia increased at all test times after administration of guanosine whereas microglia only increased in the later stages (14 days). Injected guanosine and its breakdown product guanine accumulated in the spinal cords; there was more guanine than guanosine detected. We conclude that functional improvement and remyelination after systemic administration of guanosine is due to the effect of guanosine/guanine on the proliferation of adult progenitor cells and their maturation into myelin-forming cells. This raises the possibility that administration of guanosine may be useful in the treatment of spinal cord injury or demyelinating diseases such as multiple sclerosis where quiescent oligodendroglial progenitors exist in demyelinated plaques. PMID

  15. Remyelination after chronic spinal cord injury is associated with proliferation of endogenous adult progenitor cells after systemic administration of guanosine

    PubMed Central

    Ballerini, Patrizia; Buccella, Silvana; Giuliani, Patricia; Jiang, Cai; Huang, Xinjie; Rathbone, Michel P.

    2008-01-01

    Axonal demyelination is a consistent pathological sequel to chronic brain and spinal cord injuries and disorders that slows or disrupts impulse conduction, causing further functional loss. Since oligodendroglial progenitors are present in the demyelinated areas, failure of remyelination may be due to lack of sufficient proliferation and differentiation of oligodendroglial progenitors. Guanosine stimulates proliferation and differentiation of many types of cells in vitro and exerts neuroprotective effects in the central nervous system (CNS). Five weeks after chronic traumatic spinal cord injury (SCI), when there is no ongoing recovery of function, intraperitoneal administration of guanosine daily for 2 weeks enhanced functional improvement correlated with the increase in myelination in the injured cord. Emphasis was placed on analysis of oligodendrocytes and NG2-positive (NG2+) cells, an endogenous cell population that may be involved in oligodendrocyte replacement. There was an increase in cell proliferation (measured by bromodeoxyuridine staining) that was attributable to an intensification in progenitor cells (NG2+ cells) associated with an increase in mature oligodendrocytes (determined by Rip+ staining). The numbers of astroglia increased at all test times after administration of guanosine whereas microglia only increased in the later stages (14 days). Injected guanosine and its breakdown product guanine accumulated in the spinal cords; there was more guanine than guanosine detected. We conclude that functional improvement and remyelination after systemic administration of guanosine is due to the effect of guanosine/guanine on the proliferation of adult progenitor cells and their maturation into myelin-forming cells. This raises the possibility that administration of guanosine may be useful in the treatment of spinal cord injury or demyelinating diseases such as multiple sclerosis where quiescent oligodendroglial progenitors exist in demyelinated plaques

  16. Relationship between antitumor effect and metabolites of 5-fluorouracil in combination treatment with 5-fluorouracil and guanosine in ascites Sarcoma 180 tumor system

    SciTech Connect

    Iigo, M.; Kuretani, K.; Hoshi, A.

    1983-12-01

    The antitumor activity of (6-14C)5-fluorouracil ((6-14C)FUra) against ascites Sarcoma 180 was significantly enhanced by coadministration of guanosine, and slightly by adenosine, but not by cytidine or uridine. In advanced ascites Sarcoma 180, guanosine also enhanced the action of FUra, but adenosine, uridine, and cytidine did not. The potentiation of antitumor activity by guanosine was reversed by addition of cytidine. The antitumor activity of FUra was significantly potentiated when guanosine was administered either 0 to 15 min before or 5 min after FUra. Changes in metabolites of FUra after potentiation by guanosine were investigated. The potentiation of antitumor activity of FUra by guanosine was considered to be due to an increase in incorporation of FUra into FUra-nucleotides and RNA in the tumor cells.

  17. Use of phosphoimidazolide-activated guanosine to investigate the nucleophilicity of spermine and spermidine

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Baird, E. E.; Smith, P. J.

    1995-01-01

    Guanosine 5'-phosphate 2-methylimidazolide (2-MeImpG), a labile phosphoimidazolide analog of guanosine triphosphate, was used to test the reactivity of the natural polyamines (PAs), spermine (spm) and spermidine (spd). The products are the guanosine 5'-phosphate-polyamine derivatives (PA-pG: spd-pG and spm-pG) which are quite stable in the range 4 < pH < 11. Our study is the first of which we are aware that reports on the nucleophilicity of these amines. The main findings are as follows. (i) HPLC analysis of the products indicates the formation of only two of the three possible spd products and only one of the two possible spm products. These results can be explained if only the primary amino groups of the two polyamines are reactive, while the secondary amino groups are rendered unreactive by a steric effect. The reactions of 2-MeImpG and other phosphoimidazolide derivatives of nucleosides (ImpNs) with primary and secondary monoamines support this interpretation (Kanavarioti et al. J. Org. Chem. 1995, 60, 632). (ii) The product ratio of the two spd-pG adducts derived from the primary amino groups varies between 2.40 and 0.71 in the range 6.1 < or equal to pH < or equal to 11.9. Such small variation in the product ratio can only be rationalized by the similar, but not identical, basicity of the two primary amino groups and provides strong support for a previously reported model for polyamine ionization (Onasch et. al. Biophys. Chem. 1984, 19, 245). (iii) On the basis of our kinetic determinations conditions at which the nucleophilicity of these amines is at a minimum and at which other interactions with ImpNs could be tested can be chosen.

  18. Fluorescent Sensing of Guanine and Guanosine Monophosphate with Conjugated Receptors Incorporating Aniline and Naphthyridine Moieties.

    PubMed

    Lu, Shao-Hung; Phang, Riping; Fang, Jim-Min

    2016-04-15

    Ethyne-linked naphthyridine-aniline conjugated molecules are selective sensors of decylguanine in dichloromethane and guanosine monophosphate in water (Kass = 16 000 M(-1)). The 2-acetamido-1,8-naphthyridine moiety binds with guanine in a DAA-ADD triply hydrogen-bonded motif. The aniline moiety enhances an electron-donating effect, and the substituent is tuned to attain extra hydrogen bonds, π-π stacking, and electrostatic interactions. The proposed binding modes are supported by a Job plot, ESI-MS, (1)H NMR, UV-vis, and fluorescence spectral analyses. PMID:27018895

  19. Guanosine reduces apoptosis and inflammation associated with restoration of function in rats with acute spinal cord injury

    PubMed Central

    Bendjelloul, Farid; Ballerini, Patrizia; D’Alimonte, Iolanda; Nargi, Elenora; Jiang, Cai; Huang, Xinjie; Rathbone, Michel P.

    2007-01-01

    Spinal cord injury results in progressive waves of secondary injuries, cascades of noxious pathological mechanisms that substantially exacerbate the primary injury and the resultant permanent functional deficits. Secondary injuries are associated with inflammation, excessive cytokine release, and cell apoptosis. The purine nucleoside guanosine has significant trophic effects and is neuroprotective, antiapoptotic in vitro, and stimulates nerve regeneration. Therefore, we determined whether systemic administration of guanosine could protect rats from some of the secondary effects of spinal cord injury, thereby reducing neurological deficits. Systemic administration of guanosine (8 mg/kg per day, i.p.) for 14 consecutive days, starting 4 h after moderate spinal cord injury in rats, significantly improved not only motor and sensory functions, but also recovery of bladder function. These improvements were associated with reduction in the inflammatory response to injury, reduction of apoptotic cell death, increased sparing of axons, and preservation of myelin. Our data indicate that the therapeutic action of guanosine probably results from reducing inflammation resulting in the protection of axons, oligodendrocytes, and neurons and from inhibiting apoptotic cell death. These data raise the intriguing possibility that guanosine may also be able to reduce secondary pathological events and thus improve functional outcome after traumatic spinal cord injury in humans. PMID:18404454

  20. The combination of organoselenium compounds and guanosine prevents glutamate-induced oxidative stress in different regions of rat brains.

    PubMed

    Dalla Corte, Cristiane L; Bastos, Luíza L; Dobrachinski, Fernando; Rocha, João B T; Soares, Félix A A

    2012-01-01

    This study was designed to investigate the protective effects of the combination of guanosine and 2 organoselenium compounds (ebselen and diphenyl diselenide) against glutamate-induced oxidative stress in different regions of rat brains. Glutamate caused an increase in reactive oxygen species (ROS) generation and a decrease in [(3)H]-glutamate uptake in striatal, cortical, and hippocampal slices. Guanosine, ebselen, and diphenyl diselenide prevented glutamate-induced ROS production in striatal, cortical and hippocampal slices. The combination of guanosine with organoselenium compounds was more effective against glutamate-induced ROS production than the individual compounds alone. Guanosine prevented [(3)H]-glutamate uptake inhibition in striatal, cortical, and hippocampal slices. Thus, protection against the harmful effects of glutamate is possibly due to the combination of the antioxidant properties of organoselenium compounds and the stimulatory effect of guanosine on glutamate uptake. In conclusion, the combination of antioxidants and glutamatergic system modulators could be considered a potential therapy against the prooxidant effects of glutamate. PMID:22133308

  1. The Synthesis of Guanosine 5′-Diphosphate l-Fucose from Guanosine 5′-Diphosphate 3,5-d-[3H]Mannose Catalyzed by an Enzyme Extract from Fruits of the Flax

    PubMed Central

    Barber, George A.

    1980-01-01

    An enzyme system from fruits of the flax plant is described that catalyzes the synthesis of the sugar nucleotide guanosine 5′-diphosphate l-fucose from guanosine 5′-diphosphate d-mannose with the intermediate formation of guanosine 5′-diphosphate 4-keto-6-deoxy-d-mannose. Tritium from-[3H]H2O was incorporated into the l-fucose portion of the sugar nucleotide in the course of the reaction, and tritium at the 3,5-carbons of the d-mannose moiety of GDP-d-mannose was exchanged with protons in the medium. These results support a mechanism of synthesis analogous to that proposed for the formation of l-rhamnose and other 6-deoxy sugars. PMID:16661431

  2. A Transition State Analogue for an RNA-Editing Reaction

    PubMed Central

    Haudenschild, Brittany L.; Maydanovych, Olena; Véliz, Eduardo A.; Macbeth, Mark R.; Bass, Brenda L.; Beal, Peter A.

    2007-01-01

    Deamination at C6 of adenosine in RNA catalyzed by the ADAR enzymes generates inosine at the corresponding position. Because inosine is decoded as guanosine during translation, this modification can lead to codon changes in messenger RNA. Hydration of 8-azanebularine across the C6–N1 double bond generates an excellent mimic of the transition state proposed for the hydrolytic deamination reaction catalyzed by ADARs. Here, we report the synthesis of a phosphoramidite of 8-azanebularine and its use in the preparation of RNAs mimicking the secondary structure found at a known editing site in the glutamate receptor B subunit pre-mRNA. The binding properties of analogue-containing RNAs indicate that a tight binding ligand for an ADAR can be generated by incorporation of 8-azanebularine. The observed high-affinity binding is dependent on a functional active site, the presence of one, but not the other, of ADAR2’s two double-stranded RNA-binding motifs (dsRBMs), and the correct placement of the nucleoside analogue into the sequence/structural context of a known editing site. These results advance our understanding of substrate recognition during ADAR-catalyzed RNA editing and are important for structural studies of ADAR· RNA complexes. PMID:15355102

  3. Plant Purine Nucleoside Catabolism Employs a Guanosine Deaminase Required for the Generation of Xanthosine in Arabidopsis[W

    PubMed Central

    Dahncke, Kathleen; Witte, Claus-Peter

    2013-01-01

    Purine nucleotide catabolism is common to most organisms and involves a guanine deaminase to convert guanine to xanthine in animals, invertebrates, and microorganisms. Using metabolomic analysis of mutants, we demonstrate that Arabidopsis thaliana uses an alternative catabolic route employing a highly specific guanosine deaminase (GSDA) not reported from any organism so far. The enzyme is ubiquitously expressed and deaminates exclusively guanosine and 2’-deoxyguanosine but no other aminated purines, pyrimidines, or pterines. GSDA belongs to the cytidine/deoxycytidylate deaminase family of proteins together with a deaminase involved in riboflavin biosynthesis, the chloroplastic tRNA adenosine deaminase Arg and a predicted tRNA-specific adenosine deaminase 2 in A. thaliana. GSDA is conserved in plants, including the moss Physcomitrella patens, but is absent in the algae and outside the plant kingdom. Our data show that xanthosine is exclusively generated through the deamination of guanosine by GSDA in A. thaliana, excluding other possible sources like the dephosphorylation of xanthosine monophosphate. Like the nucleoside hydrolases NUCLEOSIDE HYDROLASE1 (NSH1) and NSH2, GSDA is located in the cytosol, indicating that GMP catabolism to xanthine proceeds in a mostly cytosolic pathway via guanosine and xanthosine. Possible implications for the biosynthetic route of purine alkaloids (caffeine and theobromine) and ureides in other plants are discussed. PMID:24130159

  4. Novel Characteristics of Trypanosoma brucei Guanosine 5'-monophosphate Reductase Distinct from Host Animals

    PubMed Central

    Kimura, Chihiro; Shinohara, Takahiro; Tomiyama, Ai; Imamura, Akira; Kuwamura, Mitsuru; Nishimura, Kazuhiko; Fujimori, Ko; Shuto, Satoshi; Ishibashi, Osamu; Kubata, Bruno Kilunga; Inui, Takashi

    2016-01-01

    The metabolic pathway of purine nucleotides in parasitic protozoa is a potent drug target for treatment of parasitemia. Guanosine 5’-monophosphate reductase (GMPR), which catalyzes the deamination of guanosine 5’-monophosphate (GMP) to inosine 5’-monophosphate (IMP), plays an important role in the interconversion of purine nucleotides to maintain the intracellular balance of their concentration. However, only a few studies on protozoan GMPR have been reported at present. Herein, we identified the GMPR in Trypanosoma brucei, a causative protozoan parasite of African trypanosomiasis, and found that the GMPR proteins were consistently localized to glycosomes in T. brucei bloodstream forms. We characterized its recombinant protein to investigate the enzymatic differences between GMPRs of T. brucei and its host animals. T. brucei GMPR was distinct in having an insertion of a tandem repeat of the cystathionine β-synthase (CBS) domain, which was absent in mammalian and bacterial GMPRs. The recombinant protein of T. brucei GMPR catalyzed the conversion of GMP to IMP in the presence of NADPH, and showed apparent affinities for both GMP and NADPH different from those of its mammalian counterparts. Interestingly, the addition of monovalent cations such as K+ and NH4+ to the enzymatic reaction increased the GMPR activity of T. brucei, whereas none of the mammalian GMPR’s was affected by these cations. The monophosphate form of the purine nucleoside analog ribavirin inhibited T. brucei GMPR activity, though mammalian GMPRs showed no or only a little inhibition by it. These results suggest that the mechanism of the GMPR reaction in T. brucei is distinct from that in the host organisms. Finally, we demonstrated the inhibitory effect of ribavirin on the proliferation of trypanosomes in a dose-dependent manner, suggesting the availability of ribavirin to develop a new therapeutic agent against African trypanosomiasis. PMID:26731263

  5. Aspartame and Its Analogues

    NASA Astrophysics Data System (ADS)

    Pavlova, L. A.; Komarova, T. V.; Davidovich, Yurii A.; Rogozhin, S. V.

    1981-04-01

    The results of studies on the biochemistry of the sweet taste are briefly reviewed. The methods of synthesis of "aspartame" — a sweet dipeptide — are considered, its structural analogues are described, and quantitative estimates are made of the degree of sweetness relative to sucrose. Attention is concentrated mainly on problems of the relation between the structure of the substance and its taste in the series of aspartyl derivatives. The bibliography includes 118 references.

  6. Modulating the Cyclic Guanosine Monophosphate Substrate Selectivity of the Phosphodiesterase 3 Inhibitors by Pyridine, Pyrido[2,3-d]pyrimidine Derivatives and Their Effects upon the Growth of HT-29 Cancer Cell Line

    PubMed Central

    Abadi, Ashraf Hassan; Hany, Marwa Saeed; Elsharif, Shimaa Awadain; Eissa, Amal Abdel Haleem; Gary, Bernard DeWayne; Tinsley, Heather Nicole; Piazza, Gary Anthony

    2016-01-01

    Analogues with the scaffolds of 3-cyano-4-alkoxyphenyl-6-bromoaryl-2-pyridone and 2-amino-3-cyano-4-alkoxyphenyl-6-bromoarylpyridine were synthesized. Cyclization of the 2-amino derivatives with formic acid and formamide gave the corresponding pyrido[2,3-d]pyrimidin-4(3H)-one and the pyrido[2,3-d]pyrimidin-4-amine derivatives, respectively. Active phosphodiesterase 3 (PDE3) inhibitors were identified from each of the four aforementioned scaffolds. This is the first report that pyrido[2,3-d]pyrimidin-4(3H)-one and pyrido[2,3-d]pyrimidin-4-amine derivatives can inhibit PDE3. The analogues with the pyridone and pyrido[2,3-d]pyrimidin-4(3H)-one scaffolds inhibited both cAMP and cyclic guanosine monophosphate (cGMP) hydrolysis by PDE3, while the amine containing scaffolds were more selective for cGMP hydrolysis. This observation may set the base for substrate-selective pharmacological modulation of this important class of drug targets and with less side effects, particularly tachcardia. The dual inhibitors of PDE3 were more potent inhibitor towards the growth of HT-29 cancer cell lines. PMID:23546000

  7. Adenosine/guanosine-3',5'-bis-phosphates as biocompatible and selective Zn2+-ion chelators. Characterization and comparison with adenosine/guanosine-5'-di-phosphate.

    PubMed

    Sayer, Alon Haim; Blum, Eliav; Major, Dan Thomas; Vardi-Kilshtain, Alexandra; Levi Hevroni, Bosmat; Fischer, Bilha

    2015-04-28

    Although involved in various physiological functions, nucleoside bis-phosphate analogues and their metal-ion complexes have been scarcely studied. Hence, here, we explored the solution conformation of 2′-deoxyadenosine- and 2′-deoxyguanosine-3′,5′-bisphosphates, 3 and 4, d(pNp), as well as their Zn(2+)/Mg(2+) binding sites and binding-modes (i.e. inner- vs. outer-sphere coordination), acidity constants, stability constants of their Zn(2+)/Mg(2+) complexes, and their species distribution. Analogues 3 and 4, in solution, adopted a predominant Southern ribose conformer (ca. 84%), gg conformation around C4'-C5' and C5'-O5' bonds, and glycosidic angle in the anti-region (213-270°). (1)H- and (31)P-NMR experiments indicated that Zn(2+)/Mg(2+) ions coordinated to P5' and P3' groups of 3 and 4 but not to N7 nitrogen atom. Analogues 3 and 4 formed ca. 100-fold more stable complexes with Zn(2+)vs. Mg(2+)-ions. Complexes of 3 and 4 with Mg(2+) at physiological pH were formed in minute amounts (11% and 8%, respectively) vs. Zn(2+) complexes (46% and 44%). Stability constants of Zn(2+)/Mg(2+) complexes of analogues 3 and 4 (log KML(M) = 4.65-4.75/2.63-2.79, respectively) were similar to those of the corresponding complexes of ADP and GDP (log KML(M) = 4.72-5.10/2.95-3.16, respectively). Based on the above findings, we hypothesized that the unexpectedly low log K values of Zn(2+)-d(pNp) as compared to Zn(2+)-NDP complexes, are possibly due to formation of outer-sphere coordination in the Zn(2+)-d(pNp) complex vs. inner-sphere in the NDP-Zn(2+) complex, in addition to loss of chelation to N7 nitrogen atom in Zn(2+)-d(pNp). Indeed, explicit solvent molecular dynamics simulations of 1 and 3 for 100 ns supported this hypothesis. PMID:25797179

  8. Structural Analogues of Selfotel.

    PubMed

    Dziuganowska, Zofia A; Ślepokura, Katarzyna; Volle, Jean-Noël; Virieux, David; Pirat, Jean-Luc; Kafarski, Paweł

    2016-06-17

    A small library of phosphonopiperidylcarboxylic acids, analogues of NMDA antagonist selfotel (CGS 19755), was synthesized. First, the series of aromatic esters was obtained via a palladium-catalyzed cross-coupling reaction (Hirao coupling) of dialkyl phosphites with bromopyridinecarboxylates, followed by their hydrolysis. Then, hydrogenation of the resulting phosphonopyridylcarboxylic acids over PtO2 yielded the desired phosphonopiperidylcarboxylic acids. NMR studies indicated that the hydrogenation reaction proceeds predominantly by cis addition. Several compounds were obtained as monocrystal structures. Preliminary biological studies performed on cultures of neurons suggest that the obtained compounds possess promising activity toward NMDA receptors. PMID:27187758

  9. Analogue-to-Digital and Digital-to-Analogue Conversion.

    ERIC Educational Resources Information Center

    Gregory, Martin

    1997-01-01

    Discusses circuits for three-bit and four-bit analogue digital converters and digital analogue converters. These circuits feature slow operating speeds that enable the circuitry to be used to demonstrate the mode of operation using oscilloscopes and signal generators. (DDR)

  10. Oligomerization of activated D- and L-guanosine mononucleotides on templates containing D- and L-deoxycytidylate residues

    NASA Technical Reports Server (NTRS)

    Kozlov, I. A.; Pitsch, S.; Orgel, L. E.; Bada, J. L. (Principal Investigator)

    1998-01-01

    The oligomerization of activated D- and L- and racemic guanosine-5'-phosphoro-2-methylimidazole on short templates containing D- and L-deoxycytidylate has been studied. Results obtained with D-oligo(dC)s as templates are similar to those previously reported for experiments with a poly(C) template. When one L-dC or two consecutive L-dCs are introduced into a D-template, regiospecific synthesis of 3'-5' oligo(G)s proceeds to the end of the template, but three consecutive L-dCs block synthesis. Alternating D-,L-oligomers do not facilitate oligomerization of the D-, L-, and racemic 2-guanosine-5'-phosphoro-2-methylimidazole. We suggest that once a "predominately D-metabolism" existed, occasional L-residues in a template would not have led to the termination of self-replication.

  11. P2Y2 receptor up-regulation induced by guanosine or UTP in rat brain cultured astrocytes.

    PubMed

    Ballerini, P; Di Iorio, P; Caciagli, F; Rathbone, M P; Jiang, S; Nargi, E; Buccella, S; Giuliani, P; D'Alimonte, I; Fischione, G; Masciulli, A; Romano, S; Ciccarelli, R

    2006-01-01

    Among P2 metabotropic ATP receptors, P2Y2 subtype seems to be peculiar as its upregulation triggers important biological events in different cells types. In non-stimulated cells including astrocytes, P2Y2 receptors are usually expressed at levels lower than P2Y1 sites, however the promoter region of the P2Y2 receptors has not yet been studied and little is known about the mechanisms underlying the regulation of the expression of this ATP receptor. We showed that not only UTP and ATP are the most potent and naturally occurring agonist for P2Y2 sites, but also guanosine induced an up-regulation of astrocyte P2Y2 receptor mRNA evaluated by Northern blot analysis. We also focused our attention on this nucleoside since in our previous studies it was reported to be released by cultured astrocytes and to exert different neuroprotective effects. UTP and guanosine-evoked P2Y2 receptor up-regulation in rat brain cultured astrocytes was linked to an increased P2Y2-mediated intracellular calcium response, thus suggesting an increased P2Y2 activity. Actinomycin D, a RNA polymerase inhibitor, abrogated both UTP and guanosine-mediated P2Y2 up-regulation, thus indicating that de novo transcription was required. The effect of UTP and guanosine was also evaluated in astrocytes pretreated with different inhibitors of signal transduction pathways including ERK, PKC and PKA reported to be involved in the regulation of other cell surface receptor mRNAs. The results show that ERK1-2/MAPK pathway play a key role in the P2Y2 receptor up-regulation mediated by either UTP or guanosine. Moreover, our data suggest that PKA is also involved in guanosine-induced transcriptional activation of P2Y2 mRNA and that increased intracellular calcium levels and PKC activation may also mediate P2Y2 receptor up-regulation triggered by UTP. The extracellular release of ATP under physiological and pathological conditions has been widely studied. On the contrary, little is known about the release of

  12. X-ray characterization of mesophases of human telomeric G-quadruplexes and other DNA analogues

    PubMed Central

    Yasar, Selcuk; Schimelman, Jacob B.; Aksoyoglu, M. Alphan; Steinmetz, Nicole F.; French, Roger H.; Parsegian, V. Adrian; Podgornik, Rudolf

    2016-01-01

    Observed in the folds of guanine-rich oligonucleotides, non-canonical G-quadruplex structures are based on G-quartets formed by hydrogen bonding and cation-coordination of guanosines. In dilute 5′-guanosine monophosphate (GMP) solutions, G-quartets form by the self-assembly of four GMP nucleotides. We use x-ray diffraction to characterize the columnar liquid-crystalline mesophases in concentrated solutions of various model G-quadruplexes. We then probe the transitions between mesophases by varying the PEG solution osmotic pressure, thus mimicking in vivo molecular crowding conditions. Using the GMP-quadruplex, built by the stacking of G-quartets with no covalent linking between them, as the baseline, we report the liquid-crystalline phase behaviors of two other related G-quadruplexes: (i) the intramolecular parallel-stranded G-quadruplex formed by the 22-mer four-repeat human telomeric sequence AG3(TTAG3)3 and (ii) the intermolecular parallel-stranded G-quadruplex formed by the TG4T oligonucleotides. Finally, we compare the mesophases of the G-quadruplexes, under PEG-induced crowding conditions, with the corresponding mesophases of the canonical duplex and triplex DNA analogues. PMID:27249961

  13. X-ray characterization of mesophases of human telomeric G-quadruplexes and other DNA analogues

    DOE PAGESBeta

    Yasar, Selcuk; Schimelman, Jacob B.; Aksoyoglu, M. Alphan; Steinmetz, Nicole F.; French, Roger H.; Parsegian, V. Adrian; Podgornik, Rudolf

    2016-06-02

    We report that observed in the folds of guanine-rich oligonucleotides, non-canonical G-quadruplex structures are based on G-quartets formed by hydrogen bonding and cation-coordination of guanosines. In dilute 5'-guanosine monophosphate (GMP) solutions, G-quartets form by the self-assembly of four GMP nucleotides. We use x-ray diffraction to characterize the columnar liquid-crystalline mesophases in concentrated solutions of various model G-quadruplexes. We then probe the transitions between mesophases by varying the PEG solution osmotic pressure, thus mimicking in vivo molecular crowding conditions. Using the GMP-quadruplex, built by the stacking of G-quartets with no covalent linking between them, as the baseline, we report the liquid-crystallinemore » phase behaviors of two other related G-quadruplexes: (i) the intramolecular parallel-stranded G-quadruplex formed by the 22-mer four-repeat human telomeric sequence AG3 (TTAG3)3 and (ii) the intermolecular parallel-stranded G-quadruplex formed by the TG(4)T oligonucleotides. Finally, we compare the mesophases of the G-quadruplexes, under PEG-induced crowding conditions, with the corresponding mesophases of the canonical duplex and triplex DNA analogues.« less

  14. X-ray characterization of mesophases of human telomeric G-quadruplexes and other DNA analogues.

    PubMed

    Yasar, Selcuk; Schimelman, Jacob B; Aksoyoglu, M Alphan; Steinmetz, Nicole F; French, Roger H; Parsegian, V Adrian; Podgornik, Rudolf

    2016-01-01

    Observed in the folds of guanine-rich oligonucleotides, non-canonical G-quadruplex structures are based on G-quartets formed by hydrogen bonding and cation-coordination of guanosines. In dilute 5'-guanosine monophosphate (GMP) solutions, G-quartets form by the self-assembly of four GMP nucleotides. We use x-ray diffraction to characterize the columnar liquid-crystalline mesophases in concentrated solutions of various model G-quadruplexes. We then probe the transitions between mesophases by varying the PEG solution osmotic pressure, thus mimicking in vivo molecular crowding conditions. Using the GMP-quadruplex, built by the stacking of G-quartets with no covalent linking between them, as the baseline, we report the liquid-crystalline phase behaviors of two other related G-quadruplexes: (i) the intramolecular parallel-stranded G-quadruplex formed by the 22-mer four-repeat human telomeric sequence AG3(TTAG3)3 and (ii) the intermolecular parallel-stranded G-quadruplex formed by the TG4T oligonucleotides. Finally, we compare the mesophases of the G-quadruplexes, under PEG-induced crowding conditions, with the corresponding mesophases of the canonical duplex and triplex DNA analogues. PMID:27249961

  15. X-ray characterization of mesophases of human telomeric G-quadruplexes and other DNA analogues

    NASA Astrophysics Data System (ADS)

    Yasar, Selcuk; Schimelman, Jacob B.; Aksoyoglu, M. Alphan; Steinmetz, Nicole F.; French, Roger H.; Parsegian, V. Adrian; Podgornik, Rudolf

    2016-06-01

    Observed in the folds of guanine-rich oligonucleotides, non-canonical G-quadruplex structures are based on G-quartets formed by hydrogen bonding and cation-coordination of guanosines. In dilute 5‧-guanosine monophosphate (GMP) solutions, G-quartets form by the self-assembly of four GMP nucleotides. We use x-ray diffraction to characterize the columnar liquid-crystalline mesophases in concentrated solutions of various model G-quadruplexes. We then probe the transitions between mesophases by varying the PEG solution osmotic pressure, thus mimicking in vivo molecular crowding conditions. Using the GMP-quadruplex, built by the stacking of G-quartets with no covalent linking between them, as the baseline, we report the liquid-crystalline phase behaviors of two other related G-quadruplexes: (i) the intramolecular parallel-stranded G-quadruplex formed by the 22-mer four-repeat human telomeric sequence AG3(TTAG3)3 and (ii) the intermolecular parallel-stranded G-quadruplex formed by the TG4T oligonucleotides. Finally, we compare the mesophases of the G-quadruplexes, under PEG-induced crowding conditions, with the corresponding mesophases of the canonical duplex and triplex DNA analogues.

  16. Structural basis of thiamine pyrophosphate analogues binding to the eukaryotic riboswitch.

    PubMed

    Thore, Stéphane; Frick, Christian; Ban, Nenad

    2008-07-01

    The thiamine pyrophosphate (TPP)-sensing riboswitch is the only riboswitch found in eukaryotes. In plants, TPP regulates its own production by binding to the 3' untranslated region of the mRNA encoding ThiC, a critical enzyme in thiamine biosynthesis, which promotes the formation of an unstable splicing variant. In order to better understand the molecular basis of TPP-analogue binding to the eukaryotic TPP-responsive riboswitch, we have determined the crystal structures of the Arabidopsis thaliana TPP-riboswitch in complex with oxythiamine pyrophosphate (OTPP) and with the antimicrobial compound pyrithiamine pyrophosphate (PTPP). The OTPP-riboswitch complex reveals that the pyrimidine ring of OTPP is stabilized in its enol form in order to retain key interactions with guanosine 28 of the riboswitch previously observed in the TPP complex. The structure of PTPP in complex with the riboswitch shows that the base moiety of guanosine 60 undergoes a conformational change to cradle the pyridine ring of the PTPP. Structural information from these complexes has implications for the design of novel antimicrobials targeting TPP-sensing riboswitches. PMID:18533652

  17. Guanosine controls inflammatory pathways to afford neuroprotection of hippocampal slices under oxygen and glucose deprivation conditions.

    PubMed

    Dal-Cim, Tharine; Ludka, Fabiana K; Martins, Wagner C; Reginato, Charlise; Parada, Esther; Egea, Javier; López, Manuela G; Tasca, Carla I

    2013-08-01

    Guanosine (GUO) is an endogenous modulator of glutamatergic excitotoxicity and has been shown to promote neuroprotection in in vivo and in vitro models of neurotoxicity. This study was designed to understand the neuroprotective mechanism of GUO against oxidative damage promoted by oxygen/glucose deprivation and reoxygenation (OGD). GUO (100 μM) reduced reactive oxygen species production and prevented mitochondrial membrane depolarization induced by OGD. GUO also exhibited anti-inflammatory actions as inhibition of nuclear factor kappa B activation and reduction of inducible nitric oxide synthase induction induced by OGD. These GUO neuroprotective effects were mediated by adenosine A1 receptor, phosphatidylinositol-3 kinase and MAPK/ERK. Furthermore, GUO recovered the impairment of glutamate uptake caused by OGD, an effect that occurred via a Pertussis toxin-sensitive G-protein-coupled signaling, blockade of adenosine A2A receptors (A2A R), but not via A1 receptor. The modulation of glutamate uptake by GUO also involved MAPK/ERK activation. In conclusion, GUO, by modulating adenosine receptor function and activating MAPK/ERK, affords neuroprotection of hippocampal slices subjected to OGD by a mechanism that implicates the following: (i) prevention of mitochondrial membrane depolarization, (ii) reduction of oxidative stress, (iii) regulation of inflammation by inhibition of nuclear factor kappa B and inducible nitric oxide synthase, and (iv) promoting glutamate uptake. PMID:23713463

  18. [Cyclic Guanosine Monophosphate as a Mediator in Processes of Stress Signaling Transduction in Higher Plants].

    PubMed

    Dubovskaya, L V; Bakakina, Y S; Volotovski, I D

    2015-01-01

    Currently, biophysical mechanisms of stress signaling transduction became an object of consideration of researchers in connection with the urgent necessity to develop new techniques to enhance the sustainability and productivity of agricultural crops. The development of sensitive methods for the determination of cyclic guanosine monophosphate (cGMP) and comparative analysis of cGMP-dependent events in biological systems has contributed to progress in the understanding of the functioning of cGMP in plant cells. Currently, it is shown that cGMP as a secondary mediator is involved in such vital processes of growth and development of plants as seed germination, cell division, development of chloroplasts, flowering and regulation of stomatal movements. This review summarizes the available data in the literature about the role of cGMP in the responses of plant organisms to the action of stress factors of abiotic and biotic nature and its interaction with other intracellular mediators. With the use of existing ideas about the biophysical mechanisms of stress in plants, the basic elements of cGMP-dependent signal transduction system in a plant cell are considered. PMID:26394467

  19. Nonenzymatic template-directed synthesis on hairpin oligonucleotides. 2. Templates containing cytidine and guanosine residues

    NASA Technical Reports Server (NTRS)

    Wu, T.; Orgel, L. E.

    1992-01-01

    We have prepared hairpin oligonucleotides in which a 5'-terminal single-stranded segment contains cytidylate (C) and guanylate (G) residues. When these hairpin substrates are incubated with a mixture of cytidine 5'-phosphoro(2-methly)imidazolide (2-MeImpC) and guanosine 5'-phosphoro(2-methyl)imidazolide (2-MeImpG), the 5'-terminal segment acts as a template to facilitate sequence-specific addition of G and C residues to the 3'-terminus of the hairpin. If an isolated G residue is present at the 3'-end of the template strand, it is copied regiospecifically in the presence of 2-MeImpC and 2-MeImpG to give a product containing an isolated C residue linked to its G neighbors by 3'-5'-internucleotide bonds. However, if only 2-MeImpC is present in the reaction mixture, very little reaction occurs. Thus, the presence of 2-MeImpG catalyzes the incorporation of C. If the template strand contains a short sequence of G residues, it is copied in the presence of a mixture of 2-MeImpC and 2-MeImpG. If only 2-MeImpC is present in the reaction mixture, efficient synthesis occurs to give a final product containing one fewer C residue than the number of G residues in the template.

  20. A positive entropy change for guanosine binding and for the chemical step in the Tetrahymena ribozyme reaction.

    PubMed

    McConnell, T S; Cech, T R

    1995-03-28

    The ribozyme derived from the group I intron of Tetrahymena thermophila binds an exogenous guanosine nucleotide, which acts as the nucleophile in the sequence-specific cleavage of oligonucleotides. By examining the temperature dependence of the reaction under conditions where Km = Kd, we conclude the following: (1) Guanosine 5'-monophosphate (pG) binds to the closed ribozyme-oligonucleotide substrate complex with a positive entropy change (delta S degree' = +23 eu) and an enthalpy change (delta H degree') close to zero. This is contrary to the expectation that binding would cause increased order (negative delta S degree) and be driven by a negative delta H degree. (2) Inosine and 2-aminopurine riboside, each lacking two hydrogen-bonding moieties relative to guanosine, also bind with a positive entropy value and an unfavorable (positive) delta H degree'. From this result, we suggest that the hydrogen-bonding moieties make an enthalpic contribution to guanosine binding overcoming an intrinsic unfavorable delta H. (3) At 0 degree C, there is equally tight binding of pG in the presence and absence of oligonucleotide substrate bound to the ribozyme. Thus, energetic interactions responsible for the thermodynamic coupling between pG and oligonucleotide substrate binding seen at higher temperatures are indirect. (4) The activation barrier of the chemical step is stabilized by a positive delta S++ (+31 to 39 eu). This stabilization is seen in four reactions using substrates with two different leaving groups in the presence and absence of pG, suggesting that the entropic contribution is inherent to the active site. The positive delta S values for the chemical step and for the binding of pG can be explained by a conformational change or release of water. Thus, although hydrogen bonding contributes to binding of nucleotides to this RNA enzyme as previously thought, it is these other events which produce a positive delta S that provide the energetic driving force for binding

  1. Probing the interplay between the two steps of group I intron splicing: competition of exogenous guanosine with omega G.

    PubMed

    Zarrinkar, P P; Sullenger, B A

    1998-12-22

    One largely unexplored question about group I intron splicing is how the cleavage and ligation steps of the reaction are coordinated. We describe a simple in vitro trans-splicing model system in which both steps take place, including the exchange of ligands in the guanosine-binding site that must occur between the two steps. Using this model system, we show that the switch is accomplished by modulating the relative affinity of the binding site for the two ligands. While the terminal guanosine of the intron (omegaG) and exogenous guanosine compete for binding during the first step of splicing, no competition is apparent during the second step, when omegaG is bound tightly. These results help explain how the ribozyme orchestrates progression through the splicing reaction. In addition to providing a new tool to ask basic questions about RNA catalysis, the trans-splicing model system will also facilitate the development of therapeutically useful group I ribozymes that can repair mutant mRNAs. PMID:9922174

  2. Phosphonate analogues of aminoacyl adenylates.

    PubMed Central

    Southgate, C C; Dixon, H B

    1978-01-01

    Phosphonomethyl analogues of glycyl phosphate and valyl phosphate, i.e. NH2-CHR-CO-CH2-PO(OH)2, were synthesized and esterified with adenosine to give analogues of aminoacyl adenylates. The interaction of these adenylate analogues with valyl-tRNA synthetase from Escherichia coli was studied by fluorescence titration. The analogue of valyl phosphate has an affinity for the enzyme comparable with that of valine, but that of valyl adenylate is bound much less tightly than either valyl adenylate or corresponding derivative of valinol. The affinity of the analogue of glycyl adenylate was too low to be measured. We conclude that this enzyme interacts specifically with both the side chain and the anhydride linkage of the adenylate intermediate. PMID:743207

  3. NASA/ESMD Analogue Mission Plans

    NASA Technical Reports Server (NTRS)

    Hoffman, Stephen J.

    2007-01-01

    A viewgraph presentation exploring Earth and its analogues is shown. The topics include: 1) ESMD Goals for the Use of Earth Analogues; 2) Stakeholders Summary; 3) Issues with Current Analogue Situation; 4) Current state of Analogues; 5) External Implementation Plan (Second Step); 6) Recent Progress in Utilizing Analogues; 7) Website Layout Example-Home Page; 8) Website Layout Example-Analogue Site; 9) Website Layout Example-Analogue Mission; 10) Objectives of ARDIG Analog Initiatives; 11) Future Plans; 12) Example: Cold-Trap Sample Return; 13) Example: Site Characterization Matrix; 14) Integrated Analogue Studies-Prerequisites for Human Exploration; and 15) Rating Scale Definitions.

  4. Role of Increased Guanosine Triphosphate Cyclohydrolase-1 Expression and Tetrahydrobiopterin Levels upon T Cell Activation

    PubMed Central

    Chen, Wei; Li, Li; Brod, Torben; Saeed, Omar; Thabet, Salim; Jansen, Thomas; Dikalov, Sergey; Weyand, Cornelia; Goronzy, Jorg; Harrison, David G.

    2011-01-01

    Tetrahydrobiopterin (BH4) is an essential co-factor for the nitric-oxide (NO) synthases, and in its absence these enzymes produce superoxide (O2˙̄) rather than NO. The rate-limiting enzyme for BH4 production is guanosine triphosphate cyclohydrolase-1 (GTPCH-1). Because endogenously produced NO affects T cell function, we sought to determine whether antigen stimulation affected T cell GTPCH-1 expression and ultimately BH4 levels. Resting T cells had minimal expression of inducible NOS (NOS2), endothelial NOS (NOS3), and GTPCH-1 protein and nearly undetectable levels of BH4. Anti-CD3 stimulation of T cells robustly stimulated the coordinated expression of NOS2, NOS3, and GTPCH-1 and markedly increased both GTPCH-1 activity and T cell BH4 levels. The newly expressed GTPCH-1 was phosphorylated on serine 72 and pharmacological inhibition of casein kinase II reduced GTPCH-1 phosphorylation and blunted the increase in T cell BH4. Inhibition of GTPCH-1 with diaminohydroxypyrimidine (1 mmol/liter) prevented T cell BH4 accumulation, reduced NO production, and increased T cell O2˙̄ production, due to both NOS2 and NOS3 uncoupling. GTPCH-1 inhibition also promoted TH2 polarization in memory CD4 cells. Ovalbumin immunization of mice transgenic for an ovalbumin receptor (OT-II mice) confirmed a marked increase in T cell BH4 in vivo. These studies identify a previously unidentified consequence of T cell activation, promoting BH4 levels, NO production, and modulating T cell cytokine production. PMID:21343293

  5. Measurement of intercolumnar forces between parallel guanosine four-stranded helices.

    PubMed Central

    Mariani, P; Saturni, L

    1996-01-01

    The deoxyguanosine-5'-monophosphate in aqueous solution self-associates into stable structures, which include hexagonal and cholesteric columnar phases. The structural unit is a four-stranded helix, composed of a stacked array of Hoogsteen-bonded guanosine quartets. We have measured by osmotic stress method the force per unit length versus interaxial distance between helices in the hexagonal phase under various ionic conditions. Two contributions have been recognized: the first one is purely electrostatic, is effective at large distances, and shows a strong dependence on the salt concentration of the solution. The second contribution is short range, dominates at interaxial separations smaller than about 30-32 A, and rises steeply as the columns approach each other, preventing the coalescence of the helices. This repulsion has an exponential nature and shows a magnitude and a decay length insensitive to the ionic strength of the medium. Because these features are distinctive of the hydration force detected between phospholipid bilayers or between several linear macromolecules (DNA, polysaccharides, collagen), we conclude that the dominant force experienced by deoxyguanosine helices approaching contact is hydration repulsion. The observed decay length of about 0.7 A has been rationalized to emerge from the coupling between the 3-A decay length of water solvent and the helically ordered structure of the hydrophilic groups on the opposing surfaces. The present results agree with recent measurements, also showing the dependence of the hydration force decay on the structure of interacting surfaces and confirm the correlations between force and structure. Images FIGURE 1 PMID:8744324

  6. Positive control of lac operon expression in vitro by guanosine 5'-diphosphate 3'-diphosphate.

    PubMed

    Primakoff, P; Artz, S W

    1979-04-01

    Maximal expression of the Escherichia coli lactose operon in a coupled in vitro transcription-translation system from a Salmonella typhimurium relA mutant was strongly dependent upon addition of guanosine 5'-diphosphate 3'-diphosphate (ppGpp). Without added ppGpp, at saturating 3',5'-cyclic AMP (cAMP) concentrations, synthesis of beta-galactosidase (beta-D-galactoside galactohydrolase, EC 3.2.1.23) was reproducibly only 5-7% of that which can be obtained with 0.5-0.8 mM ppGpp. Experiments in which transcription was uncoupled from translation indicated that this 14- to 20-fold stimulation by ppGpp occurred at the level of transcription. When coupled beta-galactosidase synthesis was primed with a template containing a well-characterized mutant lac promoter (lacP(r)L8UV5), the dependence on ppGpp was greatly reduced. This result provides an important experimental control previously unavailable for verifying the significance of ppGpp effects on gene regulation in vitro; it indicates that activation of lacP(+) expression by ppGpp is specifically an effect of increased transcription initiations. Furthermore, the large ppGpp stimulation of lacP(+) DNA enabled the level of expression of this template to approach that of lacP(r)L8UV5 DNA, an observation expected from results in vivo but not obtained with other transcription-translation systems in vitro. The importance of these results is considered with respect to previous ideas on the physiological role of ppGpp as a supercontrol molecule in bacterial regulation. PMID:109832

  7. A Cyclic Guanosine Monophosphate–Dependent Pathway Can Regulate Net Hepatic Glucose Uptake in Vivo

    PubMed Central

    An, Zhibo; Winnick, Jason J.; Moore, Mary C.; Farmer, Ben; Smith, Marta; Irimia, Jose M.; Roach, Peter J.; Cherrington, Alan D.

    2012-01-01

    We previously showed that hepatic nitric oxide regulates net hepatic glucose uptake (NHGU), an effect that can be eliminated by inhibiting hepatic soluble guanylate cyclase (sGC), suggesting that the sGC pathway is involved in the regulation of NHGU. The aim of the current study was to determine whether hepatic cyclic guanosine monophosphate (cGMP) reduces NHGU. Studies were performed on conscious dogs with transhepatic catheters. A hyperglycemic-hyperinsulinemic clamp was established in the presence of portal vein glucose infusion. 8-Br-cGMP (50 µg/kg/min) was delivered intraportally, and either the glucose load to the liver (CGMP/GLC; n = 5) or the glucose concentration entering the liver (CGMP/GCC; n = 5) was clamped at 2× basal. In the control group, saline was given intraportally (SAL; n = 10), and the hepatic glucose concentration and load were doubled. 8-Br-cGMP increased portal blood flow, necessitating the two approaches to glucose clamping in the cGMP groups. NHGU (mg/kg/min) was 5.8 ± 0.5, 2.7 ± 0.5, and 4.8 ± 0.3, whereas the fractional extraction of glucose was 11.0 ± 1, 5.5 ± 1, and 8.5 ± 1% during the last hour of the study in SAL, CGMP/GLC, and CGMP/GCC, respectively. The reduction of NHGU in response to 8-Br-cGMP was associated with increased AMP-activated protein kinase phosphorylation. These data indicate that changes in liver cGMP can regulate NHGU under postprandial conditions. PMID:22688328

  8. Regulation of Escherichia coli aspartate transcarbamylase synthesis by guanosine tetraphosphate and pyrimidine ribonucleoside triphosphates.

    PubMed

    Turnbough, C L

    1983-02-01

    The effects of guanosine tetraphosphate (ppGpp) and pyrimidine ribonucleoside triphosphates on Escherichia coli aspartate transcarbamylase (ATCase) synthesis were examined. To determine the effect of ppGpp, a stringent (relA+) and relaxed (relA) isogenic pair of E. coli K-12 strains was starved for isoleucine, and the residual rate of synthesis of this enzyme was measured. It was necessary to starve the strains for uracil before the isoleucine limitation to maintain similar, low levels of UTP, the putative pyrimidine effector of ATCase synthesis. The isoleucine starvation of the stringent strain caused an immediate 10-fold increase in the intracellular concentration of ppGpp, which was coincident with the cessation of the synthesis of the enzyme. The elevated level of ppGpp then decayed until it reached an intracellular concentration similar to that found in unstarved cells. Enzyme synthesis resumed at this time. In the relaxed strain, the intracellular concentration of ppGpp did not increase upon isoleucine starvation and synthesis of the enzyme was not repressed. These experiments strongly indicated that ppGpp acts as a negative effector of ATCase synthesis. The repression of ATCase synthesis by ppGpp was demonstrated directly by using a Salmonella typhimurium (relA) in vitro coupled transcription-translation system with a lambda specialized transducing phage carrying the E. coli K-12 operon encoding the subunits of this enzyme (pyrBI) as a source of DNA. This in vitro system was also used to measure the effects of UTP and CTP on ATCase synthesis. Increasing the concentration of UTP in the in vitro reaction mixture resulted in strong repression of this synthesis, whereas increasing the CTP concentration did not affect synthesis significantly. Possible mechanisms for the regulation of pyr gene expression, including attenuation control, are discussed. PMID:6337130

  9. Involvement of Cyclic Guanosine Monophosphate-Dependent Protein Kinase I in Renal Antifibrotic Effects of Serelaxin

    PubMed Central

    Wetzl, Veronika; Schinner, Elisabeth; Kees, Frieder; Hofmann, Franz; Faerber, Lothar; Schlossmann, Jens

    2016-01-01

    Introduction: Kidney fibrosis has shown to be ameliorated through the involvement of cyclic guanosine monophosphate (cGMP) and its dependent protein kinase I (cGKI). Serelaxin, the recombinant form of human relaxin-II, increases cGMP levels and has shown beneficial effects on kidney function in acute heart failure patients. Antifibrotic properties of serelaxin are supposed to be mediated via relaxin family peptide receptor 1 and subsequently enhanced nitric oxide/cGMP to inhibit transforming growth factor-β (TGF-β) signaling. This study examines the involvement of cGKI in the antifibrotic signaling of serelaxin. Methods and Results: Kidney fibrosis was induced by unilateral ureteral obstruction in wildtype (WT) and cGKI knock-out (KO) mice. After 7 days, renal antifibrotic effects of serelaxin were assessed. Serelaxin treatment for 7 days significantly increased cGMP in the kidney of WT and cGKI-KO. In WT, renal fibrosis was reduced through decreased accumulation of collagen1A1, total collagen, and fibronectin. The profibrotic connective tissue growth factor as well as myofibroblast differentiation were reduced and matrix metalloproteinases-2 and -9 were positively modulated after treatment. Moreover, Smad2 as well as extracellular signal-regulated kinase 1 (ERK1) phosphorylation were decreased, whereas phosphodiesterase (PDE) 5a phosphorylation was increased. However, these effects were not observed in cGKI-KO. Conclusion: Antifibrotic renal effects of serelaxin are mediated via cGMP/cGKI to inhibit Smad2- and ERK1-dependent TGF-β signaling and increased PDE5a phosphorylation. PMID:27462268

  10. N-H stretching vibrations of guanosine-cytidine base pairs in solution: ultrafast dynamics, couplings, and line shapes.

    PubMed

    Fidder, Henk; Yang, Ming; Nibbering, Erik T J; Elsaesser, Thomas; Röttger, Katharina; Temps, Friedrich

    2013-02-01

    Dynamics and couplings of N-H stretching vibrations of chemically modified guanosine-cytidine (G·C) base pairs in chloroform are investigated with linear infrared spectroscopy and ultrafast two-dimensional infrared (2D-IR) spectroscopy. Comparison of G·C absorption spectra before and after H/D exchange reveals significant N-H stretching absorption in the region from 2500 up to 3300 cm(-1). Both of the local stretching modes ν(C)(NH(2))(b) of the hydrogen-bonded N-H moiety of the cytidine NH(2) group and ν(G)(NH) of the guanosine N-H group contribute to this broad absorption band. Its complex line shape is attributed to Fermi resonances of the N-H stretching modes with combination and overtones of fingerprint vibrations and anharmonic couplings to low-frequency modes. Cross-peaks in the nonlinear 2D spectra between the 3491 cm(-1) free N-H oscillator band and the bands centered at 3145 and 3303 cm(-1) imply N-H···O═C hydrogen bond character for both of these transitions. Time evolution illustrates that the 3303 cm(-1) band is composed of a nearly homogeneous band absorbing at 3301 cm(-1), ascribed to ν(G)(NH(2))(b), and a broad inhomogeneous band peaking at 3380 cm(-1) with mainly guanosine carbonyl overtone character. Kinetics and signal strengths indicate a <0.2 ps virtually complete population transfer from the excited ν(G)(NH(2))(b) mode to the ν(G)(NH) mode at 3145 cm(-1), suggesting lifetime broadening as the dominant source for the homogeneous line shape of the 3301 cm(-1) transition. For the 3145 cm(-1) band, a 0.3 ps population lifetime was obtained. PMID:23317104

  11. In Search of Enzymes with a Role in 3′, 5′-Cyclic Guanosine Monophosphate Metabolism in Plants

    PubMed Central

    Gross, Inonge; Durner, Jörg

    2016-01-01

    In plants, nitric oxide (NO)-mediated 3′, 5′-cyclic guanosine monophosphate (cGMP) synthesis plays an important role during pathogenic stress response, stomata closure upon osmotic stress, the development of adventitious roots and transcript regulation. The NO-cGMP dependent pathway is well characterized in mammals. The binding of NO to soluble guanylate cyclase enzymes (GCs) initiates the synthesis of cGMP from guanosine triphosphate. The produced cGMP alters various cellular responses, such as the function of protein kinase activity, cyclic nucleotide gated ion channels and cGMP-regulated phosphodiesterases. The signal generated by the second messenger is terminated by 3′, 5′-cyclic nucleotide phosphodiesterase (PDEs) enzymes that hydrolyze cGMP to a non-cyclic 5′-guanosine monophosphate. To date, no homologues of mammalian cGMP-synthesizing and degrading enzymes have been found in higher plants. In the last decade, six receptor proteins from Arabidopsis thaliana have been reported to have guanylate cyclase activity in vitro. Of the six receptors, one was shown to be a NO dependent guanylate cyclase enzyme (NOGC1). However, the role of these proteins in planta remains to be elucidated. Enzymes involved in the degradation of cGMP remain elusive, albeit, PDE activity has been detected in crude protein extracts from various plants. Additionally, several research groups have partially purified and characterized PDE enzymatic activity from crude protein extracts. In this review, we focus on presenting advances toward the identification of enzymes involved in the cGMP metabolism pathway in higher plants. PMID:27200049

  12. Guanosine and its modified derivatives are endogenous ligands for TLR7.

    PubMed

    Shibata, Takuma; Ohto, Umeharu; Nomura, Shosaku; Kibata, Kayoko; Motoi, Yuji; Zhang, Yan; Murakami, Yusuke; Fukui, Ryutaro; Ishimoto, Tatsushi; Sano, Shigetoshi; Ito, Tomoki; Shimizu, Toshiyuki; Miyake, Kensuke

    2016-05-01

    Toll-like receptor (TLR) 7and 8 were considered to recognize single-strand RNA (ssRNA) from viruses. Although these receptors also respond to synthetic small chemical ligands, such as CL075 and R848, it remains to be determined whether these receptors sense natural small molecules or not. In the structure of human TLR8 (huTLR8) with ssRNA, there are two ligand-binding sites: one binds a uridine and the other binds an oligoribonucleotide (ORN). This finding demonstrates that huTLR8 recognizes degradation products of ssRNA, suggesting the presence of natural small ligands. We here show that TLR7 works as the sensor for guanosine (G)/2'-deoxyguanosine (dG) in the presence of ORN where ORN strengthens TLR7 interaction with G/dG. In addition, modified nucleosides such as 7-methylguanosine, 8-hydroxyguanosine (8-OHG) and 8-hydroxydeoxyguanosine (8-OHdG) activated TLR7 with ORNs. Importantly, 8-OHdG-a well-known oxidative DNA damage marker with unknown function-induced strong cytokine production comparable to G and dG both in mouse and human immune cells. Although 8-OHdG bound TLR7/ORN with lower affinity than dG did in isothermal titration calorimetry, administered 8-OHdG was metabolically more stable than dG in the serum, indicating that 8-OHdG acts on TLR7 as an endogenous ligand in vivo To address a role of G analogs in the disease state, we also examined macrophages from Unc93b1 (D34A/D34A) mice, which suffer from TLR7-dependent systemic inflammation, and found that Unc93b1 (D34A/D34A) macrophages showed significantly enhanced response to G alone or 8-OHdG with ORN. In conclusion, our results provide evidence that G, dG, 8-OHG and 8-OHdG are novel endogenous ligands for TLR7. PMID:26489884

  13. Trichomonas vaginalis NTPDase and ecto-5'-nucleotidase hydrolyze guanine nucleotides and increase extracellular guanosine levels under serum restriction.

    PubMed

    Menezes, Camila Braz; Durgante, Juliano; de Oliveira, Rafael Rodrigues; Dos Santos, Victor Hugo Jacks Mendes; Rodrigues, Luiz Frederico; Garcia, Solange Cristina; Dos Santos, Odelta; Tasca, Tiana

    2016-05-01

    Trichomonas vaginalis is the aethiologic agent of trichomoniasis, the most common non-viral sexually transmitted disease in the world. The purinergic signaling pathway is mediated by extracellular nucleotides and nucleosides that are involved in many biological effects as neurotransmission, immunomodulation and inflammation. Extracellular nucleotides can be hydrolyzed by a family of enzymes known as ectonucleotidases including the ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) family which hydrolyses nucleosides triphosphate and diphosphate as preferential substrates and ecto-5'-nucleotidase which catalyzes the conversion of monophosphates into nucleosides. In T. vaginalis the E-NTPDase and ecto-5'-nucleotidase activities upon adenine nucleotides have already been characterized in intact trophozoites but little is known concerning guanine nucleotides and nucleoside. These enzymes may exert a crucial role on nucleoside generation, providing the purine sources for the synthesis de novo of these essential nutrients, sustaining parasite growth and survival. In this study, we investigated the hydrolysis profile of guanine-related nucleotides and nucleoside in intact trophozoites from long-term-grown and fresh clinical isolates of T. vaginalis. Knowing that guanine nucleotides are also substrates for T. vaginalis ectoenzymes, we evaluated the profile of nucleotides consumption and guanosine uptake in trophozoites submitted to a serum limitation condition. Results show that guanine nucleotides (GTP, GDP, GMP) were substrates for T. vaginalis ectonucleotidases, with expected kinetic parameters for this enzyme family. Different T. vaginalis isolates (two from the ATCC and nine fresh clinical isolates) presented a heterogeneous hydrolysis profile. The serum culture condition increased E-NTPDase and ecto-5'-nucleotidase activities with high consumption of extracellular GTP generating enhanced GDP, GMP and guanosine levels as demonstrated by HPLC, with final

  14. Hydrolysis of Guanosine Triphosphate (GTP) by the Ras·GAP Protein Complex: Reaction Mechanism and Kinetic Scheme.

    PubMed

    Khrenova, Maria G; Grigorenko, Bella L; Kolomeisky, Anatoly B; Nemukhin, Alexander V

    2015-10-01

    Molecular mechanisms of the hydrolysis of guanosine triphosphate (GTP) to guanosine diphosphate (GDP) and inorganic phosphate (Pi) by the Ras·GAP protein complex are fully investigated by using modern modeling tools. The previously hypothesized stages of the cleavage of the phosphorus-oxygen bond in GTP and the formation of the imide form of catalytic Gln61 from Ras upon creation of Pi are confirmed by using the higher-level quantum-based calculations. The steps of the enzyme regeneration are modeled for the first time, providing a comprehensive description of the catalytic cycle. It is found that for the reaction Ras·GAP·GTP·H2O → Ras·GAP·GDP·Pi, the highest barriers correspond to the process of regeneration of the active site but not to the process of substrate cleavage. The specific shape of the energy profile is responsible for an interesting kinetic mechanism of the GTP hydrolysis. The analysis of the process using the first-passage approach and consideration of kinetic equations suggest that the overall reaction rate is a result of the balance between relatively fast transitions and low probability of states from which these transitions are taking place. Our theoretical predictions are in excellent agreement with available experimental observations on GTP hydrolysis rates. PMID:26374425

  15. Light-driven artificial enzymes for selective oxidation of guanosine triphosphate using water-soluble POSS network polymers.

    PubMed

    Jeon, Jong-Hwan; Tanaka, Kazuo; Chujo, Yoshiki

    2014-09-01

    The light-driven artificial enzymes were constructed to realize unnatural reactions concerning bio-significant molecules. In this manuscript, the guanosine triphosphate (GTP)-selective oxidation is reported using the network polymers composed of polyhedral oligomeric silsesquioxane (POSS). We synthesized the water-soluble POSS network polymer containing the naphthyridine ligands to capture GTP inside the networks and the ruthenium complexes to oxidize the captured GTP under light irradiation. Initially, the binding affinities of the guanosine nucleosides to the naphthyridine ligand inside the POSS network polymer were evaluated from the emission quenching experiments. Accordingly, it was observed that the naphthyridine ligand can form the stable complex only with GTP (K(a) = 5.5 × 10(6) M(-1)). These results indicate that only GTP can be captured by the network polymer. Next, the photo-catalytic activity of the ruthenium complex-modified POSS network polymer was investigated. Finally, it was revealed that the network polymer can decompose GTP efficiently under light irradiation. This is the first example, to the best of our knowledge, to offer not only the GTP-selective host polymers but also the light-driven artificial enzyme for GTP oxidation. PMID:25026217

  16. Phosphonomethyl analogues of hexose phosphates.

    PubMed

    Webster, D; Jondorf, W R; Dixon, H B

    1976-05-01

    The analogue of fructose 1,6-bisphosphate in which the phosphate group, -O-PO3H2, on C-6 is replaced by the phosphonomethyl group, -CH2-PO3H2, was made enzymically from the corresponding analogue of 3-phosphoglycerate. It was a substrate for aldolase, which was used to form it, but not for fructose 1,6-bisphosphatase. It was hydrolysed chemically to yield the corresponding analogue of fructose 6-phosphate [i.e. 6-deoxy-6-(phosphonomethyl)-D-fructose, or, more strictly, 6,7-dideoxy-7-phosphono-D-arabino-2-heptulose]. This proved to be a substrate for the sequential actions of glucose 6-phosphate isomerase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase. Thus seven out of the nine enzymes of the glycolytic and pentose phosphate pathways so far tested catalyse the reactions of the phosphonomethyl isosteres of their substrates. PMID:7247

  17. Testing nucleoside analogues as inhibitors of Bacillus anthracis spore germination in vitro and in macrophage cell culture.

    PubMed

    Alvarez, Zadkiel; Lee, Kyungae; Abel-Santos, Ernesto

    2010-12-01

    Bacillus anthracis, the etiological agent of anthrax, has a dormant stage in its life cycle known as the endospore. When conditions become favorable, spores germinate and transform into vegetative bacteria. In inhalational anthrax, the most fatal manifestation of the disease, spores enter the organism through the respiratory tract and germinate in phagosomes of alveolar macrophages. Germinated cells can then produce toxins and establish infection. Thus, germination is a crucial step for the initiation of pathogenesis. B. anthracis spore germination is activated by a wide variety of amino acids and purine nucleosides. Inosine and l-alanine are the two most potent nutrient germinants in vitro. Recent studies have shown that germination can be hindered by isomers or structural analogues of germinants. 6-Thioguanosine (6-TG), a guanosine analogue, is able to inhibit germination and prevent B. anthracis toxin-mediated necrosis in murine macrophages. In this study, we screened 46 different nucleoside analogues as activators or inhibitors of B. anthracis spore germination in vitro. These compounds were also tested for their ability to protect the macrophage cell line J774a.1 from B. anthracis cytotoxicity. Structure-activity relationship analysis of activators and inhibitors clarified the binding mechanisms of nucleosides to B. anthracis spores. In contrast, no structure-activity relationships were apparent for compounds that protected macrophages from B. anthracis-mediated killing. However, multiple inhibitors additively protected macrophages from B. anthracis. PMID:20921305

  18. Sum-frequency generation spectroscopy of self-assembled structures of Guanosine 5‧-monophosphate on mica

    NASA Astrophysics Data System (ADS)

    Kunstelj, Klemen; Spindler, Lea; Federiconi, Francesco; Bonn, Mischa; Drevenšek-Olenik, Irena; Čopič, Martin

    2008-12-01

    The structure and ordering of Guanosine 5'-monophosphate (GMP) films self-assembled on mica from GMP salt solutions were studied by infrared-visible sum-frequency generation spectroscopy (IR-VIS SFG) and atomic force microscopy (AFM). We find that the surface self-assembly of GMP can be tuned through the concentration of the GMP solution as well as the nature of the counter ion. At low concentrations of the ammonium and the sodium GMP salt solutions, the self-assembled films are very similar, while at higher concentrations the SFG signal of ammonium GMP samples is dominated by a contribution not originating from azimuthally symmetric layers, which signifies that a helical bulk structure might be present.

  19. Human taste and umami receptor responses to chemosensorica generated by Maillard-type N²-alkyl- and N²-arylthiomethylation of guanosine 5'-monophosphates.

    PubMed

    Suess, Barbara; Brockhoff, Anne; Degenhardt, Andreas; Billmayer, Sylvia; Meyerhof, Wolfgang; Hofmann, Thomas

    2014-11-26

    Structural modification of the exocyclic amino function of guanosine 5'-monophosphate (5'-GMP) by Maillard-type reactions with reducing carbohydrates was recently found to increase the umami-enhancing activity of the nucleotide upon S-N(2)-1-carboxyalkylation and S-N(2)-(1-alkylamino)carbonylalkylation, respectively. Since the presence of sulfur atoms in synthetic N(2)-alkylated nucleotides was reported to be beneficial for sensory activity, a versatile Maillard-type modification of 5'-GMP upon reaction with glycine's Strecker aldehyde formaldehyde and organic thiols was performed in the present study. A series of N(2)-(alkylthiomethyl)guanosine and N(2)-(arylthiomethyl)guanosine 5'-monophosphates was generated and the compounds were evaluated to what extent they enhance the umami response to monosodium L-glutamate in vivo by a paired-choice comparison test using trained human volunteers and in vitro by means of cell-based umami taste receptor assay. Associated with a high umami-enhancing activity (β-value 5.1), N(2)-(propylthiomethyl)guanosine 5'-monophosphate could be generated when 5'-GMP reacted with glucose, glycine, and the onion-derived odorant 1-propanethiol, thus opening a valuable avenue to produce high-potency umami-enhancing chemosensorica from food-derived natural products by kitchen-type chemistry. PMID:25375264

  20. Lipid peroxides as endogenous oxidants forming 8-oxo-guanosine and lipid-soluble antioxidants as suppressing agents

    PubMed Central

    Kanazawa, Kazuki; Sakamoto, Miku; Kanazawa, Ko; Ishigaki, Yoriko; Aihara, Yoshiko; Hashimoto, Takashi; Mizuno, Masashi

    2016-01-01

    The oxidation of guanosine to 8-oxo-2'-deoxyguanosine (8-oxo-dG) in DNA is closely associated with induction of various diseases, but the endogenous oxidant species involved remains unclear. Hydrogen peroxides (H2O2) have been considered to be the oxidant, while lipid peroxides are another possible oxidant because generated easily in bio-membranes surrounding DNA. The oxidant potency was compared between lipid peroxides and H2O2. Linoleic acid hydroperoxides (LOOH) formed 8-oxo-dG at a higher level than H2O2 in guanosine or double-stranded DNA. In the presence of a physiological concentration of Fe2+ to produce hydroxyl radicals, LOOH was also a stronger oxidant. In a lipid micelle, LOOH markedly produced 8-oxo-dG at a concentration one-tenth of that of H2O2. Upon adding to rat hepatic mitochondria, phosphatidylcholine hydroperoxides produced 8-oxo-dG abundantly. Employing HepG2 cells after pretreated with glutathione peroxidase inhibitor, LOOH formed 8-oxo-dG more abundantly than H2O2. Then, antioxidants to suppress the 8-oxo-dG formation were examined, when the nuclei of pre-incubated HepG2 with antioxidants were exposed to LOOH. Water-soluble ascorbic acid, trolox, and N-acetyl cysteine showed no or weak antioxidant potency, while lipid-soluble 2,6-dipalmitoyl ascorbic acid, α-tocopherol, and lipid-soluble phytochemicals exhibited stronger potency. The present study shows preferential formation of 8-oxo-dG upon LOOH and the inhibition by lipid-soluble antioxidants. PMID:27499574

  1. Lipid peroxides as endogenous oxidants forming 8-oxo-guanosine and lipid-soluble antioxidants as suppressing agents.

    PubMed

    Kanazawa, Kazuki; Sakamoto, Miku; Kanazawa, Ko; Ishigaki, Yoriko; Aihara, Yoshiko; Hashimoto, Takashi; Mizuno, Masashi

    2016-07-01

    The oxidation of guanosine to 8-oxo-2'-deoxyguanosine (8-oxo-dG) in DNA is closely associated with induction of various diseases, but the endogenous oxidant species involved remains unclear. Hydrogen peroxides (H2O2) have been considered to be the oxidant, while lipid peroxides are another possible oxidant because generated easily in bio-membranes surrounding DNA. The oxidant potency was compared between lipid peroxides and H2O2. Linoleic acid hydroperoxides (LOOH) formed 8-oxo-dG at a higher level than H2O2 in guanosine or double-stranded DNA. In the presence of a physiological concentration of Fe(2+) to produce hydroxyl radicals, LOOH was also a stronger oxidant. In a lipid micelle, LOOH markedly produced 8-oxo-dG at a concentration one-tenth of that of H2O2. Upon adding to rat hepatic mitochondria, phosphatidylcholine hydroperoxides produced 8-oxo-dG abundantly. Employing HepG2 cells after pretreated with glutathione peroxidase inhibitor, LOOH formed 8-oxo-dG more abundantly than H2O2. Then, antioxidants to suppress the 8-oxo-dG formation were examined, when the nuclei of pre-incubated HepG2 with antioxidants were exposed to LOOH. Water-soluble ascorbic acid, trolox, and N-acetyl cysteine showed no or weak antioxidant potency, while lipid-soluble 2,6-dipalmitoyl ascorbic acid, α-tocopherol, and lipid-soluble phytochemicals exhibited stronger potency. The present study shows preferential formation of 8-oxo-dG upon LOOH and the inhibition by lipid-soluble antioxidants. PMID:27499574

  2. Oxidatively damaged guanosine in white blood cells and in urine of welders: associations with exposure to welding fumes and body iron stores.

    PubMed

    Pesch, Beate; Lotz, Anne; Koch, Holger M; Marczynski, Boleslaw; Casjens, Swaantje; Käfferlein, Heiko U; Welge, Peter; Lehnert, Martin; Heinze, Evelyn; Van Gelder, Rainer; Hahn, Jens-Uwe; Behrens, Thomas; Raulf, Monika; Hartwig, Andrea; Weiss, Tobias; Brüning, Thomas

    2015-08-01

    The International Agency for Research on Cancer considers the carcinogenicity of welding fume of priority for re-evaluation. Genotoxic effects in experimental animals are still inconclusive. Here, we investigated the association of personal exposure to metals in respirable welding fumes during a working shift with oxidatively damaged guanosine in DNA of white blood cells (WBC) and in postshift urine samples from 238 welders. Medians of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) were 2.35/10(6) dGuo in DNA of WBC and 4.33 µg/g creatinine in urine. The median of 8-oxo-7,8-dihydroguanosine (8-oxoGuo) was 7.03 µg/g creatinine in urine. The extent of both urinary parameters was higher in welders applying techniques with high particle emission rates to stainless steel than in tungsten inert gas welders (8-oxodGuo: 9.96 vs. 4.49 µg/L, 8-oxoGuo: 15.7 vs. 7.7 µg/L), but this apparent difference diminished after creatinine adjustment. We applied random intercept models to estimate the influence of airborne and systemic exposure to metals on oxidatively damaged guanosine in WBC and urine together with covariates. We observed a highly significant nonlinear association of urinary 8-oxoGuo with serum ferritin (P < 0.0001) and higher 8-oxoGuo concentrations for respirable iron >1,000 µg/m(3) compared to ≤57 µg/m(3). Similar effects were found for manganese. Airborne chromium but not nickel was associated with all oxidatively modified guanosine measures, whereas urinary chromium as well as nickel showed associations with urinary modified guanosines. In summary, oxidatively damaged urinary guanosine was associated with airborne and systemic exposure to metals in welders and showed a strong relation to body iron stores. PMID:25107450

  3. Muscarinic interactions of bisindolylmaleimide analogues.

    PubMed

    Lazareno, S; Popham, A; Birdsall, N J

    1998-11-01

    We have used radioligand binding studies to determine the affinities of seven bisindolylmaleimide analogues, six of which are selective inhibitors of protein kinase C, at human muscarinic M1-M4 receptors. The compounds were most potent at M1 receptors, and Ro-31-8220 was the most potent analogue, with a Kd of 0.6 microM at M1 receptors. The weakest compounds, bisindolylmaleimide IV and bisindolylmaleimide V, had Kd values of 100 microM. If it is necessary to use protein kinase C inhibitors at concentrations of 10 microM or more in studies involving muscarinic receptors then bisindolylmaleimide IV may be the most appropriate inhibitor to use. PMID:9851596

  4. Synthesis, molecular modeling and biological evaluation of novel tadalafil analogues as phosphodiesterase 5 and colon tumor cell growth inhibitors, new stereochemical perspective

    PubMed Central

    Abadi, Ashraf H.; Gary, Bernard D.; Tinsley, Heather N.; Piazza, Gary A.; Abdel-Halim, Mohammad

    2016-01-01

    The synthesis of novel tadalafil analogues in which the benzodioxole moiety is replaced by 2-bromophenyl; the chiral carbons swing from R,R to R,S, S,R and S,S; the piperazinedione ring is maintained or reduced to the 5-membered imidazolidinedione or thioxoimidazolinone is described. The prepared analogues were evaluated for their capacity to inhibit the cyclic guanosine monophosphate (cGMP) selective phosphodiesterase 5 (PDE5) isozyme and the growth of human HT-29 colon adenocarcinoma cells. The R absolute configuration of C-5 in the β-carboline-hydantoin and C-6 in the β-carboline-piperazinedione derivatives was found to be essential for the PDE5 inhibition. In addition, tadalafil analogues that were synthesized from L-tryptophan were more active than those derived from D-tryptophan, which is of economic value and expands the horizon for the discovery of new carbolines as PDE5 inhibitors. While some analogues displayed potent tumor cell growth inhibitory activity, there was no apparent correlation with their PDE5 inhibitory activity, which leads us to conclude that other PDE isozymes or PDE5 splice variants may be involved. PMID:20206015

  5. Synthesis, molecular modeling and biological evaluation of novel tadalafil analogues as phosphodiesterase 5 and colon tumor cell growth inhibitors, new stereochemical perspective.

    PubMed

    Abadi, Ashraf H; Gary, Bernard D; Tinsley, Heather N; Piazza, Gary A; Abdel-Halim, Mohammad

    2010-04-01

    The synthesis of novel tadalafil analogues in which the benzodioxole moiety is replaced by 2-bromophenyl; the chiral carbons swing from R,R to R,S, S,R and S,S; the piperazinedione ring is maintained or reduced to the 5-membered imidazolidinedione or thioxoimidazolinone is described. The prepared analogues were evaluated for their capacity to inhibit the cyclic guanosine monophosphate (cGMP) selective phosphodiesterase 5 (PDE5) isozyme and the growth of human HT-29 colon adenocarcinoma cells. The R absolute configuration of C-5 in the beta-carboline-hydantoin and C-6 in the beta-carboline-piperazinedione derivatives was found to be essential for the PDE5 inhibition. In addition, tadalafil analogues that were synthesized from l-tryptophan were more active than those derived from d-tryptophan, which is of economic value and expands the horizon for the discovery of new carbolines as PDE5 inhibitors. While some analogues displayed potent tumor cell growth inhibitory activity, there was no apparent correlation with their PDE5 inhibitory activity, which leads us to conclude that other PDE isozymes or PDE5 splice variants may be involved. PMID:20206015

  6. Substrate analogues for isoprenoid enzymes

    SciTech Connect

    Stremler, K.E.

    1987-01-01

    Diphosphonate analogues of geranyl diphosphate, resistant to degradation by phosphatases, were found to be alternate substrates for the reaction with farnesyl diphosphate synthetase isolated from avian liver. The difluoromethane analogue was shown to be the better alternate substrate, in agreement with solvolysis results which indicate that the electronegativity of the difluoromethylene unit more closely approximates that of the normal bridging oxygen. The usefulness of the C/sub 10/ difluoro analogue, for detecting low levels of isoprenoid enzymes in the presence of high levels of phosphatase activity, was demonstrated with a cell-free preparation from lemon peel. A series of C/sub 5/ through C/sub 15/ homoallylic and allylic diphosphonates, as well as two 5'-nucleotide diphosphonates, was prepared in high overall yield using the activation-displacement sequence. Radiolabeled samples of several of the allylic diphosphonates were prepared with tritium located at C1. A series of geraniols, stereospecifically deuterated at C1, was prepared. The enantiomeric purities and absolute configurations were determined by derivatization as the mandelate esters for analysis by /sup 1/H NMR. The stereochemistry of the activation-displacement sequence was examined using C1-deuterated substrates.

  7. Phosphonate analogue substrates for enolase.

    PubMed

    Anderson, V E; Cleland, W W

    1990-11-20

    Phosphonate analogues in which the bridge between C-2 and phosphorus is a CH2 group are slow substrates for yeast enolase. The pH variation of the kinetic parameters for the methylene analogue of 2-phosphoglycerate suggests that the substrate binds as a dianion and that Mg2+ can bind subsequently only if a metal ligand and the catalytic base are unprotonated. Primary deuterium isotope effects of 4-8 on V/KMg, but ones of only 1.15-1.32 on V for dehydration, show that proton removal to give the carbanion intermediate largely limits V/KMg and that a slow step follows which largely limits V (presumably carbanion breakdown). Since there is a D2O solvent isotope effect on V for the reverse reaction of 5, but not an appreciable one on the forward reaction, it appears that the slow rates with phosphonate analogues result from the fact that the carbanion intermediate is more stable than that formed from the normal substrates, and its reaction in both directions limits V. Increased stability as a result of replacement of oxygen by carbon at C-2 of the carbanion is the expected chemical behavior. PMID:2271661

  8. Policy issues in space analogues

    NASA Astrophysics Data System (ADS)

    Auger, Robin N.; Facktor, Debra D.

    Space mission planning is increasingly focusing on destinations beyond Earth orbit. Advancements in technology will inevitably be required to enable long-duration human spaceflight missions, and breakthroughs in the policy arena will also be needed to achieve success in such missions. By exploring how policy issues have been addressed in analogous extreme environments, policymakers can develop a framework for addressing these issues as they apply to long-term human spaceflight. Policy issues that need to be addressed include: crew selection, training, organization, and activities, medical testing, illness, injury, and death; communication; legal accountability and liability; mission safety and risk management; and environmental contamination. This paper outlines the approach of a study underway by The George Washington University and ANSER to examine how these policy issues have been addressed in several analogues and how the experiences of these analogues can help formulate policies for long-duration human spaceflight missions. Analogues being studied include Antarctic bases, submarine voyages, undersea stations, Biosphere 2, and the U.S. Skylab and Russian Mir space stations.

  9. Comparative Structural Dynamics of tRNA(Phe) with Respect to Hinge Region Methylated Guanosine: A Computational Approach.

    PubMed

    Sonawane, Kailas D; Bavi, Rohit S; Sambhare, Susmit B; Fandilolu, Prayagraj M

    2016-06-01

    Transfer RNAs (tRNAs) contain various uniquely modified nucleosides thought to be useful for maintaining the structural stability of tRNAs. However, their significance for upholding the tRNA structure has not been investigated in detail at the atomic level. In this study, molecular dynamic simulations have been performed to assess the effects of methylated nucleic acid bases, N (2)-methylguanosine (m(2)G) and N (2)-N (2)-dimethylguanosine (m 2 (2) G) at position 26, i.e., the hinge region of E. coli tRNA(Phe) on its structure and dynamics. The results revealed that tRNA(Phe) having unmodified guanosine in the hinge region (G26) shows structural rearrangement in the core of the molecule, resulting in lack of base stacking interactions, U-turn feature of the anticodon loop, and TΨC loop. We show that in the presence of the unmodified guanosine, the overall fold of tRNA(Phe) is essentially not the same as that of m(2)G26 and m 2 (2) G26 containing tRNA(Phe). This structural rearrangement arises due to intrinsic factors associated with the weak hydrogen-bonding patterns observed in the base triples of the tRNA(Phe) molecule. The m(2)G26 and m 2 (2) G26 containing tRNA(Phe) retain proper three-dimensional fold through tertiary interactions. Single-point energy and molecular electrostatics potential calculation studies confirmed the structural significance of tRNAs containing m(2)G26 and m 2 (2) G26 compared to tRNA with normal G26, showing that the mono-methylated (m(2)G26) and dimethylated (m 2 (2) G26) modifications are required to provide structural stability not only in the hinge region but also in the other parts of tRNA(Phe). Thus, the present study allows us to better understand the effects of modified nucleosides and ionic environment on tRNA folding. PMID:27216172

  10. Guanosine may increase absence epileptic activity by means of A2A adenosine receptors in Wistar Albino Glaxo Rijswijk rats.

    PubMed

    Lakatos, Renáta Krisztina; Dobolyi, Árpád; Todorov, Mihail Ivilinov; Kékesi, Katalin A; Juhász, Gábor; Aleksza, Magdolna; Kovács, Zsolt

    2016-06-01

    The non-adenosine nucleoside guanosine (Guo) was demonstrated to decrease quinolinic acid(QA)-induced seizures, spontaneously emerged absence epileptic seizures and lipopolysaccharide(LPS)-evoked induction of absence epileptic seizures suggesting its antiepileptic potential. It was also described previously that intraperitoneal (i.p.) injection of 20 and 50mg/kg Guo decreased the number of spike-wave discharges (SWDs) in a well investigated model of human absence epilepsy, the Wistar Albino Glaxo Rijswijk (WAG/Rij) rats during 4th (20mg/kg Guo) and 3rd as well as 4th (50mg/kg Guo) measuring hours. Guanosine can potentially decrease SWD number by means of its putative receptors but absence epileptic activity changing effects of Guo by means of increased extracellular adenosine (Ado) cannot be excluded. An increase in the dose of i.p. injected Guo is limited by its low solubility in saline, therefore, we addressed in the present study whether higher doses of Guo, diluted in sodium hydroxide (NaOH) solution, have more potent antiepileptic effect in WAG/Rij rats. We confirmed that i.p. 50mg/kg Guo decreased but, surprisingly, i.p. 100mg/kg Guo enhanced the number of SWDs in WAG/Rij rats. Combined i.p. injection of a non-selective Ado receptor antagonist theophylline (5mg/kg) or a selective Ado A2A receptor (A2AR) antagonist SCH 58261 (7-(2-phenylethyl)-5-amino-2-(2-furyl)-pyrazolo-[4,3-e]-1,2,4-triazolo[1,5-c]pyrimidine) (1mg/kg) and a cyclooxygenase 1 and 2/COX-1 and COX-2 inhibitor indomethacin (10mg/kg) with 100mg/kg Guo decreased the SWD number compared to i.p. 100mg/kg Guo alone. The results suggest that i.p. 100mg/kg Guo can increase SWD number by means of the adenosinergic system. PMID:27154620

  11. FUNCTION GENERATOR FOR ANALOGUE COMPUTERS

    DOEpatents

    Skramstad, H.K.; Wright, J.H.; Taback, L.

    1961-12-12

    An improved analogue computer is designed which can be used to determine the final ground position of radioactive fallout particles in an atomic cloud. The computer determines the fallout pattern on the basis of known wind velocity and direction at various altitudes, and intensity of radioactivity in the mushroom cloud as a function of particle size and initial height in the cloud. The output is then displayed on a cathode-ray tube so that the average or total luminance of the tube screen at any point represents the intensity of radioactive fallout at the geographical location represented by that point. (AEC)

  12. Ecstasy analogues found in cacti.

    PubMed

    Bruhn, Jan G; El-Seedi, Hesham R; Stephanson, Nikolai; Beck, Olof; Shulgin, Alexander T

    2008-06-01

    Human interest in psychoactive phenethylamines is known from the use of mescaline-containing cacti and designer drugs such as Ecstasy. From the alkaloid composition of cacti we hypothesized that substances resembling Ecstasy might occur naturally. In this article we show that lophophine, homopiperonylamine and lobivine are new minor constituents of two cactus species, Lophophora williamsii (peyote) and Trichocereus pachanoi (San Pedro). This is the first report of putatively psychoactive phenethylamines besides mescaline in these cacti. A search for further biosynthetic analogues may provide new insights into the structure-activity relationships of mescaline. An intriguing question is whether the new natural compounds can be called "designer drugs." PMID:18720674

  13. Theoretical vibrational spectroscopy of intermediates and the reaction mechanism of the guanosine triphosphate hydrolysis by the protein complex Ras-GAP.

    PubMed

    Khrenova, Maria G; Grigorenko, Bella L; Nemukhin, Alexander V

    2016-09-01

    The structures and vibrational spectra of the reacting species upon guanosine triphosphate (GTP) hydrolysis to guanosine diphosphate and inorganic phosphate (Pi) trapped inside the protein complex Ras-GAP were analyzed following the results of QM/MM simulations. The frequencies of the phosphate vibrations referring to the reactants and to Pi were compared to those observed in the experimental FTIR studies. A good correlation between the theoretical and experimental vibrational data provides a strong support to the reaction mechanism of GTP hydrolysis by the Ras-GAP enzyme system revealed by the recent QM/MM modeling. Evolution of the vibrational bands associated with the inorganic phosphate Pi during the elementary stages of GTP hydrolysis is predicted. PMID:27214270

  14. Theoretical vibrational spectroscopy of intermediates and the reaction mechanism of the guanosine triphosphate hydrolysis by the protein complex Ras-GAP

    NASA Astrophysics Data System (ADS)

    Khrenova, Maria G.; Grigorenko, Bella L.; Nemukhin, Alexander V.

    2016-09-01

    The structures and vibrational spectra of the reacting species upon guanosine triphosphate (GTP) hydrolysis to guanosine diphosphate and inorganic phosphate (Pi) trapped inside the protein complex Ras-GAP were analyzed following the results of QM/MM simulations. The frequencies of the phosphate vibrations referring to the reactants and to Pi were compared to those observed in the experimental FTIR studies. A good correlation between the theoretical and experimental vibrational data provides a strong support to the reaction mechanism of GTP hydrolysis by the Ras-GAP enzyme system revealed by the recent QM/MM modeling. Evolution of the vibrational bands associated with the inorganic phosphate Pi during the elementary stages of GTP hydrolysis is predicted.

  15. The Valles natural analogue project

    SciTech Connect

    Stockman, H.; Krumhansl, J.; Ho, C.; McConnell, V.

    1994-12-01

    The contact between an obsidian flow and a steep-walled tuff canyon was examined as an analogue for a highlevel waste repository. The analogue site is located in the Valles Caldera in New Mexico, where a massive obsidian flow filled a paleocanyon in the Battleship Rock tuff. The obsidian flow provided a heat source, analogous to waste panels or an igneous intrusion in a repository, and caused evaporation and migration of water. The tuff and obsidian samples were analyzed for major and trace elements and mineralogy by INAA, XRF, X-ray diffraction; and scanning electron microscopy and electron microprobe. Samples were also analyzed for D/H and {sup 39}Ar/{sup 4O} isotopic composition. Overall,the effects of the heating event seem to have been slight and limited to the tuff nearest the contact. There is some evidence of devitrification and migration of volatiles in the tuff within 10 meters of the contact, but variations in major and trace element chemistry are small and difficult to distinguish from the natural (pre-heating) variability of the rocks.

  16. Peroxynitrite-Dependent Zinc Release and Inactivation of Guanosine 5′-Triphosphate Cyclohydrolase 1 Instigate Its Ubiquitination in Diabetes

    PubMed Central

    Zhao, Yu; Wu, Jiliang; Zhu, Huaiping; Song, Ping; Zou, Ming-Hui

    2013-01-01

    Aberrant degradation of guanosine 5′-triphosphate cyclohydrolase 1 (GTPCH1) with consequent deficiency of tetrahydrobiopterin is considered the primary cause for endothelial dysfunction in diabetes. How GTPCH1 becomes susceptible to the degradation remains unknown. We hypothesized that oxidation and release of the zinc ion by peroxynitrite (ONOO−), a potent oxidant generated by nitric oxide and superoxide anions, instigates GTPCH1 ubiquitination and degradation. Zinc contents, GTPCH1 ubiquitination, and GTPCH1 activity were assayed in purified GTPCH1, endothelial cells, and hearts from diabetic mice. Exogenous ONOO− dose-dependently released zinc, inhibited its activity, and increased the ubiquitin binding affinity of GTPCH1 in vitro and in endothelial cells. Consistently, high glucose (30 mmol/L) inhibited GTPCH1 activity with increased ubiquitination, which was inhibited by antioxidants. Furthermore, mutation of the zinc-binding cysteine (141) (C141R or C141A) significantly reduced GTPCH1 activity and reduced its half-life but increased GTPCH1 ubiquitination, indicating an essential role of the zinc ion in maintaining the catalytic activity and stability of GTPCH1. Finally, GTPCH1 ubiquitination and degradation markedly increased in parallel with decreased GTPCH1 activity in the aortas and hearts of diabetic mice, both of which were attenuated by the inhibitors of ONOO− in mice in vivo. Taken together, we conclude that ONOO− releases zinc and inhibits GTPCH1, resulting in its ubiquitination and degradation of the enzyme. PMID:23974923

  17. Length of guanosine homopolymeric repeats modulates promoter activity of subfamily II tpr genes of Treponema pallidum ssp. pallidum.

    PubMed

    Giacani, Lorenzo; Lukehart, Sheila; Centurion-Lara, Arturo

    2007-11-01

    In Treponema pallidum, homopolymeric guanosine repeats of varying length are present upstream of both Subfamily I (tprC, D, F and I) and II (tprE, G and J) tpr genes, a group of potential virulence factors, immediately upstream of the +1 nucleotide. To investigate the influence of these poly-G sequences on promoter activity, tprE, G, J, F and I promoter regions containing homopolymeric tracts with different numbers of Gs, the ribosomal binding site and start codon were cloned in frame with the green fluorescent protein reporter gene (GFP), and promoter activity was measured both as fluorescence emission from Escherichia coli cultures transformed with the different plasmid constructs and using quantitative RT-PCR. For tprJ, G and E-derived clones, fluorescence was significantly higher with constructs containing eight Gs or fewer, while plasmids containing the same promoters with none or more Gs gave modest or no signal above the background. In contrast, tprF/I-derived clones induced similar levels of fluorescence regardless of the number of Gs within the promoter. GFP mRNA quantification showed that all of the promoters induced measurable transcription of the GFP gene; however, only for Subfamily II promoters was message synthesis inversely correlated to the number of Gs in the construct. PMID:17683506

  18. Analysis of nitric oxide-cyclic guanosine monophosphate signaling during metamorphosis of the nudibranch Phestilla sibogae Bergh (Gastropoda: Opisthobranchia).

    PubMed

    Bishop, Cory D; Pires, Anthony; Norby, Shong-Wan; Boudko, Dmitri; Moroz, Leonid L; Hadfield, Michael G

    2008-01-01

    The gas nitric oxide (NO), and in some cases its downstream second messenger, cyclic guanosine monophosphate (cGMP) function in different taxa to regulate the timing of life-history transitions. Increased taxonomic sampling is required to foster conclusions about the evolution and function of NO/cGMP signaling during life-history transitions. We report on the function and localization of NO and cGMP signaling during metamorphosis of the nudibranch Phestilla sibogae. Pharmacological manipulation of NO or cGMP production in larvae modulated responses to a natural settlement cue from the coral Porites compressa in a manner that suggest inhibitory function for NO/cGMP signaling. However, these treatments were not sufficient to induce metamorphosis in the absence of cue, a result unique to this animal. We show that induction of metamorphosis in response to the settlement cue is associated with a reduction in NO production. We documented the expression of putative NO synthase (NOS) and the production of cGMP during larval development and observed no larval cells in which NOS and cGMP were both detected. The production of cGMP in a bilaterally symmetrical group of cells fated to occupy the distal tip of rhinophores is correlated with competence to respond to the coral settlement cue. These results suggest that endogenous NO and cGMP are involved in modulating responses of P. sibogae to a natural settlement cue. We discuss these results with respect to habitat selection and larval ecology. PMID:18460091

  19. Alterations in the Cerebellar (Phospho)Proteome of a Cyclic Guanosine Monophosphate (cGMP)-dependent Protein Kinase Knockout Mouse*

    PubMed Central

    Corradini, Eleonora; Vallur, Raghavan; Raaijmakers, Linsey M.; Feil, Susanne; Feil, Robert; Heck, Albert J. R.; Scholten, Arjen

    2014-01-01

    The cyclic nucleotide cyclic guanosine monophosphate (cGMP) plays an important role in learning and memory, but its signaling mechanisms in the mammalian brain are not fully understood. Using mass-spectrometry-based proteomics, we evaluated how the cerebellum adapts its (phospho)proteome in a knockout mouse model of cGMP-dependent protein kinase type I (cGKI). Our data reveal that a small subset of proteins in the cerebellum (∼3% of the quantified proteins) became substantially differentially expressed in the absence of cGKI. More changes were observed at the phosphoproteome level, with hundreds of sites being differentially phosphorylated between wild-type and knockout cerebellum. Most of these phosphorylated sites do not represent known cGKI substrates. An integrative computational network analysis of the data indicated that the differentially expressed proteins and proteins harboring differentially phosphorylated sites largely belong to a tight network in the Purkinje cells of the cerebellum involving important cGMP/cAMP signaling nodes (e.g. PDE5 and PKARIIβ) and Ca2+ signaling (e.g. SERCA3). In this way, removal of cGKI could be linked to impaired cerebellar long-term depression at Purkinje cell synapses. In addition, we were able to identify a set of novel putative (phospho)proteins to be considered in this network. Overall, our data improve our understanding of cerebellar cGKI signaling and suggest novel players in cGKI-regulated synaptic plasticity. PMID:24925903

  20. Synthesis of the coenzymes adenosine diphosphate glucose, guanosine diphosphate glucose, and cytidine diphosphoethanolamine under primitive Earth conditions

    NASA Technical Reports Server (NTRS)

    Mar, A.; Oro, J.

    1991-01-01

    The nonenzymatic synthesis of the coenzymes adenosine diphosphate glucose (ADPG), guanosine diphosphate glucose (GDPG), and cytidine diphosphoethanolamine (CDP-ethanolamine) has been carried out under conditions considered to have been prevalent on the early Earth. The production of these compounds was performed by allowing simple precursor molecules to react under aqueous solutions, at moderate temperatures and short periods of time, with mediation by cyanamide or urea. These two condensing agents are considered to have been present in significant amounts on the primitive Earth and have been previously used in the nonenzymatic synthesis of several other important biochemical compounds. In our experiments, ADPG was obtained by heating glucose-1-phosphate (G1P) and ATP in the presence of cyanamide for 24 h at 70 degrees C. The reaction of G1P and GTP under the same conditions yielded GDPG. The cyanamide-mediated production of CDP-ethanolamine was carried out by reacting a mixture of ethanolamine phosphate and CTP for 24 h at 70 degrees C. The separation and identification of the reaction products was carried out by paper chromatography, thin-layer chromatography, high performance thin-layer chromatography, high performance liquid chromatography, both normal and reverse-phase, UV spectroscopy, enzymatic assays, and acid hydrolysis. Due to the mild conditions employed, and to the relative ease of these reactions, these studies offer a simple attractive system for the nonenzymatic synthesis of phosphorylated high-energy metabolic intermediates under conditions considered to have been prevalent on the ancient Earth.

  1. Influence of salt additives on phase transformation of guanosine 5-monophosphate disodium in anti-solvent crystallization

    NASA Astrophysics Data System (ADS)

    Nguyen, Anh-Tuan; Kang, Jeongki; Kim, Woo-Sik

    2013-06-01

    The influence of sodium chloride (NaCl) as an additive on the anti-solvent crystallization of guanosine 5-monophosphate disodium (GMP-2Na) was investigated in continuous Couette-Taylor (CT) and batch mixing tank (MT) crystallizers. The anti-solvent crystallization initially precipitated amorphous solids of GMP-2Na, which then slowly transformed into hydrate crystals in the solution. However, the phase transformation of GMP-2Na was markedly promoted by the sodium chloride additive due to the common ion effect. While the normal phase transformation in the batch MT crystallizer required over 120 min of crystallization time without using the sodium chloride additive, the process was completed within 60 min when a small amount of the salt additive was added. The phase transformation was also significantly accelerated in the continuous CT crystallizer. Without using the sodium chloride additive, 7 min of the mean residence time was required for the production of 100% hydrate GMP crystals. However, when using the sodium chloride additive, a mean residence time of only 2 min was sufficient to completely transform the amorphous solids of GMP-2Na into hydrate crystals due to the common ion effect combined with the effective fluid motion of the Taylor vortex for the mass transfer.

  2. Non-adenosine nucleoside inosine, guanosine and uridine as promising antiepileptic drugs: a summary of current literature.

    PubMed

    Kovacs, Zsolt; Kekesi, Katalin A; Juhasz, Gabor; Barna, Janos; Heja, Laszlo; Lakatos, Renata; Dobolyi, Arpad

    2015-01-01

    Adenosine (Ado) and some non-adenosine (non-Ado) nucleosides including inosine (Ino), guanosine (Guo) and uridine (Urd) are modulatory molecules in the central nervous system (CNS), regulating different physiological and pathophysiological processes in the brain such as sleep and epilepsy. Indeed, different drugs effective on adenosinergic system (e.g., Ado metabolism inhibitors, agonists and antagonists of Ado receptors) are being used in drug development for the treatment of epileptic disorders. Although (i) endogenous Ino, Guo and Urd showed anticonvulsant/antiepileptic effects (e.g., in quinolinic acid - induced seizures and in different epilepsy models such as hippocampal kindling models), and (ii) there is a need to generate new and more effective antiepileptic drugs for the treatment of drug-resistant epilepsies, our knowledge about antiepileptic influence of non-Ado nucleosides is far from complete. Thus, in this review article, we give a short summary of anticonvulsant/antiepileptic effects and mechanisms evoked by Ino, Guo, and Urd. Finally, we discuss some non-Ado nucleoside derivatives and their structures, which may be candidates as potential antiepileptic agents. PMID:25382017

  3. Intranasal guanosine administration presents a wide therapeutic time window to reduce brain damage induced by permanent ischemia in rats.

    PubMed

    Ramos, Denise Barbosa; Muller, Gabriel Cardozo; Rocha, Guilherme Botter Maio; Dellavia, Gustavo Hirata; Almeida, Roberto Farina; Pettenuzzo, Leticia Ferreira; Loureiro, Samanta Oliveira; Hansel, Gisele; Horn, Ângelo Cássio Magalhães; Souza, Diogo Onofre; Ganzella, Marcelo

    2016-03-01

    In addition to its intracellular roles, the nucleoside guanosine (GUO) also has extracellular effects that identify it as a putative neuromodulator signaling molecule in the central nervous system. Indeed, GUO can modulate glutamatergic neurotransmission, and it can promote neuroprotective effects in animal models involving glutamate neurotoxicity, which is the case in brain ischemia. In the present study, we aimed to investigate a new in vivo GUO administration route (intranasal, IN) to determine putative improvement of GUO neuroprotective effects against an experimental model of permanent focal cerebral ischemia. Initially, we demonstrated that IN [(3)H] GUO administration reached the brain in a dose-dependent and saturable pattern in as few as 5 min, presenting a higher cerebrospinal GUO level compared with systemic administration. IN GUO treatment started immediately or even 3 h after ischemia onset prevented behavior impairment. The behavior recovery was not correlated to decreased brain infarct volume, but it was correlated to reduced mitochondrial dysfunction in the penumbra area. Therefore, we showed that the IN route is an efficient way to promptly deliver GUO to the CNS and that IN GUO treatment prevented behavioral and brain impairment caused by ischemia in a therapeutically wide time window. PMID:26695181

  4. A guanosine quadruplex and two stable hairpins flank a major cleavage site in insulin-like growth factor II mRNA.

    PubMed Central

    Christiansen, J; Kofod, M; Nielsen, F C

    1994-01-01

    Insulin-like growth factor II (IGF-II) mRNAs are cleaved by an endonucleolytic event in a conserved part of their 3' untranslated region that is predicted to exhibit a complex higher-order RNA structure. In the present study, we have examined the putative secondary structures of in vitro transcripts from the conserved part of human and rat mRNAs by enzymatic and chemical probing. The results show that the cleavage site is situated between two highly structured domains. The upstream domain consists of two large hairpins, whereas the downstream domain is guanosine-rich. The guanosine-rich domain adopts a compact unimolecular conformation in Na+ or K+ but not in Li+, and it completely arrests reverse transcription in K+ but only partially in Na+, indicating the presence of an intramolecular guanosine quadruplex. The flanking higher-order structures may ensure that the cleavage site is not sequestered in stable RNA structures, thus allowing interactions with RNA or proteins at posttranscriptional stages of IGF-II expression. Images PMID:7838726

  5. CO2 Capture with Enzyme Synthetic Analogue

    SciTech Connect

    Cordatos, Harry

    2010-11-08

    Overview of an ongoing, 2 year research project partially funded by APRA-E to create a novel, synthetic analogue of carbonic anhydrase and incorporate it into a membrane for removal of CO2 from flue gas in coal power plants. Mechanism background, preliminary feasibility study results, molecular modeling of analogue-CO2 interaction, and program timeline are provided.

  6. Fully analogue photonic reservoir computer.

    PubMed

    Duport, François; Smerieri, Anteo; Akrout, Akram; Haelterman, Marc; Massar, Serge

    2016-01-01

    Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers. PMID:26935166

  7. An analogue study of intrusions.

    PubMed

    Laposa, Judith M; Alden, Lynn E

    2006-07-01

    According to cognitive theorists, intrusive trauma memories have their origin in how information during the event is processed. Two studies investigated functional cognitive strategies during medical crises that might protect against intrusions. In Study 1, interviews with health-care professionals were used to identify cognitive strategies judged to be effective in controlling emotions and dealing with medical crises. Study 2 systematically manipulated the use of those strategies in a trauma analogue film paradigm. Experimental participants reported fewer intrusions, and less fear and avoidance of film-related stimuli during the subsequent week than controls. The manipulation did not affect anxiety during the film or memory disorganization. Implications for cognitive theories of intrusion development are discussed. PMID:16125135

  8. Fully analogue photonic reservoir computer

    PubMed Central

    Duport, François; Smerieri, Anteo; Akrout, Akram; Haelterman, Marc; Massar, Serge

    2016-01-01

    Introduced a decade ago, reservoir computing is an efficient approach for signal processing. State of the art capabilities have already been demonstrated with both computer simulations and physical implementations. If photonic reservoir computing appears to be promising a solution for ultrafast nontrivial computing, all the implementations presented up to now require digital pre or post processing, which prevents them from exploiting their full potential, in particular in terms of processing speed. We address here the possibility to get rid simultaneously of both digital pre and post processing. The standalone fully analogue reservoir computer resulting from our endeavour is compared to previous experiments and only exhibits rather limited degradation of performances. Our experiment constitutes a proof of concept for standalone physical reservoir computers. PMID:26935166

  9. Laboratory study of cometary analogues

    NASA Astrophysics Data System (ADS)

    Colangeli, L.; Brucato, J.; Mennella, V.; Palumbo, P.

    In situ exploration (e.g., GIOTTO mission) and astronomical observations (e.g., ISO) of comets have provided fundamental information about the structure, chemistry and physical properties of materials present in such primordial bodies of the Solar System. Moreover, it is known that cosmic materials evolve, depending on the efficiency of active processes (e.g., thermal annealing, UV irradiation, ion bombardment, gassolid interactions) in different space environments. Thus, the properties of cometary constituents must be considered in a wider perspective, including cosmic dust formation around cold stars and evolution in the interstellar medium until the formation of proto-planetary nebulae. In this scenario, laboratory experiments provide important hints to clarify the status of cometary compounds. The laboratory work is aimed at both reproducing material properties and at simulating their evolution based on the most effective mechanisms active in space. Several techniques are used to synthesise "analogues" of cometary compounds with controlled chemical and physical characteristics. The study of optical properties, complemented by other analytical techniques, is applied to investigate the products of synthesis in the experiments. The monitoring of the effects produced by processing methods, similar to those active in space, provides information both on the reactivity of materials and on the efficiency of treatments. Such an approach is able to provide quantitative information on chemical and structural modifications produced on organic and refractory materials. The comparison of laboratory results with data coming from space observations and in situ measurements provides a powerful tool to understand the real nature of comets and to place constraints on formation and evolution pathways. The laboratory experiments on analogues gain even more relevance as a sort of training in the future perspective of analysing cometary samples returned to Earth by space missions (e

  10. Mast cell degranulation is negatively regulated by the Munc13-4-binding small-guanosine triphosphatase Rab37

    PubMed Central

    Higashio, Hironori; Satoh, Yoh-ichi; Saino, Tomoyuki

    2016-01-01

    Mast cell degranulation is regulated by the small guanosine triphosphatases (GTPases) Rab27a and Rab27b, which have distinct and opposing roles: Rab27b acts as a positive regulator through its effector protein Munc13-4, a non-neuronal isoform of the vesicle-priming Munc13 family of proteins, whereas Rab27a acts as a negative regulator through its effector protein melanophilin, by maintaining integrity of cortical filamentous actin (F-actin), a barrier to degranulation. Here we investigated the role of Rab37, one of the Rab GTPases assumed to be implicated in regulated secretion during mast cell degranulation. Using the RBL-2H3 mast cell line, we detected Rab37 on the secretory granules and found that antigen-induced degranulation was extensively increased by either knockdown of Rab37 or overexpression of a dominant-active Rab37 mutant. This hypersecretion phenotype in the Rab37-knockdown cells was suppressed by simultaneous knockdown of Rab27a and Rab27b or of Munc13-4, but not by disruption of cortical F-actin. We further found that Rab37 interacted with Munc13-4 in a GTP-independent manner and formed a Rab27-Munc13-4-Rab37 complex. These results suggest that Rab37 is a Munc13-4-binding protein that inhibits mast cell degranulation through its effector protein, by counteracting the vesicle-priming activity of the Rab27-Munc13-4 system. PMID:26931073

  11. Dynamics and couplings of N-H stretching excitations of guanosine-cytidine base pairs in solution.

    PubMed

    Yang, Ming; Szyc, Łukasz; Röttger, Katharina; Fidder, Henk; Nibbering, Erik T J; Elsaesser, Thomas; Temps, Friedrich

    2011-05-12

    N-H stretching vibrations of hydrogen-bonded guanosine-cytidine (G·C) base pairs in chloroform solution are studied with linear and ultrafast nonlinear infrared (IR) spectroscopy. Assignment of the IR-active bands in the linear spectrum is made possible by combining structural information on the hydrogen bonds in G·C base pairs with literature results of density functional theory calculations, and empirical relations connecting frequency shifts and intensity of the IR-active vibrations. A local mode representation of N-H stretching vibrations is adopted, consisting of ν(G)(NH(2))(f) and ν(C)(NH(2))(f) modes for free NH groups of G and C, and of ν(G)(NH(2))(b), ν(G)(NH), and ν(C)(NH(2))(b) modes associated with N-H stretching motions of hydrogen-bonded NH groups. The couplings and relaxation dynamics of the N-H stretching excitations are studied with femtosecond mid-infrared two-dimensional (2D) and pump-probe spectroscopy. The N-H stretching vibrations of the free NH groups of G and C have an average population lifetime of 2.4 ps. Besides a vibrational population lifetime shortening to subpicosecond values observed for the hydrogen-bonded N-H stretching vibrations, the 2D spectra reveal vibrational excitation transfer from the ν(G)(NH(2))(b) mode to the ν(G)(NH) and/or ν(C)(NH(2))(b) modes. The underlying intermode vibrational couplings are on the order of 10 cm(-1). PMID:21244064

  12. Xenopus oocyte resting potential, muscarinic responses and the role of calcium and guanosine 3',5'-cyclic monophosphate.

    PubMed Central

    Dascal, N; Landau, E M; Lass, Y

    1984-01-01

    Resting potential (r.p.) and muscarinic response mechanisms were studied in Xenopus laevis oocytes using the voltage-clamp technique. Insertion of micro-electrodes into the oocyte produced a 'shunt' membrane conductance which partially sealed after a few minutes. The oocyte resting potential (measured with a single intracellular electrode) ranged from -40 to -60 mV. Ouabain and low K+ solution depolarized both follicles and denuded oocytes. The electrogenic Na+-K+ pump was more active in the latter. In the presence of ouabain, the r.p. agreed with the constant field theory. alpha (PNa+/PK+) was 0.12 in follicles and 0.24 in denuded oocytes. beta (PCl-/PK+) was 0.4 in both. At [Na+]o lower than 70 mM, the r.p. deviated considerably from the constant field predictions. The relatively large value of alpha indicated the major role of Na+ in oocyte r.p. determination. The oocyte muscarinic response was separated into four distinct components: the fast depolarizing Cl- current, 'D1'; the slow depolarizing Cl- current, 'D2'; the slow hyperpolarizing K+ current, 'H'; and the large membrane Cl- current fluctuation, 'F'. The H response reversal potential showed a Nernst relationship to [K+] and was selectively blocked by intracellular injection of tetraethylammonium (TEA). The D1 and D2 reversal potential showed a Nernst relationship to [Cl-]. In Ca2+-deficient, EGTA-containing medium, D2 and F were abolished and D1 and H were reduced. Verapamil inhibited all responses. Increasing [Ca2+]o caused a significant increase in D1, D2 and F response amplitudes. Intracellular injection of 0.6-10 pmol guanosine 3',5'-cyclic monophosphate, induced a large outward K+ current, similar to the muscarinic H response. PMID:6086916

  13. Analysis of nitric oxide-cyclic guanosine monophosphate signaling during metamorphosis of the nudibranch Phestilla sibogae Bergh (Gastropoda: Opisthobranchia)

    PubMed Central

    Bishop, Cory D.; Pires, Anthony; Norby, Shong-Wan; Boudko, Dmitri; Moroz, Leonid L.; Hadfield, Michael G.

    2014-01-01

    SUMMARY The gas nitric oxide (NO), and in some cases its downstream second messenger, cyclic guanosine monophosphate (cGMP) function in different taxa to regulate the timing of life-history transitions. Increased taxonomic sampling is required to foster conclusions about the evolution and function of NO/cGMP signaling during life-history transitions. We report on the function and localization of NO and cGMP signaling during metamorphosis of the nudibranch Phestilla sibogae. Pharmacological manipulation of NO or cGMP production in larvae modulated responses to a natural settlement cue from the coral Porites compressa in a manner that suggest inhibitory function for NO/cGMP signaling. However, these treatments were not sufficient to induce metamorphosis in the absence of cue, a result unique to this animal. We show that induction of metamorphosis in response to the settlement cue is associated with a reduction in NO production. We documented the expression of putative NO synthase (NOS) and the production of cGMP during larval development and observed no larval cells in which NOS and cGMP were both detected. The production of cGMP in a bilaterally symmetrical group of cells fated to occupy the distal tip of rhinophores is correlated with competence to respond to the coral settlement cue. These results suggest that endogenous NO and cGMP are involved in modulating responses of P. sibogae to a natural settlement cue. We discuss these results with respect to habitat selection and larval ecology. PMID:18460091

  14. Semaphorin 3A activates the guanosine triphosphatase Rab5 to promote growth cone collapse and organize callosal axon projections.

    PubMed

    Wu, Kong-Yan; He, Miao; Hou, Qiong-Qiong; Sheng, Ai-Li; Yuan, Lei; Liu, Fei; Liu, Wen-Wen; Li, Guangpu; Jiang, Xing-Yu; Luo, Zhen-Ge

    2014-01-01

    Axon guidance (pathfinding) wires the brain during development and is regulated by various attractive and repulsive cues. Semaphorin 3A (Sema3A) is a repulsive cue, inducing the collapse of axon growth cones. In the mammalian forebrain, the corpus callosum is the major commissure that transmits information flow between the two hemispheres, and contralateral axons assemble into well-defined tracts. We found that the patterning of callosal axon projections in rodent layer II and III (L2/3) cortical neurons in response to Sema3A was mediated by the activation of Rab5, a small guanosine triphosphatase (GTPase) that mediates endocytosis, through the membrane fusion protein Rabaptin-5 and the Rab5 guanine nucleotide exchange factor (GEF) Rabex-5. Rabaptin-5 bound directly to Plexin-A1 in the Sema3A receptor complex [an obligate heterodimer formed by Plexin-A1 and neuropilin 1 (NP1)]; Sema3A enhanced this interaction in cultured neurons. Rabaptin-5 bridged the interaction between Rab5 and Plexin-A1. Sema3A stimulated endocytosis from the cell surface of callosal axon growth cones. In utero electroporation to reduce Rab5 or Rabaptin-5 impaired axon fasciculation or caused mistargeting of L2/3 callosal projections in rats. Overexpression of Rabaptin-5 or Rab5 rescued the defective callosal axon fasciculation or mistargeting of callosal axons caused by the loss of Sema3A-Plexin-A1 signaling in rats expressing dominant-negative Plexin-A1 or in NP1-deficient mice. Thus, our findings suggest that Rab5, its effector Rabaptin-5, and its regulator Rabex-5 mediate Sema3A-induced axon guidance during brain development. PMID:25161316

  15. Semaphorin 3A activates the guanosine triphosphatase Rab5 to promote growth cone collapse and organize callosal axon projections

    PubMed Central

    Wu, Kong-Yan; He, Miao; Hou, Qiong-Qiong; Sheng, Ai-Li; Yuan, Lei; Liu, Fei; Liu, Wen-Wen; Li, Guangpu; Jiang, Xing-Yu; Luo, Zhen-Ge

    2015-01-01

    Axon guidance (pathfinding) wires the brain during development and is regulated by various attractive and repulsive cues. Semaphorin 3A (Sema3A) is a repulsive cue, inducing the collapse of axon growth cones. In the mammalian forebrain, the corpus callosum is the major commissure that transmits information flow between the two hemispheres, and contralateral axons assemble into well-defined tracts. We found that the patterning of callosal axon projections in rodent layer II and III (L2/3) cortical neurons in response to Sema3A was mediated by the activation of Rab5, a small guanosine triphosphatase (GTPase) that mediates endocytosis, through the membrane fusion protein Rabaptin-5 and the Rab5 guanine nucleotide exchange factor (GEF) Rabex-5. Rabaptin-5 bound directly to Plexin-A1 in the Sema3A receptor complex [an obligate heterodimer formed by Plexin-A1 and neuropilin 1 (NP1)]; Sema3A enhanced this interaction in cultured neurons. Rabaptin-5 bridged the interaction between Rab5 and Plexin-A1. Sema3A stimulated endocytosis from the cell surface of callosal axon growth cones. In utero electroporation to reduce Rab5 or Rabaptin-5 impaired axon fasciculation or caused mistargeting of L2/3 callosal projections in rats. Over-expression of Rabaptin-5 or Rab5 rescued the defective callosal axon fasciculation or mistargeting of callosal axons caused by the loss of Sema3A–Plexin-A1 signaling in rats expressing dominant-negative Plexin-A1 or in NP1-deficient mice. Thus, our findings suggest that Rab5, its effector Rabaptin-5, and its regulator Rabex-5 mediate Sema3A-induced axon guidance during brain development. PMID:25161316

  16. Guanosine 3′,5′-bispyrophosphate coordinates global gene expression during glucose-lactose diauxie in Escherichia coli

    PubMed Central

    Traxler, Matthew F.; Chang, Dong-Eun; Conway, Tyrrell

    2006-01-01

    Guanosine 3′,5′-bispyrophosphate (ppGpp), also known as “magic spot,” has been shown to bind prokaryotic RNA polymerase to down-regulate ribosome production and increase transcription of amino acid biosynthesis genes during the stringent response to amino acid starvation. Because many environmental growth perturbations cause ppGpp to accumulate, we hypothesize ppGpp to have an overarching role in regulating the genetic program that coordinates transitions between logarithmic growth (feast) and growth arrest (famine). We used the classic glucose-lactose diauxie as an experimental system to investigate the temporal changes in transcription that accompany growth arrest and recovery in wild-type Escherichia coli and in mutants that lack RelA (ppGpp synthetase) and other global regulators, i.e., RpoS and Crp. In particular, diauxie was delayed in the relA mutant and was accompanied by a 15% decrease in the number of carbon sources used and a 3-fold overall decrease in the induction of RpoS and Crp regulon genes. Thus the data significantly expand the previously known role of ppGpp and support a model wherein the ppGpp-dependent redistribution of RNA polymerase across the genome is the driving force behind control of the stringent response, general stress response, and starvation-induced carbon scavenging. Our conceptual model of diauxie describes these global control circuits as dynamic, interconnected, and dependent upon ppGpp for the efficient temporal coordination of gene expression that programs the cell for transitions between feast and famine. PMID:16467149

  17. Absence epileptic activity changing effects of non-adenosine nucleoside inosine, guanosine and uridine in Wistar Albino Glaxo Rijswijk rats.

    PubMed

    Kovács, Z; Kékesi, K A; Dobolyi, Á; Lakatos, R; Juhász, G

    2015-08-01

    Adenosine (Ado) and non-adenosine (non-Ado) nucleosides such as inosine (Ino), guanosine (Guo) and uridine (Urd) may have regionally different roles in the regulation of physiological and pathophysiological processes in the central nervous system (CNS) such as epilepsy. It was demonstrated previously that Ino and Guo decreased quinolinic acid (QA)-induced seizures and Urd reduced penicillin-, bicuculline- and pentylenetetrazole (PTZ)-induced seizures. It has also been demonstrated that Ino and Urd may exert their effects through GABAergic system by altering the function of GABA(A) type of gamma-aminobutyric acid receptors (GABAA receptors) whereas Guo decreases glutamate-induced excitability through glutamatergic system, which systems (GABAergic and glutamatergic) are involved in pathomechanisms of absence epilepsy. Thus, we hypothesized that Ino and Guo, similarly to the previously described effect of Urd, might also decrease absence epileptic activity. We investigated in the present study whether intraperitoneal (i.p.) application of Ino (500 and 1000mg/kg), Guo (20 and 50mg/kg), Urd (500 and 1000mg/kg), GABA(A) receptor agonist muscimol (1 and 3mg/kg), GABA(A) receptor antagonist bicuculline (2 and 4mg/kg), non-selective Ado receptor antagonist theophylline (5 and 10mg/kg) and non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist (+)-5-methyl-10,11-dihydro-5H-dibenzo (a,d) cyclohepten-5,10-imine maleate (MK-801, 0.0625 and 0.1250mg/kg) alone and in combination have modulatory effects on absence epileptic activity in Wistar Albino Glaxo Rijswijk (WAG/Rij) rats. We found that Guo decreased the number of spike-wave discharges (SWDs) whereas Ino increased it dose-dependently. We strengthened that Urd can decrease absence epileptic activity. Our results suggest that Guo, Urd and their analogs could be potentially effective drugs for treatment of human absence epilepsy. PMID:26037802

  18. Plant volatile analogues strengthen attractiveness to insect.

    PubMed

    Sun, Yufeng; Yu, Hao; Zhou, Jing-Jiang; Pickett, John A; Wu, Kongming

    2014-01-01

    Green leaf bug Apolygus lucorum (Meyer-Dür) is one of the major pests in agriculture. Management of A. lucorum was largely achieved by using pesticides. However, the increasing population of A. lucorum since growing Bt cotton widely and the increased awareness of ecoenvironment and agricultural product safety makes their population-control very challenging. Therefore this study was conducted to explore a novel ecological approach, synthetic plant volatile analogues, to manage the pest. Here, plant volatile analogues were first designed and synthesized by combining the bioactive components of β-ionone and benzaldehyde. The stabilities of β-ionone, benzaldehyde and analogue 3 g were tested. The electroantennogram (EAG) responses of A. lucorum adult antennae to the analogues were recorded. And the behavior assay and filed experiment were also conducted. In this study, thirteen analogues were acquired. The analogue 3 g was demonstrated to be more stable than β-ionone and benzaldehyde in the environment. Many of the analogues elicited EAG responses, and the EAG response values to 3 g remained unchanged during seven-day period. 3 g was also demonstrated to be attractive to A. lucorum adults in the laboratory behavior experiment and in the field. Its attractiveness persisted longer than β-ionone and benzaldehyde. This indicated that 3 g can strengthen attractiveness to insect and has potential as an attractant. Our results suggest that synthetic plant volatile analogues can strengthen attractiveness to insect. This is the first published study about synthetic plant volatile analogues that have the potential to be used in pest control. Our results will support a new ecological approach to pest control and it will be helpful to ecoenvironment and agricultural product safety. PMID:24911460

  19. Plant Volatile Analogues Strengthen Attractiveness to Insect

    PubMed Central

    Sun, Yufeng; Yu, Hao; Zhou, Jing-Jiang; Pickett, John A.; Wu, Kongming

    2014-01-01

    Green leaf bug Apolygus lucorum (Meyer-Dür) is one of the major pests in agriculture. Management of A. lucorum was largely achieved by using pesticides. However, the increasing population of A. lucorum since growing Bt cotton widely and the increased awareness of ecoenvironment and agricultural product safety makes their population-control very challenging. Therefore this study was conducted to explore a novel ecological approach, synthetic plant volatile analogues, to manage the pest. Here, plant volatile analogues were first designed and synthesized by combining the bioactive components of β-ionone and benzaldehyde. The stabilities of β-ionone, benzaldehyde and analogue 3 g were tested. The electroantennogram (EAG) responses of A. lucorum adult antennae to the analogues were recorded. And the behavior assay and filed experiment were also conducted. In this study, thirteen analogues were acquired. The analogue 3 g was demonstrated to be more stable than β-ionone and benzaldehyde in the environment. Many of the analogues elicited EAG responses, and the EAG response values to 3 g remained unchanged during seven-day period. 3 g was also demonstrated to be attractive to A. lucorum adults in the laboratory behavior experiment and in the field. Its attractiveness persisted longer than β-ionone and benzaldehyde. This indicated that 3 g can strengthen attractiveness to insect and has potential as an attractant. Our results suggest that synthetic plant volatile analogues can strengthen attractiveness to insect. This is the first published study about synthetic plant volatile analogues that have the potential to be used in pest control. Our results will support a new ecological approach to pest control and it will be helpful to ecoenvironment and agricultural product safety. PMID:24911460

  20. Antimicrobial activity of resveratrol analogues.

    PubMed

    Chalal, Malik; Klinguer, Agnès; Echairi, Abdelwahad; Meunier, Philippe; Vervandier-Fasseur, Dominique; Adrian, Marielle

    2014-01-01

    Stilbenes, especially resveratrol and its derivatives, have become famous for their positive effects on a wide range of medical disorders, as indicated by a huge number of published studies. A less investigated area of research is their antimicrobial properties. A series of 13 trans-resveratrol analogues was synthesized via Wittig or Heck reactions, and their antimicrobial activity assessed on two different grapevine pathogens responsible for severe diseases in the vineyard. The entire series, together with resveratrol, was first evaluated on the zoospore mobility and sporulation level of Plasmopara viticola (the oomycete responsible for downy mildew). Stilbenes displayed a spectrum of activity ranging from low to high. Six of them, including the most active ones, were subsequently tested on the development of Botrytis cinerea (fungus responsible for grey mold). The results obtained allowed us to identify the most active stilbenes against both grapevine pathogens, to compare the antimicrobial activity of the evaluated series of stilbenes, and to discuss the relationship between their chemical structure (number and position of methoxy and hydroxy groups) and antimicrobial activity. PMID:24918540

  1. Condensed matter analogues of cosmology

    NASA Astrophysics Data System (ADS)

    Kibble, Tom; Srivastava, Ajit

    2013-10-01

    It is always exciting when developments in one branch of physics turn out to have relevance in a quite different branch. It would be hard to find two branches farther apart in terms of energy scales than early-universe cosmology and low-temperature condensed matter physics. Nevertheless ideas about the formation of topological defects during rapid phase transitions that originated in the context of the very early universe have proved remarkably fruitful when applied to a variety of condensed matter systems. The mathematical frameworks for describing these systems can be very similar. This interconnection has led to a deeper understanding of the phenomena in condensed matter systems utilizing ideas from cosmology. At the same time, one can view these condensed matter analogues as providing, at least in a limited sense, experimental access to the phenomena of the early universe for which no direct probe is possible. As this special issue well illustrates, this remains a dynamic and exciting field. The basic idea is that when a system goes through a rapid symmetry-breaking phase transition from a symmetric phase into one with spontaneously broken symmetry, the order parameter may make different choices in different regions, creating domains that when they meet can trap defects. The scale of those domains, and hence the density of defects, is constrained by the rate at which the system goes through the transition and the speed with which order parameter information propagates. This is what has come to be known as the Kibble-Zurek mechanism. The resultant scaling laws have now been tested in a considerable variety of different systems. The earliest experiments illustrating the analogy between cosmology and condensed matter were in liquid crystals, in particular on the isotropic-to-nematic transition, primarily because it is very easy to induce the phase transition (typically at room temperature) and to image precisely what is going on. This field remains one of the

  2. Space analogue studies in Antarctica

    NASA Astrophysics Data System (ADS)

    Lugg, D.; Shepanek, M.

    1999-09-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mltogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  3. Space analogue studies in Antarctica

    NASA Technical Reports Server (NTRS)

    Lugg, D.; Shepanek, M.

    1999-01-01

    Medical research has been carried out on the Australian National Antarctic Research Expeditions (ANARE) for 50 years. As an extension of this program collaborative Australian/United States research on immunology, microbiology, psychology and remote medicine has produced important data and insight on how humans adapt to the stress of extreme isolation, confinement and the harsh environment of Antarctica. An outstanding analogue for the isolation and confinement of space missions (especially planetary outposts), ANARE has been used as an international research platform by Australia and the United States since 1993. Collaborative research has demonstrated a lowered responsiveness of the immune system under the isolation and confinement of Antarctic winter-over; a reduction of almost 50% in T cell proliferation to mitogen phytohaemogglutinin, as well as changes in latent herpesvirus states and the expansion of the polyclonal latent Epstein-Barr virus infected B cell populations. Although no clinically significant disease has been found to result from these immune changes, research is currently assessing the effects of psychological factors on the immune system. This and associated research performed to date and its relevance to both organisations is discussed, and comment made on possible extensions to the program in both medical and other fields.

  4. Heterocyclic chalcone analogues as potential anticancer agents.

    PubMed

    Sharma, Vikas; Kumar, Vipin; Kumar, Pradeep

    2013-03-01

    Chalcones, aromatic ketones and enones acting as the precursor for flavonoids such as Quercetin, are known for their anticancer effects. Although, parent chalcones consist of two aromatic rings joined by a three-carbon α,β-unsaturated carbonyl system, various synthetic compounds possessing heterocyclic rings like pyrazole, indole etc. are well known and proved to be effective anticancer agents. In addition to their use as anticancer agents in cancer cell lines, heterocyclic analogues are reported to be effective even against resistant cell lines. In this connection, we hereby highlight the potential of various heterocyclic chalcone analogues as anticancer agents with a brief summary about therapeutic potential of chalcones, mechanism of anticancer action of various chalcone analogues, and current and future prospects related to the chalcones-derived anticancer research. Furthermore, some key points regarding chalcone analogues have been reviewed by analyzing their medicinal properties. PMID:22721390

  5. Synthesis and SAR of vinca alkaloid analogues.

    PubMed

    Voss, Matthew E; Ralph, Jeffery M; Xie, Dejian; Manning, David D; Chen, Xinchao; Frank, Anthony J; Leyhane, Andrew J; Liu, Lei; Stevens, Jason M; Budde, Cheryl; Surman, Matthew D; Friedrich, Thomas; Peace, Denise; Scott, Ian L; Wolf, Mark; Johnson, Randall

    2009-02-15

    Versatile intermediates 12'-iodovinblastine, 12'-iodovincristine and 11'-iodovinorelbine were utilized as substrates for transition metal based chemistry which led to the preparation of novel analogues of the vinca alkaloids. The synthesis of key iodo intermediates, their transformation into final products, and the SAR based upon HeLa and MCF-7 cell toxicity assays is presented. Selected analogues 27 and 36 show promising anticancer activity in the P388 murine leukemia model. PMID:19147348

  6. Kinetic dissection of individual steps in the poly(C)-directed oligoguanylate synthesis from guanosine 5'-monophosphate 2-methylimidazolide

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Bernasconi, C. F.; Alberas, D. J.; Baird, E. E.

    1993-01-01

    A kinetic study of oligoguanylate synthesis on a polycytidylate template, poly(C), as a function of the concentration of the activated monomer, guanosine 5'-monophosphate 2-methylimidazolide, 2-MeImpG, is reported. Reactions were run with 0.005-0.045 M 2-MeImpG in the presence of 0.05 M poly(C) at 23 degrees C. The kinetic results are consistent with a reaction scheme (eq 1) that consists of a series of consecutive steps, each step representing the addition of one molecule of 2-MeImpG to the growing oligomer. This scheme allows the calculation of second-order rate constants for every step by analyzing the time-dependent growth of each oligomer. Computer simulations of the course of reaction based on the determined rate constants and eq 1 are in excellent agreement with the product distributions seen in the HPLC profiles. In accord with an earlier study (Fakhrai, H.; Inoue, T.; Orgel, L. E. Tetrahedron 1984, 40, 39), rate constants, ki, for the formation of the tetramer and longer oligomers up to the 16-mer were found to be independent of length and somewhat higher than k3 (formation of trimer), which in turn is much higher than k2 (formation of dimer). The ki (i > or = 4), k3, and k2 values are not true second-order rate constants but vary with monomer concentration. Mechanistic models for the dimerization (Scheme I) and elongation reactions (Scheme II) are proposed that are consistent with our results. These models take into account that the monomer associates with the template in a cooperative manner. Our kinetic analysis allowed the determination of rate constants for the elementary processes of covalent bond formation between two monomers (dimerization) and between an oligomer and a monomer (elongation) on the template. A major conclusion from our study is that bond formation between two monomer units or between a primer and a monomer is assisted by the presence of additional next-neighbor monomer units. This is consistent with recent findings with hairpin

  7. Planetary habitability: lessons learned from terrestrial analogues

    NASA Astrophysics Data System (ADS)

    Preston, Louisa J.; Dartnell, Lewis R.

    2014-01-01

    Terrestrial analogue studies underpin almost all planetary missions and their use is essential in the exploration of our Solar system and in assessing the habitability of other worlds. Their value relies on the similarity of the analogue to its target, either in terms of their mineralogical or geochemical context, or current physical or chemical environmental conditions. Such analogue sites offer critical ground-truthing for astrobiological studies on the habitability of different environmental parameter sets, the biological mechanisms for survival in extreme environments and the preservation potential and detectability of biosignatures. The 33 analogue sites discussed in this review have been selected on the basis of their congruence to particular extraterrestrial locations. Terrestrial field sites that have been used most often in the literature, as well as some lesser known ones which require greater study, are incorporated to inform on the astrobiological potential of Venus, Mars, Europa, Enceladus and Titan. For example, the possibility of an aerial habitable zone on Venus has been hypothesized based on studies of life at high-altitudes in the terrestrial atmosphere. We also demonstrate why many different terrestrial analogue sites are required to satisfactorily assess the habitability of the changing environmental conditions throughout Martian history, and recommend particular sites for different epochs or potential niches. Finally, habitable zones within the aqueous environments of the icy moons of Europa and Enceladus and potentially in the hydrocarbon lakes of Titan are discussed and suitable analogue sites proposed. It is clear from this review that a number of terrestrial analogue sites can be applied to multiple planetary bodies, thereby increasing their value for astrobiological exploration. For each analogue site considered here, we summarize the pertinent physiochemical environmental features they offer and critically assess the fidelity with which

  8. Glucagonlike Peptide 2 Analogue Teduglutide

    PubMed Central

    Chaturvedi, Lakshmi S.; Basson, Marc D.

    2015-01-01

    IMPORTANCE Short bowel syndrome occurs when a shortened intestine cannot absorb sufficient nutrients or fluids. Teduglutide is a recombinant analogue of human glucagonlike peptide 2 that reduces dependence on parenteral nutrition in patients with short bowel syndrome by promoting enterocytic proliferation, increasing the absorptive surface area. However, enterocyte function depends not only on the number of cells that are present but also on differentiated features that facilitate nutrient absorption and digestion. OBJECTIVE To test the hypothesis that teduglutide impairs human intestinal epithelial differentiation. DESIGN AND SETTING We investigated the effects of teduglutide in the modulation of proliferation and differentiation in human Caco-2 intestinal epithelial cells at a basic science laboratory. This was an in vitro study using Caco-2 cells, a human-derived intestinal epithelial cell line commonly used to model enterocytic biology. EXPOSURE Cells were exposed to teduglutide or vehicle control. MAINOUTCOMESAND MEASURES We analyzed the cell cycle by bromodeoxyuridine incorporation or propidium iodide staining and flow cytometry and measured cell proliferation by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. We used quantitative reverse transcription–polymerase chain reaction to assay the expression of the enterocytic differentiation markers villin, sucrase-isomaltase, glucose transporter 2 (GLUT2), and dipeptidyl peptidase 4 (DPP-4), as well as that of the putative differentiation signals schlafen 12 (SLFN12) and caudal-related homeobox intestine-specific transcription factor (Cdx2). Villin promoter activity was measured by a luciferase-based assay. RESULTS The MTS assay demonstrated that teduglutide increased cell numbers by a mean (SD) of 10% (2%) over untreated controls at a maximal 500nM (n = 6, P < .05). Teduglutide increased bromodeoxyuridine-positive cells vs untreated controls by a mean (SD

  9. Kinetics of the template-directed oligomerization of guanosine 5'-phosphate-2-methylimidazolide: Effect of temperature on individual steps of reactionion

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.; Bernasconi, C. F.; Alberas, D. J.

    1991-01-01

    Non-enzymatic, template-directed reactions have been proposed as models for prebiological polynucleotide synthesis. Chemically activated mononucleotides react in the presence of a polynucleotide, acting as the template in a Watson-Crick base-pairing fashing, and form the complementary daughter polynucleotide. Phosphoimidazolide-activated nucleotides have been used successfully as substrates in these reactions. The kinetics of the guanosine 5'-monophosphate-2-methylimidazolide (2-MelmpG) reaction in aqueous pH 8.0 solutions in the presence and in the absence of polycytidylate (poly(C)) were studied, acting as the template at 6, 23, and 37 C. In the absence of the template, the major reaction pathway of 2-MelmpG is hydrolysis of the P-N bond to form the unreactive guanosine 5'-monophosphate (5'-GMP) and 2-methylimidazole. Concentrated solution of 2-MelmpG (greater than 0.02 M) in the absence of the template form only a small amount dinucleotide, (pG)2, but in the presence of poly(C), oligoguanylates, (pG)n with 2 less than or = n less than or = 40, can be detected. We were able to determine the rate constants for individual steps of this reaction. A summary of the conclusions is presented.

  10. Convergent syntheses of LeX analogues

    PubMed Central

    Wang, An; Hendel, Jenifer

    2010-01-01

    Summary The synthesis of three Lex derivatives from one common protected trisaccharide is reported. These analogues will be used respectively for competitive binding experiments, conjugation to carrier proteins and immobilization on gold. An N-acetylglucosamine monosaccharide acceptor was first glycosylated at O-4 with a galactosyl imidate. This coupling was performed at 40 °C under excess of BF3·OEt2 activation and proceeded best if the acceptor carried a 6-chlorohexyl rather than a 6-azidohexyl aglycon. The 6-chlorohexyl disaccharide was then converted to an acceptor and submitted to fucosylation yielding the corresponding protected 6-chlorohexyl Lex trisaccharide. This protected trisaccharide was used as a precursor to the 6-azidohexyl, 6-acetylthiohexyl and 6-benzylthiohexyl trisaccharide analogues which were obtained in excellent yields (70–95%). In turn, we describe the deprotection of these intermediates in one single step using dissolving metal conditions. Under these conditions, the 6-chlorohexyl and 6-azidohexyl intermediates led respectively to the n-hexyl and 6-aminohexyl trisaccharide targets. Unexpectedly, the 6-acetylthiohexyl analogue underwent desulfurization and gave the n-hexyl glycoside product, whereas the 6-benzylthiohexyl analogue gave the desired disulfide trisaccharide dimer. This study constitutes a particularly efficient and convergent preparation of these three Lex analogues. PMID:20485599

  11. Dolastatin 11 conformations, analogues and pharmacophore.

    PubMed

    Ali, Md Ahad; Bates, Robert B; Crane, Zackary D; Dicus, Christopher W; Gramme, Michelle R; Hamel, Ernest; Marcischak, Jacob; Martinez, David S; McClure, Kelly J; Nakkiew, Pichaya; Pettit, George R; Stessman, Chad C; Sufi, Bilal A; Yarick, Gayle V

    2005-07-01

    Twenty analogues of the natural antitumor agent dolastatin 11, including majusculamide C, were synthesized and tested for cytotoxicity against human cancer cells and stimulation of actin polymerization. Only analogues containing the 30-membered ring were active. Molecular modeling and NMR evidence showed the low-energy conformations. The amide bonds are all trans except for the one between the Tyr and Val units, which is cis. Since an analogue restricted to negative 2-3-4-5 angles stimulated actin polymerization but was inactive in cells, the binding conformation (most likely the lowest-energy conformation in water) has a negative 2-3-4-5 angle, whereas a conformation with a positive 2-3-4-5 angle (most likely the lowest energy conformation in chloroform) goes through cell walls. The highly active R alcohol from borohydride reduction of dolastatin 11 is a candidate for conversion to prodrugs. PMID:15878670

  12. Binding of rhodopsin and rhodopsin analogues to transducin, rhodopsin kinase and arrestin-1

    PubMed Central

    Araujo, Nelson A; Sanz-Rodríguez, Carlos E; Bubis, José

    2014-01-01

    AIM: To investigate the interaction of reconstituted rhodopsin, 9-cis-retinal-rhodopsin and 13-cis-retinal-rhodopsin with transducin, rhodopsin kinase and arrestin-1. METHODS: Rod outer segments (ROS) were isolated from bovine retinas. Following bleaching of ROS membranes with hydroxylamine, rhodopsin and rhodopsin analogues were generated with the different retinal isomers and the concentration of the reconstituted pigments was calculated from their UV/visible absorption spectra. Transducin and arrestin-1 were purified to homogeneity by column chromatography, and an enriched-fraction of rhodopsin kinase was obtained by extracting freshly prepared ROS in the dark. The guanine nucleotide binding activity of transducin was determined by Millipore filtration using β,γ-imido-(3H)-guanosine 5’-triphosphate. Recognition of the reconstituted pigments by rhodopsin kinase was determined by autoradiography following incubation of ROS membranes containing the various regenerated pigments with partially purified rhodopsin kinase in the presence of (γ-32P) ATP. Binding of arrestin-1 to the various pigments in ROS membranes was determined by a sedimentation assay analyzed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. RESULTS: Reconstituted rhodopsin and rhodopsin analogues containing 9-cis-retinal and 13-cis-retinal rendered an absorption spectrum showing a maximum peak at 498 nm, 486 nm and about 467 nm, respectively, in the dark; which was shifted to 380 nm, 404 nm and about 425 nm, respectively, after illumination. The percentage of reconstitution of rhodopsin and the rhodopsin analogues containing 9-cis-retinal and 13-cis-retinal was estimated to be 88%, 81% and 24%, respectively. Although only residual activation of transducin was observed in the dark when reconstituted rhodopsin and 9-cis-retinal-rhodopsin was used, the rhodopsin analogue containing the 13-cis isomer of retinal was capable of activating transducin independently of light. Moreover

  13. Classical Simulated Annealing Using Quantum Analogues

    NASA Astrophysics Data System (ADS)

    La Cour, Brian R.; Troupe, James E.; Mark, Hans M.

    2016-08-01

    In this paper we consider the use of certain classical analogues to quantum tunneling behavior to improve the performance of simulated annealing on a discrete spin system of the general Ising form. Specifically, we consider the use of multiple simultaneous spin flips at each annealing step as an analogue to quantum spin coherence as well as modifications of the Boltzmann acceptance probability to mimic quantum tunneling. We find that the use of multiple spin flips can indeed be advantageous under certain annealing schedules, but only for long anneal times.

  14. Classical Simulated Annealing Using Quantum Analogues

    NASA Astrophysics Data System (ADS)

    La Cour, Brian R.; Troupe, James E.; Mark, Hans M.

    2016-06-01

    In this paper we consider the use of certain classical analogues to quantum tunneling behavior to improve the performance of simulated annealing on a discrete spin system of the general Ising form. Specifically, we consider the use of multiple simultaneous spin flips at each annealing step as an analogue to quantum spin coherence as well as modifications of the Boltzmann acceptance probability to mimic quantum tunneling. We find that the use of multiple spin flips can indeed be advantageous under certain annealing schedules, but only for long anneal times.

  15. D-luciferin analogues: a multicolor toolbox for bioluminescence imaging.

    PubMed

    Sun, Yuan-Qiang; Liu, Jing; Wang, Pi; Zhang, Jingyu; Guo, Wei

    2012-08-20

    Colorful mixture: Three types of luciferin analogues, that is, alkylaminoluciferins, aminoselenoluciferin, and luciferins with a benzimidazole scaffold, have been reported. These analogues show excellent bioluminescent properties and great potential in bioluminescence imaging. PMID:22807027

  16. Solanapyrone analogues from a Hawaiian fungicolous fungus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four new solanayrone analogues (solanapyrones J-M; 1-4) have been isolated from an unidentified fungicolous fungus collected in Hawaii. The structures and relative configurations of these compounds were determined by analysis of ID NMR, 2D NMR, and MS data. Solanapyrone J(1) showed antifungal acti...

  17. New cytotoxic analogues of annonaceous acetogenins.

    PubMed

    Rodier, S; Le Huerou, Y; Renoux, B; Doyon, J; Renard, P; Pierré, A; Gesson, J P; Grée, R

    2001-01-01

    A series of new acetogenin analogues incorporating a central catechol moiety instead of the tetrahydrofuran ring(s) have been prepared and tested against L1210 leukemia cells. Although less potent than bullatacinone, which has the same terminal lactone, these compounds display interesting cell cycle effects. PMID:11962508

  18. Synthesis and Cytoxicity of Sempervirine and Analogues.

    PubMed

    Pan, Xiaohong; Yang, Chunying; Cleveland, John L; Bannister, Thomas D

    2016-03-01

    Sempervirine and analogues were synthesized using a route featuring Sonogashira and Larock Pd-catalyzed reactions. Structure-activity relationships were investigated using three human cancer cell lines. 10-Fluorosempervirine is the most potently cytotoxic member of the family yet described. PMID:26828413

  19. The arsonomethyl analogue of 3-phosphoglycerate.

    PubMed Central

    Adams, S R; Sparkes, M J; Dixon, H B

    1983-01-01

    4-Arsono-2-hydroxybutanoic acid, the analogue of 3-phosphoglycerate in which -CH2-AsO3H2 replaces -O-PO3H2, was synthesized. It proved to be a substrate for phosphoglycerate kinase. Its Michaelis constant was only slightly higher than that of the natural substrate, but its catalytic constant was about 1300 times smaller. PMID:6615422

  20. CO2 Capture with Enzyme Synthetic Analogue

    SciTech Connect

    Cordatos, Harry

    2010-03-01

    Project overview provides background on carbonic anhydrase transport mechanism for CO2 in the human body and proposed approach for ARPA-E project to create a synthetic enzyme analogue and utilize it in a membrane for CO2 capture from flue gas.

  1. Synthesis of lipid II phosphonate analogues.

    PubMed

    Borbás, Anikó; Herczegh, Pál

    2011-09-01

    Simple analogues of lipid II were synthesized from 3,4,6-tri-O-acetyl-2-acetamido-2-deoxy-1-thio-β-D-glucopyranose using conjugate addition onto ethylidene bisphosphonate and subsequent Wadsworth-Horner-Emmons reaction with long chain aliphatic aldehydes. PMID:21600568

  2. Synthesis and antimicrobial activity of squalamine analogue.

    PubMed

    Kim, H S; Choi, B S; Kwon, K C; Lee, S O; Kwak, H J; Lee, C H

    2000-08-01

    Synthesis and antimicrobial activity of squalamine analogue 2 are reported. The synthesis of 2 was accomplished from bisnoralcohol 3. The spermidine moiety was introduced via reductive amination of an appropriately functionalized 3beta-aminosterol with spermidinyl aldehyde 17 utilizing sodium triacetoxyborohydride as the reducing agent. Compound 2 shows weaker antimicrobial activity than squalamine. PMID:11003150

  3. [Dmt(1)]DALDA analogues modified with tyrosine analogues at position 1.

    PubMed

    Cai, Yunxin; Lu, Dandan; Chen, Zhen; Ding, Yi; Chung, Nga N; Li, Tingyou; Schiller, Peter W

    2016-08-01

    Analogues of [Dmt(1)]DALDA (H-Dmt-d-Arg-Phe-Lys-NH2; Dmt=2',6'-dimethyltyrosine), a potent μ opioid agonist peptide with mitochondria-targeted antioxidant activity were prepared by replacing Dmt with various 2',6'-dialkylated Tyr analogues, including 2',4',6'-trimethyltyrosine (Tmt), 2'-ethyl-6'-methyltyrosine (Emt), 2'-isopropyl-6'-methyltyrosine (Imt) and 2',6'-diethyltyrosine (Det). All compounds were selective μ opioid agonists and the Tmt(1)-, Emt(1) and Det(1)-analogues showed subnanomolar μ opioid receptor binding affinities. The Tmt(1)- and Emt(1)-analogues showed improved antioxidant activity compared to the Dmt(1)-parent peptide in the DPPH radical-scavenging capacity assay, and thus are of interest as drug candidates for neuropathic pain treatment. PMID:27301366

  4. Modification and translocation of Rac/Rop guanosine 5'-triphosphate-binding proteins of Scoparia dulcis in response to stimulation with methyl jasmonate.

    PubMed

    Mitamura, Toshiaki; Yamamura, Yoshimi; Kurosaki, Fumiya

    2011-01-01

    Translocation of two Rac/Rop guanosine 5'-triphosphate-binding proteins from Scoparia dulcis, Sdrac-1 and Sdrac-2, was examined employing transformed belladonna which overproduces these proteins as glutathione-S-transferase-tagged forms. The transferase activities of the fused proteins in microsomal fraction of belladonna markedly increased by the incubation with methyl jasmonate either in Sdrac-1 or Sdrac-2 transformant, while low and constant activities were observed in the untreated control. Recombinant Sdrac-2 protein was found to bind to prenyl chain in the presence of cell extracts prepared from methyl jasmonate-treated S. dulcis, however, Sdrac-1 was palmitoylated by the addition of the cell extracts. These results suggest that both Sdrac-1 and Sdrac-2 translocate to plant membranes by the stimulation with methyl jasmonate, however, targeting of these proteins is triggered by the independent modification mechanisms, palmitoylation for Sdrac-1 and prenylation for Sdrac-2. PMID:21628882

  5. Cloning and characterization of Sdga gene encoding alpha-subunit of heterotrimeric guanosine 5'-triphosphate-binding protein complex in Scoparia dulcis.

    PubMed

    Shite, Masato; Yamamura, Yoshimi; Hayashi, Toshimitsu; Kurosaki, Fumiya

    2008-11-01

    A homology-based cloning strategy yielded Sdga, a cDNA clone presumably encoding alpha-subunit of heterotrimeric guanosine 5'-triphosphate-binding protein complex, from leaf tissues of Scoparia dulcis. Phylogenetic tree analysis of G-protein alpha-subunits from various biological sources suggested that, unlike in animal cells, classification of Galpha-proteins into specific subfamilies could not be applicable to the proteins from higher plants. Restriction digests of genomic DNA of S. dulcis showed a single hybridized signal in Southern blot analysis, suggesting that Sdga is a sole gene encoding Galpha-subunit in this plant. The expression level of Sdga appeared to be maintained at almost constant level after exposure of the leaves to methyl jasmonate as analyzed by reverse-transcription polymerase chain reaction. These results suggest that Sdga plays roles in methyl jasmonate-induced responses of S. dulcis without a notable change in the transcriptional level. PMID:18981590

  6. Mechanistic Investigation of cPMP Synthase in Molybdenum Cofactor Biosynthesis Using an Uncleavable Substrate Analogue.

    PubMed

    Hover, Bradley M; Lilla, Edward A; Yokoyama, Kenichi

    2015-12-15

    Molybdenum cofactor (Moco) is essential for all kingdoms of life, plays central roles in various biological processes, and must be biosynthesized de novo. During its biosynthesis, the characteristic pyranopterin ring is constructed by a complex rearrangement of guanosine 5'-triphosphate (GTP) into cyclic pyranopterin monophosphate (cPMP) through the action of two enzymes, MoaA and MoaC. Recent studies revealed that MoaC catalyzes the majority of the transformation and produces cPMP from a unique cyclic nucleotide, 3',8-cyclo-7,8-dihydro-GTP (3',8-cH2GTP). However, the mechanism by which MoaC catalyzes this complex rearrangement is largely unexplored. Here, we report the mechanistic characterization of MoaC using an uncleavable substrate analogue, 3',8-cH2GMP[CH2]PP, as a probe to investigate the timing of cyclic phosphate formation. Using partially active MoaC variants, 3',8-cH2GMP[CH2]PP was found to be accepted by MoaC as a substrate and was converted to an analogue of the previously described MoaC reaction intermediate, suggesting that the early stage of catalysis proceeds without cyclic phosphate formation. In contrast, when it was incubated with wt-MoaC, 3',8-cH2GMP[CH2]PP caused mechanism-based inhibition. Detailed characterization of the inhibited MoaC suggested that 3',8-cH2GMP[CH2]PP is mainly converted to a molecule (compound Y) with an acid-labile triaminopyrimidinone base without an established pyranopterin structure. MS analysis of MoaC treated with 3',8-cH2GMP[CH2]PP provided strong evidence that compound Y forms a tight complex with MoaC likely through a covalent linkage. These observations are consistent with a mechanism in which cyclic phosphate ring formation proceeds in concert with the pterin ring formation. This mechanism would provide a thermodynamic driving force to complete the formation of the unique tetracyclic structure of cPMP. PMID:26575208

  7. Mechanistic Investigation of cPMP Synthase in Molybdenum Cofactor Biosynthesis Using an Uncleavable Substrate Analogue

    PubMed Central

    Hover, Bradley M.; Lilla, Edward A.; Yokoyama, Kenichi

    2016-01-01

    Molybdenum cofactor (Moco) is essential for all kingdoms of life, plays central roles in various biological processes, and must be biosynthesized de novo. During its biosynthesis, the characteristic pyranopterin ring is constructed by a complex rearrangement of guanosine 5′-triphosphate (GTP) into cyclic pyranopterin monophosphate (cPMP) through the action of two enzymes, MoaA and MoaC. Recent studies revealed that MoaC catalyzes the majority of the transformation and produces cPMP from a unique cyclic nucleotide, 3′,8-cyclo-7,8-dihydro-GTP (3′,8-cH2GTP). However, the mechanism by which MoaC catalyzes this complex rearrangement is largely unexplored. Here, we report the mechanistic characterization of MoaC using an uncleavable substrate analogue, 3′,8-cH2GMP[CH2]PP, as a probe to investigate the timing of cyclic phosphate formation. Using partially active MoaC variants, 3′,8-cH2GMP[CH2]PP was found to be accepted by MoaC as a substrate and was converted to an analogue of the previously described MoaC reaction intermediate, suggesting that the early stage of catalysis proceeds without cyclic phosphate formation. In contrast, when it was incubated with wt-MoaC, 3′,8-cH2GMP[CH2]PP caused mechanism-based inhibition. Detailed characterization of the inhibited MoaC suggested that 3′,8-cH2GMP[CH2]PP is mainly converted to a molecule (compound Y) with an acid-labile triaminopyrimidinone base without an established pyranopterin structure. MS analysis of MoaC treated with 3′,8-cH2GMP[CH2]PP provided strong evidence that compound Y forms a tight complex with MoaC likely through a covalent linkage. These observations are consistent with a mechanism in which cyclic phosphate ring formation proceeds in concert with the pterin ring formation. This mechanism would provide a thermodynamic driving force to complete the formation of the unique tetracyclic structure of cPMP. PMID:26575208

  8. Guanosine 2-NH2 groups of Escherichia coli RNase P RNA involved in intramolecular tertiary contacts and direct interactions with tRNA.

    PubMed Central

    Heide, C; Pfeiffer, T; Nolan, J M; Hartmann, R K

    1999-01-01

    We have identified by nucleotide analog interference mapping (NAIM) exocyclic NH2 groups of guanosines in RNase P RNA from Escherichia coli that are important for tRNA binding. The majority of affected guanosines represent phylogenetically conserved nucleotides. Several sites of interference could be assigned to direct contacts with the tRNA moiety, whereas others were interpreted as reflecting indirect effects on tRNA binding due to the disruption of tertiary contacts within the catalytic RNA. Our results support the involvement of the 2-NH2 groups of G292/G293 in pairing with C74 and C75 of tRNA CCA-termini, as well as formation of two consecutive base triples involving C75 and A76 of CCA-ends interacting with G292/A258 and G291/G259, respectively. Moreover, we present first biochemical evidence for two tertiary contacts (L18/P8 and L8/P4) within the catalytic RNA, whose formation has been postulated previously on the basis of phylogenetic comparative analyses. The tRNA binding interference data obtained in this and our previous studies are consistent with the formation of a consecutive nucleotide triple and quadruple between the tetraloop L18 and helix P8. Formation of the nucleotide triple (G316 and A94:U104 in wild-type E. coli RNase P RNA) is also supported by mutational analysis. For the mutant RNase P RNA carrying a G94:C104 double mutation, an additional G316-to-A mutation resulted in a restoration of binding affinity for mature and precursor tRNA. PMID:9917070

  9. Crystal Structure of the Thermus thermophilus 16 S rRNA Methyltransferase RsmC in Complex with Cofactor and Substrate Guanosine*S⃞

    PubMed Central

    Demirci, Hasan; Gregory, Steven T.; Dahlberg, Albert E.; Jogl, Gerwald

    2008-01-01

    Post-transcriptional modification is a ubiquitous feature of ribosomal RNA in all kingdoms of life. Modified nucleotides are generally clustered in functionally important regions of the ribosome, but the functional contribution to protein synthesis is not well understood. Here we describe high resolution crystal structures for the N2-guanine methyltransferase RsmC that modifies residue G1207 in 16 S rRNA near the decoding site of the 30 S ribosomal subunit. RsmC is a class I S-adenosyl-l-methionine-dependent methyltransferase composed of two methyltransferase domains. However, only one S-adenosyl-l-methionine molecule and one substrate molecule, guanosine, bind in the ternary complex. The N-terminal domain does not bind any cofactor. Two structures with bound S-adenosyl-l-methionine and S-adenosyl-l-homocysteine confirm that the cofactor binding mode is highly similar to other class I methyltransferases. Secondary structure elements of the N-terminal domain contribute to cofactor-binding interactions and restrict access to the cofactor-binding site. The orientation of guanosine in the active site reveals that G1207 has to disengage from its Watson-Crick base pairing interaction with C1051 in the 16 S rRNA and flip out into the active site prior to its modification. Inspection of the 30 S crystal structure indicates that access to G1207 by RsmC is incompatible with the native subunit structure, consistent with previous suggestions that this enzyme recognizes a subunit assembly intermediate. PMID:18667428

  10. Recent advances in topoisomerase I-targeting agents, camptothecin analogues.

    PubMed

    Kim, Dae-Kee; Lee, Namkyu

    2002-12-01

    The present review concentrates on camptothecin (CPT) analogues, the most extensively studied topoisomerase I (topo I) inhibitors, and provides concise information on the structural features of human topo I enzyme, mechanisms of interaction of CPT with topo I, structure-activity relationship study of CPT analogues including the influence of lactone stability on antitumor activity, and recent updates of valuable CPT analogues. PMID:12370044

  11. [Insulin analogues: modifications in the structure, molecular and metabolic consequences].

    PubMed

    de Luis, D A; Romero, E

    2013-01-01

    Recombinant DNA technology has provided insulin analogues for the treatment of diabetes mellitus, with an efficacy and safety that has improved the treatment of this disease. We briefly review the principal characteristics of the insulin analogues currently available. Both rapid-acting (lispro, aspart and glulisine) and long acting (glargine and determir) insulin analogues are included in this review. We describe the pharmacology of each insulin analogue, their differences with the human insulin, the administration, indication, efficacy and safety. In addition we discussed the main controversies of the use of these insulin analogues. In particular, those related with the risk of cancer and retinopathy, and their use in pregnant women. PMID:23517895

  12. Design and synthesis of new fluconazole analogues.

    PubMed

    Pore, Vandana S; Agalave, Sandip G; Singh, Pratiksha; Shukla, Praveen K; Kumar, Vikash; Siddiqi, Mohammad I

    2015-06-21

    We have synthesized new fluconazole analogues containing two different 1,2,3-triazole units in the side chain. The synthesis of new amide analogues using a variety of acids is also described. All the compounds showed very good antifungal activity. A hemolysis study of the most active compounds 6e and 13j showed that both compounds did not cause any hemolysis at the dilutions tested. These compounds did not exhibit any toxicity to L929 cells at MIC and lower concentrations. In the docking study, the overall binding mode of 6e and 13j appeared to be reasonable and provided a good insight into the structural basis of inhibition of Candida albicans Cyp51 by these compounds. PMID:25975803

  13. Synthesis of constrained analogues of tryptophan

    PubMed Central

    Negrato, Marco; Abbiati, Giorgio; Dell’Acqua, Monica

    2015-01-01

    Summary A Lewis acid-catalysed diastereoselective [4 + 2] cycloaddition of vinylindoles and methyl 2-acetamidoacrylate, leading to methyl 3-acetamido-1,2,3,4-tetrahydrocarbazole-3-carboxylate derivatives, is described. Treatment of the obtained cycloadducts under hydrolytic conditions results in the preparation of a small library of compounds bearing the free amino acid function at C-3 and pertaining to the class of constrained tryptophan analogues. PMID:26664620

  14. Synthesis and cytotoxic activity of acetogenin analogues.

    PubMed

    Rodier, S; Le Huérou, Y; Renoux, B; Doyon, J; Renard, P; Pierré, A; Gesson, J P; Grée, R

    2000-06-19

    A set of 16 new simplified analogues of acetogenins has been designed based on: (i) the replacement of the bis THF moiety of these natural products by an ethylene glycol bis ether unit; (ii) the introduction of different lipophilic side chains (alkyl, aryl, dialkylamino, O-cholesteryl); (iii) the presence of the same terminal isolactone. In vitro cytotoxic activity against L1210 leukemia is reported. PMID:10890167

  15. Efficient synthesis of esermethole and its analogues.

    PubMed

    Zhou, Yongyun; Zhao, Yuanhong; Dai, Xiaoyong; Liu, Jianping; Li, Liang; Zhang, Hongbin

    2011-06-01

    In this work, a general and flexible synthetic route towards the synthesis of pyrroloindoline alkaloids was developed. This new strategy features with a palladium mediated sequential arylation-allylation of o-bromoanilides and leads to the construction of oxindoles bearing a full carbon quaternary center. The cheap triphenylphosphine was proved to be a highly effective ligand for this one pot transformation. On the basis of this new method, esermethole and its analogues were synthesized. PMID:21472186

  16. The Brookhaven electron analogue, 1953--1957

    SciTech Connect

    Plotkin, M.

    1991-12-18

    The following topics are discussed on the Brookhaven electron analogue: L.J. Haworth and E.L. VanHorn letters; Original G.K. Green outline for report; General description; Parameter list; Mechanical Assembly; Alignment; Degaussing; Vacuum System; Injection System; The pulsed inflector; RF System; Ferrite Cavity; Pick-up electrodes and preamplifiers; Radio Frequency power amplifier; Lens supply; Controls and Power; and RF acceleration summary.

  17. Blood Loss Estimation Using Gauze Visual Analogue

    PubMed Central

    Ali Algadiem, Emran; Aleisa, Abdulmohsen Ali; Alsubaie, Huda Ibrahim; Buhlaiqah, Noora Radhi; Algadeeb, Jihad Bagir; Alsneini, Hussain Ali

    2016-01-01

    Background Estimating intraoperative blood loss can be a difficult task, especially when blood is mostly absorbed by gauze. In this study, we have provided an improved method for estimating blood absorbed by gauze. Objectives To develop a guide to estimate blood absorbed by surgical gauze. Materials and Methods A clinical experiment was conducted using aspirated blood and common surgical gauze to create a realistic amount of absorbed blood in the gauze. Different percentages of staining were photographed to create an analogue for the amount of blood absorbed by the gauze. Results A visual analogue scale was created to aid the estimation of blood absorbed by the gauze. The absorptive capacity of different gauze sizes was determined when the gauze was dripping with blood. The amount of reduction in absorption was also determined when the gauze was wetted with normal saline before use. Conclusions The use of a visual analogue may increase the accuracy of blood loss estimation and decrease the consequences related to over or underestimation of blood loss. PMID:27626017

  18. Three Efficient Methods for Preparation of Coelenterazine Analogues.

    PubMed

    Shakhmin, Anton; Hall, Mary P; Walker, Joel R; Machleidt, Thomas; Binkowski, Brock F; Wood, Keith V; Kirkland, Thomas A

    2016-07-18

    The growing popularity of bioluminescent assays has highlighted the need for coelenterazine analogues possessing properties tuned for specific applications. However, the structural diversity of known coelenterazine analogues has been limited by current syntheses. Known routes for the preparation of coelenterazine analogues employ harsh reaction conditions that limit access to many substituents and functional groups. Novel synthetic routes reported here establish simple and robust methods for synthesis and investigation of structurally diverse marine luciferase substrates. Specifically, these new routes allow synthesis of coelenterazine analogues containing various heterocyclic motifs and substituted aromatic groups with diverse electronic substituents at the R(2) position. Interesting analogues described herein were characterized by their physicochemical properties, bioluminescent half-life, light output, polarity and cytotoxicity. Some of the analogues represent leads that can be utilized in the development of improved bioluminescent systems. PMID:27305599

  19. CO2 Removal using a Synthetic Analogue of Carbonic Anhydrase

    SciTech Connect

    Cordatos, Harry

    2010-09-14

    Project attempts to develop a synthetic analogue for carbonic anhydrase and incorporate it in a membrane for separation of CO2 from coal power plant flue gas. Conference poster presents result of first 9 months of project progress including concept, basic system architecture and membrane properties target, results of molecular modeling for analogue - CO2 interaction, and next steps of testing analogue resistance to flue gas contaminants.

  20. U.S. Nuclear Regulatory Commission natural analogue research program

    SciTech Connect

    Kovach, L.A.; Ott, W.R.

    1995-09-01

    This article describes the natural analogue research program of the U.S. Nuclear Regulatory Commission (US NRC). It contains information on the regulatory context and organizational structure of the high-level radioactive waste research program plan. It also includes information on the conditions and processes constraining selection of natural analogues, describes initiatives of the US NRC, and describes the role of analogues in the licensing process.

  1. Conformationally restrained aromatic analogues of fosmidomycin and FR900098.

    PubMed

    Kurz, Thomas; Schlüter, Katrin; Pein, Miriam; Behrendt, Christoph; Bergmann, Bärbel; Walter, Rolf D

    2007-07-01

    The synthesis and in-vitro antimalarial activity of conformationally restrained bis(pivaloyloxymethyl) ester analogues of the natural product fosmidomycin is presented. In contrast to alpha-aryl-substituted analogues, conformationally restrained aromatic analogues exhibit only moderate in-vitro antimalarial activity against the chloroquine-sensitive strain 3D7 of Plasmodium falciparum. The most active derivative displays an IC(50) value of 47 microM. PMID:17611943

  2. Analogue factoring algorithm based on polychromatic interference

    NASA Astrophysics Data System (ADS)

    Tamma, Vincenzo; Garuccio, Augusto; Shih, Yanhua

    2010-08-01

    We present a novel factorization algorithm which can be computed using an analogue computer based on a polychromatic source with a given wavelength bandwidth, a multi-path interferometer and a spectrometer. The core of this algorithm stands on the measurement of the periodicity of a "factoring" function given by an exponential sum at continuous argument by recording a sequence of interferograms associated with suitable units of displacement in the inteferometer. A remarking rescaling property of such interferograms allows, in principle, the prime number decomposition of several large integers. The information about factors is encoded in the location of the inteferogram maxima.

  3. Spectroscopic study of solar twins and analogues

    NASA Astrophysics Data System (ADS)

    Datson, Juliet; Flynn, Chris; Portinari, Laura

    2015-02-01

    Context. Many large stellar surveys have been and are still being carried out, providing huge amounts of data, for which stellar physical parameters will be derived. Solar twins and analogues provide a means to test the calibration of these stellar catalogues because the Sun is the best-studied star and provides precise fundamental parameters. Solar twins should be centred on the solar values. Aims: This spectroscopic study of solar analogues selected from the Geneva-Copenhagen Survey (GCS) at a resolution of 48 000 provides effective temperatures and metallicities for these stars. We test whether our spectroscopic parameters, as well as the previous photometric calibrations, are properly centred on the Sun. In addition, we search for more solar twins in our sample. Methods: The methods used in this work are based on literature methods for solar twin searches and on methods we developed in previous work to distinguish the metallicity-temperature degeneracies in the differential comparison of spectra of solar analogues versus a reference solar reflection spectrum. Results: We derive spectroscopic parameters for 148 solar analogues (about 70 are new entries to the literature) and verify with a-posteriori differential tests that our values are well-centred on the solar values. We use our dataset to assess the two alternative calibrations of the GCS parameters; our methods favour the latest revision. We show that the choice of spectral line list or the choice of asteroid or time of observation does not affect the results. We also identify seven solar twins in our sample, three of which are published here for the first time. Conclusions: Our methods provide an independent means to differentially test the calibration of stellar catalogues around the values of a well-known benchmark star, which makes our work interesting for calibration tests of upcoming Galactic surveys. Based on observations made with ESO Telescopes at the La Silla Observatory under programme ID 077.D

  4. Phonon analogue of topological nodal semimetals

    NASA Astrophysics Data System (ADS)

    Po, Hoi Chun; Bahri, Yasaman; Vishwanath, Ashvin

    2015-03-01

    Recently, Kane and Lubensky proposed a mapping between bosonic phonon problems on isostatic lattices to chiral fermion systems based on factorization of the dynamical matrix [Nat. Phys. 10, 39 (2014)]. The existence of topologically protected zero modes in such mechanical problems is related to their presence in the fermionic system and is dictated by a local index theorem. Here we adopt the proposed mapping to construct a two-dimensional mechanical analogue of a fermionic topological nodal semimetal that hosts a robust bulk node in its linearized phonon spectrum. Such topologically protected soft modes with tunable wavevector may be useful in designing mechanical structures with fault-tolerant properties.

  5. Digitoxin Analogues with Improved Anticytomegalovirus Activity

    PubMed Central

    2014-01-01

    Cardiac glycosides are potent inhibitors of cancer cell growth and possess antiviral activities at nanomolar concentrations. In this study we evaluated the anticytomegalovirus (CMV) activity of digitoxin and several of its analogues. We show that sugar type and sugar length attached to the steroid core structure affects its anticytomegalovirus activity. Structure–activity relationship (SAR) studies identified the l-sugar containing cardiac glycosides as having improved anti-CMV activity and may lead to better understanding of how these compounds inhibit CMV replication. PMID:24900847

  6. Materials analogue of zero-stiffness structures

    NASA Astrophysics Data System (ADS)

    Kumar, Arun; Subramaniam, Anandh

    2011-04-01

    Anglepoise lamps and certain tensegrities are examples of zero-stiffness structures. These structures are in a state of neutral equilibrium with respect to changes in configuration of the system. Using Eshelby's example of an edge dislocation in a thin plate that can bend, we report the discovery of a non-trivial new class of material structures as an analogue to zero-stiffness structures. For extended positions of the edge dislocation in these structures, the dislocation experiences a zero image force. Salient features of these material structures along with the key differences from conventional zero-stiffness structures are pointed out.

  7. Antinociceptive Effect of Vardenafil on Carrageenan-Induced Hyperalgesia in Rat: involvement of Nitric Oxide/Cyclic Guanosine Monophosphate/Calcium Channels Pathway.

    PubMed

    Gediz, Ezgi İkiz; Nacitarhan, Cahit; Minareci, Edibe; Sadan, Gulay

    2015-01-01

    In this study, we aimed to investigate the peripheral antinociception effects of specific phosphodiesterase 5 (PDE-5) inhibitor vardenafil on carrageenan-induced nociception in rats, and the role of calcium besides the L-arginine- nitric oxide (NO)- cyclic guanosine monophophate (cGMP) pathway in these effects. Hyperalgesia was induced by the intraplantar injection of 0.1 mL fresh carrageenan solution to right hind-paw whereas, saline as a vehicle of carrageenan was injected to the left paw. This procedure was used for measuring mechanic nociception pressure via an analgesimeter. Pressure which produced nociception was measured before (0 minute) and after(15, 30, 60 and 120 minutes) carrageenan injection. Local administration of vardenafil produced a dose-dependent antinociceptive effect. Pretreatment with N(W)-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), oxadiazolo (4, 3, a) quinoxalin -1-one (ODQ, inhibitor of guanylyl cyclase) or A23187 (calcium ionophore) decreased the effect of vardenafil. In contrast, L-arginine (nitric oxide donor) seemed to potentiate the vardenafil-induced antinociception. Our results suggest that phosphodiesterase type-5 inhibitor vardenafil may offer a new therapeutic tool to treat pain. It's effect was probably result from L-arginine/NO-cGMP pathway activation and Ca + 2 channels are also involved. PMID:26664380

  8. Antinociceptive Effect of Vardenafil on Carrageenan-Induced Hyperalgesia in Rat: involvement of Nitric Oxide/Cyclic Guanosine Monophosphate/Calcium Channels Pathway

    PubMed Central

    Gediz, Ezgi İkiz; Nacitarhan, Cahit; Minareci, Edibe; Sadan, Gulay

    2015-01-01

    In this study, we aimed to investigate the peripheral antinociception effects of specific phosphodiesterase 5 (PDE-5) inhibitor vardenafil on carrageenan-induced nociception in rats, and the role of calcium besides the L-arginine- nitric oxide (NO)- cyclic guanosine monophophate (cGMP) pathway in these effects. Hyperalgesia was induced by the intraplantar injection of 0.1 mL fresh carrageenan solution to right hind-paw whereas, saline as a vehicle of carrageenan was injected to the left paw. This procedure was used for measuring mechanic nociception pressure via an analgesimeter. Pressure which produced nociception was measured before (0 minute) and after(15, 30, 60 and 120 minutes) carrageenan injection. Local administration of vardenafil produced a dose-dependent antinociceptive effect. Pretreatment with NW-nitro-L-arginine methyl ester (L-NAME, nitric oxide synthase inhibitor), oxadiazolo (4, 3, a) quinoxalin -1-one (ODQ, inhibitor of guanylyl cyclase) or A23187 (calcium ionophore) decreased the effect of vardenafil. In contrast, L-arginine (nitric oxide donor) seemed to potentiate the vardenafil-induced antinociception. Our results suggest that phosphodiesterase type-5 inhibitor vardenafil may offer a new therapeutic tool to treat pain. It’s effect was probably result from L-arginine/NO-cGMP pathway activation and Ca + 2 channels are also involved. PMID:26664380

  9. An Interplay among FIS, H-NS, and Guanosine Tetraphosphate Modulates Transcription of the Escherichia coli cspA Gene under Physiological Growth Conditions.

    PubMed

    Brandi, Anna; Giangrossi, Mara; Giuliodori, Anna M; Falconi, Maurizio

    2016-01-01

    CspA, the most characterized member of the csp gene family of Escherichia coli, is highly expressed not only in response to cold stress, but also during the early phase of growth at 37°C. Here, we investigate at molecular level the antagonistic role played by the nucleoid proteins FIS and H-NS in the regulation of cspA expression under non-stress conditions. By means of both probing experiments and immunological detection, we demonstrate in vitro the existence of binding sites for these proteins on the cspA regulatory region, in which FIS and H-NS bind simultaneously to form composite DNA-protein complexes. While the in vitro promoter activity of cspA is stimulated by FIS and repressed by H-NS, a compensatory effect is observed when both proteins are added in the transcription assay. Consistently with these findings, inactivation of fis and hns genes reversely affect the in vivo amount of cspA mRNA. In addition, by means of strains expressing a high level of the alarmone guanosine tetraphosphate ((p)ppGpp) and in vitro transcription assays, we show that the cspA promoter is sensitive to (p)ppGpp inhibition. The (p)ppGpp-mediated expression of fis and hns genes is also analyzed, thus clarifying some aspects of the regulatory loop governing cspA transcription. PMID:27252944

  10. Selective blockade of phosphodiesterase types 2, 5 and 9 results in cyclic 3′5′ guanosine monophosphate accumulation in retinal pigment epithelium cells

    PubMed Central

    Diederen, R M H; Heij, E C La; Ittersum, M Markerink‐van; Kijlstra, A; Hendrikse, F; de Vente, J

    2007-01-01

    Aim To investigate which phosphodiesterase (PDE) is involved in regulating cyclic 3′5′ guanosine monophosphate breakdown in retinal pigment epithelium (RPE) cells. Methods cGMP content in the cultured RPE cells (D407 cell line) was evaluated by immunocytochemistry in the presence of non‐selective or isoform‐selective PDE inhibitors in combination with the particulate guanylyl cyclase stimulator atrial natriuretic peptide (ANP) or the soluble guanylyl cyclase stimulator sodium nitroprusside (SNP). mRNA expression of PDE2, PDE5 and PDE9 was studied in cultured human RPE cells and rat RPE cell layers using non‐radioactive in situ hybridisation. Results In the absence of PDE inhibitors, cGMP levels in cultured RPE cells are very low. cGMP accumulation was readily detected in cultured human RPE cells after incubation with Bay60–7550 as a selective PDE2 inhibitor, sildenafil as a selective PDE5 inhibitor or Sch51866 as a selective PDE9 inhibitor. In the presence of PDE inhibition, cGMP content increased markedly after stimulation of the particulate guanylyl cyclase. mRNA of PDE2,PDE5 and PDE9 was detected in all cultured human RPE cells and also in rat RPE cell layers. Conclusions PDE2, PDE5 and PDE9 have a role in cGMP metabolism in RPE cells. PMID:16943225

  11. Coordination of two sequential ester-transfer reactions: exogenous guanosine binding promotes the subsequent omegaG binding to a group I intron.

    PubMed

    Bao, Penghui; Wu, Qi-Jia; Yin, Ping; Jiang, Yanfei; Wang, Xu; Xie, Mao-Hua; Sun, Tao; Huang, Lin; Mo, Ding-Ding; Zhang, Yi

    2008-12-01

    Self-splicing of group I introns is accomplished by two sequential ester-transfer reactions mediated by sequential binding of two different guanosine ligands, but it is yet unclear how the binding is coordinated at a single G-binding site. Using a three-piece trans-splicing system derived from the Candida intron, we studied the effect of the prior GTP binding on the later omegaG binding by assaying the ribozyme activity in the second reaction. We showed that adding GTP simultaneously with and prior to the esterified omegaG in a substrate strongly accelerated the second reaction, suggesting that the early binding of GTP facilitates the subsequent binding of omegaG. GTP-mediated facilitation requires C2 amino and C6 carbonyl groups on the Watson-Crick edge of the base but not the phosphate or sugar groups, suggesting that the base triple interactions between GTP and the binding site are important for the subsequent omegaG binding. Strikingly, GTP binding loosens a few local structures of the ribozyme including that adjacent to the base triple, providing structural basis for a rapid exchange of omegaG for bound GTP. PMID:18978026

  12. tRNA recognition for modification: solution probing of tRNA complexed with Escherichia coli tRNA (guanosine-1) methyltransferase.

    PubMed

    Gabryszuk, J; Holmes, W M

    1997-11-01

    The interaction of Escherichia coli tRNA (guanosine-1) methyltransferase and tRNA(1Leu) transcripts has been probed using cleavage with iodine of phosphorothioate-substituted transcripts, lead acetate, and enzymes specific for single- and double-stranded RNA. All lytic agents protect the anticodon stem-loop and variable loop regions against cleavage, and some protection is also seen in core structures of the tRNA. Residues from both strands of the anticodon stem are protected against cleavage with iodine and lead by enzyme, yet positions G37 and G36, which are crucial for catalysis and binding, are not. This suggests that these residues may undergo structural perturbation in the presence of S-adenosyl methionine. Occupancy of the AdoMet site by the product S-adenosyl-homocysteine, a potent inhibitor of the enzyme, has little or no effect on tRNA binding or protection. Enhanced reactivity with lead is seen at residues located in the anticodon stem-loop, extra-loop, and core (C34, U47c, and G49), which suggests some perturbations in RNA structure might accompany binding. PMID:9409623

  13. An Interplay among FIS, H-NS, and Guanosine Tetraphosphate Modulates Transcription of the Escherichia coli cspA Gene under Physiological Growth Conditions

    PubMed Central

    Brandi, Anna; Giangrossi, Mara; Giuliodori, Anna M.; Falconi, Maurizio

    2016-01-01

    CspA, the most characterized member of the csp gene family of Escherichia coli, is highly expressed not only in response to cold stress, but also during the early phase of growth at 37°C. Here, we investigate at molecular level the antagonistic role played by the nucleoid proteins FIS and H-NS in the regulation of cspA expression under non-stress conditions. By means of both probing experiments and immunological detection, we demonstrate in vitro the existence of binding sites for these proteins on the cspA regulatory region, in which FIS and H-NS bind simultaneously to form composite DNA-protein complexes. While the in vitro promoter activity of cspA is stimulated by FIS and repressed by H-NS, a compensatory effect is observed when both proteins are added in the transcription assay. Consistently with these findings, inactivation of fis and hns genes reversely affect the in vivo amount of cspA mRNA. In addition, by means of strains expressing a high level of the alarmone guanosine tetraphosphate ((p)ppGpp) and in vitro transcription assays, we show that the cspA promoter is sensitive to (p)ppGpp inhibition. The (p)ppGpp-mediated expression of fis and hns genes is also analyzed, thus clarifying some aspects of the regulatory loop governing cspA transcription. PMID:27252944

  14. Structural Basis of Differential Ligand Recognition by Two Classes of bis-(3-5)-cyclic Dimeric Guanosine Monophosphate-binding Riboswitches

    SciTech Connect

    K Smith; C Shanahan; E Moore; A Simon; S Strobel

    2011-12-31

    The bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) signaling pathway regulates biofilm formation, virulence, and other processes in many bacterial species and is critical for their survival. Two classes of c-di-GMP-binding riboswitches have been discovered that bind this second messenger with high affinity and regulate diverse downstream genes, underscoring the importance of RNA receptors in this pathway. We have solved the structure of a c-di-GMP-II riboswitch, which reveals that the ligand is bound as part of a triplex formed with a pseudoknot. The structure also shows that the guanine bases of c-di-GMP are recognized through noncanonical pairings and that the phosphodiester backbone is not contacted by the RNA. Recognition is quite different from that observed in the c-di-GMP-I riboswitch, demonstrating that at least two independent solutions for RNA second messenger binding have evolved. We exploited these differences to design a c-di-GMP analog that selectively binds the c-di-GMP-II aptamer over the c-di-GMP-I RNA. There are several bacterial species that contain both types of riboswitches, and this approach holds promise as an important tool for targeting one riboswitch, and thus one gene, over another in a selective fashion.

  15. Human monocyte killing of Staphylococcus aureus: modulation by agonists of cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate.

    PubMed Central

    O'Dorisio, M S; Vandenbark, G R; LoBuglio, A F

    1979-01-01

    This study was designed to test whether cyclic nucleotides play a role in the regulation of bacterial killing by human monocytes. Agents were tested for their ability to activate monocyte adenylate or guanylate cyclase in cell-free preparations, to increase cyclic adenosine 3',5'-monophosphate (cAMP) or cyclic guanosine 3',5'-monophosphate (cGMP) in intact human monocytes, and to modulate monocyte-induced killing of Staphylococcus aureus in vitro. Prostaglandin E1 and cholera toxin activated monocyte adenylate cyclase and inhibited monocyte killing of S. aureus. An adenylate cyclase inhibitor, RMI 12330A, reversed the prostaglandin E1-mediated inhibition of bacterial killing, thus implicating cAMP as the intracellular mediator of this inhibition. In contrast, monocyte cGMP levels were increased 5- and 17-fold by 5-hydroxytryptamine and N-methyl-N' -nitro-N-nitrosoguanidine, respectively, but neither agent was effective in modulating monocyte bactericidal activity. Thus, modulation of bactericidal activity in human monocytes did not conform to the yin/yang theory of opposing actions by cAMP and cGMP, for although monocyte-mediated killing of S. aureus was inhibited by cAMP agonists, it was not enhanced by cGMP agonists. PMID:44704

  16. Transforming growth factor-β inhibits IQ motif containing guanosine triphosphatase activating protein 1 expression in lung fibroblasts via the nuclear factor-κB signaling pathway.

    PubMed

    Zong, Chuanyue; Zhang, Xianlong; Xie, Ying; Cheng, Jiawen

    2015-07-01

    IQ motif containing guanosine triphosphatase activating protein 1 (IQGAP1) is associated with idiopathic pulmonary fibrogenesis (IPF); however, characterization of the expression of IQGAP1 in lung fibroblasts has remained elusive. The present study therefore evaluated IQGAP1 expression in mouse and human lung fibroblasts under fibrotic conditions via western blot analysis. It was revealed that IQGAP1 expression levels were significantly decreased in lung fibroblasts isolated from bleomycin-challenged mice than in those of control mice. Transforming growth factor-β (TGF-β) induced differentiation, as well as decreased expression of IQGAP1 in WI-38 cells human lung fibroblasts. Furthermore, inhibition of nuclear factor (NF)-κB activation restored the TGF-β-induced inhibition of IQGAP1 expression in WI-38 cells. In lysophosphatidic acid (LPA)-challenged WI-38 cells, the expression of IQGAP1 was also decreased, while neutralized anti-TGF-β antibody treatment restored the LPA-induced inhibition of IQGAP1 expression. These data indicated that TGF-β inhibited IQGAP1 expression in lung fibroblasts via the NF-κB signaling pathway, presenting a potential novel therapeutic target for the treatment of IPF. PMID:25684348

  17. Adenosine 3′:5′-cyclic monophosphate- and guanosine 3′:5′-cyclic monophosphate-dependent protein kinases: Possible homologous proteins

    PubMed Central

    Lincoln, Thomas M.; Corbin, Jackie D.

    1977-01-01

    The properties of purified mammalian adenosine 3′:5′-cyclic monophosphate (cAMP)- and guanosine 3′:5′-cyclic monophosphate (cGMP)-dependent protein kinases were compared. Several physical characteristics of the two enzymes were similar, including size, shape, affinity for cyclic nucleotide binding, and Km for ATP. In addition, the amino acid composition of the two proteins indicated a close composition homology (70-90%). Both cyclic nucleotide-dependent protein kinases catalyzed phosphorylation of rat liver pyruvate kinase (EC 2.7.1.40) and fructose 1,6-diphosphatase (EC 3.1.3.11), rabbit skeletal muscle glycogen synthase (EC 2.4.1.11) and phosphorylase b kinase (EC 2.7.1.38), and calf thymus histone H2b. The phosphorylation of several synthetic peptides and of trypsin-sensitive and trypsin-insensitive sites in glycogen synthase suggested similar recognition sites on the protein substrates for the two kinases. The cAMP-dependent protein kinase was the better catalyst with each protein or peptides substrate. The results suggest that the two enzymes evolved from a common ancestral protein. Images PMID:198777

  18. Cloning and characterization of a gene encoding Rac/Rop-like monomeric guanosine 5'-triphosphate-binding protein from Scoparia dulcis.

    PubMed

    Mitamura, Toshiaki; Shite, Masato; Yamamura, Yoshimi; Kurosaki, Fumiya

    2009-06-01

    A cDNA clone, designated Sd-racrop (969 bp), was isolated from seedlings of Scoparia dulcis. This gene contains an open reading frame encoding the protein of 197 amino acid residues with high homology to Rac/Rop small guanosine 5'-triphosphate-binding proteins from various plant sources. In Southern hybridization analysis, the restriction digests prepared from genomic DNA of S. dulcis showed a main signal together with a few weakly hybridized bands. The transcriptional level of Sd-racrop showed a transient decrease by exposure of the leaf tissues of S. dulcis to the ethylene-generating reagent 2-chloroethylphosphonic acid. However, an appreciable increase in gene expression was reproducibly observed upon treatment of the plant with methyl jasmonate. These results suggest that the Sd-racrop product plays roles in ethylene- and methyl jasmonate-induced responses of S. dulcis accompanying the change in the transcriptional level, however, the cellular events mediated by this protein toward these external stimuli would be regulated by various mechanisms. PMID:19483328

  19. DNA 3' pp 5' G de-capping activity of aprataxin: effect of cap nucleoside analogs and structural basis for guanosine recognition

    DOE PAGESBeta

    Chauleau, Mathieu; Jacewicz, Agata; Shuman, Stewart

    2015-05-24

    DNA3' pp 5'G caps synthesized by the 3'-PO4/5'-OH ligase RtcB have a strong impact on enzymatic reactions at DNA 3'-OH ends. Aprataxin, an enzyme that repairs A5'pp5'DNA ends formed during abortive ligation by classic 3'-OH/5'-PO4 ligases, is also a DNA 3' de-capping enzyme, converting DNAppG to DNA3'p and GMP. By taking advantage of RtcB's ability to utilize certain GTP analogs to synthesize DNAppN caps, we show that aprataxin hydrolyzes inosine and 6-O-methylguanosine caps, but is not adept at removing a deoxyguanosine cap. We report a 1.5 Å crystal structure of aprataxin in a complex with GMP, which reveals that: (i)more » GMP binds at the same position and in the same anti nucleoside conformation as AMP; and (ii) aprataxin makes more extensive nucleobase contacts with guanine than with adenine, via a hydrogen bonding network to the guanine O6, N1, N2 base edge. Alanine mutations of catalytic residues His147 and His149 abolish DNAppG de-capping activity, suggesting that the 3' de-guanylylation and 5' de-adenylylation reactions follow the same pathway of nucleotidyl transfer through a covalent aprataxin-(His147)–NMP intermediate. Alanine mutation of Asp63, which coordinates the guanosine ribose hydroxyls, impairs DNAppG de-capping.« less

  20. The electrical properties of Mars analogue dust

    NASA Astrophysics Data System (ADS)

    Merrison, J.; Jensen, J.; Kinch, K.; Mugford, R.; Nørnberg, P.

    2004-03-01

    Dust is a major environmental factor on the surface and in the atmosphere of Mars. Knowing the electrical charge state of this dust would be of both scientific interest and important for the safety of instruments on the Martian surface. In this study the first measurements have been performed of dust electrification using suspended Mars analogue material. This has been achieved by attracting suspended dust onto electrodes placed inside a Mars simulation wind tunnel. The Mars analogue used was from Salten Skov in Denmark, this contained a high concentration of ferric oxide precipitate. Once suspended, this dust was found to consist of almost equal quantities of negatively (46±6%) and positively (44±15%) charged grains. These grains were estimated to typically carry a net charge of around 10 5e, this is sufficient to dominate the processes of adhesion and cohesion of this suspended dust. Evidence is presented for electrostatic aggregation of the dust while in suspension. Development of a simple instrument for measuring electrical charging of the suspended dust on Mars will be discussed.

  1. Long-term predictions using natural analogues

    SciTech Connect

    Ewing, R.C.

    1995-09-01

    One of the unique and scientifically most challenging aspects of nuclear waste isolation is the extrapolation of short-term laboratory data (hours to years) to the long time periods (10{sup 3}-10{sup 5} years) required by regulatory agencies for performance assessment. The direct validation of these extrapolations is not possible, but methods must be developed to demonstrate compliance with government regulations and to satisfy the lay public that there is a demonstrable and reasonable basis for accepting the long-term extrapolations. Natural systems (e.g., {open_quotes}natural analogues{close_quotes}) provide perhaps the only means of partial {open_quotes}validation,{close_quotes} as well as data that may be used directly in the models that are used in the extrapolation. Natural systems provide data on very large spatial (nm to km) and temporal (10{sup 3}-10{sup 8} years) scales and in highly complex terranes in which unknown synergisms may affect radionuclide migration. This paper reviews the application (and most importantly, the limitations) of data from natural analogue systems to the {open_quotes}validation{close_quotes} of performance assessments.

  2. Self-Powered Analogue Smart Skin.

    PubMed

    Shi, Mayue; Zhang, Jinxin; Chen, Haotian; Han, Mengdi; Shankaregowda, Smitha A; Su, Zongming; Meng, Bo; Cheng, Xiaoliang; Zhang, Haixia

    2016-04-26

    The progress of smart skin technology presents unprecedented opportunities for artificial intelligence. Resolution enhancement and energy conservation are critical to improve the perception and standby time of robots. Here, we present a self-powered analogue smart skin for detecting contact location and velocity of the object, based on a single-electrode contact electrification effect and planar electrostatic induction. Using an analogue localizing method, the resolution of this two-dimensional smart skin can be achieved at 1.9 mm with only four terminals, which notably decreases the terminal number of smart skins. The sensitivity of this smart skin is remarkable, which can even perceive the perturbation of a honey bee. Meanwhile, benefiting from the triboelectric mechanism, extra power supply is unnecessary for this smart skin. Therefore, it solves the problems of batteries and connecting wires for smart skins. With microstructured poly(dimethylsiloxane) films and silver nanowire electrodes, it can be covered on the skin with transparency, flexibility, and high sensitivity. PMID:27010713

  3. Functional Analysis: The Use of Analogues in Applied Settings.

    ERIC Educational Resources Information Center

    Stichter, Janine Peck

    2001-01-01

    This article suggests possible applications of experimental analyses using analogues to empirically verify results of functional assessments in classrooms for students with autism and related disabilities. Analogue assessments involve creating conditions in which antecedents and consequences are held constant and specific variables suspected to…

  4. Space Analogue Environments: Are the Populations Comparable?

    NASA Astrophysics Data System (ADS)

    Sandal, G. M.

    Background: Much of our present understanding about psychology in space is based on studies of groups operating in so-called analogue environments where personnel are exposed to many of the same stressors as those experienced by astronauts in space. One possible problem with extrapolating results is that personnel operating in various hazardous and confined environments might differ in characteristics influencing coping, interaction, and performance. The object of this study was to compare the psychological similarity of these populations in order to get a better understanding of whether this extrapolation is justifiable. The samples investigated include polar crossings (N= 22), personnel on Antarctic research stations (N= 183), several military occupations (N= 187), and participants in space simulation studies (N=20). Methods: Personnel in each of these environments were assessed using the Personality Characteristic Inventory (PCI) and Utrecht Coping List (UCL). The PCI is a multidimensional trait assessment battery that measures various aspects of achievement orientation and social competence. The UCL is a questionnaire designed to assess habitual coping strategies when encountering stressful or demanding situations. Results: Only minor differences in use of habitual coping strategies were evident across the different samples. In relation to personality scores, the military subjects and participants in space simulation studies indicated higher competitiveness and negative instrumentality compared to both the personnel on Antarctic research stations and participants in polar expedition. Among the personnel on Antarctic research stations, significant gender differences were found with women scoring lower on competitiveness, negative instrumentality and impatience/irritability. Compared to the other samples, the participants in polar expeditions were found to be more homogeneous in personality and no significant gender differences were evident on the traits that

  5. GTP but not GDP analogues promote association of ADP-ribosylation factors, 20-kDa protein activators of cholera toxin, with phospholipids and PC-12 cell membranes.

    PubMed

    Walker, M W; Bobak, D A; Tsai, S C; Moss, J; Vaughan, M

    1992-02-15

    ADP-ribosylation factors (ARFs) are a family of approximately 20-kDa guanine nucleotide-binding proteins initially identified by their ability to enhance cholera toxin ADP-ribosyltransferase activity in the presence of GTP. ARFs have been purified from both membrane and cytosolic fractions. ARF purified from bovine brain cytosol requires phospholipid plus detergent for high affinity guanine nucleotide binding and for optimal enhancement of cholera toxin ADP-ribosyltransferase activity. The phospholipid requirements, combined with a putative role for ARF in vesicular transport, suggested that the soluble protein might interact reversibly with membranes. A polyclonal antibody against purified bovine ARF (sARF II) was used to detect ARF by immunoblot in membrane and soluble fractions from rat pheochromocytoma (PC-12) cell homogenates. ARF was predominantly cytosolic but increased in membranes during incubation of homogenates with nonhydrolyzable GTP analogues guanosine 5'-O-(3-thiotriphosphate), guanylyl-(beta gamma-imido)-diphosphate, and guanylyl-(beta gamma-methylene)-diphosphate, and to a lesser extent, adenosine 5'-O-(3-thiotriphosphate). GTP, GDP, GMP, and ATP were inactive. Cytosolic ARF similarly associated with added phosphatidylserine, phosphatidylinositol, or cardiolipin in GTP gamma S-dependent fashion. ARF binding to phosphatidylserine was reversible and coincident with stimulation of cholera toxin-catalyzed ADP-ribosylation. These observations may reflect a mechanism by which ARF could cycle between soluble and membrane compartments in vivo. PMID:1737779

  6. Development of new mitomycin C and porfiromycin analogues.

    PubMed

    Iyengar, B S; Lin, H J; Cheng, L; Remers, W A; Bradner, W T

    1981-08-01

    New mitomycin C and porfiromycin analogues were prepared by treating mitomycin A and N-methylmitomycin A with a variety of amines, including aziridines, allylamines, propargylamines, chloroalkylamines, hydroxyalkylamines, glycine derivatives, aralkylamines, and heterocyclic amines. All analogues were evaluated against P-388 murine leukemia and selected ones were examined for their leukopenic properties. Certain analogues were found to be superior to mitomycin C in potency, efficacy, and therapeutic ratio in the P-388 assay. The most active substituents at the mitosane 7 position included aziridine, 2-methylaziridine, propargylamine, furfurylamine, methyl glycinate, and 3-aminopyridine. Mitomycin A and the 7-aziridino, 7-(2-methylaziridino), and 3-aminopyridine analogues were less leukopenic than mitomycin C. Certain other analogues, including propargylamino and methyl glycinate, were highly leukopenic. The three compounds tested against B-16 melanoma in mice were significantly more effective than mitomycin C in this assay. Previously established structure--activity relationships were found inadequate to account for all of the new data. PMID:7328599

  7. Synthesis and biological activity of tetralone abscisic acid analogues.

    PubMed

    Nyangulu, James M; Nelson, Ken M; Rose, Patricia A; Gai, Yuanzhu; Loewen, Mary; Lougheed, Brenda; Quail, J Wilson; Cutler, Adrian J; Abrams, Suzanne R

    2006-04-01

    Bicyclic analogues of the plant hormone abscisic acid (ABA) were designed to incorporate the structural elements and functional groups of the parent molecule that are required for biological activity. The resulting tetralone analogues were predicted to have enhanced biological activity in plants, in part because oxidized products would not cyclize to forms corresponding to the inactive catabolite phaseic acid. The tetralone analogues were synthesized in seven steps from 1-tetralone and a range of analogues were accessible through a second route starting with 2-methyl-1-naphthol. Tetralone ABA 8 was found to have greater activity than ABA in two bioassays. The absolute configuration of (+)-8 was established by X-ray crystallography of a RAMP hydrazone derivative. The hydroxymethyl compounds 10 and 11, analogues for studying the roles of 8- and 9-hydroxy ABA 3 and 6, were also synthesized and found to be active. PMID:16557330

  8. Solution Processed PEDOT Analogues in Electrochemical Supercapacitors.

    PubMed

    Österholm, Anna M; Ponder, James F; Kerszulis, Justin A; Reynolds, John R

    2016-06-01

    We have designed fully soluble ProDOTx-EDOTy copolymers that are electrochemically equivalent to electropolymerized PEDOT without using any surfactants or dispersants. We show that these copolymers can be incorporated as active layers in solution processed thin film supercapacitors to demonstrate capacitance, stability, and voltage similar to the values of those that use electrodeposited PEDOT as the active material with the added advantage of the possibility for large scale, high-throughput processing. These Type I supercapacitors provide exceptional cell voltages (up to 1.6 V), highly symmetrical charge/discharge behavior, promising long-term stability exceeding 50 000 charge/discharge cycles, as well as energy (4-18 Wh/kg) and power densities (0.8-3.3 kW/kg) that are comparable to those of electrochemically synthesized analogues. PMID:27195798

  9. Derivatisable Cyanobactin Analogues: A Semisynthetic Approach

    PubMed Central

    Oueis, Emilia; Adamson, Catherine; Mann, Greg; Ludewig, Hannes; Redpath, Philip; Migaud, Marie

    2015-01-01

    Abstract Many natural cyclic peptides have potent and potentially useful biological activities. Their use as therapeutic starting points is often limited by the quantities available, the lack of known biological targets and the practical limits on diversification to fine‐tune their properties. We report the use of enzymes from the cyanobactin family to heterocyclise and macrocyclise chemically synthesised substrates so as to allow larger‐scale syntheses and better control over derivatisation. We have made cyclic peptides containing orthogonal reactive groups, azide or dehydroalanine, that allow chemical diversification, including the use of fluorescent labels that can help in target identification. We show that the enzymes are compatible and efficient with such unnatural substrates. The combination of chemical synthesis and enzymatic transformation could help renew interest in investigating natural cyclic peptides with biological activity, as well as their unnatural analogues, as therapeutics. PMID:26507241

  10. Involvement of nitric oxide-cyclic guanosine monophosphate pathway in the antidepressant-like effect of tropisetron and ondansetron in mice forced swimming test and tail suspension test.

    PubMed

    Haj-Mirzaian, Arya; Kordjazy, Nastaran; Amiri, Shayan; Haj-Mirzaian, Arvin; Amini-Khoei, Hossien; Ostadhadi, Sattar; Dehpour, AhmadReza

    2016-06-01

    Antidepressant-like effects of 5-hydroxytryptamine subtype 3 (5-HT3) antagonists including tropisetron and ondansetron have been previously demonstrated in the literature. It was reported that stimulation of 5-HT3 receptors activate the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway, which is involved in regulation of behavioral and emotional functions. In our study, treating animals with tropisetron (5, 10, and 30mg/kg) and ondansetron (0.01 and 0.1µg/kg) significantly decreased the immobility time in forced swimming test (FST) and tail-suspension test (TST). Co-administration of subeffective doses of tropisetron (1mg/kg) and ondansetron (0.001µg/kg) with subeffective dose of l-NAME (10mg/kg, nonselective NO synthase (NOS) inhibitor) and 7-nitroindazole (25mg/kg, neural NOS inhibitor) exerted antidepressant-like effect in FST and TST, while aminoguanidine (50mg/kg, inducible NOS inhibitor) did not enhance the antidepressant-like effect of 5-HT3 antagonists. Besides, l-arginine (750mg/kg, NO precursor) and sildenafil (5mg/kg, phosphodiesterase inhibitor) suppressed the anti-immobility effect of 5-HT3 antagonists. None of the treatments altered the locomotor behavior of mice in open-field test. Also, hippocampal (but not cortical) nitrite level was significantly lower in tropisetron and ondansetron-treated mice compared with saline-injected mice. Also, co-administration of 7-nitroindazole with tropisetron or ondansetron caused a significant decrease in hippocampal nitrite levels. In conclusion, we suggest that antidepressant-like effect of tropisetron and ondansetron are partially mediated by modulation of NO-cGMP pathway. PMID:27001377

  11. Mitogenic signaling pathways of growth factors can be distinguished by the involvement of pertussis toxin-sensitive guanosine triphosphate-binding protein and of protein kinase C.

    PubMed Central

    Nishizawa, N; Okano, Y; Chatani, Y; Amano, F; Tanaka, E; Nomoto, H; Nozawa, Y; Kohno, M

    1990-01-01

    We have examined the possible involvements of pertussis toxin (PT)-sensitive guanosine triphosphate (GTP)-binding protein (Gp) and protein kinase C (PKC) in the mitogenic signaling pathways of various growth factors by the use of PT-pretreated and/or 12-O-tetradecanoyl phorbol-13-acetate (TPA)-pretreated mouse fibroblasts. Effects of PT pretreatment (inactivation of PT-sensitive Gp) and TPA pretreatment (depletion of PKC) on mitogen-induced DNA synthesis varied significantly and systematically in response to growth factors: mitogenic responses of cells to thrombin, bombesin, and bradykinin were almost completely abolished both in PT- and TPA-pretreated cells; responses to epidermal growth factor (EGF), platelet-derived growth factor (PDGF), and vanadate were reduced to approximately 50% both in PT- and TPA-pretreated cells compared with native cells; response to basic fibroblast growth factor (bFGF) was not affected in PT-pretreated cells but was inhibited to some extent in TPA-pretreated cells. Thus, growth factors examined have been classified into three groups with regard to the involvements of PT-sensitive Gp and PKC in their signal transduction pathways. Binding of each growth factor to its receptor was not affected significantly by pretreatment of cells with PT or TPA. Inhibitory effects of PT and TPA pretreatment on each mitogen-induced DNA synthesis were not additive, suggesting that the functions of PT-sensitive Gp and PKC lie on an identical signal transduction pathway. Although all three groups of mitogens activated PKC, signaling of each growth factor depends to a varying extent on the function of PKC. Our results indicate that a single peptide growth factor such as EGF, PDGF, or bFGF acts through multiple signaling pathways to induce cell proliferation. Images PMID:2129194

  12. Inhibition of the nitric oxide/cyclic guanosine monophosphate pathway limited the cardioprotective effect of post-conditioning in hearts with apical myocardial infarction.

    PubMed

    Correa, Francisco; Buelna-Chontal, Mabel; Chagoya, Victoria; García-Rivas, Gerardo; Vigueras, Rosa María; Pedraza-Chaverri, José; García-Niño, Wylly Ramsés; Hernández-Pando, Rogelio; León-Contreras, Juan Carlos; Zazueta, Cecilia

    2015-10-15

    Reperfusion damage involves opening of the mitochondrial permeability transition pore (mPTP) and loss of ATP synthesis. Several cardioprotective pathways are activated by ischemic or pharmacological post-conditioning (PC). The mechanisms that are activated by PC in no co-morbidity murine models include: activation of rescue kinases, oxidative stress reduction, glycolytic flux regulation and preservation of ATP synthesis. However, relatively scarce efforts have been made to define whether the efficacy of PC signaling is blunted by risk factors or systemic diseases associated with ischemic heart pathology. Experimental evidence has shown that the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling is a main mechanism activated by PC in hearts without pathological history. In this work we evaluated the participation of the NO pathway, through downstream kinase activation and inhibition of mPTP in hearts with previous infarct. Myocardial infarction was induced with a single dose of isoproterenol (85 mg/kg i.p.) to male Wistar rats. After 24 h, the hearts were mounted into the Langendorff system and subjected to 30 min of ischemia and 60 min of reperfusion. PC consisted of 5 cycles of 30 s of reperfusion/30 s of ischemia, then the hearts were reperfused with or without inhibitors of the NO/cGMP pathway. PC activates the NO/cGMP pathway, as increased cGMP and NO levels were detected in isoproterenol-treated hearts. The cardioprotective effect of PC was abolished with both L-NAME (inhibitor of constitutive NO synthase) and ODQ (inhibitor of soluble guanylate cyclase), whereas the NO donor (DETA-NO) restored cardioprotection even in the presence of L-NAME or ODQ. We also found that mitochondrial structure and function was preserved in PC hearts. We conclude that PC exerts cardioprotection in hearts with previous infarct by maintaining mitochondrial structure and function through NO-dependent pathway. PMID:26387613

  13. Association of blood lead levels with urinary F2-8α Isoprostane and 8-hydroxy-2-deoxy-Guanosine concentrations in first-grade Uruguayan children

    PubMed Central

    Roy, Aditi; Queirolo, Elena; Peregalli, Fabiana; Mañay, Nelly; Martínez, Gabriela; Kordas, Katarzyna

    2015-01-01

    Oxidative stress (OS) is a potential molecular mechanism for lead-induced toxicities, yet, we have limited understanding of the relation between low-level lead (Pb) exposure and OS, especially in children. This cross-sectional study examines the association between blood lead level (BLL) and two OS markers—urinary F2-8α isoprostane or isoprostane (a marker of lipid peroxidation) and 8-hydroxy-2-deoxy-Guanosine or 8-OH-dG (a marker of DNA damage) in 211 children, aged 5–8 years, from Montevideo, Uruguay. The role of dietary intakes of vitamin C and zinc in modifying the relation between BLL and OS was also examined. The mean (SD) BLL of the study children was 4.7 (2.2) μg/dL, with 30.2% children having BLL ≥5 μg/dL, the current reference level set by the US Centre for Disease Control for identifying, monitoring and management of children with elevated BLL. In covariate-adjusted analysis, there was a weak positive association between BLL and urinary isoprostane (adjusted for specific gravity) [β = 0.09, p< 0.1]. No association was found between children’s BLL and urinary 8-OH-dG. Interactions between dietary intakes of vitamin C or zinc and BLL on OS biomarkers were not consistent. However, when BLL and vitamin C or BLL and zinc were modeled together, BLL was independently associated with isoprostane concentration [β = 0.10, p< 0.05] but vitamin C or zinc intake was not. These findings suggest that there may be a potential adverse effect of BLL on OS in children with low-level Pb exposure. There is a need to study the effects of Pb on other OS measures, as well as the role of OS in mediating low-level Pb toxicity on functional outcomes. PMID:25863186

  14. Neuroprotection Promoted by Guanosine Depends on Glutamine Synthetase and Glutamate Transporters Activity in Hippocampal Slices Subjected to Oxygen/Glucose Deprivation.

    PubMed

    Dal-Cim, Tharine; Martins, Wagner C; Thomaz, Daniel T; Coelho, Victor; Poluceno, Gabriela Godoy; Lanznaster, Débora; Vandresen-Filho, Samuel; Tasca, Carla I

    2016-05-01

    Guanosine (GUO) has been shown to act as a neuroprotective agent against glutamatergic excitotoxicity by increasing glutamate uptake and decreasing its release. In this study, a putative effect of GUO action on glutamate transporters activity modulation was assessed in hippocampal slices subjected to oxygen and glucose deprivation (OGD), an in vitro model of brain ischemia. Slices subjected to OGD showed increased excitatory amino acids release (measured by D-[(3)H]aspartate release) that was prevented in the presence of GUO (100 µM). The glutamate transporter blockers, DL-TBOA (10 µM), DHK (100 µM, selective inhibitor of GLT-1), and sulfasalazine (SAS, 250 µM, Xc(-) system inhibitor) decreased OGD-induced D-aspartate release. Interestingly, DHK or DL-TBOA blocked the decrease in glutamate release induced by GUO, whereas SAS did not modify the GUO effect. GUO protected hippocampal slices from cellular damage by modulation of glutamate transporters, however selective blockade of GLT-1 or Xc- system only did not affect this protective action of GUO. OGD decreased hippocampal glutamine synthetase (GS) activity and GUO recovered GS activity to control levels without altering the kinetic parameters of GS activity, thus suggesting GUO does not directly interact with GS. Additionally, the pharmacological inhibition of GS activity with methionine sulfoximine abolished the effect of GUO in reducing D-aspartate release and cellular damage evoked by OGD. Altogether, results in hippocampal slices subjected to OGD show that GUO counteracts the release of excitatory amino acids, stimulates the activity of GS, and decreases the cellular damage by modulation of glutamate transporters activity. PMID:26858177

  15. Roles of insulin, guanosine 5'-[gamma-thio]triphosphate and phorbol 12-myristate 13-acetate in signalling pathways of GLUT4 translocation.

    PubMed Central

    Todaka, M; Hayashi, H; Imanaka, T; Mitani, Y; Kamohara, S; Kishi, K; Tamaoka, K; Kanai, F; Shichiri, M; Morii, N; Narumiya, S; Ebina, Y

    1996-01-01

    Insulin, guanosine 5'-[gamma-thio]triphosphate (GTP[S] and phorbol 12-myristate 13-acetate (PMA) trigger the translocation of Gl UT4 (type 4 glucose transporter; insulin-sensitive glucose transporter) from an intracellular pool to the cell surface. We have developed a highly sensitive and quantitative method to detect GLUT4 immunologically on the surface of intact 3T3-L1 adipocytes and Chinese hamster ovary (CHO) cells, using c-myc epitope-tagged GLUT4 (GLUT4myc). We examined the roles of insulin, GTP[S] and PMA in the signalling pathways of GLUT4 translocation in the CHO cell system. Among small molecular GTP-binding proteins, ras, rab3D, rad and rho seem to be candidates as signal transmitters of insulin-stimulated GLUT4 translocation. Overexpression of wild-type H-ras and the dominant negative mutant H-rass17N in our cell system respectively enhanced and blocked insulin-stimulated activation of mitogen-activated protein kinase, but did not affect insulin-stimulated GLUT4 translocation. Overexpression of rab3D or rad in the cells did not affect GLUT4 translocation triggered by insulin, GTP[S] or PMA. Treatment with Botulinum C3 exoenzyme, a specific inhibitor of rho, had no effect on GLUT4 translocation induced by insulin, GTP[S] or PMA. Therefore these small molecular GTP-binding proteins are not likely to be involved in GLUT4 translocation. In addition, insulin, GTP[S] and PMA apparently stimulate GLUT4 translocation through independent pathways. PMID:8645171

  16. Kinetics of the interaction of translation factor SelB from Escherichia coli with guanosine nucleotides and selenocysteine insertion sequence RNA.

    PubMed

    Thanbichler, M; Bock, A; Goody, R S

    2000-07-01

    The kinetics of the interaction of GTP and GDP with SelB, the specific translation factor for the incorporation of selenocysteine into proteins, have been investigated using the stopped-flow method. Useful signals were obtained using intrinsic (i.e. tryptophan) fluorescence, the fluorescence of methylanthraniloyl derivatives of nucleotides, or fluorescence resonance energy transfer from tryptophan to the methylanthraniloyl group. The affinities of SelB for GTP (K(d) = 0.74 micrometer) and GDP (K(d) = 13.4 micrometer) were considerably lower than those of other translation factors. Of functional significance is the fact that the rate constant for GDP release from its complex with SelB (15 s(-)(1)) is many orders of magnitude larger than for elongation factor Tu, explaining why a GDP/GTP exchange factor is not required for the action of SelB. In contrast, the rate of release of GTP is 2 orders of magnitude slower and not significantly faster than for elongation factor Tu. Using a fluorescently labeled 17-nucleotide RNA minihelix that represents a binding site for the protein and that is part of the fdhF selenocysteine insertion sequence element positioned immediately downstream of the UGA triplet coding for selenocysteine incorporation, the kinetics of the interaction were studied. The high affinity of the interaction (K(d) approximately 1 nm) appeared to be increased even further when selenocysteyl-tRNA(Sec) was bound to SelB, but to be independent of the presence or nature of the guanosine nucleotide at the active site. These results suggest that the affinity of SelB for its RNA binding site is maximized when charged tRNA is bound and decreases to allow dissociation and reading of codons downstream of the selenocysteine codon after selenocysteine peptide bond formation. PMID:10781605

  17. DNA 3' pp 5' G de-capping activity of aprataxin: effect of cap nucleoside analogs and structural basis for guanosine recognition

    SciTech Connect

    Chauleau, Mathieu; Jacewicz, Agata; Shuman, Stewart

    2015-05-24

    DNA3' pp 5'G caps synthesized by the 3'-PO4/5'-OH ligase RtcB have a strong impact on enzymatic reactions at DNA 3'-OH ends. Aprataxin, an enzyme that repairs A5'pp5'DNA ends formed during abortive ligation by classic 3'-OH/5'-PO4 ligases, is also a DNA 3' de-capping enzyme, converting DNAppG to DNA3'p and GMP. By taking advantage of RtcB's ability to utilize certain GTP analogs to synthesize DNAppN caps, we show that aprataxin hydrolyzes inosine and 6-O-methylguanosine caps, but is not adept at removing a deoxyguanosine cap. We report a 1.5 Å crystal structure of aprataxin in a complex with GMP, which reveals that: (i) GMP binds at the same position and in the same anti nucleoside conformation as AMP; and (ii) aprataxin makes more extensive nucleobase contacts with guanine than with adenine, via a hydrogen bonding network to the guanine O6, N1, N2 base edge. Alanine mutations of catalytic residues His147 and His149 abolish DNAppG de-capping activity, suggesting that the 3' de-guanylylation and 5' de-adenylylation reactions follow the same pathway of nucleotidyl transfer through a covalent aprataxin-(His147)–NMP intermediate. Alanine mutation of Asp63, which coordinates the guanosine ribose hydroxyls, impairs DNAppG de-capping.

  18. Current european regulatory perspectives on insulin analogues.

    PubMed

    Enzmann, Harald G; Weise, Martina

    2011-01-01

    Insulin analogues are increasingly considered as an alternative to human insulin in the therapy of diabetes mellitus. Insulin analogues (IAs) are chemically different from human insulin and may have different pharmacokinetic or pharmacodynamic properties. The significance of the modifications of the insulin molecule for the safety profile of IAs must be considered. This review describes the regulatory procedure and the expectations for the scientific content of European marketing authorization applications for innovative IAs submitted to the European Medicines Agency. Particular consideration is given to a potential cancer hazard. Specific regulatory guidance on how to address a possible carcinogenic or tumor promoting effect of innovative IAs in non-clinical studies is available. After marketing authorization, the factual access of patients to the new product will be determined to great extent by health technology assessment bodies, reimbursement decisions and the price. Whereas the marketing authorization is a European decision, pricing and reimbursement are national or regional responsibilities. The assessment of benefit and risk by the European Medicines Agency is expected to influence future decisions on price and reimbursement on a national or regional level. Collaborations between regulatory agencies and health technology assessment bodies have been initiated on European and national level to facilitate the use of the European Medicines Agency's benefit risk assessment as basis on which to build the subsequent health technology assessment. The option for combined or joint scientific advice procedures with regulators and health technology assessment bodies on European level or on a national level in several European Member States may help applicants to optimize their development program and dossier preparation in regard of both European marketing authorization application and reimbursement decisions. PMID:21736748

  19. Natural analogues of nuclear waste glass corrosion.

    SciTech Connect

    Abrajano, T.A. Jr.; Ebert, W.L.; Luo, J.S.

    1999-01-06

    This report reviews and summarizes studies performed to characterize the products and processes involved in the corrosion of natural glasses. Studies are also reviewed and evaluated on how well the corrosion of natural glasses in natural environments serves as an analogue for the corrosion of high-level radioactive waste glasses in an engineered geologic disposal system. A wide range of natural and experimental corrosion studies has been performed on three major groups of natural glasses: tektite, obsidian, and basalt. Studies of the corrosion of natural glass attempt to characterize both the nature of alteration products and the reaction kinetics. Information available on natural glass was then compared to corresponding information on the corrosion of nuclear waste glasses, specifically to resolve two key questions: (1) whether one or more natural glasses behave similarly to nuclear waste glasses in laboratory tests, and (2) how these similarities can be used to support projections of the long-term corrosion of nuclear waste glasses. The corrosion behavior of basaltic glasses was most similar to that of nuclear waste glasses, but the corrosion of tektite and obsidian glasses involves certain processes that also occur during the corrosion of nuclear waste glasses. The reactions and processes that control basalt glass dissolution are similar to those that are important in nuclear waste glass dissolution. The key reaction of the overall corrosion mechanism is network hydrolysis, which eventually breaks down the glass network structure that remains after the initial ion-exchange and diffusion processes. This review also highlights some unresolved issues related to the application of an analogue approach to predicting long-term behavior of nuclear waste glass corrosion, such as discrepancies between experimental and field-based estimates of kinetic parameters for basaltic glasses.

  20. Evolving a polymerase for hydrophobic base analogues.

    PubMed

    Loakes, David; Gallego, José; Pinheiro, Vitor B; Kool, Eric T; Holliger, Philipp

    2009-10-21

    Hydrophobic base analogues (HBAs) have shown great promise for the expansion of the chemical and coding potential of nucleic acids but are generally poor polymerase substrates. While extensive synthetic efforts have yielded examples of HBAs with favorable substrate properties, their discovery has remained challenging. Here we describe a complementary strategy for improving HBA substrate properties by directed evolution of a dedicated polymerase using compartmentalized self-replication (CSR) with the archetypal HBA 5-nitroindole (d5NI) and its derivative 5-nitroindole-3-carboxamide (d5NIC) as selection substrates. Starting from a repertoire of chimeric polymerases generated by molecular breeding of DNA polymerase genes from the genus Thermus, we isolated a polymerase (5D4) with a generically enhanced ability to utilize HBAs. The selected polymerase. 5D4 was able to form and extend d5NI and d5NIC (d5NI(C)) self-pairs as well as d5NI(C) heteropairs with all four bases with efficiencies approaching, or exceeding, those of the cognate Watson-Crick pairs, despite significant distortions caused by the intercalation of the d5NI(C) heterocycles into the opposing strand base stack, as shown by nuclear magnetic resonance spectroscopy (NMR). Unlike Taq polymerase, 5D4 was also able to extend HBA pairs such as Pyrene: varphi (abasic site), d5NI: varphi, and isocarbostyril (ICS): 7-azaindole (7AI), allowed bypass of a chemically diverse spectrum of HBAs, and enabled PCR amplification with primers comprising multiple d5NI(C)-substitutions, while maintaining high levels of catalytic activity and fidelity. The selected polymerase 5D4 promises to expand the range of nucleobase analogues amenable to replication and should find numerous applications, including the synthesis and replication of nucleic acid polymers with expanded chemical and functional diversity. PMID:19778048

  1. Functionalized Congener Approach to Muscarinic Antagonists: Analogues of Pirenzepine

    PubMed Central

    Karton, Yishai; Bradbury, Barton J.; Baumgold, Jesse; Paek, Robert; Jacobson, Kenneth A.

    2012-01-01

    The M1-selective muscarinic receptor antagonist pirenzepine (5,11-dihydro-11-[(4-methyl-1-piperazinyl)acetyl]-6H-pyrido[2,3-b] [1,4]benzodiazepin-6-one) was derivatized to explore points of attachment of functionalized side chains for the synthesis of receptor probes and ligands for affinity chromatography. The analogues prepared were evaluated in competitive binding assays versus [3H]-N-methylscopolamine at four muscarinic receptor subtypes (m1AChR-m4AChR) in membranes from rat heart tissue and transfected A9L cells. 9-(Hydroxymethyl)pirenzepine, 8-(methylthio)pirenzepine, and a series of 8-aminosulfonyl derivatives were synthesized. Several 5-substituted analogues of pirenzepine also were prepared. An alternate series of analogues substituted on the 4-position of the piperazine ring was prepared by reaction of 4-desmethylpirenzepine with various electrophiles. An N-chloroethyl analogue of pirenzepine was shown to form a reactive aziridine species in aqueous buffer yet failed to affinity label muscarinic receptors. Within a series of aminoalkyl analogues, the affinity increased as the length of the alkyl chain increased. Shorter chain analogues were generally much less potent than pirenzepine, and longer analogues (7–10 carbons) were roughly as potent as pirenzepine at m1 receptors, but were nonselective. Depending on the methylene chain length, acylation or alkyl substitution of the terminal amine also influenced the affinity at muscarinic receptors. PMID:2066986

  2. The preparation of zaragozic acid A analogues by directed biosynthesis.

    PubMed

    Chen, T S; Petuch, B; MacConnell, J; White, R; Dezeny, G; Arison, B; Bergstrom, J D; Colwell, L; Huang, L; Monaghan, R L

    1994-11-01

    Zaragozic acid A analogues are produced by an unidentified sterile fungus when it is exogenously supplied with 2-thiophenecarboxylic acid, 3-thiophenecarboxylic acid, 2-furoic acid, 2-fluorobenzoic acid, 3-fluorobenzoic acid, or 4-fluorobenzoic acid. The analogues carry 2-thiophenyl, 3-thiophenyl, 2-furyl, o-fluorophenyl, m-fluorophenyl, or p-fluorophenyl group, respectively, at C-6' of the C-1 alkyl side chain replacing the phenyl group of natural zaragozic acid A. All the new analogues of zaragozic acid A possess picomolar inhibitory activity against squalene synthase in vitro. PMID:8002393

  3. Synthesis, antiarrhythmic activity, and toxicological evaluation of mexiletine analogues.

    PubMed

    Roselli, Mariagrazia; Carocci, Alessia; Budriesi, Roberta; Micucci, Matteo; Toma, Maddalena; Di Cesare Mannelli, Lorenzo; Lovece, Angelo; Catalano, Alessia; Cavalluzzi, Maria Maddalena; Bruno, Claudio; De Palma, Annalisa; Contino, Marialessandra; Perrone, Maria Grazia; Colabufo, Nicola Antonio; Chiarini, Alberto; Franchini, Carlo; Ghelardini, Carla; Habtemariam, Solomon; Lentini, Giovanni

    2016-10-01

    Four mexiletine analogues have been tested for their antiarrhythmic, inotropic, and chronotropic effects on isolated guinea pig heart tissues and to assess calcium antagonist activity, in comparison with the parent compound mexiletine. All analogues showed from moderate to high antiarrhythmic activity. In particular, three of them (1b,c,e) were more active and potent than the reference drug, while exhibiting only modest or no negative inotropic and chronotropic effects and vasorelaxant activity, thus showing high selectivity of action. All compounds showed no cytotoxicity and 1b,c,d did not impair motor coordination. All in, these new analogues exhibit an interesting cardiovascular profile and deserve further investigation. PMID:27267000

  4. Recent developments in naturally derived antimalarials: cryptolepine analogues.

    PubMed

    Wright, Colin W

    2007-06-01

    Increasing resistance of Plasmodium falciparum to commonly used antimalarial drugs has made the need for new agents increasingly urgent. In this paper, the potential of cryptolepine, an alkaloid from the West African shrub Cryptolepis sanguinolenta, as a lead towards new antimalarial agents is discussed. Several cryptolepine analogues have been synthesized that have promising in-vitro and in-vivo antimalarial activity. Studies on the antimalarial modes of action of these analogues indicate that they may have different or additional modes of action to the parent compound. Elucidation of the mode of action may facilitate the development of more potent antimalarial cryptolepine analogues. PMID:17637183

  5. Lanthanum inhibition of Vibrio cholerae and Escherichia coli enterotoxin-induced enterosorption and its effects on intestinal mucosa cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate levels.

    PubMed Central

    Leitch, G J; Amer, M S

    1975-01-01

    Several trivalent cations, including lanthanum (La3+), inhibited the secretion (enterosorption) induced by the enterotoxins of Vibrio cholerae and Escherichia coli in the rabbit ileum in vivo. High concentrations (greater than 10 mM) of La3+ were required to inhibit cholera enterotoxin (CE)-induced enterosorption, probably because of the adsorption of the La3+ often potentiated the CE-induced enterosorption. If luminal La3+ exposure followed CE exposure, some recovery of the enterosorptive response was observed. The longer the lag between the CE exposure and the La3+ exposure, the greater was the recovery of the enterosorptive response. Lanthanum inhibited HCO3- secretion more than Cl- secretion. By altering the luminal fluid pH at the time of La3+ exposure, it was found that La3+ was adsorbed to negatively charged luminal sites, having an apparent pK between 2.5 and 3.0. Although La3+ antagonized the enterosorptive response to CE, it mimicked rather than antagonized the cyclic adenosine 3',5'-monophosphate elevation and cyclic guanosine 3',5'-monophosphate depression induced by the toxin. It is therefore concluded that the La3+ inhibition of the CE-induced enterosorption must have occurred at a site following the generation of the cyclic nucleotides. Cholera enterotoxin caused complex time-dependent changes in the mucosal cyclic adenosine 3',5'-monophosphate and cyclic guanosine 3',5'-monophosphate levels, as revealed by studying tissue cyclic adenosine 3',5'-monophosphate/cyclic guanosine 3',5'-monophosphate ratios. The possible roles these two cyclic nucleotides may play in the pathogenesis of the cholera diarrhea are discussed. PMID:164410

  6. INX-08189, a Phosphoramidate Prodrug of 6-O-Methyl-2′-C-Methyl Guanosine, Is a Potent Inhibitor of Hepatitis C Virus Replication with Excellent Pharmacokinetic and Pharmacodynamic Properties▿

    PubMed Central

    Vernachio, John H.; Bleiman, Blair; Bryant, K. Dawn; Chamberlain, Stanley; Hunley, Damound; Hutchins, Jeff; Ames, Brenda; Gorovits, Elena; Ganguly, Babita; Hall, Andrea; Kolykhalov, Alexander; Liu, Yule; Muhammad, Jerry; Raja, Nicholas; Walters, C. Robin; Wang, Jin; Williams, Karen; Patti, Joseph M.; Henson, Geoffrey; Madela, Karolina; Aljarah, Mohamed; Gilles, Arnaud; McGuigan, Christopher

    2011-01-01

    INX-08189 is an aryl-phosphoramidate of 6-O-methyl-2′-C-methyl guanosine. INX-08189 was highly potent in replicon assays, with a 50% effective concentration of 10 ± 6 nM against hepatitis C genotype 1b at 72 h. The inhibitory effect on viral replication was rapid, with a 50% effective concentration (EC50) of 35 ± 8 nM at 24 h. An intracellular 2′-C-methyl guanosine triphosphate (2′-C-MeGTP) concentration of 2.43 ± 0.42 pmol/106 cells was sufficient to achieve 90% inhibition of viral replication. In vitro resistance studies confirmed that the S282T mutation in the NS5b gene conferred an approximately 10-fold reduction in sensitivity to INX-08189. However, the complete inhibition of S282T mutant replicons still could be achieved with an EC90 of 344 ± 170 nM. Drug combination studies of INX-08189 and ribavirin indicated significant synergy in antiviral potency both in wild-type and S282T-expressing replicons. Genotype 1b replicons could be cleared after 14 days of culture when exposed to as little as 20 nM INX-08189. No evidence of mitochondrial toxicity was observed after 14 days of INX-08189 exposure in both HepG2 and CEM human cell lines. In vivo studies of rats and cynomolgus monkeys demonstrated that 2′-C-MeGTP concentrations in liver equivalent to the EC90 could be attained after a single oral dose of INX-08189. Rat liver 2′-C-MeGTP concentrations were proportional to dose, sustained for greater than 24 h, and correlated with plasma concentrations of the nucleoside metabolite 2′-C-methyl guanosine. The characteristics displayed by INX-08189 support its continued development as a clinical candidate for the treatment of chronic HCV infection. PMID:21357300

  7. INX-08189, a phosphoramidate prodrug of 6-O-methyl-2'-C-methyl guanosine, is a potent inhibitor of hepatitis C virus replication with excellent pharmacokinetic and pharmacodynamic properties.

    PubMed

    Vernachio, John H; Bleiman, Blair; Bryant, K Dawn; Chamberlain, Stanley; Hunley, Damound; Hutchins, Jeff; Ames, Brenda; Gorovits, Elena; Ganguly, Babita; Hall, Andrea; Kolykhalov, Alexander; Liu, Yule; Muhammad, Jerry; Raja, Nicholas; Walters, C Robin; Wang, Jin; Williams, Karen; Patti, Joseph M; Henson, Geoffrey; Madela, Karolina; Aljarah, Mohamed; Gilles, Arnaud; McGuigan, Christopher

    2011-05-01

    INX-08189 is an aryl-phosphoramidate of 6-O-methyl-2'-C-methyl guanosine. INX-08189 was highly potent in replicon assays, with a 50% effective concentration of 10±6 nM against hepatitis C genotype 1b at 72 h. The inhibitory effect on viral replication was rapid, with a 50% effective concentration (EC50) of 35±8 nM at 24 h. An intracellular 2'-C-methyl guanosine triphosphate (2'-C-MeGTP) concentration of 2.43±0.42 pmol/10(6) cells was sufficient to achieve 90% inhibition of viral replication. In vitro resistance studies confirmed that the S282T mutation in the NS5b gene conferred an approximately 10-fold reduction in sensitivity to INX-08189. However, the complete inhibition of S282T mutant replicons still could be achieved with an EC90 of 344±170 nM. Drug combination studies of INX-08189 and ribavirin indicated significant synergy in antiviral potency both in wild-type and S282T-expressing replicons. Genotype 1b replicons could be cleared after 14 days of culture when exposed to as little as 20 nM INX-08189. No evidence of mitochondrial toxicity was observed after 14 days of INX-08189 exposure in both HepG2 and CEM human cell lines. In vivo studies of rats and cynomolgus monkeys demonstrated that 2'-C-MeGTP concentrations in liver equivalent to the EC90 could be attained after a single oral dose of INX-08189. Rat liver 2'-C-MeGTP concentrations were proportional to dose, sustained for greater than 24 h, and correlated with plasma concentrations of the nucleoside metabolite 2'-C-methyl guanosine. The characteristics displayed by INX-08189 support its continued development as a clinical candidate for the treatment of chronic HCV infection. PMID:21357300

  8. Actions of Thyroid Hormone Analogues on Chemokines

    PubMed Central

    Glinsky, Gennadi V.

    2016-01-01

    The extracellular domain of plasma membrane integrin αvβ3 contains a receptor for thyroid hormone (L-thyroxine, T4; 3,5,3′-triiodo-L-thyronine, T3); this receptor also binds tetraiodothyroacetic acid (tetrac), a derivative of T4. Tetrac inhibits the binding of T4 and T3 to the integrin. Fractalkine (CX3CL1) is a chemokine relevant to inflammatory processes in the CNS that are microglia-dependent but also important to normal brain development. Expression of the CX3CL1 gene is downregulated by tetrac, suggesting that T4 and T3 may stimulate fractalkine expression. Independently of its specific receptor (CX3CR1), fractalkine binds to αvβ3 at a site proximal to the thyroid hormone-tetrac receptor and changes the physical state of the integrin. Tetrac also affects expression of the genes for other CNS-relevant chemokines, including CCL20, CCL26, CXCL2, CXCL3, and CXCL10. The chemokine products of these genes are important to vascularity of the brain, particularly of the choroid plexus, to inflammatory processes in the CNS and, in certain cases, to neuroprotection. Thyroid hormones are known to contribute to regulation of each of these CNS functions. We propose that actions of thyroid hormone and hormone analogues on chemokine gene expression contribute to regulation of inflammatory processes in brain and of brain blood vessel formation and maintenance. PMID:27493972

  9. Radiolabeled Somatostatin Analogue Therapy Of Gastroenteropancreatic Cancer.

    PubMed

    Bodei, Lisa; Kwekkeboom, Dik J; Kidd, Mark; Modlin, Irvin M; Krenning, Eric P

    2016-05-01

    Peptide receptor radionuclide therapy (PRRT) has been utilized for more than two decades and has been accepted as an effective therapeutic modality in the treatment of inoperable or metastatic gastroenteropancreatic neuroendocrine neoplasms (NENs) or neuroendocrine tumors (NETs). The two most commonly used radiopeptides for PRRT, (90)Y-octreotide and (177)Lu-octreotate, produce disease-control rates of 68%-94%, with progression-free survival rates that compare favorably with chemotherapy, somatostatin analogues, and newer targeted therapies. In addition, biochemical and symptomatic responses are commonly observed. In general, PRRT is well tolerated with only low to moderate toxicity in most individuals. In line with the need to place PRRT in the therapeutic sequence of gastroenteropancreatic NENs, a recently sponsored phase III randomized trial in small intestine NENs treated with (177)Lu-octreotate vs high-dose octreotide long-acting release demonstrated that (177)Lu-octreotate significantly improved progression-free survival. Other strategies that are presently being developed include combinations with targeted therapies or chemotherapy, intra-arterial PRRT, and salvage treatments. Sophisticated molecular tools need to be incorporated into the management strategy to more effectively define therapeutic efficacy and for an early identification of adverse events. The strategy of randomized controlled trials is a key issue to standardize the treatment and establish the position of PRRT in the therapeutic algorithm of NENs. PMID:27067503

  10. Actions of Thyroid Hormone Analogues on Chemokines.

    PubMed

    Davis, Paul J; Glinsky, Gennadi V; Lin, Hung-Yun; Mousa, Shaker A

    2016-01-01

    The extracellular domain of plasma membrane integrin αvβ3 contains a receptor for thyroid hormone (L-thyroxine, T4; 3,5,3'-triiodo-L-thyronine, T3); this receptor also binds tetraiodothyroacetic acid (tetrac), a derivative of T4. Tetrac inhibits the binding of T4 and T3 to the integrin. Fractalkine (CX3CL1) is a chemokine relevant to inflammatory processes in the CNS that are microglia-dependent but also important to normal brain development. Expression of the CX3CL1 gene is downregulated by tetrac, suggesting that T4 and T3 may stimulate fractalkine expression. Independently of its specific receptor (CX3CR1), fractalkine binds to αvβ3 at a site proximal to the thyroid hormone-tetrac receptor and changes the physical state of the integrin. Tetrac also affects expression of the genes for other CNS-relevant chemokines, including CCL20, CCL26, CXCL2, CXCL3, and CXCL10. The chemokine products of these genes are important to vascularity of the brain, particularly of the choroid plexus, to inflammatory processes in the CNS and, in certain cases, to neuroprotection. Thyroid hormones are known to contribute to regulation of each of these CNS functions. We propose that actions of thyroid hormone and hormone analogues on chemokine gene expression contribute to regulation of inflammatory processes in brain and of brain blood vessel formation and maintenance. PMID:27493972

  11. Interaction of tRNA with tRNA (guanosine-1)methyltransferase: binding specificity determinants involve the dinucleotide G36pG37 and tertiary structure.

    PubMed

    Redlak, M; Andraos-Selim, C; Giege, R; Florentz, C; Holmes, W M

    1997-07-22

    The sequence G37pG36 is present in all tRNA species recognized and methylated by the Escherichia coli modification enzyme tRNA (guanosine-1)methyltransferase. We have examined whether this dinucleotide sequence provides the base specific recognition signal for this enzyme and have assessed the role of the remaining tRNA in recognition. E. coli tRNAHis and yeast tRNAAsp were substituted with G at positions 36 and 37 and were found to be excellent substrates for methylation. This suggested that the general tRNA structure can be specifically bound by the enzyme. In addition, heterologous tRNA species including fully modified tRNA1Leu are excellent inhibitors of tRNA1Leu transcript methylation. Analyses of structural variants of yeast tRNAAsp and E. coli tRNA1Leu demonstrate clearly that the core tertiary structures of tRNA are required for recognition and that G37 must be in the correct position in space relative to important contacts elsewhere in the molecule. This latter conclusion was reached because the addition of one to three stacked base pairs in the anticodon stem of tRNA1Leu dramatically alters activity. In this case, the G37 base is rotated away from the correct position in space relative to other tRNA contact sites. The acceptor stem structure is required for optimal activity since deletion of three or five base pairs is detrimental to activity; however, specific base sequence may not be important because (i) the addition of three stacked base pairs of different sequence had little effect on activity and (ii) heterologous tRNAs with little or no sequence homology in the acceptor stem are excellent substrates. Both poly G and GpG are potent and specific inhibitors of enzyme activity and are minimal substrates which can be methylated, forming m1G. Taken together, these studies suggest that 1MGT can bind the general tRNA structure and that the crucial base-pair contacts are G37 and G36. PMID:9220956

  12. Pharmacokinetic Profile and Acute Toxicological Properties of a Novel Radiosensitizer Cytosine-Phosphate-Guanosine Oligodeoxynucleotide 107 in Mice Following Intravenous and Orthotopic Administration.

    PubMed

    Cen, Yanyan; Li, Xiaoli; Yin, Zhiwei; Yan, Zifei; Liu, Dan; Peng, Wei; Pan, Feng; Zhou, Hong

    2015-10-01

    The synthetic cytosine-phosphate-guanosine oligodeoxynucleotide 107 (CpG ODN107) is a novel radiosensitizer for glioma treatment. However, the information related to its pharmacokinetics and toxicity remains unclear. Therefore, the plasma pharmacokinetics, distribution, elimination, and acute toxicity of CpG ODN107 in mice were investigated in the present experiments. The results from the liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay showed that the plasma elimination half-life (t1/2β) of CpG ODN107 in BALB/c mice varied slightly with the dose, and it was 0.65, 0.49, and 0.50 h at the intravenous doses of 2.5, 5, and 10 mg/kg, respectively. CpG ODN107 rapidly and widely distributed in organs/tissues, except the brain and testes. The highest concentrations were found in the liver (28.6% of the administered dose after 0.5 h) and the kidneys (5.7% of the administered dose after 1 h). CpG ODN107 (0.3, 3, and 30 μg/mL) could highly bind to human and mouse plasma proteins in vitro. CpG ODN107 in the forms of prototype was excreted in urine (1.79%) and feces (0.91%), and its shortened metabolites were excreted in urine (2.1%) and feces (2.2%) within the first 24 h. The mice in vivo optical image showed CpG ODN107 labeled with Alexa Fluor 680 fluorochrome (AF680) accumulated in the brain after orthotopic injection, eliminated very slowly, and excreted in urine compared with poly T labeled with AF680. The median lethal dose (LD50) of CpG ODN107 was 75.7 mg/kg for mice; this dose only could produce apparent spleen and liver damage, in line with the distribution features of CpG ODN. In conclusion, our present pharmacokinetic and toxicity investigation will provide helpful information to further pharmacodynamic and pharmacokinetic research of CpG ODN107 and other oligodeoxynucleotide drugs in the future. PMID:26213852

  13. Elevated intracranial dopamine impairs the glutamate‑nitric oxide‑cyclic guanosine monophosphate pathway in cortical astrocytes in rats with minimal hepatic encephalopathy.

    PubMed

    Ding, Saidan; Huang, Weilong; Ye, Yiru; Yang, Jianjing; Hu, Jiangnan; Wang, Xiaobin; Liu, Leping; Lu, Qin; Lin, Yuanshao

    2014-09-01

    In a previous study by our group memory impairment in rats with minimal hepatic encephalopathy (MHE) was associated with the inhibition of the glutamate‑nitric oxide‑cyclic guanosine monophosphate (Glu‑NO‑cGMP) pathway due to elevated dopamine (DA). However, the effects of DA on the Glu‑NO‑cGMP pathway localized in primary cortical astrocytes (PCAs) had not been elucidated in rats with MHE. In the present study, it was identified that when the levels of DA in the cerebral cortex of rats with MHE and high‑dose DA (3 mg/kg)‑treated rats were increased, the co‑localization of N‑methyl‑d‑aspartate receptors subunit 1 (NMDAR1), calmodulin (CaM), nitric oxide synthase (nNOS), soluble guanylyl cyclase (sGC) and cyclic guanine monophosphate (cGMP) with the glial fibrillary acidic protein (GFAP), a marker protein of astrocytes, all significantly decreased, in both the MHE and high‑dose DA‑treated rats (P<0.01). Furthermore, NMDA‑induced augmentation of the expression of NMDAR1, CaM, nNOS, sGC and cGMP localized in PCAs was decreased in MHE and DA‑treated rats, as compared with the controls. Chronic exposure of cultured cerebral cortex PCAs to DA treatment induced a dose‑dependent decrease in the concentration of intracellular calcium, nitrites and nitrates, the formation of cGMP and the expression of NMDAR1, CaM, nNOS and sGC/cGMP. High doses of DA (50 µM) significantly reduced NMDA‑induced augmentation of the formation of cGMP and the contents of NMDAR1, CaM, nNOS, sGC and cGMP (P<0.01). These results suggest that the suppression of DA on the Glu‑NO‑cGMP pathway localized in PCAs contributes to memory impairment in rats with MHE. PMID:25059564

  14. Elevated intracranial dopamine impairs the glutamate-nitric oxide-cyclic guanosine monophosphate pathway in cortical astrocytes in rats with minimal hepatic encephalopathy

    PubMed Central

    DING, SAIDAN; HUANG, WEILONG; YE, YIRU; YANG, JIANJING; HU, JIANGNAN; WANG, XIAOBIN; LIU, LEPING; LU, QIN; LIN, YUANSHAO

    2014-01-01

    In a previous study by our group memory impairment in rats with minimal hepatic encephalopathy (MHE) was associated with the inhibition of the glutamate-nitric oxide-cyclic guanosine monophosphate (Glu-NO-cGMP) pathway due to elevated dopamine (DA). However, the effects of DA on the Glu-NO-cGMP pathway localized in primary cortical astrocytes (PCAs) had not been elucidated in rats with MHE. In the present study, it was identified that when the levels of DA in the cerebral cortex of rats with MHE and high-dose DA (3 mg/kg)-treated rats were increased, the co-localization of N-methyl-d-aspartate receptors subunit 1 (NMDAR1), calmodulin (CaM), nitric oxide synthase (nNOS), soluble guanylyl cyclase (sGC) and cyclic guanine monophosphate (cGMP) with the glial fibrillary acidic protein (GFAP), a marker protein of astrocytes, all significantly decreased, in both the MHE and high-dose DA-treated rats (P<0.01). Furthermore, NMDA-induced augmentation of the expression of NMDAR1, CaM, nNOS, sGC and cGMP localized in PCAs was decreased in MHE and DA-treated rats, as compared with the controls. Chronic exposure of cultured cerebral cortex PCAs to DA treatment induced a dose-dependent decrease in the concentration of intracellular calcium, nitrites and nitrates, the formation of cGMP and the expression of NMDAR1, CaM, nNOS and sGC/cGMP. High doses of DA (50 μM) significantly reduced NMDA-induced augmentation of the formation of cGMP and the contents of NMDAR1, CaM, nNOS, sGC and cGMP (P<0.01). These results suggest that the suppression of DA on the Glu-NO-cGMP pathway localized in PCAs contributes to memory impairment in rats with MHE. PMID:25059564

  15. Effects of Prostaglandin Analogues on Aqueous Humor Outflow Pathways

    PubMed Central

    Winkler, Nelson S.

    2014-01-01

    Abstract Elevated intraocular pressure (IOP) is the most prevalent risk factor for glaucoma. All treatments, whether surgical or pharmaceutical, are aimed at lowering IOP. Prostaglandin analogues are a first line therapy for glaucoma due to their ability to reduce IOP, once-daily dosing, efficacy, and minimal side-effect profile. Whereas prostaglandin analogues have been known to alter aqueous humor outflow through the unconventional (uveoscleral) pathway, more recent evidence suggests their action also occurs through the conventional (trabecular) pathway. Understanding how prostaglandin analogues successfully lower IOP is important, as this information may lead to the discovery of new molecular targets for future therapeutic intervention. This review explores the current understanding of prostaglandin analogue biology as it pertains to IOP reduction and improved aqueous humor outflow facility. PMID:24359106

  16. Practical enantiospecific syntheses of lysobisphosphatidic acid and its analogues.

    PubMed

    Jiang, Guowei; Xu, Yong; Prestwich, Glenn D

    2006-02-01

    We describe a versatile, efficient, and practical method for the preparation of enantiomerically pure lysobisphosphatidic acid (LBPA), bisether analogues, and phosphorothioate analogues of LBPA from solketal. Phosphorylation of a protected sn-2-O-oleoyl glycerol with 2-cyanoethyl bis(N,N-diisopropylamino)phosphite, followed by oxidation and deprotection, generated the enantiomers of 2,2'-LBPA. The corresponding phosphorothioate analogues were obtained by oxidation with sulfur. The (R,R) and (S,S) enantiomers of both LBPA and phosphorothioate LBPA were synthesized from (S)- and (R)-solketal, respectively. The ether analogue of (S,S)-lysobisphosphatidic acid (LBPA) and its enantiomer were synthesized from the same enantiomer (S)-solketal by simply changing the sequence of deprotection steps. PMID:16438504

  17. Structural analogues of diosgenyl saponins: synthesis and anticancer activity.

    PubMed

    Kaskiw, Matthew J; Tassotto, Mary Lynn; Mok, Mac; Tokar, Stacey L; Pycko, Roxanne; Th'ng, John; Jiang, Zi-Hua

    2009-11-15

    Saponins display various biological activities including anti-tumor activity. Recently intensive research has been focused on developing saponins for tumor therapies. The diosgenyl saponin dioscin is one of the most common steroidal saponins and exhibits potent anticancer activity in several human cancer cells through apoptosis-inducing pathways. In this paper, we describe the synthesis of several diosgenyl saponin analogues containing either a 2-amino-2-deoxy-beta-d-glucopyranosyl residue or an alpha-l-rhamnopyranosyl-(1-->4)-2-amino-2-deoxy-beta-d-glucopyranosyl residue with different acyl substituents on the amino group. The cytotoxic activity of these compounds was evaluated in MCF-7 breast cancer cells and HeLa cervical cancer cells. Structure-activity relationship studies show that the disaccharide saponin analogues are in general less active than their corresponding monosaccharide analogues. The incorporation of an aromatic nitro functionality into these saponin analogues does not exhibit significant effect on their cytotoxic activity. PMID:19819703

  18. Cell-Cycle Analyses Using Thymidine Analogues in Fission Yeast

    PubMed Central

    Anda, Silje; Boye, Erik; Grallert, Beata

    2014-01-01

    Thymidine analogues are powerful tools when studying DNA synthesis including DNA replication, repair and recombination. However, these analogues have been reported to have severe effects on cell-cycle progression and growth, the very processes being investigated in most of these studies. Here, we have analyzed the effects of 5-ethynyl-2′-deoxyuridine (EdU) and 5-Chloro-2′-deoxyuridine (CldU) using fission yeast cells and optimized the labelling procedure. We find that both analogues affect the cell cycle, but that the effects can be mitigated by using the appropriate analogue, short pulses of labelling and low concentrations. In addition, we report sequential labelling of two consecutive S phases using EdU and 5-bromo-2′-deoxyuridine (BrdU). Furthermore, we show that detection of replicative DNA synthesis is much more sensitive than DNA-measurements by flow cytometry. PMID:24551125

  19. Synthesis of a stable and orally bioavailable englerin analogue.

    PubMed

    Fash, David M; Peer, Cody J; Li, Zhenwu; Talisman, Ian J; Hayavi, Sima; Sulzmaier, Florian J; Ramos, Joe W; Sourbier, Carole; Neckers, Leonard; Figg, W Douglas; Beutler, John A; Chain, William J

    2016-06-01

    Synthesis of analogues of englerin A with a reduced propensity for hydrolysis of the glycolate moiety led to a compound which possessed the renal cancer cell selectivity of the parent and was orally bioavailable in mice. PMID:27107948

  20. Efficient total syntheses and biological activities of two teixobactin analogues.

    PubMed

    Parmar, Anish; Iyer, Abhishek; Vincent, Charlotte S; Van Lysebetten, Dorien; Prior, Stephen H; Madder, Annemieke; Taylor, Edward J; Singh, Ishwar

    2016-04-26

    The discovery of the new antibiotic teixobactin has been timely in the race for unearthing novel antibiotics wherein the emergence of drug resistant bacteria poses a serious threat worldwide. Herein, we present the total syntheses and biological activities of two teixobactin analogues. This approach is simple, efficient and has several advantages: it uses commercially available building blocks (except AllocHN-d-Thr-OH), has a single purification step and a good recovery (22%). By using this approach we have synthesised two teixobactin analogues and established that the d-amino acids are critical for the antimicrobial activity of these analogues. With continuing high expectations from teixobactin, this work can be regarded as a stepping stone towards an in depth study of teixobactin, its analogues and the quest for synthesising similar molecules. PMID:26984316

  1. Defining Analytical Strategies for Mars Sample Return with Analogue Missions

    NASA Astrophysics Data System (ADS)

    Osinski, G. R.; Sapers, H. M.; Francis, R.; Pontefract, A.; Tornabene, L. L.; Haltigin, T.

    2016-05-01

    The characterization of biosignatures in MSR samples will require integrated, cross-platform laboratory analyses carefully correlated and calibrated with Rover-based technologies. Analogue missions provide context for implementation and assessment.

  2. From BPA to its analogues: Is it a safe journey?

    PubMed

    Usman, Afia; Ahmad, Masood

    2016-09-01

    Bisphenol-A (BPA) is one of the most abundant synthetic chemicals in the world due to its uses in plastics. Its widespread exposure vis-a-vis low dose effects led to a reduction in its safety dose and imposition of ban on its use in infant feeding bottles. This restriction paved the way for the gradual market entry of its analogues. However, their structural similarity to BPA has put them under surveillance for endocrine disrupting potential. The application of these analogues is increasing and so are the studies reporting their toxicity. This review highlights the reasons which led to the ban of BPA and also reports the exposure and toxicological data available on its analogues. Hence, this compilation is expected to answer in a better way whether the replacement of BPA by these analogues is safer or more harmful? PMID:27262103

  3. Carbacaprazamycins: Chemically Stable Analogues of the Caprazamycin Nucleoside Antibiotics.

    PubMed

    Ichikawa, Satoshi; Yamaguchi, Mayumi; Hsuan, Lee Shang; Kato, Yuta; Matsuda, Akira

    2015-04-10

    Carbacaprazamycins, which are chemically stable analogues of caprazamycins, were designed and synthesized. These analogues were active against drug-resistant bacterial pathogens such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci, and their activities were comparable to those of the parent caprazamycins. The effect of treatment with carbacaprazamycin on morphological changes in S. aureus indicated that the mode of action was completely different from those of existing peptidoglycan inhibitors. PMID:27622529

  4. Analogue and digital linear modulation techniques for mobile satellite

    NASA Technical Reports Server (NTRS)

    Whitmarsh, W. J.; Bateman, A.; Mcgeehan, J. P.

    1990-01-01

    The choice of modulation format for a mobile satellite service is complex. The subjective performance is summarized of candidate schemes and voice coder technologies. It is shown that good performance can be achieved with both analogue and digital voice systems, although the analogue system gives superior performance in fading. The results highlight the need for flexibility in the choice of signaling format. Linear transceiver technology capable of using many forms of narrowband modulation is described.

  5. Amphiphilic Tobramycin Analogues as Antibacterial and Antifungal Agents

    PubMed Central

    Shrestha, Sanjib K.; Fosso, Marina Y.; Green, Keith D.

    2015-01-01

    In this study, we investigated the in vitro antifungal activities, cytotoxicities, and membrane-disruptive actions of amphiphilic tobramycin (TOB) analogues. The antifungal activities were established by determination of MIC values and in time-kill studies. Cytotoxicity was evaluated in mammalian cell lines. The fungal membrane-disruptive action of these analogues was studied by using the membrane-impermeable dye propidium iodide. TOB analogues bearing a linear alkyl chain at their 6″-position in a thioether linkage exhibited chain length-dependent antifungal activities. Analogues with C12 and C14 chains showed promising antifungal activities against tested fungal strains, with MIC values ranging from 1.95 to 62.5 mg/liter and 1.95 to 7.8 mg/liter, respectively. However, C4, C6, and C8 TOB analogues and TOB itself exhibited little to no antifungal activity. Fifty percent inhibitory concentrations (IC50s) for the most potent TOB analogues (C12 and C14) against A549 and Beas 2B cells were 4- to 64-fold and 32- to 64-fold higher, respectively, than their antifungal MIC values against various fungi. Unlike conventional aminoglycoside antibiotics, TOB analogues with alkyl chain lengths of C12 and C14 appear to inhibit fungi by inducing apoptosis and disrupting the fungal membrane as a novel mechanism of action. Amphiphilic TOB analogues showed broad-spectrum antifungal activities with minimal mammalian cell cytotoxicity. This study provides novel lead compounds for the development of antifungal drugs. PMID:26033722

  6. Bisphenol A and Its Analogues Activate Human Pregnane X Receptor

    PubMed Central

    Sui, Yipeng; Ai, Ni; Park, Se-Hyung; Rios-Pilier, Jennifer; Perkins, Jordan T.; Welsh, William J.

    2012-01-01

    Background: Bisphenol A (BPA) is a base chemical used extensively in many consumer products. BPA and its analogues are present in environmental and human samples. Many endocrine-disrupting chemicals, including BPA, have been shown to activate the pregnane X receptor (PXR), a nuclear receptor that functions as a master regulator of xenobiotic metabolism. However, the detailed mechanism by which these chemicals activate PXR remains unknown. Objective: We investigated the mechanism by which BPA interacts with and activates PXR and examined selected BPA analogues to determine whether they bind to and activate PXR. Methods: Cell-based reporter assays, in silico ligand–PXR docking studies, and site-directed mutagenesis were combined to study the interaction between BPA and PXR. We also investigated the influence of BPA and its analogues on the regulation of PXR target genes in human LS180 cells. Results: We found that BPA and several of its analogues are potent agonists for human PXR (hPXR) but do not affect mouse PXR activity. We identified key residues within hPXR’s ligand-binding pocket that constitute points of interaction with BPA. We also deduced the structural requirements of BPA analogues that activate hPXR. BPA and its analogues can also induce PXR target gene expression in human LS180 cells. Conclusions: The present study advances our understanding of the mechanism by which BPA interacts with and activates human PXR. Activation of PXR by BPA may explain some of the adverse effects of BPA in humans. PMID:22214767

  7. Analogue gravitational phenomena in Bose-Einstein condensates

    NASA Astrophysics Data System (ADS)

    Finazzi, Stefano

    2012-08-01

    Analogue gravity is based on the simple observation that perturbations propagating in several physical systems can be described by a quantum field theory in a curved spacetime. While phenomena like Hawking radiation are hardly detectable in astrophysical black holes, these effects may be experimentally tested in analogue systems. In this Thesis, focusing on Bose-Einstein condensates, we present our recent results about analogue models of gravity from three main perspectives: as laboratory tests of quantum field theory in curved spacetime, for the techniques that they provide to address various issues in general relativity, and as toy models of quantum gravity. The robustness of Hawking-like particle creation is investigated in flows with a single black hole horizon. Furthermore, we find that condensates with two (white and black) horizons develop a dynamical instability known in general relativity as black hole laser effect. Using techniques borrowed from analogue gravity, we also show that warp drives, which are general relativistic spacetimes allowing faster-than-light travel, are unstable. Finally, the cosmological constant issue is investigated from an analogue gravity perspective and relativistic Bose-Einstein condensates are proposed as new analogue systems with novel interesting properties.

  8. Cladribine Analogues via O6-(Benzotriazolyl) Derivatives of Guanine Nucleosides

    PubMed Central

    Satishkumar, Sakilam; Vuram, Prasanna K.; Relangi, Siva Subrahmanyam; Gurram, Venkateshwarlu; Zhou, Hong; Kreitman, Robert J.; Montemayor, Michelle M. Martínez; Yang, Lijia; Kaliyaperumal, Muralidharan; Sharma, Somesh; Pottabathini, Narender; Lakshman, Mahesh K.

    2016-01-01

    Cladribine, 2-chloro-2′-deoxyadenosine, is a highly efficacious clinically used nucleoside for the treatment of hairy cell leukemia. It is also being evaluated against other lymphoid malignancies and has been a molecule of interest for well over half a century. In continuation of our interest on the amide bond-activation in purine nucleosides via the use of (benzotriazol-1yl-oxy)tris(dimethylamino)phosphonium hexafluorophosphate, we have evaluated the use of O6-(benzotriazol-1-yl)-2′-deoxyguanosine as a potential precursor to cladribine and its analogues. These compounds, after appropriate deprotection, were assessed for their biological activities and the data are presented herein. Against hairy cell leukemia (HCL), T-cell lymphoma (TCL), and chronic lymphocytic leukemia (CLL) cladribine was the most active against all. The bromo analogue of cladribine showed comparable activity to the ribose analogue of cladribine against HCL, but was more active against TCL and CLL. The bromo ribo analogue of cladribine possessed activity, but was least active among the C6-NH2-containing compounds. Substitution with alkyl groups at the exocyclic amino group appears detrimental to activity, and only the C6 piperidinyl cladribine analogue demonstrated any activity. Against adenocarcinoma MDA-MB-231 cells, only cladribine and its ribose analogue were most active. PMID:26556315

  9. Vascular disrupting activity of combretastatin analogues.

    PubMed

    Porcù, Elena; Salvador, Alessia; Primac, Irina; Mitola, Stefania; Ronca, Roberto; Ravelli, Cosetta; Bortolozzi, Roberta; Vedaldi, Daniela; Romagnoli, Romeo; Basso, Giuseppe; Viola, Giampietro

    2016-08-01

    Tubulin binding agents (TBAs) are drugs commonly used in cancer therapy as antimitotics. In the last years it has been described that TBAs, like combretastatin A-4 (CA-4), present also vascular disrupting activity and among its derivatives we identified three analogues endowed with potent microtubule depolymerizing activity, higher than that of the lead compound. In this paper we have investigated the anti-vascular activity of these derivatives. We tested the anti-angiogenic effects in human umbilical endothelial cells (HUVEC) and in vivo in chick chorioallantoic membrane assay (CAM), and in a syngeneic tumor mouse model. The three molecules, compound 1: 1-(3,4,5-trimethoxyphenyl)-5-(4-ethoxyphenyl)-1H-1,2,4-triazole; compound 2: (1-(3,4,5-trimethoxyphenyl)-5-(4-ethoxyphenyl)-1H-tetrazole, compound-3 (4-amino-2-p-tolylaminothiazol-5-yl)-(3,4,5-trimethoxyphenyl)-methanone) showed a moderate effect on the growth of HUVEC cells at concentrations below 200nM. At lower concentrations (5-20nM), in particular compound 2, they induced inhibition of capillary tube formation, inhibition of endothelial cell migration and affected endothelial cell morphology as demonstrated by the alteration of the microfilaments network. Moreover, they also increased permeability of HUVEC cells in a time dependent manner. In addition, compounds 1 and 3, as well as the reference compound CA-4, inhibited VEGF-induced phosphorylation of VE-cadherin and in addition compound 3 prevented the VEGF-induced phosphorylation of FAK. In CAM assay, both compounds 2 and 3 efficiently counteracted the strong angiogenic response induced by bFGF, even at the lowest concentration used (1pmol/egg). Moreover in a syngenic mouse model, compounds 1-3 after a single i.p. injection (30mg/kg), showed a stronger reduction of microvascular density. Altogether our results identified these derivatives as potential new vascular disrupting agents candidates. PMID:27235861

  10. Somatostatin Analogues for Receptor Targeted Photodynamic Therapy

    PubMed Central

    Kaščáková, Slávka; Hofland, Leo J.; De Bruijn, Henriette S.; Ye, Yunpeng; Achilefu, Samuel; van der Wansem, Katy; van der Ploeg-van den Heuvel, Angelique; van Koetsveld, Peter M.; Brugts, Michael P.; van der Lelij, Aart-Jan; Sterenborg, Henricus J. C. M.; ten Hagen, Timo L. M.; Robinson, Dominic J.; van Hagen, Martin P.

    2014-01-01

    Photodynamic therapy (PDT) is an established treatment modality, used mainly for anticancer therapy that relies on the interaction of photosensitizer, light and oxygen. For the treatment of pathologies in certain anatomical sites, improved targeting of the photosensitizer is necessary to prevent damage to healthy tissue. We report on a novel dual approach of targeted PDT (vascular and cellular targeting) utilizing the expression of neuropeptide somatostatin receptor (sst2) on tumor and neovascular-endothelial cells. We synthesized two conjugates containing the somatostatin analogue [Tyr3]-octreotate and Chlorin e6 (Ce6): Ce6-K3-[Tyr3]-octreotate (1) and Ce6-[Tyr3]-octreotate-K3-[Tyr3]-octreotate (2). Investigation of the uptake and photodynamic activity of conjugates in-vitro in human erythroleukemic K562 cells showed that conjugation of [Tyr3]-octreotate with Ce6 in conjugate 1 enhances uptake (by a factor 2) in cells over-expressing sst2 compared to wild-type cells. Co-treatment with excess free Octreotide abrogated the phototoxicity of conjugate 1 indicative of a specific sst2-mediated effect. In contrast conjugate 2 showed no receptor-mediated effect due to its high hydrophobicity. When compared with un-conjugated Ce6, the PDT activity of conjugate 1 was lower. However, it showed higher photostability which may compensate for its lower phototoxicity. Intra-vital fluorescence pharmacokinetic studies of conjugate 1 in rat skin-fold observation chambers transplanted with sst2+ AR42J acinar pancreas tumors showed significantly different uptake profiles compared to free Ce6. Co-treatment with free Octreotide significantly reduced conjugate uptake in tumor tissue (by a factor 4) as well as in the chamber neo-vasculature. These results show that conjugate 1 might have potential as an in-vivo sst2 targeting photosensitizer conjugate. PMID:25111655

  11. Hydrophobic surfactant proteins and their analogues.

    PubMed

    Walther, Frans J; Waring, Alan J; Sherman, Mark A; Zasadzinski, Joseph A; Gordon, Larry M

    2007-01-01

    Lung surfactant is a complex mixture of phospholipids and four surfactant-associated proteins (SP-A, SP-B, SP-C and SP-D). Its major function in the lung alveolus is to reduce surface tension at the air-water interface in the terminal airways by the formation of a surface-active film enriched in surfactant lipids, hence preventing cellular collapse during respiration. Surfactant therapy using bovine or porcine lung surfactant extracts, which contain only polar lipids and native SP-B and SP-C, has dramatically improved the therapeutic outcomes of preterm infants with respiratory distress syndrome (RDS). One important goal of surfactant researchers is to replace animal-derived therapies with fully synthetic preparations based on SP-B and SP-C, produced by recombinant technology or peptide synthesis, and reconstituted with selected synthetic lipids. Here, we review recent research developments with peptide analogues of SP-B and SP-C, designed using either the known primary sequence and three-dimensional (3D) structure of the native proteins or, alternatively, the known 3D structures of closely homologous proteins. Such SP-B and SP-C mimics offer the possibility of studying the mechanisms of action of the respective native proteins, and may allow the design of optimized surfactant formulations for specific pulmonary diseases (e.g., acute lung injury (ALI) or acute respiratory distress syndrome (ARDS)). These synthetic surfactant preparations may also be a cost-saving therapeutic approach, with better quality control than may be obtained with animal-based treatments. PMID:17575474

  12. Habitability & Astrobiology Research in Mars Terrestrial Analogues

    NASA Astrophysics Data System (ADS)

    Foing, Bernard

    2014-05-01

    We performed a series of field research campaigns (ILEWG EuroMoonMars) in the extreme Utah desert relevant to Mars environments, and in order to help in the interpretation of Mars missions measurements from orbit (MEX, MRO) or from the surface (MER, MSL), or Moon geochemistry (SMART-1, LRO). We shall give an update on the sample analysis in the context of habitability and astrobiology. Methods & Results: In the frame of ILEWG EuroMoonMars campaigns (2009 to 2013) we deployed at Mars Desert Research station, near Hanksville Utah, a suite of instruments and techniques [A, 1, 2, 9-11] including sample collection, context imaging from remote to local and microscale, drilling, spectrometers and life sensors. We analyzed how geological and geochemical evolution affected local parameters (mineralogy, organics content, environment variations) and the habitability and signature of organics and biota. Among the important findings are the diversity in the composition of soil samples even when collected in close proximity, the low abundances of detectable PAHs and amino acids and the presence of biota of all three domains of life with significant heterogeneity. An extraordinary variety of putative extremophiles was observed [3,4,9]. A dominant factor seems to be soil porosity and lower clay-sized particle content [6-8]. A protocol was developed for sterile sampling, contamination issues, and the diagnostics of biodiversity via PCR and DGGE analysis in soils and rocks samples [10, 11]. We compare the 2009 campaign results [1-9] to new measurements from 2010-2013 campaigns [10-12] relevant to: comparison between remote sensing and in-situ measurements; the study of minerals; the detection of organics and signs of life. Keywords: field analogue research, astrobiology, habitability, life detection, Earth-Moon-Mars, organics References [A] Foing, Stoker & Ehrenfreund (Editors, 2011) "Astrobiology field Research in Moon/Mars Analogue Environments", Special Issue of International

  13. Kinetic preference for the 3'-5'-linked dimer in the reaction of guanosine 5'-phosphorylmorpholinamide with deoxyguanosine 5'-phosphoryl-2-methylimidazolide as a function of poly(C) concentration

    NASA Technical Reports Server (NTRS)

    Kanavarioti, A.

    1998-01-01

    The formation of the internucleotide bond in diguanylate synthesis was studied in aqueous solution at pH 8 and 0.2 M Mg2+ in the presence and absence of polycytidylate, poly(C). The investigation was simplified by using guanosine 5'-phosphorylmorpholinamide, mor-pG, which can act only as a nucleophile, and deoxyguanosine 5'-phosphoryl-2-methylimidazolide, 2-MeImpdG, which can act only as an electrophile. The time-dependent product distribution was monitored by high-performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LC/MS). In the absence of poly(C) the reaction between mor-pG and 2-MeImpdG yielded small amounts of the dimer mor-pGpdG with a regioselectivity of 2'-5':3'-5' = 3.5. In the presence of poly(C) dimer yields increased and a reversal in regioselectivity occurred; both effects were in proportion to the concentration of the polymer. The results can be quantitatively explained with the proposition that poly(C), acting as the template, catalyzes the reaction between template-bound monomers by about a factor of 4-5 over the reaction in solution and yields dimers with a regioselectivity of 2'-5':3'-5' approximately 0.33. These findings illustrate the intrinsic preference of guanosine monomers to correctly self-assemble on the appropriate template.

  14. Incorporation of tryptophan analogues into the lantibiotic nisin.

    PubMed

    Zhou, Liang; Shao, Jinfeng; Li, Qian; van Heel, Auke J; de Vries, Marcel P; Broos, Jaap; Kuipers, Oscar P

    2016-05-01

    Lantibiotics are posttranslationally modified peptides with efficient inhibitory activity against various Gram-positive bacteria. In addition to the original modifications, incorporation of non-canonical amino acids can render new properties and functions to lantibiotics. Nisin is the most studied lantibiotic and contains no tryptophan residues. In this study, a system was constructed to incorporate tryptophan analogues into nisin, which included the modification machinery (NisBTC) and the overexpression of tryptophanyl-tRNA synthetase (TrpRS). Tryptophan and three different tryptophan analogues (5-fluoroTrp (5FW), 5-hydroxyTrp (5HW) and 5-methylTrp (5MeW)) were successfully incorporated at four different positions of nisin (I1W, I4W, M17W and V32W). The incorporation efficiency of tryptophan analogues into mutants I1W, M17W and V32W was over 97 %, while the mutant I4W showed relatively low incorporation efficiency (69-93 %). The variants with 5FW showed relatively higher production yield, while 5MeW-containing variants showed the lowest yield. The dehydration efficiency of serines or threonines was affected by the tryptophan mutants of I4W and V32W. The affinity of the peptides for the cation-ion exchange and reverse phase chromatography columns was significantly reduced when 5HW was incorporated. The antimicrobial activity of IIW and its 5FW analogue both decreased two times compared to that of nisin, while that of its 5HW analogue decreased four times. The 5FW analogue of I4W also showed two times decreased activity than nisin. However, the mutant M17W and its 5HW analogue both showed 32 times reduced activity relative to that of nisin. PMID:26872656

  15. Phosphonate analogues of carboxypeptidase A substrates are potent transition-state analogue inhibitors.

    PubMed

    Hanson, J E; Kaplan, A P; Bartlett, P A

    1989-07-25

    Analogues of tri- and tetrapeptide substrates of carboxypeptidase A in which the scissile peptide linkage is replaced with a phosphonate moiety (-PO2--O-) were synthesized and evaluated as inhibitors of the enzyme. The inhibitors terminated with either L-lactate or L-phenyllactate [designated (O) Ala and (O) Phe, respectively] in the P1' position. Transition-state analogy was shown for a series of 14 tri- and tetrapeptide derivatives containing the structure RCO-AlaP-(O)Ala [RCO-AP(O)A, AP indicates the phosphonic acid analogue of alanine] by the correlation of the Ki values for the inhibitors and the Km/kcat values for the corresponding amide substrates. This correlation supports a transition state for the enzymatic reaction that resembles the tetrahedral intermediate formed upon addition of water to the scissile carbonyl group. The inhibitors containing (O) Phe at the P1' position proved to be the most potent reversible inhibitors of carboxypeptidase A reported to date: the dissociation constants of ZAFP(O)F, ZAAP(O)F, and ZFAP(O)F are 4, 3, and 1 pM, respectively. Because of the high affinity of these inhibitors, their dissociation constants could not be determined by steady-state methods. Instead, the course of the association and dissociation processes was monitored for each inhibitor as its equilibrium with the enzyme was established in both the forward and reverse directions. A phosphonamidate analogue, ZAAPF, in which the peptide linkage is replaced with a -PO2-NH- moiety, was prepared and shown to hydrolyze rapidly at neutral pH (t1/2 = 20 min at pH 7.5). This inhibitor is bound an order of magnitude less tightly than the corresponding phosphonate, ZAAP(O)F, a result that contrasts with the 840-fold higher affinity of phosphonamidates for thermolysin [Bartlett, P. A., & Marlowe, C. K. (1987) Science 235, 569-571], a zinc peptidase with a similar arrangement of active-site catalytic residues. PMID:2790000

  16. Spectral analysis of lunar analogue samples

    NASA Astrophysics Data System (ADS)

    Offringa, Marloes; Foing, Bernard

    2016-04-01

    Analyses of samples derived from terrestrial analogue sites are used to study lunar processes in their geological context (Foing, Stoker, Ehrenfreund, 2011). For this study samples from the volcanic region of the Eifel, Germany collected during field campaigns (Foing et al., 2010), are analyzed with a variety of spectrometers. The aim is to obtain a database of analyzed samples that could be used as a reference for future in situ measurements. Equipment used in the laboratory consists of a Fourier Transform Infrared (FTIR) spectrometer, an X-Ray Fluorescence (XRF) spectrometer, a Raman laser spectrometer, as well as UV-VIS and NIR reflectance spectrometers. The Raman, UV-VIS and NIR are also used in combination with the EXoGeoLab mock-up lander during field campaigns (Foing, Stoker, Ehrenfreund, 2011). Calibration of the UV-VIS and NIR reflectance spectrometers is the main focus of this research in order to obtain the clearest spectra. The calibration of the UV-VIS and NIR reflectance spectrometers requires the use of a good light source as well as suitable optical fibers to create a signal that covers the widest range in wavelengths available. To eliminate noise towards the edges of this range, multiple measurements are averaged and data is processed by dividing the signal by reference spectra. Calibration of the devices by creating a new dark and reference spectra has to take place after every sample measurement. In this way we take into account changes that occur in the signal due to the eating of the devices during the measurements. Moreover, the integration time is adjusted to obtain a clear signal without leading to oversaturation in the reflectance spectrum. The typical integration times for the UV-VIS reflectance spectrometer vary between 1 - 18 s, depending on the amount of daylight during experiments. For the NIR reflectance spectrometer the integration time resulting in the best signals is approximately 150 ms in combination with a broad spectrum light

  17. Iron isotopes in an Archean ocean analogue

    NASA Astrophysics Data System (ADS)

    Busigny, Vincent; Planavsky, Noah J.; Jézéquel, Didier; Crowe, Sean; Louvat, Pascale; Moureau, Julien; Viollier, Eric; Lyons, Timothy W.

    2014-05-01

    Iron isotopes have been extensively used to trace the history of microbial metabolisms and the redox evolution of the oceans. Archean sedimentary rocks display greater variability in iron isotope ratios and more markedly negative values than those deposited in the Proterozoic and Phanerozoic. This increased variability has been linked to changes in either water column iron cycling or the extent of benthic microbial iron reduction through time. We tested these contrasting scenarios through a detailed study of anoxic and ferruginous Lac Pavin (France), which can serve as a modern analogue of the Archean ocean. A depth-profile in the water column of Lac Pavin shows a remarkable increase in dissolved Fe concentration (0.1-1200 μM) and δ56Fe values (-2.14‰ to +0.31‰) across the oxic-anoxic boundary to the lake bottom. The largest Fe isotope variability is found at the redox boundary and is related to partial oxidation of dissolved ferrous iron, leaving the residual Fe enriched in light isotopes. The analysis of four sediment cores collected along a lateral profile (one in the oxic layer, one at the redox boundary, one in the anoxic zone, and one at the bottom of the lake) indicates that bulk sediments, porewaters, and reactive Fe mostly have δ56Fe values near 0.0 ± 0.2‰, similar to detrital iron. In contrast, pyrite δ56Fe values in sub-chemocline cores (60, 65, and 92 m) are highly variable and show significant deviations from the detrital iron isotope composition (δ56Fepyrite between -1.51‰ and +0.09‰; average -0.93‰). Importantly, the pyrite δ56Fe values mirror the δ56Fe of dissolved iron at the redox boundary—where near quantitative sulfate and sulfide drawdown occurs—suggesting limited iron isotope fractionation during iron sulfide formation. This finding has important implications for the Archean environment. Specifically, this work suggests that in a ferruginous system, most of the Fe isotope variability observed in sedimentary pyrites can

  18. Terrestrial research in Mars analogue environments

    NASA Astrophysics Data System (ADS)

    Osipov, G.

    Fatty acids (FA) content was measured by GC-MS SIM technique in Sulfide ores of present day (Mid-Atlantic Ridge and others) and ancient (Ural Paleocene, Russia) black smokers; Early Proterozoic kerites of Volyn; Siberian, Canadian and Antarctic permafrosts and also in rocks of East-European platform Achaean crystalline basement. Analysis was shown presence those and only those fatty acids which are specific to microorganisms. FA with 12 up 19 of carbon atoms are thought to be a bacterial biomass sign. 3-Hydroxy fatty acids also found in samples and are strong specific markers of gram-negative bacteria. Cultivation yield living bacteria in some cases. The East-European platform Achaean crystalline basement rocks opened by Vorotilov Deep Well (VDW) drilled through Puchezh-Katunski impact structure were studied within depths 2575 - 2805 m. 34 microbial lipid markers were detected by GC-MS and 22 species were identified. Bacteria of g. Bacillus reached 6,8 % in subsurface communities. However, members of gg. Clostridium (37,1 - 33,2 %) and Rhodococcus (27,6 - 33,7 %) were absolute dominants within studied depth interval. Some lipid patterns of kerite samples could be assessed to definite genera or, in special cases, to species of contemporary microorganisms. For instance, 2-hydroxylauric acid is specific to Pseudomonas putida group or Acinetobacter spp., and hydroxymyristic together with hydroxypalmitic are specific to P.cepacea and cyanobacteria. 3-hydroxystearic acid was known as component of Acetobacter diazothrophycus and Gloebacter violaceous cyanobacterium. 10-hydroxystearic acid associated with Nocardia spp., which oxidizes oleic acid in organic substrates. 10-methylhexadecanoic (10Me16) acid together with 10Me14, 10Me15 and 10Me17 analogues are markers of actinomycetes. Significant part of Black Smokers organic matter is probably biogenic. Fatty acid features strongly assigns it to bacterial, microeucariotic and planta cells. Par example 3-hydroxy acids are

  19. Review of insulin and its analogues in diabetes mellitus.

    PubMed

    Mane, Krishnappa; Chaluvaraju, Kc; Niranjan, Ms; Zaranappa, Tr; Manjuthej, Tr

    2012-03-01

    Diabetes is a metabolic disorder where in human body does not produce or properly uses insulin, a hormone that is required to convert sugar, starches and other food into energy. Diabetes finally leads to more complications and to prevent these complications insulin and its analogues are used. After more than half a century of treating diabetics with animal insulin's, recombinant DNA technologies and advanced protein chemistry made human insulin preparations available in the early 1980s. As the next step, over the last decade, insulin analogues were constructed by changing the structure of the native protein with the goal of improving the therapeutic properties of it, because the pharmacokinetic characteristics of rapid, intermediate and long-acting preparations of human insulin make it almost impossible to achieve sustained normoglycemia. The first clinically available insulin analogue, lispro, confirmed the hopes by showing that improved glycaemic control can be achieved without an increase in hypoglycaemic events. Two new insulin analogues, insulin glargine and insulin aspart, have recently been approved for clinical use in the United States and several other analogues are being intensively tested. PMID:24826038

  20. Synthesis and cytotoxic activities of semisynthetic zearalenone analogues.

    PubMed

    Tadpetch, Kwanruthai; Kaewmee, Benyapa; Chantakaew, Kittisak; Kantee, Kawalee; Rukachaisirikul, Vatcharin; Phongpaichit, Souwalak

    2016-08-01

    Zearalenone is a β-resorcylic acid macrolide with various biological activities. Herein we report the synthesis and cytotoxic activities of 34 zearalenone analogues against human oral epidermoid carcinoma (KB) and human breast adenocarcinoma (MCF-7) cells as well as noncancerous Vero cells. Some zearalenone analogues showed moderately enhanced cytotoxic activities against the two cancer cell lines. We have discovered the potential lead compounds with diminished or no cytotoxicity to Vero cells. Preliminary structure-activity relationship studies revealed that the double bond at the 1' and 2' positions of zearalenone core was crucial for cytotoxic activities on both cell lines. In addition, for zearalenol analogues, the unprotected hydroxyl group at C-2 and an alkoxy substituent at C-4 played key roles on cytotoxic effects of both cell lines. PMID:27311894

  1. Synthesis and Biological Evaluation of New (-)-Englerin Analogues.

    PubMed

    López-Suárez, Laura; Riesgo, Lorena; Bravo, Fernando; Ransom, Tanya T; Beutler, John A; Echavarren, Antonio M

    2016-05-01

    We report the synthesis and biological evaluation of a series of (-)-englerin A analogues obtained along our previously reported synthetic route based on a stereoselective gold(I) cycloaddition process. This synthetic route is a convenient platform to access analogues with broad structural diversity and has led us to the discovery of unprecedented and easier-to-synthesize derivatives with an unsaturation in the cyclopentyl ring between C4 and C5. We also introduce novel analogues in which the original isopropyl motif has been substituted with cyclohexyl, phenyl, and cyclopropyl moieties. The high selectivity and growth-inhibitory activity shown by these new derivatives in renal cancer cell lines opens new ways toward the final goal of finding effective drugs for the treatment of renal cell carcinoma (RCC). PMID:27005578

  2. Migrastatin analogues target fascin to block tumour metastasis

    SciTech Connect

    Chen, L.; Jakoncic, J.; Yang, S.; Zhang, J.; Huang, X.Y.

    2010-04-15

    Tumour metastasis is the primary cause of death of cancer patients. Development of new therapeutics preventing tumour metastasis is urgently needed. Migrastatin is a natural product secreted by Streptomyces, and synthesized migrastatin analogues such as macroketone are potent inhibitors of metastatic tumour cell migration, invasion and metastasis. Here we show that these migrastatin analogues target the actin-bundling protein fascin to inhibit its activity. X-ray crystal structural studies reveal that migrastatin analogues bind to one of the actin-binding sites on fascin. Our data demonstrate that actin cytoskeletal proteins such as fascin can be explored as new molecular targets for cancer treatment, in a similar manner to the microtubule protein tubulin.

  3. Membrane-permeable Triphosphate Prodrugs of Nucleoside Analogues.

    PubMed

    Gollnest, Tristan; Dinis de Oliveira, Thiago; Rath, Anna; Hauber, Ilona; Schols, Dominique; Balzarini, Jan; Meier, Chris

    2016-04-18

    The metabolic conversion of nucleoside analogues into their triphosphates often proceeds insufficiently. Rate-limitations can be at the mono-, but also at the di- and triphosphorylation steps. We developed a nucleoside triphosphate (NTP) delivery system (TriPPPro-approach). In this approach, NTPs are masked by two bioreversible units at the γ-phosphate. Using a procedure involving H-phosphonate chemistry, a series of derivatives bearing approved, as well as potentially antivirally active, nucleoside analogues was synthesized. The enzyme-triggered delivery of NTPs was demonstrated by pig liver esterase, in human T-lymphocyte cell extracts and by a polymerase chain reaction using a prodrug of thymidine triphosphate. The TriPPPro-compounds of some HIV-inactive nucleoside analogues showed marked anti-HIV activity. For cellular uptake studies, a fluorescent TriPPPro-compound was prepared that delivered the triphosphorylated metabolite to intact CEM cells. PMID:27008042

  4. The metabolic and mitogenic properties of basal insulin analogues

    PubMed Central

    2013-01-01

    Context Retrospective, observational studies have reported an association between diabetes treatment with insulin and a higher incidence of cancer. Objective Overview the literature for in vitro and in vivo studies of the metabolic and mitogenic properties of basal insulin analogues and assess the implications for clinical use. Methods Relevant studies were identified through PubMed and congress abstract database searches; data on metabolic and mitogenic signalling in relation to insulin treatment of diabetes are included in this review. Results The balance of evidence shows that although some analogues have demonstrated mitogenic potency in some in vitro studies in cancer cell lines, these findings do not translate to the in vivo setting in animals or to the clinical setting in humans. Conclusions The current consensus is that there is no clinical or in vivo evidence to indicate that any commercially available insulin analogue has carcinogenic effects. Large-scale, prospective clinical and observational studies will further establish any potential link. PMID:23373726

  5. Analogue modelling of syntectonic leucosomes in migmatitic schists

    NASA Astrophysics Data System (ADS)

    Druguet, Elena; Carreras, Jordi

    2006-10-01

    Migmatites from the Cap de Creus tectonometamorphic belt display a wide variety of structures, from those formed when the leucosomes were melt-bearing, to those developed during solid-state deformation. The observed field structures have been modelled by means of analogue experiments. The materials used in the models are layered plasticine as a schist analogue, and chocolate as analogue of the crystallizing leucosome. A model for the development of syntectonic migmatites is proposed in which initial melt-bearing patches, preferentially formed within fertile pelitic layers, progressively evolve towards lens-shaped veins. Furthermore, heterogeneous deformation of anisotropic metasediments facilitates formation of extensional sites for further melt accumulation and transport. Melt crystallization implies a rapid increase in effective viscosity of leucosomes producing a reversal in competence contrast with respect to the enclosing schists. During the whole process, deformation localizes around crystallizing veins, giving rise to different and contrasting structures for melt-bearing and for solid-state stages.

  6. Nicorandil analogues containing NO-donor furoxans and related furazans.

    PubMed

    Boschi, D; Cena, C; Di Stilo, A; Fruttero, R; Gasco, A

    2000-07-01

    The synthesis and in vitro vasodilating properties of hybrid compounds in which furoxan (1,2,5-oxadiazole 2-oxide) moieties, endowed with different NO-donor properties, were substituted for the nitroxy function of Nicorandil are reported. The corresponding cyanoguanidine analogues are also considered. This approach has led to a series of vasorelaxing compounds devoid of affinity for K(ATP) channels, whose activity is prevalently due to their ability to activate sGC, at the concentrations of the experiments. Related furazan (1,2,5-oxadiazole) derivatives, unable to release nitric oxide were also prepared and studied for control. The amide analogues of Nicorandil display feeble vasorelaxing action not involving the activation of K+ channels, while in the guanidine analogues, this mechanism seems to underlie this action. PMID:10976520

  7. Analogue peptides for the immunotherapy of human acute myeloid leukemia.

    PubMed

    Hofmann, Susanne; Mead, Andrew; Malinovskis, Aleksandrs; Hardwick, Nicola R; Guinn, Barbara-Ann

    2015-11-01

    The use of peptide vaccines, enhanced by adjuvants, has shown some efficacy in clinical trials. However, responses are often short-lived and rarely induce notable memory responses. The reason is that self-antigens have already been presented to the immune system as the tumor develops, leading to tolerance or some degree of host tumor cell destruction. To try to break tolerance against self-antigens, one of the methods employed has been to modify peptides at the anchor residues to enhance their ability to bind major histocompatibility complex molecules, extending their exposure to the T-cell receptor. These modified or analogue peptides have been investigated as stimulators of the immune system in patients with different cancers with variable but sometimes notable success. In this review we describe the background and recent developments in the use of analogue peptides for the immunotherapy of acute myeloid leukemia describing knowledge useful for the application of analogue peptide treatments for other malignancies. PMID:26438084

  8. Relative benefits of linear analogue and advanced digital hearing aids.

    PubMed

    Wood, Sally A; Lutman, Mark E

    2004-03-01

    Speech recognition performance and self-reported benefit from linear analogue and advanced (digital) hearing aids were compared in 100 first-time hearing aid users with mild-to-moderate sensorineural hearing loss fitted monaurally with a behind-the-ear (BTE) hearing aid in a single-blind randomized crossover trial. Subjects used each aid for 5 weeks in turn, with aid order balanced across subjects. Three alternative models of digital hearing aid were assigned to subjects according to a balanced design. Aid type was disguised to keep subjects blind within practical limitations. Aided speech recognition performance in noise was measured at speech levels of 65 and 75dB at a speech-to-noise ratio (SNR) of +2dB for closed sets of single words. Self-rated benefit was measured using the Abbreviated Profile of Hearing Aid Benefit (APHAB) and the Glasgow Hearing Aid Benefit Profile (GHABP). Quality of life, hearing aid use and user preferences were also assessed. Speech recognition scores with the digital aids were significantly better at 75dB than with the analogue aids Self-reported benefit (APHAB, GHABP) and improvement in quality of life were generally not significantly different between analogue and digital aids, although aversiveness measured with the APHAB was significantly lower with digital aids, and satisfaction measured with the GHABP was greater. The digital aids were preferred significantly more often than the analogue aids, with 61 subjects choosing their digital aid, 26 choosing the analogue aid, and nine being equivocal. Overall, this study shows advantages for advanced digital over simple linear analogue aids in terms of both objective and subjective outcomes, although average differences are not large. PMID:15198378

  9. The Object-analogue approach for probabilistic forecasting

    NASA Astrophysics Data System (ADS)

    Frediani, M. E.; Hopson, T. M.; Anagnostou, E. N.; Hacker, J.

    2015-12-01

    The object-analogue is a new method to estimate forecast uncertainty and to derive probabilistic predictions of gridded forecast fields over larger regions rather than point locations. The method has been developed for improving the forecast of 10-meter wind speed over the northeast US, and it can be extended to other forecast variables, vertical levels, and other regions. The object-analogue approach combines the analog post-processing technique (Hopson 2005; Hamill 2006; Delle Monache 2011) with the Method for Object-based Diagnostic Evaluation (MODE) for forecast verification (Davis et al 2006a, b). Originally, MODE is used to verify mainly precipitation forecasts using features of a forecast region represented by an object. The analog technique is used to reduce the NWP systematic and random errors of a gridded forecast field. In this study we use MODE-derived objects to characterize the wind fields forecasts into attributes such as object area, centroid location, and intensity percentiles, and apply the analogue concept to these objects. The object-analogue method uses a database of objects derived from reforecasts and their respective reanalysis. Given a real-time forecast field, it searches the database and selects the top-ranked objects with the most similar set of attributes using the MODE fuzzy logic algorithm for object matching. The attribute probabilities obtained with the set of selected object-analogues are used to derive a multi-layer probabilistic prediction. The attribute probabilities are combined into three uncertainty layers that address the main concerns of most applications: location, area, and magnitude. The multi-layer uncertainty can be weighted and combined or used independently in such that it provides a more accurate prediction, adjusted according to the application interest. In this study we present preliminary results of the object-analogue method. Using a database with one hundred storms we perform a leave-one-out cross-validation to

  10. Tumor imaging and therapy using radiolabeled somatostatin analogues.

    PubMed

    de Jong, Marion; Breeman, Wout A P; Kwekkeboom, Dik J; Valkema, Roelf; Krenning, Eric P

    2009-07-21

    Molecular imaging plays an essential role in balancing the clinical benefits and risks of radionuclide-based cancer therapy. To effectively treat individual patients, careful assessment of biodistribution, dosimetry, and toxicity is essential. In this Account, we describe advances that combine features of molecular imaging and radionuclide therapy to provide new avenues toward individualized cancer treatment. Selective receptor-targeting radiopeptides have emerged as an important class of radiopharmaceuticals for molecular imaging and therapy of tumors that overexpress peptide receptors on the cell membrane. After such peptides labeled with gamma-emitting radionuclides bind to their receptors, they allow clinicians to visualize receptor-expressing tumors non-invasively. Peptides labeled with beta-particle emitters could also eradicate receptor-expressing tumors. The somatostatin receptors, which are overexpressed in a majority of neuroendocrine tumors, represent the first and best example of targets for radiopeptide-based imaging and radionuclide therapy. The somatostatin analogue (111)In-octreotide permits the localization and staging of neuroendocrine tumors that express the appropriate somatostatin receptors. Newer modified somatostatin analogues, including Tyr(3)-octreotide and Tyr(3)-octreotate, are successfully being used for tumor imaging and radionuclide therapy. Because there are few effective therapies for patients with inoperable or metastasized neuroendocrine tumors, this therapy is a promising novel treatment option for these patients. Peptide receptor imaging and radionuclide therapy can be combined in a single probe, called a "theranostic". To select patients who are likely to benefit from this type of intervention, we first use a peptide analogue labeled with a diagnostic radionuclide to obtain a scan. Selected patients will be treated using the same or a similar peptide analogue labeled with a therapeutic radionuclide. The development of such