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1

Quantum-mechanical analysis of the structure of phosphoric acid complexes with methyl methacrylate and methyl trimethylacetate  

NASA Astrophysics Data System (ADS)

The structures of such model fragments of poly(methyl methacrylate) as methyl methacrylate and methyl trimethylacetate, and of its complexes with phosphoric acid, are optimized by means of density functional theory using the B3LYP hybrid functional in combination with the 6-31++G** basis set. The effect of dimethylformamide on methyl trimethylacetate complexes with phosphoric acid is considered, and the possibility of proton transfer is studied.

Krestyaninov, M. A.; Kiselev, M. G.; Safonova, L. P.

2013-12-01

2

Polymerization of amino acid methyl esters via their copper complexes  

Microsoft Academic Search

Polymerization of glycine methyl ester catalyzed by cupric ions in organic solvents yields oligoglycines with a degree of polymerization up to nine. With a trifunctional amino acid, the yeild and degree of polymerization were much lower. Extension of this reaction to an aqueous medium was not successful even when copper ions were complexed with substances like montmorillonite or fatty acids.

A. Brack; D. Louembe; G. Spach

1975-01-01

3

The platinum hydrido-methyl complex: A frozen reaction intermediate?  

SciTech Connect

Methane activation by transition metals has been a topic of growing interest during the past decade, due to economic interest in methane conversion and chemistry. Reactions of platinum-argon complexes Pt{sup +}Ar{sub m}, m = 1--6, with methane (CH{sub 4}) and methane-d{sub 4} (CD{sub 4}) were investigated by means of FT-ICR mass spectrometry and DFT calculations. Ligand exchange reactions are observed for Pt{sup +}Ar{sub m}, m = 2--6, in which up to four argon ligands are replaced by methane. In contrast, the bare platinum ion and platinum solvated with one argon ligand lead to the formation of a platinum-carbene complex. Gibbs free enthalpies from ligand exchange reactions of Pt{sup +}CH{sub 4} with CD{sub 4} and H{sub 2}O provide evidence for the inserted hydrido-methyl complex HPt{sup +}CH{sub 4} with CD{sub 4} (and the reverse reaction). This is attributed to the inability of the platinum cation to form more than three covalent bonds.

Achatz, U.; Beyer, M.; Joos, S.; Fox, B.S.; Niedner-Schatteburg, G.; Bondybey, V.E.

1999-10-14

4

Copper(II) complexes of imino-bis(methyl phosphonic acid) with some bio-relevant ligands. Equilibrium studies and hydrolysis of glycine methyl ester through complex formation  

Microsoft Academic Search

Binary and ternary complexes of Cu(II) involving imino-bis(methyl phosphonic acid) (IdP) abbreviated as H4A and some selected bio-ligands, amino acids, peptides and DNA constituents (L), were examined. Cu(II) forms CuA and CuAH complexes with IdP. Ternary complexes are formed in a stepwise mechanism whereby iminodiphosphonic acid binds to Cu(II), followed by coordination of amino acid, peptide or DNA. The concentration

Ahmed A. El-Sherif; Mohamed M. Shoukry

2005-01-01

5

Photoreactive inclusion complex of aryliodonium salt encapsulated by methylated-?-cyclodextrin  

Microsoft Academic Search

A novel photoreactive inclusion complex (PIC) with an excellent water solubility was obtained by the complexation of methylated-?-cyclodextrin (Me-?-CD) with the hydrophobic 4,4?-dimethyl diphenyliodonium salt (DMDPI). The photoreactivity of the complex PIC was examined by the kinetic studies in order to evaluate the influence of Me-?-CD complexation. The photoreactive rate was enhanced in the photolysis of PIC compared with the

Shujing Li; Feipeng Wu; Erjian Wang; Lidong Li

2008-01-01

6

CpG Methylation of DNA Restricts Prereplication Complex Assembly in Xenopus Egg Extracts  

Microsoft Academic Search

In a Xenopus egg replication system, the origin recognition complex (ORC) does not bind to CpG methylated DNA and DNA replication is inhibited. Insertion of low density CpG DNA of at least 1.2 kb into methylated plasmids rescues both replication and ORC binding. Using this pseudo-origin, we find that ORC binding is restricted to low-CpG-density DNA; however, MCM is loaded

Kevin J. Harvey; John Newport

2003-01-01

7

Mi2 complex couples DNA methylation to chromatin remodelling and histone deacetylation  

Microsoft Academic Search

Methylation of DNA at the dinucleotide CpG is essential for mammalian development and is correlated with stable transcriptional silencing. This transcriptional silencing has recently been linked at a molecular level to histone deacetylation through the demonstration of a physical association between histone deacetylases and the methyl CpG-binding protein MeCP2 (refs 4,5). We previously purified a histone deacetylase complex from Xenopus

Paul A. Wade; Anne Gegonne; Peter L. Jones; Esteban Ballestar; Florence Aubry; Alan P. Wolffe

1999-01-01

8

Different Ezh2-Containing Complexes Target Methylation of Histone H1 or Nucleosomal Histone H3  

Microsoft Academic Search

Human Enhancer of Zeste homolog (Ezh2) is a histone lysine methyltransferase (HKMT) associated with transcriptional repression. Ezh2 is present in several distinct complexes, one of which, PRC2, we characterized previously. Here we report an additional Ezh2 complex, PRC3. We show that the Ezh2 complexes exhibit differential targeting of specific histones for lysine methylation dependent upon the context of the histone

Andrei Kuzmichev; Thomas Jenuwein; Paul Tempst; Danny Reinberg

2004-01-01

9

SMYD2-dependent HSP90 methylation promotes cancer cell proliferation by regulating the chaperone complex formation.  

PubMed

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that facilitates the maturation of a wide range of proteins, and it has been recognized as a crucial facilitator of oncogene addiction and cancer cell survival. Although HSP90 function is regulated by a variety of post-translational modifications, the physiological significance of methylation has not fully been elucidated. Here we demonstrate that HSP90AB1 is methylated by the histone methyltransferase SMYD2 and that it plays a critical role in human carcinogenesis. HSP90AB1 and SMYD2 can interact through the C-terminal region of HSP90AB1 and the SET domain of SMYD2. Both in vitro and in vivo methyltransferase assays revealed that SMYD2 could methylate HSP90AB1 and mass spectrometry analysis indicated lysines 531 and 574 of HSP90AB1 to be methylated. These methylation sites were shown to be important for the dimerization and chaperone complex formation of HSP90AB1. Furthermore, methylated HSP90AB1 accelerated the proliferation of cancer cells. Our study reveals a novel mechanism for human carcinogenesis via methylation of HSP90AB1 by SMYD2, and additional functional studies may assist in developing novel strategies for cancer therapy. PMID:24880080

Hamamoto, Ryuji; Toyokawa, Gouji; Nakakido, Makoto; Ueda, Koji; Nakamura, Yusuke

2014-08-28

10

INVOLVED IN DE NOVO 2-containing complex involved in RNA-directed DNA methylation in Arabidopsis  

SciTech Connect

At least three pathways control maintenance of DNA cytosine methylation in Arabidopsis thaliana. However, the RNA-directed DNA methylation (RdDM) pathway is solely responsible for establishment of this silencing mark. We previously described INVOLVED IN DE NOVO 2 (IDN2) as being an RNA-binding RdDM component that is required for DNA methylation establishment. In this study, we describe the discovery of two partially redundant proteins that are paralogous to IDN2 and that form a stable complex with IDN2 in vivo. Null mutations in both genes, termed IDN2-LIKE 1 and IDN2-LIKE 2 (IDNL1 and IDNL2), result in a phenotype that mirrors, but does not further enhance, the idn2 mutant phenotype. Genetic analysis suggests that this complex acts in a step in the downstream portion of the RdDM pathway. We also have performed structural analysis showing that the IDN2 XS domain adopts an RNA recognition motif (RRM) fold. Finally, genome-wide DNA methylation and expression analysis confirms the placement of the IDN proteins in an RdDM pathway that affects DNA methylation and transcriptional control at many sites in the genome. Results from this study identify and describe two unique components of the RdDM machinery, adding to our understanding of DNA methylation control in the Arabidopsis genome.

Ausin, Israel; Greenberg, Maxim V.C.; Simanshu, Dhirendra K.; Hale, Christopher J.; Vashisht, Ajay A.; Simon, Stacey A.; Lee, Tzuu-fen; Feng, Suhua; Española, Sophia D.; Meyers, Blake C.; Wohlschlegel, James A.; Patel, Dinshaw J.; Jacobsen, Steven E. (UCLA); (MSKCC); (Delaware)

2012-10-23

11

Kinetics of DNA methylation inheritance by the Dnmt1-including complexes during the cell cycle  

PubMed Central

Background The clonal transmission of lineage-specific DNA methylation patterns in a mammalian genome during the cellular division is a crucial biological process controlled by the DNA methyltransferase Dnmt1, mainly. To investigate possible dynamic mechanisms of DNA methylation inheritance during the cell cycle, we used a Proximity Ligation In Situ Assay (P-LISA) to analyze the kinetic of formation and DNA recruitment of Dnmt1-including complexes. Results P-LISA, sequential chromatin immunoprecipitation and quantitative methylation specific PCR revealed that the Dnmt1/PCNA/UHRF1-including complexes are mainly formed and recruited on DNA during the S-phase of cell cycle, while the formation and the DNA recruitment of several Dnmt1/transcription factors-including complexes are not S-phase dependent but are G0/G1 and/or G2/M phases dependent. Conclusion Our data confirm that DNA methylation inheritance occurs in S-phase, and demonstrate that DNA methylation inheritance can also occur in G0/G1 and G2/M phases of the cell cycle.

2012-01-01

12

Characterization of hydrophilic poly(methyl methacrylate)s containing iminodiacetic acid and their complexes  

Microsoft Academic Search

Copolymers (PMGI) containing iminodiacetic acid were obtained from copolymerization of methyl methacrylate and a chelating monomer, glycidyl methacrylate–iminodiacetic acid (GMA–IDA), with potassium persulfate as an initiator. Cu(II)–PMGI complexes were prepared by mixing PMGI and copper sulfate solution. The PMGI copolymers and Cu(II)–PMGI complexes were characterized by differential scanning calorimetry, infrared and 13C solid-state nuclear magnetic resonance spectroscopy. The glass transition

T. C. Chang; C. C. Shih; C. P. Yin; H. B. Chen; T. R. Wu

2005-01-01

13

Signaling within a Coactivator Complex: Methylation of SRC-3/AIB1 Is a Molecular Switch for Complex Disassembly?  

PubMed Central

Recent studies indicate that steroid receptor-mediated transcriptional initiation is a cyclical process involving multiple rounds of coactivator assembly and disassembly. Steroid receptor coactivator 3 (SRC-3) coactivator phosphorylation has been shown to regulate coactivator complex assembly, but the mechanisms by which coactivator disassembly is triggered are not well understood. In this study, we provide in vitro and in vivo evidence that members of the SRC coactivator family serve as substrates for the enzymatic coactivator coactivator-associated arginine methyltransferase 1 (CARM1). Methylation of SRC-3 was localized to an arginine in its CARM1 binding region and correlated with decreased estrogen receptor alpha-mediated transcription, as seen with both cell-based and in vitro transcription assays. Consistent with this finding, we demonstrated that methylation promotes dissociation of the SRC-3/CARM1 coactivator complex. Methylation of SRC-3 is regulated by estrogen signaling in MCF7 cells and serves as a molecular switch for disassembly of the SRC-3 transcriptional coactivator complex. We propose that CARM1 is a dual-function coactivator, as it not only activates transcription by modifying core histone tails but also terminates hormone signaling by disassembly of the coactivator complex.

Feng, Qin; Yi, Ping; Wong, Jiemin; O'Malley, Bert W.

2006-01-01

14

Methyl groups as probes for proteins and complexes in in-cell NMR experiments.  

PubMed

Studying protein components of large intracellular complexes by in-cell NMR has so far been impossible because the backbone resonances are unobservable due to their slow tumbling rates. We describe a methodology that overcomes this difficulty through selective labeling of methyl groups, which possess more favorable relaxation behavior. Comparison of different in-cell labeling schemes with three different proteins, calmodulin, NmerA, and FKBP, shows that selective labeling with [(13)C]methyl groups on methionine and alanine provides excellent sensitivity with low background levels at very low costs. PMID:15174883

Serber, Zach; Straub, Wesley; Corsini, Lorenzo; Nomura, Anson M; Shimba, Nobuhisa; Craik, Charles S; Ortiz de Montellano, Paul; Dötsch, Volker

2004-06-01

15

CCR4/NOT complex associates with the proteasome and regulates histone methylation  

PubMed Central

The proteasome regulates histone lysine methylation and gene transcription, but how it does so is poorly understood. To better understand this process, we used the epistatic miniarray profile (E-MAP) approach to identify factors that genetically interact with proteasomal subunits. In addition to members of the Set1 complex that mediate histone H3 lysine 4 methylation (H3K4me), we found that deleting members of the CCR4/NOT mRNA processing complex exhibit synthetic phenotypes when combined with proteasome mutants. Further biochemical analyses revealed physical associations between CCR4/NOT and the proteasome in vivo. Consistent with the genetic and biochemical interactions linking CCR4/NOT with proteasome and Set1-mediated methylation, we find that loss of Not4 decreases global and gene-specific H3K4 trimethylation (H3K4me3) and decreases 19S proteasome recruitment to the PMA1 gene. Similar to proteasome regulation of histone methylation, loss of CCR4/NOT members does not affect ubiquitinated H2B. Mapping of Not4 identified the RING finger domain as essential for H3K4me3, suggesting a role for ubiquitin in this process. Consistent with this idea, loss of the Not4-interacting protein Ubc4, a known ubiquitin-conjugating enzyme, decreases H3K4me3. These studies implicate CCR4/NOT in the regulation of H3K4me3 through a ubiquitin-dependent pathway that likely involves the proteasome.

Laribee, R. Nicholas; Shibata, Yoichiro; Mersman, Douglas P.; Collins, Sean R.; Kemmeren, Patrick; Roguev, Assen; Weissman, Jonathan S.; Briggs, Scott D.; Krogan, Nevan J.; Strahl, Brian D.

2007-01-01

16

CCR4/NOT complex associates with the proteasome and regulates histone methylation.  

PubMed

The proteasome regulates histone lysine methylation and gene transcription, but how it does so is poorly understood. To better understand this process, we used the epistatic miniarray profile (E-MAP) approach to identify factors that genetically interact with proteasomal subunits. In addition to members of the Set1 complex that mediate histone H3 lysine 4 methylation (H3K4me), we found that deleting members of the CCR4/NOT mRNA processing complex exhibit synthetic phenotypes when combined with proteasome mutants. Further biochemical analyses revealed physical associations between CCR4/NOT and the proteasome in vivo. Consistent with the genetic and biochemical interactions linking CCR4/NOT with proteasome and Set1-mediated methylation, we find that loss of Not4 decreases global and gene-specific H3K4 trimethylation (H3K4me3) and decreases 19S proteasome recruitment to the PMA1 gene. Similar to proteasome regulation of histone methylation, loss of CCR4/NOT members does not affect ubiquitinated H2B. Mapping of Not4 identified the RING finger domain as essential for H3K4me3, suggesting a role for ubiquitin in this process. Consistent with this idea, loss of the Not4-interacting protein Ubc4, a known ubiquitin-conjugating enzyme, decreases H3K4me3. These studies implicate CCR4/NOT in the regulation of H3K4me3 through a ubiquitin-dependent pathway that likely involves the proteasome. PMID:17389396

Laribee, R Nicholas; Shibata, Yoichiro; Mersman, Douglas P; Collins, Sean R; Kemmeren, Patrick; Roguev, Assen; Weissman, Jonathan S; Briggs, Scott D; Krogan, Nevan J; Strahl, Brian D

2007-04-01

17

On the complexation of quercetin with methyl-?-cyclodextrin: photostability and antioxidant studies  

Microsoft Academic Search

Quercetin, a plant-derived flavonoid, has been extensively investigated for a wide range of potential health benefits linked\\u000a to its antioxidant properties. Unfortunately the topical administration of this molecule is restricted by its fast photodegradation.\\u000a In the attempt to overcome this limitation the inclusion complex between quercetin (Q) and methyl-?-cyclodextrin (Me-?-CD)\\u000a was prepared and previously investigated by a molecular modelling study,

M. E. Carlotti; S. Sapino; E. Ugazio; G. Caron

2011-01-01

18

Preparation, crystal structure and thermal stability of porous lanthanide complexes with 5-methyl isophthalic acid  

Microsoft Academic Search

Three lanthanide complexes 1–3 with 5-methyl isophthalic acid (5-CH3-H2bdc) were prepared under hydrothermal conditions, two have formula Eu2(5-CH3-bdc)3(EtOH) (2) and [Er(5-CH3-bdc)1.5] · (H2O) (3) and were characterized by X-ray single crystal diffraction. In 2, there are two europium(III) ions in seven-coordinate pentagonal bipyramid and eight-coordinate bicapped trigonal prism geometries. Complex 2 is a 3-D porous structure with 1-D channels (potential

Qiufeng An; Yixia Ren; Sanping Chen; Shengli Gao

2008-01-01

19

Nickel, copper and zinc complexes of (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl)-acetic acid  

Microsoft Academic Search

An ester of an imine containing dicarboxylic acid (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl)-acetic acid methyl ester was prepared by the reaction of methylbromoacetate with 5-methyl-thiazol-2-ylamine. Base hydrolysis of this ester with sodium hydroxide gives the corresponding disodium salt of the diacid. The disodium salt of (2-methoxycarbonylmethylimino-5-methyl-thiazol-3-yl)-acetic acid (Na2L) forms a mononuclear hexacoordinated complex [Ni(L)(H2O)3]2H2O] with nickel, whereas it forms a pentacoordinated coordination polymer with

W. Marjit Singh; Jubaraj B. Baruah

2008-01-01

20

DNA Methylation Profiling of the Human Major Histocompatibility Complex: A Pilot Study for the Human Epigenome Project  

PubMed Central

The Human Epigenome Project aims to identify, catalogue, and interpret genome-wide DNA methylation phenomena. Occurring naturally on cytosine bases at cytosine–guanine dinucleotides, DNA methylation is intimately involved in diverse biological processes and the aetiology of many diseases. Differentially methylated cytosines give rise to distinct profiles, thought to be specific for gene activity, tissue type, and disease state. The identification of such methylation variable positions will significantly improve our understanding of genome biology and our ability to diagnose disease. Here, we report the results of the pilot study for the Human Epigenome Project entailing the methylation analysis of the human major histocompatibility complex. This study involved the development of an integrated pipeline for high-throughput methylation analysis using bisulphite DNA sequencing, discovery of methylation variable positions, epigenotyping by matrix-assisted laser desorption/ionisation mass spectrometry, and development of an integrated public database available at http://www.epigenome.org. Our analysis of DNA methylation levels within the major histocompatibility complex, including regulatory exonic and intronic regions associated with 90 genes in multiple tissues and individuals, reveals a bimodal distribution of methylation profiles (i.e., the vast majority of the analysed regions were either hypo- or hypermethylated), tissue specificity, inter-individual variation, and correlation with independent gene expression data.

2004-01-01

21

Structure of the yeast tRNA m7G methylation complex.  

PubMed

Loss of N7-methylguanosine (m7G) modification is involved in the recently discovered rapid tRNA degradation pathway. In yeast, this modification is catalyzed by the heterodimeric complex composed of a catalytic subunit Trm8 and a noncatalytic subunit Trm82. We have solved the crystal structure of Trm8 alone and in complex with Trm82. Trm8 undergoes subtle conformational changes upon Trm82 binding which explains the requirement of Trm82 for activity. Cocrystallization with the S-adenosyl-methionine methyl donor defines the putative catalytic site and a guanine binding pocket. Small-angle X-ray scattering in solution of the Trm8-Trm82 heterodimer in complex with tRNA(Phe) has enabled us to propose a low-resolution structure of the ternary complex which defines the tRNA binding mode of Trm8-Trm82 and the structural elements contributing to specificity. PMID:18184583

Leulliot, Nicolas; Chaillet, Maxime; Durand, Dominique; Ulryck, Nathalie; Blondeau, Karine; van Tilbeurgh, Herman

2008-01-01

22

Methylated Trivalent Arsenic-Glutathione Complexes are More Stable than their Arsenite Analog  

PubMed Central

The trivalent arsenic glutathione complexes arsenic triglutathione, methylarsonous diglutathione, and dimethylarsinous glutathione are key intermediates in the mammalian metabolism of arsenite and possibly represent the arsenic species that are transported from the liver to the kidney for urinary excretion. Despite this, the comparative stability of the arsenic-sulfur bonds in these complexes has not been investigated under physiological conditions resembling hepatocyte cytosol. Using size-exclusion chromatography and a glutathione-containing phosphate buffered saline mobile phase (5 or 10 mM glutathione, pH 7.4) in conjunction with an arsenic-specific detector, we chromatographed arsenite, monomethylarsonous acid, and dimethylarsinous acid. The on-column formation of the corresponding arsenic-glutathione complexes between 4 and 37°C revealed that methylated arsenic-glutathione complexes are more stable than arsenic triglutathione. The relevance of these results with regard to the metabolic fate of arsenite in mammals is discussed.

Percy, Andrew J.; Gailer, Jurgen

2008-01-01

23

Absorption spectrometric study of molecular complex formation between [60]fullerene and a series of methylated pyridines.  

PubMed

[60]fullerene has been shown to form 1:1 molecular complexes with pyridine and some methylated pyridines such as 2-picoline, 3-picoline, 4-picoline, 2,6-lutidine and 2,4,6-collidine in CCl4 medium by absorption spectrometric method. Well defined charge transfer (CT) bands have been observed for complexes of C60 with all the pyridines studied except 4-picoline. From an analysis of the trends in the CT absorption bands the ionisation potentials of the methylpyridines have been determined. The electron affinity of C60 has also been determined from the spectral data. The formation constants of the complexes exhibit a very good linear free energy relationship from which the Hammett p parameter for the complexation process is found to be -2.96. PMID:12396038

Bhattacharya, Sumanta; Banerjee, Manas; Mukherjee, Asok K

2002-10-01

24

Absorption spectrometric study of molecular complex formation between [60]fullerene and a series of methylated pyridines  

NASA Astrophysics Data System (ADS)

[60]fullerene has been shown to form 1:1 molecular complexes with pyridine and some methylated pyridines such as 2-picoline, 3-picoline, 4-picoline, 2,6-lutidine and 2,4,6-collidine in CCl 4 medium by absorption spectrometric method. Well defined charge transfer (CT) bands have been observed for complexes of C 60 with all the pyridines studied except 4-picoline. From an analysis of the trends in the CT absorption bands the ionisation potentials of the methylpyridines have been determined. The electron affinity of C 60 has also been determined from the spectral data. The formation constants of the complexes exhibit a very good linear free energy relationship from which the Hammett ? parameter for the complexation process is found to be -2.96.

Bhattacharya, Sumanta; Banerjee, Manas; Mukherjee, Asok K.

2002-10-01

25

Analysis of the NuRD subunits reveals a histone deacetylase core complex and a connection with DNA methylation.  

PubMed

ATP-dependent nucleosome remodeling and core histone acetylation and deacetylation represent mechanisms to alter nucleosome structure. NuRD is a multisubunit complex containing nucleosome remodeling and histone deacetylase activities. The histone deacetylases HDAC1 and HDAC2 and the histone binding proteins RbAp48 and RbAp46 form a core complex shared between NuRD and Sin3-histone deacetylase complexes. The histone deacetylase activity of the core complex is severely compromised. A novel polypeptide highly related to the metastasis-associated protein 1, MTA2, and the methyl-CpG-binding domain-containing protein, MBD3, were found to be subunits of the NuRD complex. MTA2 modulates the enzymatic activity of the histone deacetylase core complex. MBD3 mediates the association of MTA2 with the core histone deacetylase complex. MBD3 does not directly bind methylated DNA but is highly related to MBD2, a polypeptide that binds to methylated DNA and has been reported to possess demethylase activity. MBD2 interacts with the NuRD complex and directs the complex to methylated DNA. NuRD may provide a means of gene silencing by DNA methylation. PMID:10444591

Zhang, Y; Ng, H H; Erdjument-Bromage, H; Tempst, P; Bird, A; Reinberg, D

1999-08-01

26

Methyl-transfer reaction to alkylthiol catalyzed by a simple vitamin B 12 model complex using zinc powder  

Microsoft Academic Search

The catalytic methyl-transfer reaction from methyl tosylate to 1-octanethiol was carried out in the presence of a simple vitamin B12 model complex, [Co(III){(C2C3)(DO)(DOH)pn}Br2], with zinc powder as the reducing reagent at 50°C. Such a catalytic reaction proceeded via the formation and dissociation of a cobalt–carbon bond in the simple vitamin B12 model complex under non-enzymatic conditions. The mechanism for the

Ling Pan; Keishiro Tahara; Takahiro Masuko; Yoshio Hisaeda

2011-01-01

27

Complexes of polyadenylic acid and the methyl esters of amino acids  

NASA Technical Reports Server (NTRS)

A study of amino acid methyl esters binding to polyadenylic acid supports the theory that the genetic code originated through weak but selective affinities between amino acids and nucleotides. NMR, insoluble complex analysis, and ultraviolet spectroscopy are used to illustrate a correlation between the hydrophybicities of A amino acids and their binding constants, which, beginning with the largest, are in the order of Phe (having nominally a hydrophobic AAA anticodon), Ile, Leu, Val and Gly (having a hydrophilic anticodon with no A). In general, the binding constants are twice the values by Reuben and Polk (1980) for monomeric AMP, which suggests that polymer amino acids are interacting with only one base. No real differences are found betwen poly A binding for free Phe, Phe methyl ester or Phe amide, except that the amide value is slightly lower.

Khaled, M. A.; Mulins, D. W., Jr.; Swindle, M.; Lacey, J. C., Jr.

1983-01-01

28

Decoding of Methylated Histone H3 Tail by the Pygo-BCL9 Wnt Signaling Complex  

PubMed Central

Summary Pygo and BCL9/Legless transduce the Wnt signal by promoting the transcriptional activity of ?-catenin/Armadillo in normal and malignant cells. We show that human and Drosophila Pygo PHD fingers associate with their cognate HD1 domains from BCL9/Legless to bind specifically to the histone H3 tail methylated at lysine 4 (H3K4me). The crystal structures of ternary complexes between PHD, HD1, and two different H3K4me peptides reveal a unique mode of histone tail recognition: efficient histone binding requires HD1 association, and the PHD-HD1 complex binds preferentially to H3K4me2 while displaying insensitivity to methylation of H3R2. Therefore, this is a prime example of histone tail binding by a PHD finger (of Pygo) being modulated by a cofactor (BCL9/Legless). Rescue experiments in Drosophila indicate that Wnt signaling outputs depend on histone decoding. The specificity of this process provided by the Pygo-BCL9/Legless complex suggests that this complex facilitates an early step in the transition from gene silence to Wnt-induced transcription.

Fiedler, Marc; Sanchez-Barrena, Maria Jose; Nekrasov, Maxim; Mieszczanek, Juliusz; Rybin, Vladimir; Muller, Jurg; Evans, Phil; Bienz, Mariann

2008-01-01

29

Organization of Plasmodium falciparum spliceosomal core complex and role of arginine methylation in its assembly  

PubMed Central

Background Splicing and alternate splicing are the two key biological processes that result in the generation of diverse transcript and protein isoforms in Plasmodium falciparum as well as in other eukaryotic organisms. Not much is known about the organization of splicing machinery and mechanisms in human malaria parasite. Present study reports the organization and assembly of Plasmodium spliceosome Sm core complex. Methods Presence of all the seven Plasmodium Sm-like proteins in the intra-erythrocytic stages was assessed based on the protein(s) expression analysis using immuno-localization and western blotting. Localization/co-localization studies were performed by immunofluorescence analysis on thin parasite smear using laser scanning confocal microscope. Interaction studies were carried out using yeast two-hybrid analysis and validated by in vitro pull-down assays. PfPRMT5 (arginine methyl transferase) and PfSmD1 interaction analysis was performed by pull-down assays and the interacting proteins were identified by MALDI-TOF spectrometry. Results PfSm proteins are expressed at asexual blood stages of the parasite and show nucleo-cytoplasmic localization. Protein-protein interaction studies showed that PfSm proteins form a heptameric complex, typical of spliceosome core complex as shown in humans. Interaction of PfSMN (survival of motor neuron, tudor domain containing protein) or PfTu-TSN (Tudor domain of Tudor Staphylococcal nuclease) with PfSmD1 proteins was found to be methylation dependent. Co-localization by immunofluorescence and co-immunoprecipitation studies suggested an association between PfPRMT5 and PfSmD1, indicating the role of arginine methylation in assembly of Plasmodium spliceosome complex. Conclusions Plasmodium Sm-like proteins form a heptameric ring-like structure, although the arrangement of PfSm proteins slightly differs from human splicing machinery. The data shows the interaction of PfSMN with PfSmD1 and this interaction is found to be methylation dependent. PfPRMT5 probably exists as a part of methylosome complex that may function in the cytoplasmic assembly of Sm proteins at asexual blood stages of P. falciparum.

2013-01-01

30

Synthesis and phosphorescent properties of the copolymers of N-vinylcarbazole, methyl methacrylate and iridium complex  

NASA Astrophysics Data System (ADS)

The copolymers containing carbazole unit and iridium complexes, such as (Ir(bpy)2Cl, Ir(mbpy)2Cl and Ir(Brbpy)2Cl, were synthesized via radical copolymerization of N-vinylcarbazole, methyl methacrylate and iridium complex. The synthesized copolymers were characterized by FT-IR, UV-Vis absorption spectroscopy and photoluminescence (PL) spectroscopy, respectively. According to the results, the copolymers (Ir(Brbpy)2Cl/PVK and Ir(mbpy)2Cl/PVK) exhibit yellow phosphorescence with an emission peak at around 553 nm under UV-visible light in the solid state. The results also reveal almost complete energy transfer from the host carbazole segments to the guest Ir complex in the copolymer film when the Ir content reaches 1.0 wt.%. The synthesized copolymers are good candidates as blue or yellow phosphorescent materials for PLED applications.

Wang, Wen; Zhou, Minglu; Liang, Luying; Lin, Meijuan; Ling, Qidan

2014-03-01

31

Allele-Specific Methylation Occurs at Genetic Variants Associated with Complex Disease  

PubMed Central

We hypothesize that the phenomenon of allele-specific methylation (ASM) may underlie the phenotypic effects of multiple variants identified by Genome-Wide Association studies (GWAS). We evaluate ASM in a human population and document its genome-wide patterns in an initial screen at up to 380,678 sites within the genome, or up to 5% of the total genomic CpGs. We show that while substantial inter-individual variation exists, 5% of assessed sites show evidence of ASM in at least six samples; the majority of these events (81%) are under genetic influence. Many of these cis-regulated ASM variants are also eQTLs in peripheral blood mononuclear cells and monocytes and/or in high linkage-disequilibrium with variants linked to complex disease. Finally, focusing on autoimmune phenotypes, we extend this initial screen to confirm the association of cis-regulated ASM with multiple complex disease-associated variants in an independent population using next-generation bisulfite sequencing. These four variants are implicated in complex phenotypes such as ulcerative colitis and AIDS progression disease (rs10491434), Celiac disease (rs2762051), Crohn's disease, IgA nephropathy and early-onset inflammatory bowel disease (rs713875) and height (rs6569648). Our results suggest cis-regulated ASM may provide a mechanistic link between the non-coding genetic changes and phenotypic variation observed in these diseases and further suggests a route to integrating DNA methylation status with GWAS results.

Hutchinson, John N.; Raj, Towfique; Fagerness, Jes; Stahl, Eli; Viloria, Fernando T.; Gimelbrant, Alexander; Seddon, Johanna; Daly, Mark; Chess, Andrew; Plenge, Robert

2014-01-01

32

Methyl Dynamics of a Ca2+-Calmodulin-Peptide Complex from NMR/SRLS  

PubMed Central

We developed the slowly relaxing local structure (SRLS) approach for analyzing NMR spin relaxation in proteins. SRLS accounts for dynamical coupling between the tumbling of the protein and the local motion of the probe, and for general tensorial properties. It is the generalization of the traditional model-free (MF) method, which does not account for mode-coupling and treats only simple tensiorial properties. SRLS is applied herein to 2H relaxation of 13CDH2 groups in the complex of Ca2+?calmodulin with the peptide smMLCKp. Literature data comprising 2H T1 and T2 acquired at 14.1 and 17.6 T, and 288, 295, 308 and 320 K, are used. We find that mode-coupling is a small effect for methyl dynamics. On the other hand, general tensorial properties are important. In particular, it is important to allow for the asymmetry of the local spatial restrictions, which can be represented in SRLS by a rhombic local ordering tensor with components S02 and S22. Here, we find that ?0.2?S02?0.5 and ?0.4?S22?0. MF features a single "generalized" order parameter, S, confined to the 0–0.316 range. The parameter S is inaccurate, having absorbed unaccounted for effects, notably S22?0. We find that the methionine methyls (the other methyl types) reorient with rates of 8.6×109–21.4×109 (0.67×109–6.5×109) 1/s. The corresponding activation energies are 10 (10–27) kJ/mol. By contrast, MF yields inaccurate effective local motional correlation times, ?e, with non-physical temperature-dependence. Thus, the problematic S-, and ?e-based MF picture of methyl dynamics has been replaced with an insightful physical picture based on a local ordering tensor related to structural features, and a local diffusion tensor that yields accurate activation energies.

Shapiro, Yury E.; Polimeno, Antonino; Freed, Jack H.; Meirovitch, Eva

2011-01-01

33

Thermal and spectroscopic studies of scandium complex of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone  

NASA Astrophysics Data System (ADS)

The scandium complexes of Sc(PMBP) 3·H 2O (non-crystal) and Sc(PMBP) 3 (crystal) with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) were prepared and characterized by thermal analysis, IR, NMR and MS spectroscopies. The crystal structure of the complex, obtained by X-ray analysis, indicates that PMBP is a bidentate ligand in the complex and that the Sc atom is six-coordinate and is in a meridional octahedral environment. The order of the ring current effect on the pyrazolone ring is Sc(PMBP) 3 >PMBP(enol)> PMBP(keto). The metal to ligand stoichiometry was found to be 1:3. The crystalline complex melts at 209 °C, followed by degradation at about 310 °C, with the beginning of decomposition. The enthalpy of melting was found to be 61 kJ/mol. On the other hand, the non-crystalline complex was found to change into a crystalline complex at 176 °C with an exothermic reaction before melting at 217 °C. The IR band observed at approximately, 450 cm -1 is possibly due to the stretching of the Sc-O bond.

Akama, Yoshifumi; Sawada, Tadanobu; Ueda, Toyotoshi

2005-08-01

34

High-nuclearity manganese and iron complexes with the anionic ligand methyl salicylimidate.  

PubMed

The three novel clusters [Mn6O4(OMe)2(OAc)4(Mesalim)4] (3), [Mn8O2(OH)2(OMe)12(OAc)2(Mesalim)4] (4), and [Fe10O4(OMe)14Cl2(Mesalim)6] (5) have been synthesized from a simple bidentate ligand HMesalim (HMesalim = methyl salicylimidate). Starting from the mononuclear complex [Mn(Mesalim)2(OAc)(MeOH)].MeOH (1), either the hexanuclear complex 3 or the octanuclear complex 4 is obtained after recrystallization, depending upon the reaction conditions and solvents used. Similarly, starting from the purple-colored mononuclear complex [Fe(Mesalim)2Cl] (2), the orange-colored decanuclear iron(III) cluster 5 has been obtained upon recrystallization from methanol. Complex 3, which could also be prepared directly from manganese acetate and the ligand, has a face-sharing double-cubane [Mn6O6] core, unique in transition metal chemistry. Compounds 4 and 5 are composed of [M3O4] partial cubanes. All complexes belong to a class of oxo-bridged cubic close-packed molecular clusters resembling the metal oxide/hydroxide ores. Complex 4 exhibits intramolecular ferromagnetic interactions, as evidenced from dc magnetic susceptibility studies (1.8-300 K), resulting in a high-spin ground state, probably with S(T) = 8. Complex 4 displays single molecule magnet behavior as indicated by frequency and temperature dependences of its ac susceptibility. An Arrhenius plot gave relatively large experimental activation energy of 36.0 K. The magnetic properties of complexes 3 and 5 are dominated by antiferromagnetic interactions leading to zero-spin ground states. PMID:16903727

Godbole, Meenal D; Roubeau, Olivier; Mills, Allison M; Kooijman, Huub; Spek, Anthony L; Bouwman, Elisabeth

2006-08-21

35

Vitamin B(12) model complex catalyzed methyl transfer reaction to alkylthiol under electrochemical conditions with sacrificial electrode.  

PubMed

Catalytic methyl transfer reactions from methyl tosylate to 1-octanethiol catalyzed by heptamethyl cobyrinate perchlorate, [Cob(II)7C(1)ester]ClO(4), were investigated under electrochemical conditions. As a model study for the cobalamin-dependent methyl transfer reaction from methyltetrahydrofolate to homocysteine, controlled-potential electrolyses were carried out at -1.0 V vs. Ag/AgCl using a zinc plate as the sacrificial anode at 50 degrees C in the dark. A turnover behaviour for the methyl transfer reaction was observed for the first time under non-enzymatic reaction conditions. Co(I) species, which is generated from the continuous electrolysis of [Cob(II)7C(1)ester]ClO(4), and its methylated CH(3)-Co complex were found to be important intermediates. The mechanism for such a methyl transfer reaction was investigated by product analysis, electronic spectroscopy and ESR spin-trapping experiments. A simple vitamin B(12) model complex was also utilized as the catalyst for the methyl transfer reaction. PMID:19885539

Pan, Ling; Shimakoshi, Hisashi; Masuko, Takahiro; Hisaeda, Yoshio

2009-11-28

36

Synthesis and structural characterization of rac-2-[(diphenylphosphino)methyl]ferrocenecarboxylic acid, its selected derivatives and some rhodium complexes  

Microsoft Academic Search

rac-2-[(Diphenylphosphino)methyl]ferrocenecarboxylic acid (1) was prepared in a good yield from rac-2-(N,N-dimethylaminomethyl)bromoferrocene (2) via rac-2-(hydroxymethyl)bromoferrocene (4) and rac-2-[(diphenylphosphino)methyl]bromoferrocene (5), and further converted to the respective phosphine oxide (6), phosphine sulfide (7) and methyl ester (8). The phosphines 1 and 8 were studied as ligands in rhodium complexes. The reaction of di-?-chloro-bis[chloro-(?5-pentamethylcyclopentadienyl)rhodium(III)] with the stoichiometric amounts of 1 and 8 yielded the

Martin Lama?; Ivana Císa?ová; Petr Št?pni?ka

2005-01-01

37

Nimesulide/methyl ?-cyclodextrin inclusion complexes: physicochemical characterization, solubility, dissolution, and biological studies.  

PubMed

Nimesulide (NIM) is an insoluble nonsteroidal anti-inflammatory drug (NSAID). Complexation of drug with methyl ?-cyclodextrin was evaluated to improve solubility and dissolution rate of NIM. Complexation was achieved via a coevaporation technique to obtain different drug to polymer molar ratios (1:1, 1:2, and 1:3). The physicochemical characterization of the systems using powder X-ray diffraction and infrared spectroscopy was carried out to understand the influence of this technological process on the physical status of single components and complex systems and to detect possible interactions between drug and carrier. Moreover, quantitative solubility and in vitro dissolution studies of NIM alone and NIM inclusion complexes were studied in the dissolution media of phosphate buffer pH?5.5 and 7.4. The analysis provided existence of a molecular interaction between drug and carrier together in the complex state. The study showed that the inclusion systems enhanced of drug solubility, dissolution rate, and anti-inflammatory activity. PMID:24648149

Auda, Sayed H

2014-03-01

38

Synthesis, structural features, and methyl methacrylate polymerisation of binuclear zinc(II) complexes with tetradentate pyrazolyl ligands  

NASA Astrophysics Data System (ADS)

The reaction of ZnCl2 with ancillary ligands, including 1,4-bis-(N,N-di-(1H-pyrazolyl-1-methyl)amine)benzene (L1) and 4,4?-bis-(N,N-di(1H-pyrazolyl-1-methyl)phenyl)methane (L2), in ethanol yields Zn(II) chloride complexes, i.e., 1,4-bis-(N,N-di-(1H-pyrazolyl-1-methyl)amine)benzene(dichloro)Zn(II) [L1Zn2Cl4] and 4,4?-bis-(N,N-di-(1H-pyrazolyl-1-methyl)phenyl)methane(dichloro)Zn(II) [L2Zn2Cl4]. The X-ray crystal structures of Zn(II) complexes revealed that they are binuclear, and each zinc atom has a distorted tetrahedral geometry which involves a nitrogen atom from two pyrazole groups and two chloro ligands. The catalytic activity of [L1Zn2Cl4] and [L2Zn2Cl4] for the polymerisation of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) increased by twofold compared to the corresponding monomeric Zn(II) complex, N,N-bis(1H-pyrazolyl-1-methyl)aniline(dichloro)Zn(II) [LZnCl2], at 60 °C.

Kim, Sunghoon; Kim, Dongil; Lee, Ha-Jin; Lee, Hyosun

2014-04-01

39

Synthesis, spectra and crystal structure of 2-({[3-(methyl{3-[(2-hydroxybenzylidene)amino]propyl} amino)propyl]imino}methyl)phenol copper(II) complex  

Microsoft Academic Search

A copper(II) complex, [Cu(salenN3], [salenN3H2=2-({[3-(methyl{3-[(2-hydroxybenzylidene)amino]propyl}amino)propyl]imino}methyl)phenol] was synthesized and characterized by elemental analyses, FTIR spectra and single crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21\\/c with a=6.877(3), b=14.109(6), c=20.106(8)Å, ?=92.231(14)°, V=1949.5(14)Å3. The salen ligand loses two phenolic hydrogens being a dianion and coordinates to the copper(II) ion as a pentadentate ligand through its two O and three

Veysel T. Yilmaz; Ismail Degirmencioglu; Omer Andac; Serdar Karabocek; Alexandra M. Z. Slawin

2003-01-01

40

Synthesis, spectra and crystal structure of 2-(?[3-(methyl?3-[(2-hydroxybenzylidene)amino]propyl? amino)propyl]imino?methyl)phenol copper(II) complex  

NASA Astrophysics Data System (ADS)

A copper(II) complex, [Cu(salenN3], [salenN3H2=2-({[3-(methyl{3-[(2-hydroxybenzylidene)amino]propyl}amino)propyl]imino}methyl)phenol] was synthesized and characterized by elemental analyses, FTIR spectra and single crystal X-ray diffraction. The complex crystallizes in the monoclinic space group P21/ c with a=6.877(3), b=14.109(6), c=20.106(8) Å, ?=92.231(14)°, V=1949.5(14) Å 3. The salen ligand loses two phenolic hydrogens being a dianion and coordinates to the copper(II) ion as a pentadentate ligand through its two O and three N atoms. The copper(II) complex is five-coordinate, lying between perfect square pyramidal and trigonal-bipyramidal extremes. Use of the structural index parameter ( ?) for five coordinate metal complexes indicated that the copper(II) complex exhibits a grater tendency toward trigonal-based-pyramidal geometry ( ?>0.5). The individual molecules in the crystal are held together by C-H⋯? and H⋯H interactions. The IR and electronic spectra of the complex were discussed in detail.

Yilmaz, Veysel T.; Degirmencioglu, Ismail; Andac, Omer; Karabocek, Serdar; Slawin, Alexandra M. Z.

2003-06-01

41

Study on inclusion complex of cyclodextrin with methyl xanthine derivatives by fluorimetry  

NASA Astrophysics Data System (ADS)

The inclusion complexes of ?-cyclodextrin (?-CD) and HP-?-cyclodextrin (HP-?-CD) with caffeine, theophylline and theobromine were investigated by fluorimetry. Various factors affecting the formation of inclusion complexes were discussed in detail including forming time, pH effect and temperature. The results indicate that inclusion process was affected seriously by laying time and pH. The forming time of ?-CD inclusion complexes is much longer than that of HP-?-CD. The optimum pH range is about 7-12 for caffeine, 8-10 for TP, 10.5-12 for TB. The intensities of their fluorescence increase with the decreasing of temperature. Their maximum excitation wavelengths are all in the range of 280-290 nm. The emission wavelength of caffeine and theophylline are both in the range of 340-360 nm, and that of theobromine is about 325 nm. The fluorescence signals are intensified with the increasing concentration of CD. The stoichiometry of the inclusion complexes of CD with these three methyl xanthine derivatives are all 1:1 and the formation constant are all calculated.

Wei, Yan-Li; Ding, Li-Hua; Dong, Chuan; Niu, Wei-Ping; Shuang, Shao-Min

2003-10-01

42

Intramolecular reductive elimination of methane from a dinuclear palladium complex containing methyl and hydride on adjacent palladium centers  

SciTech Connect

The preparation, isolation, and determination of structure of a dinuclear palladium complex containing methyl and hydride on adjacent palladium atoms its facile 1,1-dinuclear intramolecular elimination of methane are reported. The complex was isolated as its tetraphenylborate salt and was fully characterized including its x-ray structure. Reductive elimination from the deuterated complex containing deutride on one palladium and trideuteriomethyl on the other gave a quantitative yield of methane. 16 references, 3 figures.

Kellenberger, B.; Young, S.J.; Stille, J.K.

1985-01-01

43

Different alternatives for stability constant determination of Zr and Hf 2-methyl lactate complexes by cation exchange  

Microsoft Academic Search

Three different alternatives are applied for the determination of the stability constants of zirconium and hafnium complexes\\u000a with 2-methyl lactic acid using cation exchange. Calculations based on the exchange equilibria of the highly charged metal\\u000a cations and the positively charged ligand complexes rather than that of the hydrolysed complex species are worked out according\\u000a to SCHUBERT and FRONAEUS, respectively. The

H. F. Aly; M. A. El-Haggan; A. A. Abdel-Rassoul

1976-01-01

44

RNA Methylation by the MIS Complex Regulates a Cell Fate Decision in Yeast  

PubMed Central

For the yeast Saccharomyces cerevisiae, nutrient limitation is a key developmental signal causing diploid cells to switch from yeast-form budding to either foraging pseudohyphal (PH) growth or meiosis and sporulation. Prolonged starvation leads to lineage restriction, such that cells exiting meiotic prophase are committed to complete sporulation even if nutrients are restored. Here, we have identified an earlier commitment point in the starvation program. After this point, cells, returned to nutrient-rich medium, entered a form of synchronous PH development that was morphologically and genetically indistinguishable from starvation-induced PH growth. We show that lineage restriction during this time was, in part, dependent on the mRNA methyltransferase activity of Ime4, which played separable roles in meiotic induction and suppression of the PH program. Normal levels of meiotic mRNA methylation required the catalytic domain of Ime4, as well as two meiotic proteins, Mum2 and Slz1, which interacted and co-immunoprecipitated with Ime4. This MIS complex (Mum2, Ime4, and Slz1) functioned in both starvation pathways. Together, our results support the notion that the yeast starvation response is an extended process that progressively restricts cell fate and reveal a broad role of post-transcriptional RNA methylation in these decisions.

Agarwala, Sudeep D.; Blitzblau, Hannah G.; Hochwagen, Andreas; Fink, Gerald R.

2012-01-01

45

Reaction of 2-methyl-1,3-dioxolan with vinylethynylmagnesium bromide and the structure of the iotsich complex  

Microsoft Academic Search

Conclusions 1.2-Methyl-1,3-dioxolan quantitatively precipitates magnesium bromide and vinylethynylmagnesium bromide (VEMB) from the etherate of the corresponding Iotsich complex, bis-(vinylethynyl)-magnesium remaining in the solution. The composition of the mixture of insoluble dioxolanates has been studied.2.The reaction of 1,3-dioxolans with VEMB is considered as a coordinate nucleophilic exchange taking place by a cyclic mechanism with the participation of an “acetal-magnesium bromide complex,”

B. A. Trofimov; A. S. Atavin; S. E. Orlova

1966-01-01

46

On the Mechanism of Multiple Lysine Methylation by the Human Mixed Lineage Leukemia Protein-1 (MLL1) Core Complex*?  

PubMed Central

Transcription in eukaryotic genomes depends on enzymes that regulate the degree of histone H3 lysine 4 (H3K4) methylation. The mixed lineage leukemia protein-1 (MLL1) is a member of the SET1 family of H3K4 methyltransferases and is frequently rearranged in acute leukemias. Despite sequence comparisons that predict that SET1 family enzymes should only monomethylate their substrates, mono-, di-, and trimethylation of H3K4 has been attributed to SET1 family complexes in vivo and in vitro. To better understand this paradox, we have biochemically reconstituted and characterized a five-component 200-kDa MLL1 core complex containing human MLL1, WDR5, RbBP5, Ash2L, and DPY-30. We demonstrate that the isolated MLL1 SET domain is a slow monomethyltransferase and that tyrosine 3942 of MLL1 prevents di- and trimethylation of H3K4. In contrast, a complex containing the MLL1 SET domain, WDR5, RbBP5, Ash2L, and DPY-30, displays a marked ?600-fold increase in enzymatic activity but only to the dimethyl form of H3K4. Single turnover kinetic experiments reveal that the reaction leading to H3K4 dimethylation involves the transient accumulation of a monomethylated species, suggesting that the MLL1 core complex uses a non-processive mechanism to catalyze multiple lysine methylation. We have also discovered that the non-SET domain components of the MLL1 core complex possess a previously unrecognized methyltransferase activity that catalyzes H3K4 dimethylation within the MLL1 core complex. Our results suggest that the mechanism of multiple lysine methylation by the MLL1 core complex involves the sequential addition of two methyl groups at two distinct active sites within the complex.

Patel, Anamika; Dharmarajan, Venkatasubramanian; Vought, Valarie E.; Cosgrove, Michael S.

2009-01-01

47

Beta-Phosphinoethylboranes as Ambiphilic Ligands in Nickel-Methyl Complexes  

SciTech Connect

The ambiphilic {beta}-phosphinoethylboranes Ph{sub 2}PCH{sub 2}CH{sub 2}BR{sub 2} (BR{sub 2} = BCy{sub 2} (1a), BBN (1b)), which feature a ethano spacer CH{sub 2}CH{sub 2} between the Lewis acidic boryl and Lewis basic phosphino groups, were synthesized in nearly quantitative yields via the hydroboration of vinyldiphenylphosphine. Compounds 1a and 1b were fully characterized by elemental analysis, and by NMR and IR spectroscopy. X-ray crystallographic studies of compound 1b revealed infinite helical chains of the molecules connected through P{hor_ellipsis}B donor-acceptor interactions. The ability of these ambiphilic ligands to concurrently act as donors and acceptors was highlighted by their reactions with (dmpe)NiMe{sub 2}. Zwitterionic complexes (dmpe)NiMe(Ph{sub 2}PCH{sub 2}CH{sub 2}BCy{sub 2}Me) (2a) and (dmpe)NiMe(Ph{sub 2}PCH{sub 2}CH{sub 2}[BBN]Me) (2b) were generated via the abstraction of one of the methyl groups, forming a borate, and intramolecular coordination of the phosphine moiety to the resulting cationic metal center. Compound 2b was characterized by X-ray crystallography. Furthermore, B(C{sub 6}F{sub 5}){sub 3} abstracts the methyl group of a coordinated borate ligand to generate a free, 3-coordinate borane center in [(dmpe)NiMe(1a)]{sup +}[MeB(C{sub 6}F{sub 5}){sub 3}]{sup -} (3).

Fischbach, Andreas; Bazinet, Patrick R.; Waterman, Rory; Tilley, T. Don

2007-10-28

48

Stability constants of thorium(IV) complexes with aryl- bis -(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl) methane ligands  

Microsoft Academic Search

Stability constants of complexes of aryl-bis-(5-hydroxy-3-methyl-1-phenyl-4-pyrazolyl) methane [ArBPyM] derivatives with thorium(IV) ions were determined by the potentiometric method at 30°C and an ionic strength of 0.1 mol·dm-3 (KNO3) in 75% (v\\/v) dioxane-water. The evaluation of the titration data indicated that four kinds of complexes ([ThL]2+, [ThLOH]+, [ThL2], and [ThL(OH)2]2-) were formed. The formation constants for all [ThL]2+ and [ThL2] complexes

S. L. Stefan

1994-01-01

49

Complexation of NpO2+ with N-methyl-iminodiacetic Acid: in Comparison with Iminodiacetic and Dipicolinic Acids  

SciTech Connect

Complexation of Np(V) with N-methyl-iminodiacetic acid (MIDA) in 1 M NaClO{sub 4} solution was studied with multiple techniques including potentiometry, spectrophotometry, and microcalorimetry. The 1:2 complex, NpO{sub 2}(MIDA){sub 2}{sup 3-} was identified for the first time in aqueous solution. The correlation between its optical absorption properties and symmetry was discussed, in comparison with Np(V) complexes with two structurally related nitrilo-dicarboxylic acids, iminodiacetic acid (IDA) and dipicolinic acid (DPA). The order of the binding strength (DPA > MIDA > IDA) is explained by the difference in the structural and electronic properties of the ligands. In general, the nitrilo-dicarboxylates form stronger complexes with Np(V) than oxy-dicarboxylates due to a much more favorable enthalpy of complexation.

Tian, Guoxin; Rao, Linfeng

2010-10-01

50

Generation of a genomic tiling array of the human Major Histocompatibility Complex (MHC) and its application for DNA methylation analysis  

PubMed Central

Background The major histocompatibility complex (MHC) is essential for human immunity and is highly associated with common diseases, including cancer. While the genetics of the MHC has been studied intensively for many decades, very little is known about the epigenetics of this most polymorphic and disease-associated region of the genome. Methods To facilitate comprehensive epigenetic analyses of this region, we have generated a genomic tiling array of 2 Kb resolution covering the entire 4 Mb MHC region. The array has been designed to be compatible with chromatin immunoprecipitation (ChIP), methylated DNA immunoprecipitation (MeDIP), array comparative genomic hybridization (aCGH) and expression profiling, including of non-coding RNAs. The array comprises 7832 features, consisting of two replicates of both forward and reverse strands of MHC amplicons and appropriate controls. Results Using MeDIP, we demonstrate the application of the MHC array for DNA methylation profiling and the identification of tissue-specific differentially methylated regions (tDMRs). Based on the analysis of two tissues and two cell types, we identified 90 tDMRs within the MHC and describe their characterisation. Conclusion A tiling array covering the MHC region was developed and validated. Its successful application for DNA methylation profiling indicates that this array represents a useful tool for molecular analyses of the MHC in the context of medical genomics.

Tomazou, Eleni M; Rakyan, Vardhman K; Lefebvre, Gregory; Andrews, Robert; Ellis, Peter; Jackson, David K; Langford, Cordelia; Francis, Matthew D; Backdahl, Liselotte; Miretti, Marcos; Coggill, Penny; Ottaviani, Diego; Sheer, Denise; Murrell, Adele; Beck, Stephan

2008-01-01

51

Anionic lanthanide complexes with 3-methyl-1-phenyl-4-formylpyrazole-5-one and hydroxonium as counter ion  

PubMed Central

A series of [H3O]+[LnL4]?·nH2O complexes (n = 1–3, Ln = Nd, (1), Sm (2), Eu (3), Tb (4); HL = 3-methyl-1-phenyl-4-formylpyrazole-5-one) were synthesized and characterized. The structures of the SmIII and EuIII complexes were investigated by X-ray diffraction. The isostructutal crystalls 2 and 3 consist the tetrakis [LnL4]? anions which are linked by H-bonding with the hydroxonium counter-ion and water molecules. The lanthanide ion is situated in the center of distorted tetragonal antiprism formed by eight oxygen atoms of 4-formyl-5-hydroxypyrazolonate anions. The TbIII and SmIII complexes show strong luminescence in solid state, whereas the EuIII and NdIII complexes show low luminescence activity.

Shul'gin, Victor F.; Konnik, Oleg V.; Abkhairova, Susana V.; Gusev, Alexey N.; Meshkova, Svetlana B.; Kiriyak, Anna V.; Rusanov, Eduard B.; Hasegawa, Miki; Linert, Wolfgang

2013-01-01

52

Synthesis and antimicrobial studies of 1-methyl-2-dimethylaminoethyl-substituted benzimidazolium salts and N-heterocyclic carbene–silver complexes  

Microsoft Academic Search

The synthesis and antimicrobial studies of 1-methyl-2-dimethylaminoethyl-substituted carbene precursors and silver complexes are reported. The carbene precursors (1a–d) have been prepared from 1-methyl-2-dimethylaminoethyl-substituted benzimidazole and various alkyl halides. The silver–NHC complexes (2a–d) were synthesized from the benzimidazolium salts and Ag2O in dichloromethane at room temperature. The new compounds were characterized by H NMR, C NMR, FT-IR, and elemental analyses. The

Beyhan Y???t; Yetk?n Gök; ?lknur Özdem?r; Selam? Günal

2012-01-01

53

Regulation of muscle development by DPF3, a novel histone acetylation and methylation reader of the BAF chromatin remodeling complex  

PubMed Central

Chromatin remodeling and histone modifications facilitate access of transcription factors to DNA by promoting the unwinding and destabilization of histone–DNA interactions. We present DPF3, a new epigenetic key factor for heart and muscle development characterized by a double PHD finger. DPF3 is associated with the BAF chromatin remodeling complex and binds methylated and acetylated lysine residues of histone 3 and 4. Thus, DPF3 may represent the first plant homeodomains that bind acetylated lysines, a feature previously only shown for the bromodomain. During development Dpf3 is expressed in the heart and somites of mouse, chicken, and zebrafish. Morpholino knockdown of dpf3 in zebrafish leads to incomplete cardiac looping and severely reduced ventricular contractility, with disassembled muscular fibers caused by transcriptional deregulation of structural and regulatory proteins. Promoter analysis identified Dpf3 as a novel downstream target of Mef2a. Taken together, DPF3 adds a further layer of complexity to the BAF complex by representing a tissue-specific anchor between histone acetylations as well as methylations and chromatin remodeling. Furthermore, this shows that plant homeodomain proteins play a yet unexplored role in recruiting chromatin remodeling complexes to acetylated histones.

Lange, Martin; Kaynak, Bogac; Forster, Ulrike B.; Tonjes, Martje; Fischer, Jenny J.; Grimm, Christina; Schlesinger, Jenny; Just, Steffen; Dunkel, Ilona; Krueger, Tammo; Mebus, Siegrun; Lehrach, Hans; Lurz, Rudi; Gobom, Johan; Rottbauer, Wolfgang; Abdelilah-Seyfried, Salim; Sperling, Silke

2008-01-01

54

MBD3L1 is a transcriptional repressor that interacts with methyl-CpG-binding protein 2 (MBD2) and components of the NuRD complex.  

PubMed

Methyl-CpG-binding domain proteins 2 and 3 (MBD2 and MBD3) are transcriptional repressors that contain methyl-CpG binding domains and are components of a CpG-methylated DNA binding complex named MeCP1. Methyl-CpG-binding protein 3-like 1 (MBD3L1) is a protein with substantial homology to MBD2 and MBD3, but it lacks the methyl-CpG binding domain. MBD3L1 interacts with MBD2 and MBD3 in vitro and in yeast two-hybrid assays. Gel shift experiments with a CpG-methylated DNA probe indicate that recombinant MBD3L1 can supershift an MBD2-methylated DNA complex. In vivo, MBD3L1 associates with and colocalizes with MBD2 but not with MBD3 and is recruited to 5-methylcytosine-rich pericentromeric heterochromatin in mouse cells. In glutathione S-transferase pull-down assays MBD3L1 is found associated with several known components of the MeCP1.NuRD complex, including HDAC1, HDAC2, MTA2, MBD2, RbAp46, and RbAp48, but MBD3 is not found in the MBD3L1-bound fraction. MBD3L1 enhances transcriptional repression of methylated DNA by MBD2. The data are consistent with a role of MBD3L1 as a methylation-dependent transcriptional repressor that may interchange with MBD3 as an MBD2-interacting component of the NuRD complex. MBD3L1 knockout mice were created and were found to be viable and fertile, indicating that MBD3L1 may not be essential or there is functional redundancy (through MBD3) in this pathway. Overall, this study reveals additional complexities in the mechanisms of transcriptional repression by the MBD family proteins. PMID:15456747

Jiang, Chun-Ling; Jin, Seung-Gi; Pfeifer, Gerd P

2004-12-10

55

Complex methyl group and hydrogen-bonded proton motions in terms of the Arrhenius and Schrödinger equations.  

PubMed

Equations for the temperature dependence of the spectral densities J(is)(m)(momega(I) +/-omega(T)), where m=1, 2, omega(I) and omega(T) are the resonance and tunnel splitting angular frequencies, in the presence of a complex motion, have been derived. The spin pairs of the protons or deuterons of the methyl group perform a complex motion consisting of three component motions. Two of them involve mass transportation over the barrier and through the barrier. They are characterized by k((H)) (Arrhenius) and k((T)) (Schrödinger) rate constants, respectively. The third motion causes fluctuations of the frequencies (nomega(I)+/-omega(T)) and it is related to the lifetime of the methyl spin at the energy level influenced by the rotor-bath interactions. These interactions induce rapid transitions, changing the symmetry of the torsional sublevels either from A to E or from E(a) to E(b). The correlation function for this third motion (k((omega)) rate constant) has been proposed by Müller-Warmuth et al. The spectral densities of the methyl group hindered rotation (k((H)), k((T)) and k((omega)) rate constants) differ from the spectral densities of the proton transfer (k((H)) and k((T)) rate constants) because three compound motions contribute to the complex motion of the methyl group. The recently derived equation [Formula: see text] , where [Formula: see text] and [Formula: see text] are the fraction and energy of particles with energies from zero to E(H), is taken into account in the calculations of the spectral densities. This equation follows from Maxwell's distribution of thermal energy. The spectral densities derived are applied to analyse the experimental temperature dependencies of proton and deuteron spin-lattice relaxation rate in solids containing the methyl group. A wide range of temperatures from zero Kelvin up to the melting point is considered. It has been established that the motion characterized by k((omega)) influences the spin-lattice relaxation up to the temperature T(tun) only. This temperature is directly determined by the equation C(p)T=E(H) (thermal energy=activation energy), where C(p) is the molar heat capacity. Probably the cessation of the third motion is a result of the de Broglie wavelength related to this motion becoming too short. As shown recently, the potential barrier can be an obstacle for the de Broglie wave. The theoretical equations derived in this paper are compared to those known in the literature. PMID:18023155

Latanowicz, L

2008-01-01

56

Metal(ii) complexes synthesized based on quinoline-2,3-dicarboxylate as electrocatalysts for the degradation of methyl orange.  

PubMed

Based on quinoline-2,3-dicarboxylic acid (H2L), two metal(ii) complexes formulated as MnL(phen)(H2O)·H2O (phen = 1,10-phenanthroline) () and Co(HL)2(PPA)·4H2O (PPA = N(1),N(4)-di(pyridin-4-yl)terephthalamide) () were synthesized and structurally characterized by single-crystal X-ray diffraction. Both complexes and exhibit one-dimensional (1D) chain-like structures, in which stable five-membered rings are observed. Different chains are linked by strong ?-? stacking interactions into a three-dimensional (3D) supramolecular architecture. Both complexes can increase the degradation rate of methyl orange (MO), which is expected to be associated with their electrocatalytic activities for the H2 evolution reaction from water. PMID:24741675

Gong, Yun; Zhang, Miao Miao; Qin, Jian Bo; Li, Jian; Meng, Jiang Ping; Lin, Jian Hua

2014-05-13

57

STRUCTURES AND BINDING ENERGIES OF METHYL TERT-BUTYL ETHER-WATER COMPLEXES  

EPA Science Inventory

Methyl tert-butyl ether (MTBE) is a well-known environmental contaminant owing to its high solubility in water. Since the early 1990s, MTBE has been added to gasoline to improve air quality in some metropolitan areas of the United States. Improved air quality was, however, achiev...

58

Complex Formation Equilibria Between Zinc(II), Nitrilo-tris(Methyl Phosphonic Acid) and Some Bio-relevant Ligands. The Kinetics and Mechanism for Zinc(II) Ion Promoted Hydrolysis of Glycine Methyl Ester  

Microsoft Academic Search

Binary and ternary complexes of zinc(II) involving nitrilo-tris(methyl phosphonic acid (H6A) and amino acids, peptides (HL), or DNA constituents have been investigated. The stoichiometry and stability constants for\\u000a the complexes formed are reported. The results show that ternary complexes are formed in a stepwise manner whereby nitrilo-tris(methylphosphonic\\u000a acid) binds to zinc(II), which is then followed by coordination of an amino

Mahmoud M. A. Mohamed; Ahmed A. El-Sherif

2010-01-01

59

A TDG/CBP/RAR? ternary complex mediates the retinoic acid-dependent expression of DNA methylation-sensitive genes.  

PubMed

The thymine DNA glycosylase (TDG) is a multifunctional enzyme, which is essential for embryonic development. It mediates the base excision repair (BER) of G:T and G:U DNA mismatches arising from the deamination of 5-methyl cytosine (5-MeC) and cytosine, respectively. Recent studies have pointed at a role of TDG during the active demethylation of 5-MeC within CpG islands. TDG interacts with the histone acetylase CREB-binding protein (CBP) to activate CBP-dependent transcription. In addition, TDG also interacts with the retinoic acid receptor ? (RAR?), resulting in the activation of RAR? target genes. Here we provide evidence for the existence of a functional ternary complex containing TDG, CBP and activated RAR?. Using global transcriptome profiling, we uncover a coupling of de novo methylation-sensitive and RA-dependent transcription, which coincides with a significant subset of CBP target genes. The introduction of a point mutation in TDG, which neither affects overall protein structure nor BER activity, leads to a significant loss in ternary complex stability, resulting in the deregulation of RA targets involved in cellular networks associated with DNA replication, recombination and repair. We thus demonstrate for the first time a direct coupling of TDG's epigenomic and transcription regulatory function through ternary complexes with CBP and RAR?. PMID:24394593

Léger, Hélène; Smet-Nocca, Caroline; Attmane-Elakeb, Amel; Morley-Fletcher, Sara; Benecke, Arndt G; Eilebrecht, Sebastian

2014-02-01

60

ADP-ribose polymers localized on Ctcf-Parp1-Dnmt1 complex prevent methylation of Ctcf target sites  

PubMed Central

PARylation [poly(ADP-ribosyl)ation] is involved in the maintenance of genomic methylation patterns through its control of Dnmt1 [DNA (cytosine-5)-methyltransferase 1] activity. Our previous findings indicated that Ctcf (CCCTC-binding factor) may be an important player in key events whereby PARylation controls the unmethylated status of some CpG-rich regions. Ctcf is able to activate Parp1 [poly(ADP-ribose) polymerase 1], which ADP-ribosylates itself and, in turn, inhibits DNA methylation via non-covalent interaction between its ADP-ribose polymers and Dnmt1. By such a mechanism, Ctcf may preserve the epigenetic pattern at promoters of important housekeeping genes. The results of the present study showed Dnmt1 as a new protein partner of Ctcf. Moreover, we show that Ctcf forms a complex with Dnmt1 and PARylated Parp1 at specific Ctcf target sequences and that PARylation is responsible for the maintenance of the unmethylated status of some Ctcf-bound CpGs. We suggest a mechanism by which Parp1, tethered and activated at specific DNA target sites by Ctcf, preserves their methylation-free status.

Zampieri, Michele; Guastafierro, Tiziana; Calabrese, Roberta; Ciccarone, Fabio; Bacalini, Maria G.; Reale, Anna; Perilli, Mariagrazia; Passananti, Claudio; Caiafa, Paola

2011-01-01

61

Complex formation equilibria of palladium(II) complexes involving N, N?-dimethylethylenediamine, DNA constituents and cyclobutane dicarboxylic acid. The catalysis of glycine methyl ester hydrolysis through complex formation  

Microsoft Academic Search

Mixed-ligand complex formation equilibria of Pd(Me2en)–CBDCA–DNA constituent have been investigated (Me2en=N,N?-dimethylethylenediamine, CBDCA=cyclobutane dicarboxylic acid). The results show ring opening of CBDCA and monodentate complexation of the DNA constituent. Stoichiometries and stability constants of the complexes were determined at 25°C and at constant 0.1 M ionic strength. The kinetics of base hydrolysis of glycine methyl ester in presence of Pd(Me2en)2+ complex

Mahmoud M. A Mohamed; Mohamed M Shoukry

2002-01-01

62

Novel square arrangements in tetranuclear and octanuclear iron(III) complexes with asymmetric iron environments created by the unsymmetric bridging ligand N,N,Nâ²-tris((N-methyl)-2-benzimidazolylmethyl)-Nâ²-methyl-1,3-diamino-2-propanol  

Microsoft Academic Search

The synthesis and characterization of novel tetranuclear and octanuclear iron(III) complexes with structures based on a nearly square arrangement of four iron ions are reported. Reaction of ferric nitrate, sodium acetate, and the unsymmetrical binucleating ligand HBMDP, where HBMDP is N,N,Nâ²-tris((N-methyl)-2-benzimidazolylmethyl)-Nâ²-methyl-1,3-diamino-2-propanol, in acetone\\/water yields the tetranuclear iron complex [Feâ(μ-O)â(μ-BMDP)â-(μ-OAc)â]{sup 4+}, which exhibits coordination number asymmetry. The structure of [Feâ(μ-O)â(μ-BMDP)â(μ-OAc)â](NOâ)â(OH)·12HâO has

J. H. Jr. Satcher; S. R. Parkin; M. M. Olmstead; B. C. Noll; A. L. Balch; M. W. Droege; L. May

1998-01-01

63

Four Ni(II) complexes with the new cyclam-methylimidazole ligand 1-[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane.  

PubMed

Although it has not proved possible to crystallize the newly prepared cyclam-methylimidazole ligand 1-[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane (L(Im1)), the trans and cis isomers of an Ni(II) complex, namely trans-aqua{1-[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane}nickel(II) bis(perchlorate) monohydrate, [Ni(C(15)H(30)N(6))(H(2)O)](ClO(4))(2)·H(2)O, (1), and cis-aqua{1-[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane}nickel(II) bis(perchlorate), [Ni(C(15)H(30)N(6))(H(2)O)](ClO(4))(2), (2), have been prepared and structurally characterized. At different stages of the crystallization and thermal treatment from which (1) and (2) were obtained, a further two compounds were isolated in crystalline form and their structures also analysed, namely trans-{1-[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane}(perchlorato)nickel(II) perchlorate, [Ni(ClO(4))(C(15)H(30)N(6))]ClO(4), (3), and cis-{1,8-bis[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane}nickel(II) bis(perchlorate) 0.24-hydrate, [Ni(C(20)H(36)N(6))](ClO(4))(2)·0.24H(2)O, (4); the 1,8-bis[(1-methyl-1H-imidazol-2-yl)methyl]-1,4,8,11-tetraazacyclotetradecane ligand is a minor side product, probably formed in trace amounts in the synthesis of L(Im1). The configurations of the cyclam macrocycles in the complexes have been analysed and the structures are compared with analogues from the literature. PMID:22552303

De Candia, Ariel G; Molnar, Matias; Slep, Leonardo D; Baggio, Ricardo

2012-05-01

64

The Drosophila methyl-DNA binding protein MBD2\\/3 interacts with the NuRD complex via p55 and MI2  

Microsoft Academic Search

BACKGROUND: Methyl-DNA binding proteins help to translate epigenetic information encoded by DNA methylation into covalent histone modifications. MBD2\\/3 is the only candidate gene in the Drosophila genome with extended homologies to mammalian MBD2 and MBD3 proteins, which represent a co-repressor and an integral component of the Nucleosome Remodelling and Deacetylase (NuRD) complex, respectively. An association of Drosophila MBD2\\/3 with the

Joachim Marhold; Alexander Brehm; Katja Kramer

2004-01-01

65

Synthesis of N-Methyl-2-Thioimidazole Resin and Its Complex Behavior for Noble Metal Ions  

Microsoft Academic Search

The functional group capacity and the percentage of functional group conversion of crosslinked polystyrene resin bearing N-methyl-2-thioimidazole (MTIR) synthesized under optimum conditions are as high as 4.08 mmol\\/g resin and 96.0%, respectively. The apparent activation energies of sorption of MTIR for Au(III) and Pt(IV) are 13.1 and 13.4 kJ\\/mol, respectively. The sorption behavior of MTIR for Au(III), Pt(IV), and Pd(II)

Yi-Yong Chen; Guo-Ping Cai; Nai-Dong Wang

1990-01-01

66

Spectrophotometric study of molecular complex formation between o-chloranil and a series of methylated pyridines  

NASA Astrophysics Data System (ADS)

o-Chloranil has been shown to form 1:1 molecular complexes with pyridine and 2-, 3- and 4-picolines in CCl 4 medium. Isosbestic points have been found but charge-transfer bands could not be detected. The formation constants of the complexes exhibit a very good linear free energy relationship from which the Hammett ? parameter for the complexation reaction is found to be -3.67.

Ray, Asim Kumar; Bhattacharya, Sumanta; Banerjee, Manas; Mukherjee, Asok K.

2002-05-01

67

Nonradiative Decay Dynamics of METHYL-4-HYDROXYCINNAMATE and its Monohydrated Complex Revealed by Picosecond Pump-Probe Spectroscopy  

NASA Astrophysics Data System (ADS)

The lifetimes of methyl 4-hydroxycinnamate (OMpCA) and its mono-hydrated complex (OMpCA-H_2O) in the S_1 state have been measured by picosecond pump-probe spectroscopy in a supersonic beam. For OMpCA, the lifetime of the S_1 - S_0 origin is 8 - 9 ps. On the other hand, the lifetime of OMpCA-H_2O complex at the origin is 930 ps, which is 100 times longer than that. Furthermore, in the complex the S_1 lifetime shows rapid decrease at an energy of 200 cm-1 above the origin and becomes as short as 9 ps at 500 cm-1. Theoretical calculations with symmetry-adapted cluster-configuration interaction (SAC-CI) method suggest that in OMpCA, the trans - cis isomerization occurs smoothly without a barrier on the S_1surface, while in OMpCA-H_2O complex, there exists a barrier along the isomerization coordinate. The calculated barrier height of OMpCA-H_2O is in good agreement with that estimated from the lifetime measurements.

Ebata, T.; Shimada, D.; Kusaka, R.; Inokuchi, Y.; Ehara, M.

2012-06-01

68

Proteomic Analysis of ?-Amino-3-hydroxy-5-methyl-4-isoxazole Propionate Receptor Complexes*  

PubMed Central

The AMPA receptor (AMPA-R) is a major excitatory neurotransmitter receptor in the brain. Identifying and characterizing the neuronal proteins interacting with AMPA-Rs have provided important information about the molecular mechanisms underlying synaptic transmission and plasticity. In this study, to identify more AMPA-R interactors in vivo, we performed proteomic analyses of AMPA-R complexes from the brain. AMPA-R complexes were isolated from the brain through various combinations of biochemical techniques for solubilization, enrichment, and immunoprecipitation. Mass spectrometry analyses of these isolated complexes identified several novel components of the AMPA-R complexes as well as some previously identified components. The identification of these novel components helps to further define the complex mechanisms involved in the regulation of AMPA receptor function and synaptic plasticity.

Kang, Myoung-Goo; Nuriya, Mutsuo; Guo, Yurong; Martindale, Kevin D.; Lee, Daniel Z.; Huganir, Richard L.

2012-01-01

69

Zinc complex based on 2-(5-methyl-2-hydroxyphenyl)benzotriazole: synthesis and electroluminescence characteristics.  

PubMed

Zinc (II) [2-(5-methyl-2-hydroxyphenyl)benzotriazole] (Zn(MHB)2) was synthesized and characterized by FT-NMR, FT-IR, UV-Vis, XPS and elemental analysis. The photoluminescence of Zn(MHB)2 was measured at 516 nm from the DMF solution. The HOMO (6.6 eV) and LUMO (3.1 eV) energy levels of Zn(MHB)2 were estimated from the measurement of cyclic voltammetry. The devices with structure of ITO/NPB/Zn(MHB)2/Alq3/LiF/Al were constructed to investigate their electroluminescent (EL) performance. Zn(MHB)2 was found to be a good hole-blocking material in the EL devices. PMID:19198393

Park, Jeong-Keun; Kim, Dong-Eun; Hoanh, Trinh Dac; Kwon, Young-Soo; Lee, Burm-Jong

2008-10-01

70

RNA-directed DNA methylation: an epigenetic pathway of increasing complexity.  

PubMed

RNA-directed DNA methylation (RdDM) is the major small RNA-mediated epigenetic pathway in plants. RdDM requires a specialized transcriptional machinery that comprises two plant-specific RNA polymerases - Pol IV and Pol V - and a growing number of accessory proteins, the functions of which in the RdDM mechanism are only partially understood. Recent work has revealed variations in the canonical RdDM pathway and identified factors that recruit Pol IV and Pol V to specific target sequences. RdDM, which transcriptionally represses a subset of transposons and genes, is implicated in pathogen defence, stress responses and reproduction, as well as in interallelic and intercellular communication. PMID:24805120

Matzke, Marjori A; Mosher, Rebecca A

2014-06-01

71

MBD3L2 interacts with MBD3 and components of the NuRD complex and can oppose MBD2-MeCP1-mediated methylation silencing.  

PubMed

MBD2 and MBD3 are two proteins that contain methyl-CpG binding domains and have a transcriptional repression function. Both proteins are components of a large CpG-methylated DNA binding complex named MeCP1, which consists of the nucleosome remodeling and histone deacetylase complex Mi2-NuRD and MBD2. MBD3L2 (methyl-CpG-binding protein 3-like 2) is a protein with substantial homology to MBD2 and MBD3, but it lacks the methyl-CpG-binding domain. Unlike MBD3L1, which is specifically expressed in haploid male germ cells, MBD3L2 expression is more widespread. MBD3L2 interacts with MBD3 in vitro and in vivo, co-localizes with MBD3 but not MBD2, and does not localize to methyl-CpG-rich regions in the nucleus. In glutathione S-transferase pull-down assays, MBD3L2 is found associated with several known components of the Mi2-NuRD complex, including HDAC1, HDAC2, MTA1, MBD3, p66, RbAp46, and RbAp48. Gel shift experiments with nuclear extracts and a CpG-methylated DNA probe indicate that recombinant MBD3L2 can displace a form of the MeCP1 complex from methylated DNA. MBD3L2 acts as a transcriptional repressor when tethered to a GAL4-DNA binding domain. Repression by GAL4-MBD3L2 is relieved by MBD2 and vice versa, and repression by MBD2 from a methylated promoter is relieved by MBD3L2. The data are consistent with a role of MBD3L2 as a transcriptional modulator that can interchange with MBD2 as an MBD3-interacting component of the NuRD complex. Thus, MBD3L2 has the potential to recruit the MeCP1 complex away from methylated DNA and reactivate transcription. PMID:15701600

Jin, Seung-Gi; Jiang, Chun-Ling; Rauch, Tibor; Li, Hongwei; Pfeifer, Gerd P

2005-04-01

72

Spectroscopic Studies of Zinc Benzenethiolate Complexes: Electron Transfer to Methyl Viologen. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

Mononuclear and tetranuclear zinc benzenethiolate complexes are studied by both spectroscopic and electrochemical methods. Zn(SPh)4 2- and Zn4(SPh)102- represent tetrahedral fragments of the cubic zinc sulfide lattice. The structured absorption spectra of...

T. Turk U. Resch M. A. Fox A. Vogler

1992-01-01

73

Carbohydrate/monomer complexes in aqueous polymerizations: methylated-beta-cyclodextrin mediated aqueous polymerization of hydrophobic methacrylic monomers.  

PubMed

Hydrophobic methacrylic monomers were polymerized in aqueous media using methylated (1.8)-beta-cyclodextrin (MeCD) additives. Hydrophobic monomers tert-butyl methacrylate (tBuMA), cyclohexyl methacrylate (CMA), and 2-ethylhexyl methacrylate (2EHMA) were each dissolved in chloroform with MeCD. Chloroform was then evaporated to yield solid monomer/cyclodextrin complexes. Complexes were shown by 1H NMR and thermogravimetric analysis (TGA) to have molar ratios of monomer to MeCD as high as 0.72/1.00. The water-soluble complexes were readily polymerized in aqueous media using free radical initiation. During polymerization, hydrophobic methacrylic polymers precipitated and the majority of MeCD remained in solution. Poly(alkyl methacrylates) synthesized via this method exhibited number-average molecular weights ranging from 50,000 to 150,000 with polydispersities from 3.2 to 5.5 depending on monomer structure, and isolated yields were as high as 86%. Additionally, corresponding methacrylic/carbohydrate films were prepared and examined. High molecular weight poly(tBuMA), poly(CMA), and poly(2EHMA) were blended with MeCD to produce optically clear films with as high as 20 wt % MeCD. Differential scanning calorimetry (DSC) characterization indicated that the glass transition temperatures of these novel carbohydrate blends were controllable over a 20 degrees C range depending on the relative concentration of each component. PMID:11710190

Madison, P H; Long, T E

2000-01-01

74

Vibrational spectra and structure of some oxalic acid/substituted pyridine (methyl-, amino-, and dihalogeno-) complexes: Hydrogen bond features  

NASA Astrophysics Data System (ADS)

The Raman and infrared spectra of some polycrystalline substituted pyridine/oxalic acid complexes have been investigated and assignments in terms of group frequencies are given. Various hydrogen bonds (NH⋯O, OH⋯O, OH⋯N) are distinguished and crystal structures are proposed. For the stronger bases (methyl- or aminopyridines with pka ? 6) proton transfer occurs. The 1/1 complex contains infinite chains of hydrogen oxalate ions linked by strong OH⋯O hydrogen bonds with vOH between 2000 and 800 cm -1. R OH⋯O distances are 2.47-2.62 Å). The substituted pyridinium cations are linked to the chain backbone by medium NH⋯O hydrogen bonds with NH⋯O lengths of 2.71-2.81 Å. The 3,5-dichloropyridine forms a 2/1 adduct without proton transfer, in accordance with its pka (0.6), and strong OH⋯N hydrogen bonds occur (vOH about 2000 cm -1 and R OH⋯N = 2.65 Å). Finally, the 2,6-dihalogenopyridine derivatives do not form complex with oxalic acid, presumably because of steric hindrance.

Lautié, A.; Belabbes, Y.

1996-12-01

75

Combinatorial study of cofluorescence of rare earth organic complexes doped in the poly(methyl methacrylate) matrix.  

PubMed

The luminescence enhancement effect of different kinds and contents of rare earth complexe (RE(DBM)3Phen, RE = Dy, La, Gd, Sm, Y; DBM = dibenzoylmethane; Phen = 1,10-phenanthroline) sensitized Eu(DBM)3Phen doped in poly(methyl methacrylate) (PMMA) matrix was investigated using the combinatorial method. The efficiency of the luminescence enhancement increases with a decrease in the weight percentage of the Eu(DBM)3Phen and an increase in the molecular weight of the PMMA in the systems. Among these sensitization ion complexes, La(DBM)3Phen shows the highest sensitization efficiency. At the optimal content of 5 wt % Eu(DBM)3Phen and 350,000 g/mol weight average molecular weight (Mw) of PMMA, the maximum sensitization efficiency of La(DBM)3Phen is approximately 20 times. We believe that the PMMA with high molecular weight enwraps the rare earth complexes and keeps the donors and acceptors close, which results in the effective intermolecular energy transfer and, consequently, the high sensitization efficiency. PMID:15638482

Ding, Jian Jun; Jiu, Hong Fang; Bao, Jun; Lu, Jie Cheng; Gui, Wan Ru; Zhang, Qi Jin; Gao, Chen

2005-01-01

76

Transcriptional repression by the methyl-CpG-binding protein MeCP2 involves a histone deacetylase complex  

Microsoft Academic Search

Cytosine residues in the sequence 5'CpG (cytosine-guanine) are often postsynthetically methylated in animal genomes. CpG methylation is involved in long-term silencing of certain genes during mammalian development, and in repression of viral genomes,. The methyl-CpG-binding proteins MeCP1 (ref. 5) and MeCP2 (ref. 6) interact specifically with methylated DNA and mediate transcriptional repression. Here we study the mechanism of repression by

Xinsheng Nan; Huck-Hui Ng; Colin A. Johnson; Carol D. Laherty; Bryan M. Turner; Robert N. Eisenman; Adrian Bird

1998-01-01

77

Protein-arginine Methyltransferase 1 (PRMT1) Methylates Ash2L, a Shared Component of Mammalian Histone H3K4 Methyltransferase Complexes*  

PubMed Central

Multiple enzymes and enzymatic complexes coordinately regulate the addition and removal of post-translational modifications on histone proteins. The oncoprotein Ash2L is a component of the mixed lineage leukemia (MLL) family members 1–4, Setd1A, and Setd1B mammalian histone H3K4 methyltransferase complexes and is essential to maintain global trimethylation of histone H3K4. However, regulation of these complexes at the level of expression and activity remains poorly understood. In this report, we demonstrate that Ash2L is methylated on arginine residues both in vitro and in cells. We found that both protein-arginine methyltransferases 1 and 5 methylate Arg-296 within Ash2L. These findings are the first to demonstrate that post-translational modifications occur on the Ash2L protein and provide a novel example of cross-talk between chromatin-modifying enzyme complexes.

Butler, Jill S.; Zurita-Lopez, Cecilia I.; Clarke, Steven G.; Bedford, Mark T.; Dent, Sharon Y. R.

2011-01-01

78

Complexing behaviour of Schiff bases derived from 3-acetyl-4-hydroxy-6-methyl-2H-pyran-2-one  

SciTech Connect

By reaction of 3-acetyl-r-hydroxy-6-methyl-2H-pyran-2-one (HDh, dehydroacetic acid) with H{sub 2}NR (R = Me, nPr or nBu) and HN(CH{sub 2}CH{sub 2}NH{sub 2}){sub 2} the related Schiff bases HDHR and H{sub 2}Dh{sub 2}T were obtained. All ligands react with uranyl nitrate yielding 1:2 adducts. In the uranyl acetate-HDhR systems adduct formation and ligand deprotonation should occur, depending on solvent, reaction time and hydration, whereas H{sub 2}Dh{sub 2}T undergoes total deprotonation in the presence of uranyl acetate to give (UO{sub 2}(Dh{sub 2}T)). Ligands and complexes have been characterized by ir and nmr ({sup 1}H and {sup 13}C) spectroscopy and, in some cases, by thermogravimetric measurements. The action of the amines on the preformed (UO{sub 2}(Dh){sub 2}) complex is discussed.

Fregona, D.; Faraglia, G. (Metallorganica e Analitica dell'Univ., Padova (Italy)); Sitran, S. (Inst. di Chimica e Tecnologia dei Radioelementi del C.N.R., Padova (Italy))

1992-01-01

79

Multiple Histone Methyl and Acetyltransferase Complex Components Bind the HLA-DRA Gene  

Microsoft Academic Search

Major histocompatibility complex class II (MHC-II) genes are fundamental components that contribute to adaptive immune responses. While characterization of the chromatin features at the core promoter region of these genes has been studied, the scope of histone modifications and the modifying factors responsible for activation of these genes are less well defined. Using the MHC-II gene HLA-DRA as a model,

Nancy M. Choi; Jeremy M. Boss

2012-01-01

80

Structural Basis for the Recognition of Methylated Histone H3K36 by the Eaf3 Subunit of Histone Deacetylase Complex Rpd3S  

PubMed Central

SUMMARY Deacetylation of nucleosomes by the Rpd3S histone deacetylase along the path of transcribing RNA polymerase II regulates access to DNA, contributing to faithful gene transcription. The association of Rpd3S with chromatin requires its Eaf3 subunit, which binds histone H3 methylated at lysine 36 (H3K36). Eaf3 is also part of NuA4 acetyltransferase that recognizes methylated H3K4. Here we show that Eaf3 in Saccharomyces cerevisiae contains a chromo barrel-related domain that binds methylated peptides, including H3K36 and H3K4, with low specificity and millimolar-range affinity. Nuclear magnetic resonance structure determination of Eaf3 bound to methylated H3K36 was accomplished by engineering a linked Eaf3-H3K36 molecule with a chemically incorporated methyllysine analog. Our study uncovers the molecular details of Eaf3-methylated H3K36 complex formation, and suggests that, in the cell, Eaf3 can only function within a framework of combinatorial interactions. This work also provides a general method for structure determination of low-affinity protein complexes implicated in methyllysine recognition.

Xu, Chao; Cui, Gaofeng; Botuyan, Maria Victoria; Mer, Georges

2008-01-01

81

1-Methyl-4-phenylpyridinium-induced cell death via autophagy through a Bcl-2/Beclin 1 complex-dependent pathway.  

PubMed

Several lines of evidence suggest that the mechanism underlying drug-induced neuronal apoptosis is initiated by the increased production of reactive oxygen species (ROS). 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a neurotoxin, has been shown to initiate an apoptotic cascade by increasing ROS in the dopaminergic neurons of the substantia nigra, leading to the morphological and physiological features associated with Parkinson's disease. Recently, it has been reported that autophagy, a type of programmed cell death independent of the apoptotic cascade, also plays a role in neuronal damage. Although autophagy is negatively regulated by the mammalian target of rapamycin receptor (mTOR), there is some evidence showing a novel function for the anti-apoptotic protein Bcl-2. Bcl-2 is proposed to play a role in negatively regulating autophagy by blocking an essential protein in the signaling pathway, Beclin 1. Nevertheless, it is unclear whether autophagy is also correlated with apoptotic signaling in 1-methyl-4-phenylpyridinium (MPP(+)) toxicity. Therefore, we hypothesized that the MPP(+) toxicity generally associated with initiating the apoptotic signaling cascade also increases an autophagic phenotype in neuronal cells. Using the SK-N-SH dopaminergic cell lines, we demonstrate that MPP(+) increases the expression of microtubule-associated protein light chain 3 (LC3-II), an autophagosome membrane marker and the mTOR signaling pathway, and Beclin 1 while decreasing the Bcl-2 levels. Moreover, these expressions correlate with a decreased binding ratio between Bcl-2 and Beclin 1, in effect limiting the regulation of the downstream autophagic markers, such as LC3-II. Our results indicate that MPP(+) can induce autophagy in SK-N-SH cells by decreasing the Bcl-2/Beclin 1 complex. PMID:24326530

Nopparat, Chutikorn; Porter, James E; Ebadi, Manuchair; Govitrapong, Piyarat

2014-02-01

82

Synthesis, crystal structures and intermolecular interactions of two Mn(II) complexes with 4,4?-bipy and methyl benzoates  

NASA Astrophysics Data System (ADS)

Two manganese complexes containing 4,4'-bipyridine and methyl benzoate as ligands have been prepared and crystallized by solvent evaporation method in DMF. The single crystal X-ray crystallographic analyses reveal that the complexes crystallize in monoclinic system. Crystal of 1 [Mn2(4,4'-bipy)2 (o-MBA)4]n has space group of P21/c with unit cell parameters of a = 17.508 (Å), b = 11.6229 (Å), c = 27.983 (Å), ? = 128.123°, V = 4.4797 nm3, empirical formula: C52H44Mn2N4O8, Mr = 962.79, Z = 4, Dc = 1.428 g/cm3, ? = 0.625 mm-1, and F(000) = 1992. The crystal of 2 [Mn (4,4'-bipy)(m-MBA)2]n belongs to space group C2/c with a = 16.079 (Å), b = 11.652 (Å), c = 24.887 (Å), ? = 92.02°, V = 4.660 nm3, empirical formula: C26H22MnN2O4, Mr = 481.40, Z = 8, Dc = 1.372 g/cm3, ? = 1.179 mm-1, F(000) = 1992. The weak interactions in structures are observed from the X-ray crystallographic data. These include the Csbnd H⋯O hydrogen bonds, ?-? stacking and Csbnd H⋯? interactions found in 1. The different strength of intermolecular interaction in the structures is reflected on their different thermal stability of the two complexes measured by thermal gravimetric analysis and the 2D-IR correlation spectroscopy. The study of weak interactions is meaningful to provide supporting data for potential application in molecular biology.

Xin-Jian, Wu; Yi-Ping, Chen; Ze-Min, Xia; Su-Zhi, Ge; Feng, Chai; Ling-Yan, Zhao; Jian-Zhong, Chen

2013-03-01

83

Synthesis, spectroscopic characterization and biological evaluation studies of Schiff's base derived from naphthofuran-2-carbohydrazide with 8-formyl-7-hydroxy-4-methyl coumarin and its metal complexes  

NASA Astrophysics Data System (ADS)

Metal complexes of the type ML2, where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and L = Schiff's base derived from the condensation of naphthofuran-2-carbohydrazide with 8-formyl-7-hydroxy-4-methyl coumarin have been synthesized. The chelation of the complexes have been elucidated in the light of analytical, IR, UV-vis, 1H NMR, mass, ESR spectral data, thermal and magnetic studies. The measured molar conductance values indicate that, the complexes are non-electrolytic in nature. The redox behavior of one of the synthesized metal complexes was investigated by cyclic voltammetry. The Schiff's base and its metal complexes have been screened for their in vitro antibacterial and antifungal activities by MIC method. The DNA cleavage activities of all the complexes were studied by agarose gel electrophoresis method. In addition, the free ligand along with its complexes has been studied for their antioxidant activity.

Halli, M. B.; Sumathi, R. B.; Kinni, Mallikarjun

2012-12-01

84

The metal complexes of heterocyclic ?-diketones and their derivatives—VII. The synthesis, structure and i.r. spectral studies of 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5 (HPMTFP) and its divalent metal complexes  

NASA Astrophysics Data System (ADS)

The divalent metal complexes of Be, Mn, Co, Ni, Cu, Zn, Hg, Pb, and Mg with 1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5, (HPMTFP) have been prepared for the first time. The metal complexes were characterized by means of elemental analyses, conductivity measurements, proton NMR and i.r. spectroscopy, and it is concluded that the ligand, HPMTFP, reacts as a bidentate enol forming neutral metal chelates. The i.r. spectra were measured between 4000-200 cm -1 and assignments are proposed for the observed frequencies. Replacement of the methyl group by CF 3 group in the acetyl moiety of 1-phenyl-3-methyl-4-acetyl-pyrazolone-5, HPMAP, is found to increase the C ?O and C ?C bond strengths and decrease that of the M?O bond. The magnitudes of M?O stretching frequencies show good agreement with the Irving—Williams stability order Cu > Ni > Co > Mn > Zn.

Okafor, Emmanuel Chukwuemeka

85

Equilibrium investigation of complex formation reactions involving copper(II), nitrilo-tris(methyl phosphonic acid) and amino acids, peptides or DNA constitutents. The kinetics, mechanism and correlation of rates with complex stability for metal ion promoted hydrolysis of glycine methyl ester  

Microsoft Academic Search

The complex formation reactions of [Cu(NTP)(OH2)] (NTP?=?nitrilo-tris(methyl phosphonic acid)) with some selected bio-relevant ligands containing different functional groups, are investigated. Stoichiometry and stability constants for the complexes formed are reported. The results show that the ternary complexes are formed in a stepwise mechanism whereby NTP binds to copper(II), followed by coordination of amino acid, peptide or DNA. Copper(II) is found

Ahmed A. El-Sherif; Mohamed M. Shoukry

2006-01-01

86

Bis(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine complexes of copper(II), nickel(II), and cobalt(II)  

Microsoft Academic Search

A series of Cu(II), Co(II), and Ni(II) complexes of bis-(3,5-dimethyl-pyrazolyl-1-methyl)-(3-phosphanyl-propyl)-amine C15H26N5P (1), prepared from 3-aminopropylphosphine and 1-hydroxymethyl-3,5-dimethylpyrazole were characterized. The nature of bonding and the geometry of the complexes have been deduced from elemental analysis, infrared, electronic, H NMR, P NMR spectra, magnetic susceptibility, and conductivity measurements. The studies indicate octahedral geometry for nickel complex and square pyramidal geometry for

P. Tharmaraj; D. Kodimunthiri; C. D. Sheela; P. Prakash

2009-01-01

87

The preparation, characterization, crystal structure and biological activities of some copper(II) complexes of the 2-benzoylpyridine Schiff bases of S-methyl- and S-benzyldithiocarbazate  

Microsoft Academic Search

The complexes [Cu(NNS)X] (HNNS represents the 2-benzoylpyridine Schiff bases of S-methyl- or S-benzyldithiocarbazate; X?Cl, Br, NO3) have been prepared and characterized by a variety of physico-chemical techniques. Magnetic and spectral evidence support a square-planar structure for the [Cu(Bp?SR)X] (Bp?SR=the benzoylpyridine Schiff bases; R?CH3, CH2C6H5; X?Cl, Br) and [Cu(Bp?SMe)NO3] complexes and a five-coordinate distorted square-pyramidal structure for the [Cu(Bp?SBz)NO3] complex. The

M. E. Hossain; M. N. Alam; J. Begum; M. Akbar Ali; M. Nazimuddin; F. E. Smith; R. C. Hynes

1996-01-01

88

A High Molar Extinction Coefficient Bisterpyridyl Homoleptic Ru(II) Complex with trans-2-Methyl-2-butenoic Acid Functionality: Potential Dye for Dye-Sensitized Solar Cells.  

PubMed

In our continued efforts in the synthesis of ruthenium(II) polypyridine complexes as potential dyes for use in varied applications, such as the dye-sensitized solar cells (DSSCs), this work particularly describes the synthesis, absorption spectrum, redox behavior and luminescence properties of a new homoleptic ruthenium(II) complex bearing a simple trans-2-methyl-2-butenoic acid functionality as the anchoring ligand on terpyridine moiety. The functionalized terpyridine ligand: 4'-(trans-2-methyl-2-butenoic acid)-terpyridyl (L1) was synthesized by aryl bromide substitution on terpyridine in a basic reaction condition under palladium carbide catalysis. In particular, the photophysical and redox properties of the complex formulated as: bis-4'-(trans-2-methyl-2-butenoic acid)-terpyridyl ruthenium(II) bis-hexafluorophosphate [Ru(L1)(2)(PF(6))(2)] are significantly better compared to those of [Ru(tpy)(2)](2+) and compare well with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical and redox properties of the complex may be attributed partly to the presence of a substituted ?,?-unsaturated carboxylic acid moiety leading to increase in the length of ?-conjugation bond thereby enhancing the MLCT-MC (Metal-to-ligand-charge transfer-metal centred) energy gap, and to the reduced difference between the minima of the excited and ground states potential energy surfaces. PMID:22489165

Adeloye, Adewale O; Olomola, Temitope O; Adebayo, Akinbulu I; Ajibade, Peter A

2012-01-01

89

A High Molar Extinction Coefficient Bisterpyridyl Homoleptic Ru(II) Complex with trans-2-Methyl-2-butenoic Acid Functionality: Potential Dye for Dye-Sensitized Solar Cells  

PubMed Central

In our continued efforts in the synthesis of ruthenium(II) polypyridine complexes as potential dyes for use in varied applications, such as the dye-sensitized solar cells (DSSCs), this work particularly describes the synthesis, absorption spectrum, redox behavior and luminescence properties of a new homoleptic ruthenium(II) complex bearing a simple trans-2-methyl-2-butenoic acid functionality as the anchoring ligand on terpyridine moiety. The functionalized terpyridine ligand: 4?-(trans-2-methyl-2-butenoic acid)-terpyridyl (L1) was synthesized by aryl bromide substitution on terpyridine in a basic reaction condition under palladium carbide catalysis. In particular, the photophysical and redox properties of the complex formulated as: bis-4?-(trans-2-methyl-2-butenoic acid)-terpyridyl ruthenium(II) bis-hexafluorophosphate [Ru(L1)2(PF6)2] are significantly better compared to those of [Ru(tpy)2]2+ and compare well with those of the best emitters of Ru(II) polypyridine family containing tridentate ligands. Reasons for the improved photophysical and redox properties of the complex may be attributed partly to the presence of a substituted ?,?-unsaturated carboxylic acid moiety leading to increase in the length of ?-conjugation bond thereby enhancing the MLCT-MC (Metal-to-ligand-charge transfer-metal centred) energy gap, and to the reduced difference between the minima of the excited and ground states potential energy surfaces.

Adeloye, Adewale O.; Olomola, Temitope O.; Adebayo, Akinbulu I.; Ajibade, Peter A.

2012-01-01

90

Crystal structures of copper(II) nitrate complexes containing 4,4'-bipyridyl and halogen-substituted 2-[(2-hydroxyethylimino)methyl]phenols  

NASA Astrophysics Data System (ADS)

The crystal structures of (?-4,4’-bipyridyl)-di{nitrato-2,4-dibromo-6-[(2-hydroxyethylimino)methyl]phenolo (1-)copper} ( I), (?-4,4’-bipyridyl)-di{nitrato-2,4-dichloro-6-[(2-hydroxyethylimino)methyl]phenolo(1-)copper} ( II), and (?-4,4’-bipyridyl)-{4-chloro-2-[(2-hydroxyethylimino)methyl]phenolo(2-)copper-nitrato-4-chloro-2-[(2-hydroxyethylimino)methyl]phenolo(1-)copper} tetrahydrate ( III) are determined. The crystal structures of compounds I and II contain binuclear complexes, in which each copper atom is coordinated by the singly deprotonated tridentate molecule of the corresponding azomethine, the monodentate nitrate ion, and bipyridyl that plays the role of a bridge between the central atoms. In the structures of compounds I and II, the coordination polyhedra of the copper atoms are slightly distorted tetragonal pyramids. The pyramid base is formed by the imine and bipyridyl nitrogen atoms and the phenol and alcohol oxygen atoms. The axial vertices of the pyramids are occupied by the oxygen atoms of the monodentate nitrato groups. The crystal structure of compound III involves tetranuclear complexes in which the coordination polyhedra of the central copper atoms are (4 + 1 + 1) bipyramids. The base of these bipyramids is formed by the imine and bipyridyl nitrogen atoms and the phenol and alcohol oxygen atoms. One apical vertex is occupied by the bridging phenol oxygen atom of the nearest complex. The sixth coordination site of the first copper atom is occupied by the chlorine atom of the salicylidene fragment of the neighboring complex related to the initial complex through the center of symmetry. In turn, the sixth coordination site of the second copper atom is occupied by the oxygen atom of the monodentate nitrato group.

Chumakov, Yu. M.; Tsapkov, V. I.; Petrenko, P. A.; Popovski, L. G.; Simonov, Yu. A.; Bocelli, G.; Gulea, A. P.

2009-03-01

91

Crystal structures of copper(II) nitrate complexes containing 4,4'-bipyridyl and halogen-substituted 2-[(2-hydroxyethylimino)methyl]phenols  

SciTech Connect

The crystal structures of ({mu}-4,4'-bipyridyl)-di{l_brace}nitrato-2,4-dibromo-6-[(2-hydroxyethylimino)methyl] phenolo (1-)copper{r_brace} (I), ({mu}-4,4'-bipyridyl)-di{l_brace}nitrato-2,4-dichloro-6-[(2-hydroxyethylimino)methyl] phenolo(1-)copper{r_brace} (II), and ({mu}-4,4'-bipyridyl)-{l_brace}4-chloro-2-[(2-hydroxyethylimino)methyl]phenolo(2-) copper-nitrato-4-chloro-2-[(2-hydroxyethylimino)methyl]phenolo(1-)copper{r_brace} tetrahydrate (III) are determined. The crystal structures of compounds I and II contain binuclear complexes, in which each copper atom is coordinated by the singly deprotonated tridentate molecule of the corresponding azomethine, the monodentate nitrate ion, and bipyridyl that plays the role of a bridge between the central atoms. In the structures of compounds I and II, the coordination polyhedra of the copper atoms are slightly distorted tetragonal pyramids. The pyramid base is formed by the imine and bipyridyl nitrogen atoms and the phenol and alcohol oxygen atoms. The axial vertices of the pyramids are occupied by the oxygen atoms of the monodentate nitrato groups. The crystal structure of compound III involves tetranuclear complexes in which the coordination polyhedra of the central copper atoms are (4 + 1 + 1) bipyramids. The base of these bipyramids is formed by the imine and bipyridyl nitrogen atoms and the phenol and alcohol oxygen atoms. One apical vertex is occupied by the bridging phenol oxygen atom of the nearest complex. The sixth coordination site of the first copper atom is occupied by the chlorine atom of the salicylidene fragment of the neighboring complex related to the initial complex through the center of symmetry. In turn, the sixth coordination site of the second copper atom is occupied by the oxygen atom of the monodentate nitrato group.

Chumakov, Yu. M., E-mail: chumakov.xray@phys.asm.md [Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of); Tsapkov, V. I. [State University of Moldova (Moldova, Republic of); Petrenko, P. A. [Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of); Popovski, L. G. [State University of Moldova (Moldova, Republic of); Simonov, Yu. A. [Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of); Bocelli, G. [National Research Council (IMEM-CNR), Institute of Materials for Electronics and Magnetism (Italy); Gulea, A. P. [State University of Moldova (Moldova, Republic of)

2009-03-15

92

Use of Poly(methyl methacrylate-co-methacrylic acid) Membranes in the Ultrafiltration of Aqueous Fe Solutions by Complexing with Poly(vinyl pyrrolidone) and Dextran  

Microsoft Academic Search

In this study water soluble complexible polymers, poly(vinyl pyrrolidone) (PVP) and dextran, were used for the ultrafiltration (UF) of aqueous Fe solutions by using poly(methyl methacrylate-co-methacrylic acid) (PMMA-co-MA) membranes. Effects of polymer concentration and pH on the volume collected in the filtration of Fe solutions and percent retentions (R%) were examined. It was determined that increase in polymer concentration decreased

Gülsen Asman

2009-01-01

93

Synthesis, photophysical and electrochemical properties of a mixed bipyridyl-phenanthrolyl ligand Ru(II) heteroleptic complex having trans-2-methyl-2-butenoic acid functionalities.  

PubMed

In this work, two ligands: 4-(trans-2-Methyl-2-butenoic acid)-2,2'-bipyridine) (L(1)) and 5-(trans-2-methyl-2-butenoic acid)-1,10-phenanthroline (L(2)), with the corresponding mixed-ligand heteroleptic Ru(II) complex were synthesized and characterized by FT-IR, 1H-, 13C-NMR spectroscopy and elemental analysis. The influence of the mixed functionalized polypyridyl ruthenium(II) complex on the photophysical and electrochemical properties were investigated and compared to individual single-ligand homoleptic complexes. Interestingly, the mixed-ligand complex formulated as [RuL(1)L(2)(NCS)(2)] exhibits broad and intense metal-to-ligand charge transfer (MLCT) absorption with a high molar extinction coefficient (?(max) = 514 nm, ? = 69,700 M(-1) cm(-1)), better than those of individual single-ligand complexes, [Ru(L(1))(2)(NCS)(2)] and [Ru(L(2))(2)(NCS)(2)], and a strong photoluminescence intensity ratio in the red region at ?(em) = 686 nm. The electrochemical properties of the complex indicated that the redox processes are ligand-based. PMID:21963625

Adeloye, Adewale O

2011-01-01

94

Modelling neurotransmitter functions: a laser spectroscopic study of (1S,2S)-N-methyl pseudoephedrine and its complexes with achiral and chiral molecules.  

PubMed

Wavelength and mass resolved resonance-enhanced two photon ionization (R2PI) excitation spectra of (1S,2S)-N-methyl pseudoephedrine (MPE) and its complexes with several achiral and chiral solvent molecules, including water (W), methyl (R)-lactate (L(R)), methyl (S)-lactate (L(S)), (R)-2-butanol (B(R)), and (S)-2-butanol (B(S)), have been recorded after a supersonic molecular beam expansion and examined in the light of ab initio calculations. The spectral patterns of the selected complexes have been interpreted in terms of the specific hydrogen-bond interactions operating in the diastereomeric complexes, whose nature in turn depends on the structure and the configuration of the solvent molecule. The obtained results confirm the view that a representative neurotransmitter molecule, like MPE, "communicates" with the enantiomers of a chiral substrate through different, specific interactions. These findings can be regarded as a further contribution to modelling neurotransmitter functions in biological systems. PMID:16688345

Giardini Guidoni, A; Paladini, A; Piccirillo, S; Rondino, F; Satta, M; Speranza, M

2006-05-21

95

Crystal structures of bis-ligand complexes of copper(II) with 2-[(2-hydroxyethylamino)-methyl]-4,6-dinitrophenol, 2,4-dichloro-6-[(2-hydroxyethylamino)-methyl]phenol, and 2,4-dibromo-6-[(2-hydroxyethylamino)-methyl]phenol  

SciTech Connect

The crystal structures of bis{l_brace}2,4-dibromo-6-[(2-hydroxyethylamino)-methyl]phenolato{r_brace}copper (I), bis{l_brace}2,4-dichloro-6-[(2-hydroxyethylamino)-methyl]phenolato{r_brace}copper (II), and bis{l_brace}2-[(2-hydroxyethylamino)-methyl]-4,6-dinitrophenolato{r_brace}copper (III) in which the metal atom is located at the center of symmetry are determined using X-ray diffraction. Crystals of compounds I and II are isostructural. The copper atom in the structures of compounds I and I coordinates two singly deprotonated bidentate molecules of the ligand through the phenol oxygen atoms and the azomethine nitrogen atoms with the formation of a distorted planar square. In the crystals, complexes I and II form one-dimensional infinite chains along the b axis. In the structure of compound III, the coordination polyhedron of the central atom is an elongated tetragonal bipyramid with the base formed by the azomethine nitrogen atoms and the phenol oxygen atoms. Both vertices of the bipyramid are occupied by the oxygen atoms of the amino alcohol groups of the neighboring complexes, which are related to the initial complex through the center of symmetry. In turn, the oxygen atoms of the alcohol groups of the initial complex are located at the vertices of the coordination bipyramids of the metal atoms of the neighboring centrosymmetric complexes, thus forming infinite polymer chains along the a axis.

Chumakov, Yu. M. [Academy of Sciences of Moldova, Institute of Applied Physics (Moldova, Republic of)], E-mail: chumakov.xray@phys.asm.md; Tsapkov, V. I. [State University of Moldova (Moldova, Republic of); Bocelli, G. [National Research Council (IMEM-CNR), Institute of Materials for Electronics and Magnetism (Italy); Palomares-Sanchez, S. A.; Ortiz, R. S. [Universidad Autonoma de San Luis Potosi, Facultad de Ciencias (Mexico); Gulea, A. P. [State University of Moldova (Moldova, Republic of)

2007-02-15

96

Synthesis, crystal structure, DNA binding and photo-induced DNA cleavage activity of ( S-methyl- l-cysteine)copper(II) complexes of heterocyclic bases  

Microsoft Academic Search

Ternary S-methyl-l-cysteine (SMe-l-cys) copper(II) complexes [Cu(SMe-l-cys)(B)(H2O)](X) (1–4), where the heterocyclic base B is 2,2?-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyridoquinoxaline (dpq, 3) and dipyridophenazine (dppz, 4), and X is ClO4- (1–3) or NO3- (4), are prepared and their DNA binding and cleavage properties studied. Complexes 2 and 4 are structurally characterized by X-ray crystallography. Both the crystal structures show distorted

Ashis K. Patra; Munirathinam Nethaji; Akhil R. Chakravarty

2007-01-01

97

Two nickel(II) bis[(pyridin-2-yl)methyl]amine complexes with homophthalic and benzene-1,2,4,5-tetracarboxylic acids.  

PubMed

Two new Ni(II) complexes involving the ancillary ligand bis[(pyridin-2-yl)methyl]amine (bpma) and two different carboxylate ligands, i.e. homophthalate [hph; systematic name: 2-(2-carboxylatophenyl)acetate] and benzene-1,2,4,5-tetracarboxylate (btc), namely catena-poly[[aqua{bis[(pyridin-2-yl)methyl]amine-?(3)N,N',N''}nickel(II)]-?-2-(2-carboxylatophenyl)aceteto-?(2)O:O'], [Ni(C9H6O4)(C12H13N3)(H2O)]n, and (?-benzene-1,2,4,5-tetracarboxylato-?(4)O(1),O(2):O(4),O(5))bis(aqua{bis[(pyridin-2-yl)methyl]amine-?(3)N,N',N''}nickel(II)) bis(triaqua{bis[(pyridin-2-yl)methyl]amine-?(3)N,N',N''}nickel(II)) benzene-1,2,4,5-tetracarboxylate hexahydrate, [Ni2(C10H2O8)(C12H13N3)2(H2O)2]·[Ni(C12H13N3)(H2O)3]2(C10H2O8)·6H2O, (II), are presented. Compound (I) is a one-dimensional polymer with hph acting as a bridging ligand and with the chains linked by weak C-H...O interactions. The structure of compound (II) is much more complex, with two independent Ni(II) centres having different environments, one of them as part of centrosymmetric [Ni(bpma)(H2O)]2(btc) dinuclear complexes and the other in mononuclear [Ni(bpma)(H2O)3](2+) cations which (in a 2:1 ratio) provide charge balance for btc(4-) anions. A profuse hydrogen-bonding scheme, where both coordinated and crystal water molecules play a crucial role, provides the supramolecular linkage of the different groups. PMID:24898954

Atria, Ana María; Garland, Maria Teresa; Baggio, Ricardo

2014-06-15

98

Stereospecific ligands and their complexes. Part XIX. Synthesis, characterization, circular dichroism and antimicrobial activity of oxalato and malonato-(S,S)-ethylenediamine-N,N?-di-2-(3-methyl)butanoato-chromate(III) complexes  

NASA Astrophysics Data System (ADS)

The s-cis-[Cr(S,S-eddv)L]-complexes (1,2) (S,S-eddv = (S,S)-ethylenediamine-N,N?-di-2-(3-methyl)butanoato ion; L = oxalate or malonate ion) were prepared. The complexes were purified by ion-exchange chromatography. The geometry of the complexes has been supposed on the basis of the infrared and electronic absorption spectra, and the absolute configurations of the isolated s-cis-[Cr(S,S-eddv)L]-complexes have been predicted on the basis of their circular dichroism (CD) spectra. Also, the results of thermal decomposition have been discussed. Antimicrobial activity of the prepared complexes (1-4) was investigated against 28 species of microorganisms. Testing was performed by microdilution method and minimum inhibitory concentrations (MIC) and minimum microbicidal concentration (MMC) have been determined. Complexes demonstrated in generally low antibacterial and antifungal activity.

Ili?, Dragoslav; Jevti?, Verica V.; Radojevi?, Ivana D.; Vasi?, Sava M.; Stefanovi?, Olgica D.; ?omi?, Ljiljana R.; Vasojevi?, Miorad M.; Jeli?, Miodrag Ž.; Koval'chuk, Tatyana V.; Loginova, Natalia V.; Trifunovi?, Sre?ko R.

2013-10-01

99

SODs, DNA binding and cleavage studies of new Mn(III) complexes with 2-((3-(benzyloxy)pyridin-2-ylimino)methyl)phenol  

NASA Astrophysics Data System (ADS)

Newly synthesized ligand [2-((3-(benzyloxy)pyridin-2-ylimino)methyl)phenol] (Bpmp) react with manganese(II) to form mononuclear complexes [Mn(phen)(Bpmp)(CH3COO)(H2O)]·4H2O (1), (phen = 1,10-phenanthroline) and [Mn(Bpmp)2(CH3COO)(H2O)]·5H2O (2). These complexes were characterized by elemental analysis, IR, 1H NMR, Mass, UV-vis spectral studies. Molar conductance and thermogravimetric analysis of these complexes were also recorded. The in vitro SOD mimic activity of Mn(III) complexes were carried out and obtained with good result. The DNA-binding properties of the complexes 1 and 2 were investigated by UV-spectroscopy, fluorescence spectroscopy and viscosity measurements. The spectral results suggest that the complexes 1 and 2 can bind to Calf thymus DNA by intercalation mode. The cleavage properties of these complexes with super coiled pUC19 have been studied using the gel electrophoresis method, wherein both complexes 1 and 2 displayed chemical nuclease activity in the absence and presence of H2O2via an oxidative mechanism. All the complexes inhibit the growth of both Gram positive and Gram negative bacteria to competent level. The MIC was determined by microtiter method.

Shivakumar, L.; Shivaprasad, K.; Revanasiddappa, Hosakere D.

2013-04-01

100

Convergent evolution of chromatin modification by structurally distinct enzymes: comparative enzymology of histone H3 Lys²? methylation by human polycomb repressive complex 2 and vSET.  

PubMed

H3K27 (histone H3 Lys27) methylation is an important epigenetic modification that regulates gene transcription. In humans, EZH (enhancer of zeste homologue) 1 and EZH2 are the only enzymes capable of catalysing methylation of H3K27. There is great interest in understanding structure-function relationships for EZH2, as genetic alterations in this enzyme are thought to play a causal role in a number of human cancers. EZH2 is challenging to study because it is only active in the context of the multi-subunit PRC2 (polycomb repressive complex 2). vSET is a viral lysine methyltransferase that represents the smallest protein unit capable of catalysing H3K27 methylation. The crystal structure of this minimal catalytic protein has been solved and researchers have suggested that vSET might prove useful as an EZH2 surrogate for the development of active site-directed inhibitors. To test this proposition, we conducted comparative enzymatic analysis of human EZH2 and vSET and report that, although both enzymes share similar preferences for methylation of H3K27, they diverge in terms of their permissiveness for catalysing methylation of alternative histone lysine sites, their relative preferences for utilization of multimeric macromolecular substrates, their active site primary sequences and, most importantly, their sensitivity to inhibition by drug-like small molecules. The cumulative data led us to suggest that EZH2 and vSET have very distinct active site structures, despite the commonality of the reaction catalysed by the two enzymes. Hence, the EZH2 and vSET pair of enzymes represent an example of convergent evolution in which distinct structural solutions have developed to solve a common catalytic need. PMID:23679895

Swalm, Brooke M; Hallenbeck, Kenneth K; Majer, Christina R; Jin, Lei; Scott, Margaret Porter; Moyer, Mikel P; Copeland, Robert A; Wigle, Tim J

2013-07-15

101

Complex-formation reactions of dicholoro(S-methyl-L-cysteine)palladium(II) with bio-relevant ligands. Labilization induced by S-donor chelates.  

PubMed

The complex-formation equilibria of [Pd(SMC)(H2O)2]+, where SMC = S-methyl-l-cysteinate, with bio-relevant ligands such as amino acids, peptides, dicarboxylic acids and DNA constituents were studied and their formation constants were determined. The binding mode of the ligands containing various functional groups was studied and the speciation diagrams were evaluated. The kinetics of base hydrolysis of amino acid esters bound to [Pd(SMC)(H2O)2]+ was studied in aqueous solution at 25 degrees C and 0.1 M ionic strength. The effect of solvent polarity and temperature on the hydrolysis of coordinated glycine methyl ester was investigated. The activation parameters are evaluated and discussed. PMID:18239833

Shehata, Mohamed R; Shoukry, Mohamed M; Nasr, Fatma M H; van Eldik, Rudi

2008-02-14

102

Synthesis of conducting polyelectrolyte complexes of polyaniline and poly(2-acrylamido-3-methyl-1-propanesulfonic acid) catalyzed by pH-stable palm tree peroxidase.  

PubMed

Comparison of the stability of five plant peroxidases (horseradish, royal palm tree leaf, soybean, and cationic and anionic peanut peroxidases) was carried out under acidic conditions favorable for synthesis of polyelectrolyte complexes of polyaniline (PANI). It demonstrates that palm tree peroxidase has the highest stability. Using this peroxidase as a catalyst, the enzymatic synthesis of polyelectrolyte complexes of PANI and poly(2-acrylamido-3-methyl-1-propanesulfonic acid) (PAMPS) was developed. The template polymerization of aniline was carried out in aqueous buffer at pH 2.8. Varying the concentrations of aniline, PAMPS, and hydrogen peroxide as reagents, favorable conditions for production of PANI were determined. UV-vis-NIR absorption and EPR demonstrated that PAMPS and PANI formed the electroactive complex similar to PANI doped traditionally using low molecular weight sulfonic acids. The effect of pH on conformational variability of the complex was evaluated by UV-vis spectroscopy. Atomic force microscopy showed that a size of the particles of the PANI-PAMPS complexes varied between 10 and 25 nm, depending on a concentration of PAMPS in the complex. The dc conductivity of the complexes depends also on the content of PAMPS, the higher conductivity being for the complexes containing the lower content of the polymeric template. PMID:15877353

Caramyshev, Alexei V; Evtushenko, Evgeny G; Ivanov, Viktor F; Barceló, Alfonso Ros; Roig, Manuel G; Shnyrov, Valery L; van Huystee, Robert B; Kurochkin, Iliya N; Vorobiev, Andrey Kh; Sakharov, Ivan Yu

2005-01-01

103

Synthesis, characterization, antimicrobial activity and carbonic anhydrase enzyme inhibitor effects of salicilaldehyde-N-methyl p-toluenesulfonylhydrazone and its Palladium(II), Cobalt(II) complexes.  

PubMed

We report the synthesis of the ligand, salicilaldehyde-N-methyl p-toluenesulfonylhydrazone (salptsmh) derived from p-toluenesulfonicacid-1-methylhydrazide (ptsmh) and its Pd(II) and Co(II) metal complexes were synthesized for the first time. The structure of the ligand and their complexes were investigated using elemental analysis, magnetic susceptibility, molar conductance and spectral (IR, NMR and LC-MS) measurements. Salptsmh has also been characterized by single crystal X-ray diffraction. (1)H and (13)C shielding tensors for crystal structure were calculated with GIAO/DFT/B3LYP/6-311++G(d,p) methods in CDCl3. The complexes were found to have general composition [ML2]. The results of elemental analysis showed 1:2 (metal/ligand) stoichiometry for all the complex. Magnetic and spectral data indicate a square planar geometry for Pd(II) complex and a distorted tetrahedral geometry for Co(II) complexes. The ligand and its metal chelates have been screened for their antimicrobial activities using the disk diffusion method against the selected Gram positive bacteria: Bacillus subtilis, Bacillus cereus, Staphylococcus aureus, Enterococcus faecalis, Gram negative bacteria: Eschericha coli, Pseudomonas aeruginosa, Klebsiella pneumonia. The inhibition activities of these compounds on carbonic anhydrase II (CA II) and carbonic anhydrase I (CA I) have been investigated by comparing IC50 and Ki values and it has been found that Pd(II) complex have more enzyme inhibition efficiency than salptsmh and Co(II) complex. PMID:24835932

Alyar, Saliha; Adem, Sevki

2014-10-15

104

The metal complexes of heterocyclic ?-diketones and their derivatives—VI. The synthesis, structure and i.r. spectral studies of some new metal(II) complexes of 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP)  

NASA Astrophysics Data System (ADS)

The monovalent metal complex of Na and the divalent metal complexes of Be, Mn, Co, Ni, Cu, Zn, Mg, Ba, Hg and Pb with 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP), have been synthesized. It is shown that HPMBP behaves like a bidentate enol forming neutral metal chelates through the carbonyl and enolic hydroxyl groups. Characterization of the complexes were by means of elemental analyses, conductivity measurements, i.r. and proton NMR spectroscopy. The i.r. spectra were recorded between 4000 and 200 cm -1 and assignments are proposed for the observed frequencies. Replacement of the methyl group of the 4-acetyl moiety by the phenyl group in the metal chelates of 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 (HPMAP), is found to decrease the C ?O, C ?C and M?O stretching frequencies of the chelate ring. The magnitudes of the M?O stretching frequencies for the transition metals show good agreement with the Irving—Williams stability order Cu>Ni>Co>Zn>Mn.

Okafor, Emmanuel Chukwuemeka

105

Grafting of methyl methacrylate to cellulose and polypropylene with UV and ionising radiation in the presence of additives including CT complexes  

NASA Astrophysics Data System (ADS)

Detailed studies of the grafting of polar methyl methacrylate (MMA) to two representative backbone polymers, cellulose and polypropylene (PPE) in the presence of additives, using ionising radiation and UV as initiating sources, are reported. The results are compared with analogous grafting work with non polar styrene previously studied. The additives chosen for examination were predominantly components used in radiation curing formulations since grafting and curing are known to be mechanistically related. The additives were mineral acid, photoinitiators, vinyl ethers, oligomers, polyfunctional monomers including multifunctional acrylates (MFAs) and methacrylates (MFMAs). For the first time charge transfer (CT) monomer complexes have been used as additives in the current work. The CT complexes themselves, being monomers, have also been directly radiation grafted to cellulose. Mechanisms for the above grafting processes are proposed. The significance of this grafting work in analogous radiation curing is discussed. The grafting of the CT complexes, themselves, is shown to lead to new copolymers with potential industrial applications.

Garnett, John L.; Ng, Loo-Teck; Viengkhou, Visay

1999-10-01

106

Syntheses, structures and thermal stabilities of eight 1-((benzotriazol-yl)methyl)-1H-1,3-imidazole complexes based on different anions  

NASA Astrophysics Data System (ADS)

The main aim of the work herein presented is to investigate the influence of different anions on the structures of a series of complexes. Through the self-assembly of a new unsymmetrical ligand 1-((benzotriazol-yl)methyl)-1H-1,3-imidazole (bmi) with M(NO 3) 2 or MSO 4 [M = Zn(II), Co(II), Cd(II), Cu(II)], a series of new complexes, [M(bmi) 2(NO 3) 2] n [M = Zn ( 1), Co ( 2), Cd ( 3), Cu ( 4)] and [M(bmi)(H 2O) 4(SO 4)]·2H 2O [M = Zn ( 5), Co ( 6), Cd ( 7), Cu ( 8)], have been synthesized. X-ray diffraction analyses revealed that the bmi ligands coordinate to the central metal ions with bridging bidentate mode leading to polynuclear isostructural complexes ( 1- 4) in the reactions of nitrates with bmi. While in the reactions of sulfates with bmi, the bmi ligands coordinate to the central metal ions with a simple monodentate mode resulting in isostructural mononuclear complexes ( 5- 8). These results suggest that the change of anion can influence the coordination modes of the ligand, and then influence the structures of the complexes. The thermal analysis studies indicate that nitrate-containing complexes 1- 4 are more stable than the sulfate-containing complexes 5- 8.

Meng, Xiangru; Zhu, Xiaoqing; Qi, Yongfang; Hou, Hongwei; Fan, Yaoting

2009-09-01

107

Antioxidant, DNA binding and nuclease activities of heteroleptic copper(II) complexes derived from 2-((2-(piperazin-1-yl)ethylimino)methyl)-4-substituted phenols and diimines.  

PubMed

A series of heteroleptic copper(II) complexes of the type [CuL(1-4)(diimine)](ClO4)2 (1-8) [L(1-4)=2-((2-(piperazin-1-yl)ethylimino)methyl)-4-substituted phenols, and diimine=2,2'-bipyridyl (bpy) or 1,10-phenanthroline (phen)], have been synthesized and characterized by spectroscopic methods. The IR spectra of complexes indicate the presence of uncoordinated perchlorate anions and the electronic spectra revealed the square pyramidal geometry with N4O coordination environment around copper(II) nuclei. Electrochemical studies of the mononuclear complexes evidenced one-electron irreversible reduction wave in the cathodic region. The EPR spectra of complexes with g|| (2.206-2.214) and A|| (154-172×10(-)(4)cm(-)(1)) values support the square-based CuN3O coordination chromophore and the presence of unpaired electron localized in [Formula: see text] ground state. Antioxidant studies against DPPH revealed effective radical scavenging properties of the synthesized complexes. Binding studies suggest that the heteroleptic copper(II) complexes interact with calf thymus DNA (CT-DNA) through minor-groove and electrostatic interaction, and all the complexes display pronounced nuclease activity against supercoiled pBR322 DNA. PMID:24998685

Ravichandran, J; Gurumoorthy, P; Imran Musthafa, M A; Kalilur Rahiman, A

2014-12-10

108

Genome-wide analysis of histone methylation reveals chromatin state-based complex regulation of differential gene transcription and function of CD8 memory T cells  

PubMed Central

Summary Memory lymphocytes are characterized by their ability to exhibit a rapid response to the recall antigen, in which differential transcription plays a significant role, yet the underlying mechanism is not understood. We report here a genome-wide analysis of histone methylation on two histone H3 lysine residues (H3K4me3 and H3K27me3) and gene expression profiles in naïve and memory CD8 T cells. We found that a general correlation exists between the levels of gene expression and the levels of H3K4me3 (positive correlation) and H3K27me3 (negative correlation) across the gene body. These correlations display four distinct modes: repressive, active, poised, and bivalent, reflecting different functions of these genes. Furthermore, a permissive chromatin state of each gene is established by a combination of different histone modifications. Our findings reveal a complex regulation by histone methylation in differential gene expression and suggest that histone methylation may be responsible for memory CD8 T cell function.

Araki, Yasuto; Wang, Zhibin; Zang, Chongzhi; Wood, William H.; Schones, Dustin; Cui, Kairong; Roh, Tae-Young; Lhotsky, Brad; Wersto, Robert P.; Peng, Weiqun; Becker, Kevin G.; Zhao, Keji; Weng, Nan-ping

2009-01-01

109

Kinetics of substitution reactions of transition metal complexes in 1,3-dioxolan-2-one + water and 4-methyl-1,3-dioxolan-2-one + water solvent mixtures  

Microsoft Academic Search

Rate constants are reported and discussed for several substitutions of inorganic complexes in ethylene carbonate (1,3-dioxolan-2-one) + water and in propylene carbonate (4-methyl-1,3-dioxolan-2-one) + water solvent mixtures. The reactions include aquation ofcis- and oftrans-[Co(en)2Cl2]+, aquation oftrans-[Cr(OH2)4Cl2]+, bromide substitution at [Pd(Et4dien)Cl]+, thiourea substitution atcis-[Pt(4-NCpy)2Cl2], and aquation and cyanide attack at [Fe(X-phen)3]2+ cations.

Michael J. Blandamer; John Burgess; Stephen J. Hamshere; Fikry M. Mekhail

1979-01-01

110

Synthesis of Pd(II) coordination complexes of ( S)-4-isobutyl-2-methyl-2-oxazoline and ( S)-2-(2,2-dimethylpropyl)-4-isopropyl-2-oxazoline  

Microsoft Academic Search

(S)-4-Isobutyl-2-methyl-2-oxazoline (1) was obtained from ethyl acetimidate hydrochloride and l-leucinol in 81% yield. (S)-2-(2,2-Dimethylpropyl)-4-isopropyl-2-oxazoline (2) was synthesized from 3,3-dimethylbutyryl chloride and l-valinol in two steps in a total yield of 44%. Reactions of oxazolines 1 and 2 with Pd(OAc)2 in AcOH or MeCN at different temperatures followed by treatment with LiCl resulted in the formation of the corresponding coordination complexes

Relindis Y. Mawo; Diane M. Johnson; Irina P. Smoliakova

2008-01-01

111

The toluene-Ar complex: S0 and S1 van der Waals modes, changes to methyl rotation, and torsion-van der Waals vibration coupling  

NASA Astrophysics Data System (ADS)

The methyl rotor and van der Waals vibrational levels in the S1 and S0 states of toluene-Ar have been investigated by the technique of two-dimensional laser induced fluorescence (2D-LIF). The S0 van der Waals and methyl rotor levels are reported for the first time, while improved S1 values are presented. The correlations seen in the 2D-LIF images between the S0 and S1 states lead to a reassignment of key features in the S1 <-- S0 excitation spectrum. This reassignment reveals that there are significant changes in the methyl rotor levels in the complex compared with those in bare toluene, particularly at low m. The observed rotor energies are explained by the introduction of a three-fold, V3, term in the torsion potential (this term is zero in toluene) and a reduction in the height of the six-fold, V6, barriers in S0 and S1 from their values in bare toluene. The V3 term is larger in magnitude than the V6 term in both S0 and S1. The constants determined are |V3(S1)| = 33.4 +/- 1.0 cm-1, |V3(S0)| = 20.0 +/- 1.0 cm-1, V6(S1) = -10.7 +/- 1.0 cm-1, and V6(S0) = -1.7 +/- 1.0 cm-1. The methyl rotor is also found to couple with van der Waals vibration; specifically, the m'' = 2 rotor state couples with the combination level involving one quantum of the long axis bend and m'' = 1. The coupling constant is determined to be 1.9 cm-1, which is small compared with the values typically reported for torsion-vibration coupling involving ring modes.

Gascooke, Jason R.; Lawrance, Warren D.

2013-02-01

112

In situ synthesis of mononuclear copper(II) complexes of the new tridentate ligand bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine.  

PubMed

Two mononuclear copper complexes, {bis[(3,5-dimethyl-1H-pyrazol-1-yl-?N(2))methyl]amine-?N}(3,5-dimethyl-1H-pyrazole-?N(2))(perchlorato-?O)copper(II) perchlorate, [Cu(ClO(4))(C(5)H(8)N(2))(C(12)H(19)N(5))]ClO(4), (I), and {bis[(3,5-dimethyl-1H-pyrazol-1-yl-?N(2))methyl]amine-?N}bis(3,5-dimethyl-1H-pyrazole-?N(2))copper(II) bis(hexafluoridophosphate), [Cu(C(5)H(8)N(2))(2)(C(12)H(19)N(5))](PF(6))(2), (II), have been synthesized by the reactions of different copper salts with the tripodal ligand tris[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine (TDPA) in acetone-water solutions at room temperature. Single-crystal X-ray diffraction analysis revealed that they contain the new tridentate ligand bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine (BDPA), which cannot be obtained by normal organic reactions and has thus been captured in the solid state by in situ synthesis. The coordination of the Cu(II) ion is distorted square pyramidal in (I) and distorted trigonal bipyramidal in (II). The new in situ generated tridentate BDPA ligand can act as a meridional or facial ligand during the process of coordination. The crystal structures of these two compounds are stabilized by classical hydrogen bonding as well as intricate nonclassical hydrogen-bond interactions. PMID:21979969

Yu, Fan

2011-10-01

113

Synthesis, Characterization, and Photochemical Studies of Some Copper Complexes of Schiff Bases Derived from 3?Hydrazino?6?methyl[1,2,4]triazin?5(4H)one  

Microsoft Academic Search

Cu(II) complexes of new bidentate and tridentate Schiff bases derived from the condensation of 3?hydrazino?6?methyl[1,2,4]triazin?5(4H)one and aromatic aldehyde derivatives were synthesized and characterized. The structure of the complexes proposed according to elemental analyses, molar conductance, IR UV?Visible absorption spectra is square?planar. The thermodecomposition kinetics of the complexes were investigated under non?isothermal condition. TG and DTG curves indicated that the complexes

Ahmed H. Osman; Magda S. Saleh; Sanaa M. Mahmoud

2004-01-01

114

Half-sandwich dichloro, alkyl chloro, dialkyl, alkyl methyl and amido methyl imido cyclopentadienyl niobium and tantalum(V) complexes. Dynamic behaviour of amido imido tantalum derivatives  

Microsoft Academic Search

Reactions of NbCp?Cl4 (Cp?=?5-C5H4SiMe3) and TaCp*Cl2Me2 (Cp*=?5-C5Me5) with two equivalents of NHR1SiMe3 and two equivalents of CNR1 (M=Nb, R1=2,6-Me2C6H3; 2,6-iPr2C6H3; SiMe3; M=Ta, R1=2,6-Me2C6H3), respectively, gave the dichloro imido derivatives [MCpCl2(NR1)] (M=Nb, Cp=Cp?, R1=2,6-Me2C6H3, 1; 2,6-iPr2C6H3, 2; SiMe3, 3; M=Ta, Cp=Cp*, 4). Alkyl chloro imido complexes [MCpClR(NR1)], (R1=2,6-Me2C6H3; M=Nb, Cp=Cp?, R=Me, 5; Cp*, 6; M=Ta, Cp=Cp*, R=Me, 7; NMe2, 8; OtBu,

Aurora Castro; Mikhail V Galakhov; Manuel Gómez; Fernando Sánchez

1999-01-01

115

Sildenafil citrate attenuates a complex maze impairment induced by intracerebroventricular infusion of the NOS inhibitor Nomega-nitro-L-arginine methyl ester.  

PubMed

In a previous study, our laboratory reported that sildenafil citrate, a cyclic nucleotide phosphodiesterase type 5 inhibitor, reversed a learning impairment in rats induced by systemic inhibition of nitric oxide synthase (60 mg/kg, i.p., Nomega-nitro-L-arginine methyl ester; L-NAME). To limit the peripheral effects of L-NAME and further localize the site of action of sildenafil, L-NAME (48 microg, i.c.v.) was infused bilaterally into the lateral cerebral ventricles 30 min prior to maze training. Saline or sildenafil citrate (1.5 or 3.0 mg/kg, i.p.) was administered systemically 15 min before training. Drug injections occurred 24 h after pretraining rats to avoid foot shock on a one-way active avoidance straight runway. Following drug treatment, the rats received 15 training trials on a 14-unit T-maze task that requires learning a complex sequence of turns to avoid mild foot shock. This complex maze paradigm is sensitive to aging and blockade of cholinergic, N-methyl-D-aspartate and nitric oxide signaling systems. Behavioral measures of performance included deviations from the correct pathway (errors), runtime from start to goal (latency), shock frequency and shock duration. Statistical analysis revealed that central infusion of L-NAME impaired maze performance and that sildenafil (3.0 mg/kg) significantly attenuated the impairment. These results suggest that sildenafil citrate may serve as a cognitive enhancer by modulating central nitric oxide/cGMP signal transduction following N-methyl-D-aspartate receptor activation. This pathway has been implicated in age-related cognitive decline and may be a useful target for pharmacological intervention of neurodegenerative disease. PMID:17362916

Devan, Bryan D; Pistell, Paul J; Daffin, Lee W; Nelson, Christopher M; Duffy, Kara B; Bowker, Jonna L; Bharati, Ila S; Sierra-Mercado, Demetrio; Spangler, Edward L; Ingram, Donald K

2007-06-01

116

The synthesis, characterization and spectral studies of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with N,Nbis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl) methyl]amino}butyl) N?,N?-dihydroxyethanediimidamide  

Microsoft Academic Search

Co, Ni, Cu, Zn and Cd complexes of N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]amino}butyl)N?,N?-dihydroxyethanediimidamide (LH2) were synthesized and characterized by elemental analyses, IR, H- and C-NMR spectra, electronic spectra, magnetic susceptibility measurements, conductivity measurements and thermogravimetric analyses (TGA). The Co, Ni and Cu complexes of LH2 were synthesized with 1?:?2 metal ligand stoichiometry. Zn and Cd complexes with LH2 have a metal ligand ratio of

E. Canpolat; M. Kaya

2005-01-01

117

A pivotal role for reductive methylation in the de novo crystallization of a ternary complex composed of Yersinia pestis virulence factors YopN, SycN and YscB.  

PubMed

Structural studies of a ternary complex composed of the Yersina pestis virulence factors YopN, SycN and YscB were initially hampered by poor solubility of the individual proteins. Co-expression of all three proteins in Escherichia coli yielded a well behaved complex, but this sample proved to be recalcitrant to crystallization. As crystallization efforts remained fruitless, even after the proteolysis-guided engineering of a truncated YopN polypeptide, reductive methylation of lysine residues was employed to alter the surface properties of the complex. The methylated complex yielded crystals that diffracted X-rays to a maximal resolution of 1.8 A. The potential utility of reductive methylation as a remedial strategy for high-throughput structural biology was further underscored by the successful modification of a selenomethionine-substituted sample. PMID:15502305

Schubot, Florian D; Waugh, David S

2004-11-01

118

Conductivity, Mechanical and Thermal Studies on Poly(methyl methacrylate)-Based Polymer Electrolytes Complexed with Lithium Tetraborate and Propylene Carbonate  

NASA Astrophysics Data System (ADS)

A series of different composition ratio of polymer electrolytes based on poly(methyl methacrylate) (PMMA) as host polymer, lithium tetraborate (Li2B4O7) as salt, and propylene carbonate (PC) as plasticizer is produced by solution casting method. Fourier transform infrared (FTIR) spectroscopy studies are used to confirm the formation of polymer electrolyte complex. PMMA: Li2B4O7: PC (52.5:22.5:25.0 wt.%) is obtained as the highest conducting polymer electrolyte with a conductivity of 5.14 × 10-6 S/cm at room temperature (23 °C). The temperature-dependent conductivity of the polymer films shows Arrhenius-like behavior which reveals that the charge carriers move in a liquid-like environment. The addition of PC decreases the Young's modulus and stress at peak values of the complexes. Thermogravimetric analysis (TGA) is employed to study the thermal stability of the electrolytes.

Ramesh, S.; Bing, Khoo Ne

2012-01-01

119

Synthesis and room temperature single crystal EPR studies of a dinickel complex having an Ni2(?-phenoxide)2 2+ unit supported by a macrocyclic ligand environment [Ni2(L)2(OClO3)2] [L = 2-[(4-methyl-pyridin-2-ylimino)-methyl]-phenol  

Microsoft Academic Search

A bimetallic nickel(II) complex with the ligand Hsalamp (2 -((4-methyl- pyridin-2-ylimino)-methyl)-phenol), having the molecular formula, Ni2C26H22 N4O10Cl2, is synthesized and characterized by elemental, UV -Vis, IR and EPR studies. The IR spectrum confirms the presence of coordinated perchlorate ion and the UV-Vis. spectrum substantiates that the geometry around the metal ion is distorted square pyramidal. In the solvent methanol, the

R. Srinivasan; I. Sougandi; R. Venkatesan; P. Sambasiva Rao

2003-01-01

120

Metal-catalysed oxidation processes in thiosemicarbazones: new complexes with the ligand N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide.  

PubMed

The coordination behaviour of a new thiosemicarbazone Schiff-base building block, N-{2-([4-N-ethylthiosemicarbazone]methyl)phenyl}-p-toluenesulfonamide, H2L1 (1), incorporating a bulky tosyl group, towards Mn II, Fe II, Co II, Ni II, Cu II, Zn II, Cd II, Ag I, Sn II, and Pb II has been investigated by means of an electrochemical preparative procedure. Most metal complexes of L1 have the general formula [M(L1)]2.nX (M=Mn, Fe, Co, Ni, Cu, Cd, Pb; n=0-4, X=H2O or CH3CN), as confirmed by the structure of [Pb(L1)]2 (15), in which the lone pair on lead is stereochemically active. This lead(II) complex shows an intense fluorescence emission with a quantum yield of 0.13. In the case of silver, the complex formed was found to possess a stoichiometry of [Ag2(L1)]2.3H2O. During reactions with manganese and copper metals, interesting catalysed processes have been found to take place, with remarkable consequences regarding the ligand skeleton structure. In synthesising the manganese complex, we obtained an unexpected dithiolate thiosemicarbazone tosyl ligand, H2L2, as a side-product, which has been fully characterised, including by X-ray diffraction analysis. In the case of copper, the solid complex has the formula [CuL1]2, but the crystallised product shows the copper atoms coordinated to a new cyclised thiosemicarbazone ligand, H2L3, as in the structures of the complexes [Cu(L3)]2.CH3CN (8) and [Cu(L3)(H2O)]2.CH3CN.H2O (9). The zinc complex [Zn(L1)]4 (12) displays a particular tetranuclear zeolite-type structure capable of hosting small molecules or ions, presumably through hydrogen bonding. PMID:17918755

Pedrido, Rosa; Romero, María J; Bermejo, Manuel R; González-Noya, Ana M; García-Lema, Iria; Zaragoza, Guillermo

2008-01-01

121

Synthesis, characterization, crystal structure and antibacterial activities of transition metal(II) complexes of the schiff base 2-[(4-methylphenylimino)methyl]-6-methoxyphenol.  

PubMed

Five transition metal(II) complexes, [ML(2)Cl(2)] 1 approximately 5, were synthesized from the reaction of MCl(2) x nH(2)O (M = Mn, Co, Ni, Cu, Cd) and the Schiff base ligand 2-[(4-methylphenylimino)methyl]-6-methoxyphenol (C(15)H(15)NO(2), L), obtained by condensation of o-vanillin (2-hydroxy-3-methoxybenzaldehyde) with p-toluidine. They were characterized by elemental analysis, molar conductance, FT-IR spectra, thermal analysis. The structure of complex 1 was determined by single-crystal X-ray diffraction. Its crystal structure is of monoclinic system, space group P2(1)/c with a = 9.0111(18) A, b = 11.222(2) A, c =28.130 (6) A, alpha = 90 masculine, beta = 92.29(3) masculine, gamma = 90 masculine, V = 2867.6(10) A(3), Z = 4. The Mn atom is six-coordinate and displays distorted octahedral geometry.The Schiff base ligand and its complexes have been tested in vitro to evaluate their antibacterial activity against bacteria, viz., Escherichia coli, Staphylococcus aureus and Bacillus subtilis. It has been found that the complexes have higher activity than the corresponding free Schiff base ligand against the same bacteria. PMID:19471194

Yu, Yu-Ye; Xian, Hui-Duo; Liu, Jian-Feng; Zhao, Guo-Liang

2009-01-01

122

Excited state complex formation between methyl glyoxal and some aromatic bio-molecules: a fluorescence quenching study  

NASA Astrophysics Data System (ADS)

Fluorescence quenching of some important aromatic bio-molecules (ABM) such as 3-aminophthalhydrazide (luminol), tryptophan (Try), phenylalanine and tyrosine (Tyr) by methyl glyoxal (MG) has been studied employing different spectroscopic techniques. The interaction of MG with ABM in the excited state has been analysed using Stern-Volmer (S-V) mechanism. In the case of MG-luminol system time correlated single photon counting (TCSPC) technique has also been applied to explain the S-V mechanism. The bimolecular rate constants obtained are found to be higher than the rate constant for diffusion controlled process. A plausible explanation of the quenching mechanism has been discussed on the basis of hydrogen bonding, charge transfer and energy transfer interaction between the colliding species.

Banerjee, D.; Mandal, A.; Mukherjee, S.

2003-01-01

123

Protein complex interactor analysis and differential activity of KDM3 subfamily members towards H3K9 methylation.  

PubMed

Histone modifications play an important role in chromatin organization and gene regulation, and their interpretation is referred to as epigenetic control. The methylation levels of several lysine residues in histone tails are tightly controlled, and JmjC domain-containing proteins are one class of broadly expressed enzymes catalyzing methyl group removal. However, several JmjC proteins remain uncharacterized, gaps persist in understanding substrate recognition, and the integration of JmjC proteins into signaling pathways is just emerging. The KDM3 subfamily is an evolutionarily conserved group of histone demethylase proteins, thought to share lysine substrate specificity. Here we use a systematic approach to compare KDM3 subfamily members. We show that full-length KDM3A and KDM3B are H3K9me1/2 histone demethylases whereas we fail to observe histone demethylase activity for JMJD1C using immunocytochemical and biochemical approaches. Structure-function analyses revealed the importance of a single amino acid in KDM3A implicated in the catalytic activity towards H3K9me1/2 that is not conserved in JMJD1C. Moreover, we use quantitative proteomic analyses to identify subsets of the interactomes of the 3 proteins. Specific interactor candidates were identified for each of the three KDM3 subfamily members. Importantly, we find that SCAI, a known transcriptional repressor, interacts specifically with KDM3B. Taken together, we identify substantial differences in the biology of KDM3 histone demethylases, namely enzymatic activity and protein-protein interactions. Such comparative approaches pave the way to a better understanding of histone demethylase specificity and protein function at a systems level and are instrumental in identifying the more subtle differences between closely related proteins. PMID:23593242

Brauchle, Michael; Yao, Zhiping; Arora, Rishi; Thigale, Sachin; Clay, Ieuan; Inverardi, Bruno; Fletcher, Joy; Taslimi, Paul; Acker, Michael G; Gerrits, Bertran; Voshol, Johannes; Bauer, Andreas; Schübeler, Dirk; Bouwmeester, Tewis; Ruffner, Heinz

2013-01-01

124

Protein Complex Interactor Analysis and Differential Activity of KDM3 Subfamily Members Towards H3K9 Methylation  

PubMed Central

Histone modifications play an important role in chromatin organization and gene regulation, and their interpretation is referred to as epigenetic control. The methylation levels of several lysine residues in histone tails are tightly controlled, and JmjC domain-containing proteins are one class of broadly expressed enzymes catalyzing methyl group removal. However, several JmjC proteins remain uncharacterized, gaps persist in understanding substrate recognition, and the integration of JmjC proteins into signaling pathways is just emerging. The KDM3 subfamily is an evolutionarily conserved group of histone demethylase proteins, thought to share lysine substrate specificity. Here we use a systematic approach to compare KDM3 subfamily members. We show that full-length KDM3A and KDM3B are H3K9me1/2 histone demethylases whereas we fail to observe histone demethylase activity for JMJD1C using immunocytochemical and biochemical approaches. Structure-function analyses revealed the importance of a single amino acid in KDM3A implicated in the catalytic activity towards H3K9me1/2 that is not conserved in JMJD1C. Moreover, we use quantitative proteomic analyses to identify subsets of the interactomes of the 3 proteins. Specific interactor candidates were identified for each of the three KDM3 subfamily members. Importantly, we find that SCAI, a known transcriptional repressor, interacts specifically with KDM3B. Taken together, we identify substantial differences in the biology of KDM3 histone demethylases, namely enzymatic activity and protein-protein interactions. Such comparative approaches pave the way to a better understanding of histone demethylase specificity and protein function at a systems level and are instrumental in identifying the more subtle differences between closely related proteins.

Brauchle, Michael; Yao, Zhiping; Arora, Rishi; Thigale, Sachin; Clay, Ieuan; Inverardi, Bruno; Fletcher, Joy; Taslimi, Paul; Acker, Michael G.; Gerrits, Bertran; Voshol, Johannes; Bauer, Andreas; Schubeler, Dirk; Bouwmeester, Tewis; Ruffner, Heinz

2013-01-01

125

Catalytic Synthesis of 2Methyl1,4Naphthoquinone (Vitamin K3) Over Silica-Supported Aminomethyl Phosphine-Ru(II), Pd(II), and Co(II) Complexes  

Microsoft Academic Search

Ru(II), Pd(II), and Co(II) complexes of the free ditertiary aminomethylphosphine ligand, N,N-bis(diphenylphosphinomethyl)aminopropyltriethoxysilane [(EtO)3Si(CH2)3 N(CH2PPh2)2] (DIPAPTES), and its SiO2-DIPAPES have been synthesized under a nitrogen atmosphere using Schlenk techniques. All the complexes were used as catalysts for the oxidation of 2-methyl naphthalene (2MN) to give 2-methyl-1,4-naphthoquinone (vitamin K3, menadione, 2MNQ) in the presence of hydrogen peroxide as a clean and cheap

Serhan Uru?; Mustafa Kele?; Osman Serinda?

2010-01-01

126

Synthesis of Silica-Supported Platinum(II) and Nickel(II) Complexes of Bis (Diphenylphosphinomethyl)Amino Ligand: Applications as Catalysts for the Synthesis of 2Methyl1,4Naphthoquinone (Vitamin K 3 )  

Microsoft Academic Search

Pt(II) and Ni(II) complexes of N,N-bis(diphenylphosphinomethyl)aminopropyltriethoxysilane [(CH3CH2O)3Si(CH2)3N(CH2PPh2)2] (DIPAPTES) and silica supported [SiO2–(DIPAPES)] ligands have been synthesized under nitrogen atmosphere using Schlenk method and characterized by using atomic\\u000a absorption, FT-IR, NMR (1H and 31P) and elemental analysis techniques. All the complexes were used as catalysts for the oxidation of 2-methyl naphthalene (2MN)\\u000a to 2-methyl-1,4-naphthoquinone (vitamin K3, menadione, 2MNQ) using hydrogen peroxide

Serhan Uru?; Mustafa Kele?; Osman Serinda?

2010-01-01

127

Dielectric relaxation spectroscopy of heteronuclear cobalt(II)-copper(II) complex of 1-phenyl-3-methyl-5-pyrazolone  

NASA Astrophysics Data System (ADS)

A bright green CoCu(PMP)(OH) 2(H 2O) 2 complex was synthesized. Its structure was elucidated and characterized by different spectroscopic techniques. Both cobalt and copper atoms attain tetrahedral geometry. The complex was investigated by the dielectric relaxation spectroscopy. The dielectric parameters are discussed in terms of temperature and frequency changes. The conductivity of the complex decreased as the temperature increased in the temperature range 30-100 °C, while above this temperature range stepwise increase in the conductivity was observed.

Masoud, Mamdouh S.; Ali, Alaa E.; Mohamed, Rabah H.; Mostafa, M. Abd El Zaher

2005-12-01

128

Effects of methyl substituent on the charge-transfer complexations of dicarbazolylalkanes with p-chloranil, tetracyanoethylene and tetracyanoquinodimethane  

NASA Astrophysics Data System (ADS)

Series of 1, n-dicarbazolylalkanes and 1, n-di(3-methylcarbazolyl)alkanes (where n = 1-5) were synthesized and the molar extinction coefficients, equilibrium constants, enthalpies, and entropies of their charge-transfer (CT) complexes with the ?-acceptors p-chloranil, tetracyanoethylene, and tetracyanoquinodimethane were investigated. 1, n-Di(3-methylcarbazolyl)alkanes formed CT complexes with higher equilibrium constants, more negative enthalpies and entropies than 1, n-dicarbazolylalkanes. Vibrational spectra of CT complexes of one of the donor molecules (1,4-dicarbazolylbutane) with all three acceptors were compared.

Asker, Erol; Uzkara, Ece; Zeybek, Orhan

2011-09-01

129

Effects of methyl substituent on the charge-transfer complexations of dicarbazolylalkanes with p-chloranil, tetracyanoethylene and tetracyanoquinodimethane.  

PubMed

Series of 1,n-dicarbazolylalkanes and 1,n-di(3-methylcarbazolyl)alkanes (where n=1-5) were synthesized and the molar extinction coefficients, equilibrium constants, enthalpies, and entropies of their charge-transfer (CT) complexes with the ?-acceptors p-chloranil, tetracyanoethylene, and tetracyanoquinodimethane were investigated. 1,n-Di(3-methylcarbazolyl)alkanes formed CT complexes with higher equilibrium constants, more negative enthalpies and entropies than 1,n-dicarbazolylalkanes. Vibrational spectra of CT complexes of one of the donor molecules (1,4-dicarbazolylbutane) with all three acceptors were compared. PMID:21700488

Asker, Erol; Uzkara, Ece; Zeybek, Orhan

2011-09-01

130

The metal complexes of heterocyclic ?-diketones and their derivatives—V. The synthesis, structure and i.r. spectral studies of metal(II) complexes of 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 (HPMAP)  

NASA Astrophysics Data System (ADS)

The divalent metal complexes of Be, Mn, Co, Ni, Cu, Zn, Pb, Hg and Ba with 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 (HPMAP), have been synthesized for the first time. It is shown that even though the ligand, HPMAP, has four potential coordination sites, it behaves like a bidentate enol forming neutral metal chelates through the carbonyl and enolic hydroxyl groups. The complexes were characterized by means of elemental analyses, conductivity measurements, i.r. proton NMR spectroscopy. Proton magnetic resonance spectral data for some of the chelates have been recorded and discussed. The i.r. spectra of HPMAP and its chelates have been measured between 4000 and 200 cm -1 and assignments are proposed for the observed frequencies. Replacement of a methyl group in the acetylacetonate by the pyrazolone moiety fused to the chelate ring has been found to strengthen the C …O and M?O bonds and weaken the C …C bond of the chelate ring. The magnitudes of M?O stretching frequencies for the transition metals follow very closely the Irving-Williams stability order Cu > Ni > Zn > Co > Mn.

Okafor, Emmanuel Chukwuemeka

131

Synthesis, Characterization and Antitumor Activity of Some Metal Complexes of S-Methyl-N-(3-hydroxy-5-hydroxymethyl-2-methylypyrid-5-yl)methylenedithiocarbazate  

Microsoft Academic Search

Complexes of Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Pt(II) with S-methyl-N-(3-hydroxy-5-hydroxymethyl-2-methylpyrid-4-yl)-methylenedithiocarbazate (H2L) were isolated and characterized by elemental analysis, molar conductance, magnetic susceptibilities and spectroscopic studies. On the basis of these studies the following structures are suggested: a monomeric, high-spin, five-coordinate structure for [Mn(H2L)(H2O) Cl]Cl, a dimeric, high spin, thiolo-bridged, five-coordinate structure for [Fe(HL)Cl]Cl, [Cu(HL)(H2O)]Cl and [M(H2L)Cl]Cl (M =

M. Kumar; A. Kumar; P. H. Madhuranath; N. S. Gupta; N. K. Jha; M. Mohan

1990-01-01

132

Methylation matters  

PubMed Central

DNA methylation is not just for basic scientists any more. There is a growing awareness in the medical field that having the correct pattern of genomic methylation is essential for healthy cells and organs. If methylation patterns are not properly established or maintained, disorders as diverse as mental retardation, immune deficiency, and sporadic or inherited cancers may follow. Through inappropriate silencing of growth regulating genes and simultaneous destabilisation of whole chromosomes, methylation defects help create a chaotic state from which cancer cells evolve. Methylation defects are present in cells before the onset of obvious malignancy and therefore cannot be explained simply as a consequence of a deregulated cancer cell. Researchers are now able to detect with exquisite sensitivity the cells harbouring methylation defects, sometimes months or years before the time when cancer is clinically detectable. Furthermore, aberrant methylation of specific genes has been directly linked with the tumour response to chemotherapy and patient survival. Advances in our ability to observe the methylation status of the entire cancer cell genome have led us to the unmistakable conclusion that methylation abnormalities are far more prevalent than expected. This methylomics approach permits the integration of an ever growing repertoire of methylation defects with the genetic alterations catalogued from tumours over the past two decades. Here we discuss the current knowledge of DNA methylation in normal cells and disease states, and how this relates directly to our current understanding of the mechanisms by which tumours arise.???Keywords: methylation; cancer

Costello, J.; Plass, C.

2001-01-01

133

Poly(Tertiary Phosphines and Arsines)- XII. Some Metal Complexes of Methylated DI- and Tri (Tertiary Phosphines).  

National Technical Information Service (NTIS)

Metal complexes of the di(tertiary phosphine) (CH3)2PCH2Ch2P(C6H5)2 of the types (diphos) MCl2 (M=Ni, Co, Pd, and Pt), (diphos)M(CO)4 (M=Cr, Mo, and W), ((diphos)2-RhCl2)(+), and (diphosFe2(CO)2(C5H5)2 have been prepared by standard methods. Metal complex...

R. B. King J. A. Zinich J. C. Cloyd

1974-01-01

134

Electronic and optical response of Ru(II) complexes functionalized by methyl, carboxylate groups: joint theoretical and experimental study  

Microsoft Academic Search

New photovoltaic and photocatalysis applications have been recently proposed based on the hybrid Ru(II)-bipyridine-complex\\/semiconductor quantum dot systems. In order to attach the complex to the surface of a semiconductor, a linking bridge - a carboxyl group - is added to one or two of the 2,2-bipyridine ligands. Such changes in the ligand structure, indeed, affect electronic and optical properties and

Tretiak; Sergei

2008-01-01

135

Exploring the reactivity of tungsten bis(imido) dimethyl complexes with methyl aluminium reagents: implications for ethylene dimerization.  

PubMed

The reaction of [WCl2(NAr)2(DME)] (1) with excess Me3Al affords the dimethyl complex [WMe2(N{Ar}AlMe2{mu-Cl})(NAr)] (2), which on treatment with THF or MeAlCl2 yields [WMe2(NAr)2(THF)] (3) and [WMe2(N{Ar}AlMe(Cl){mu-Cl})(NAr)] (5), respectively. Complex 3 is unstable in solution dissociating to form [WMe2(NAr)2] (4) that may be isolated as an adduct with PMe3, [WMe2(NAr)2(PMe3)] (6). While complex 2 is inert towards ethylene, complex 3 reacts rapidly to afford a mixture of methane and but-1-ene (1:4). Neither complex 2 nor 3 react with propylene. Reaction of 3 with a C2H4/C2D4 (1:1) affords a mixture of isotopomers that is consistent with complete isotopic scrambling. The structures of complexes 1, 2, and 3 have been determined by X-ray diffraction. PMID:20567750

Wright, William R H; Batsanov, Andrei S; Howard, Judith A K; Tooze, Robert P; Hanton, Martin J; Dyer, Philip W

2010-08-14

136

Comparison of the self-exchange and interfacial charge-transfer rate constants for methyl- versus tert-butyl-substituted Os(III) polypyridyl complexes.  

PubMed

Differences in the self-exchange and interfacial electron-transfer rate constants have been evaluated for a relatively unhindered Os(III/II) redox system, osmium(III/II) tris(4,4'-di-methyl-2,2'-bipyridyl), [Os(Me2bpy)3]3+/2+, relative to those of a relatively hindered system, osmium(III/II) tris(4,4'-di-tert-butyl-2,2'-bipyridyl), [Os(t-Bu2bpy)3]3+/2+. In contrast to the predicted increase in rate constant by a factor of 2-3 due to the difference in reorganization energy of the two complexes, introduction of the tert-butyl functionality decreased the self-exchange rate constant, as measured by NMR line-broadening techniques, by a factor of approximately 50 as compared to that of the analogous methyl-substituted osmium complex. Steady-state current density versus potential measurements, in conjunction with differential capacitance versus potential measurements, were used to compare the interfacial electron-transfer rate constants at n-type ZnO electrodes of [Os(t-Bu2bpy)3]3+/2+ and [Os(Me2bpy)3]3+/2+. The interfacial electron-transfer rate constant for the reduction of [Os(t-Bu2bpy)3]3+ was 100 times smaller than that for [Os(Me2bpy)3]3+. The results indicate that the tert-butyl group can act as a spacer on an outer-sphere redox couple and significantly decrease the electronic coupling of the electron-transfer reaction in both self-exchange and interfacial electron-transfer processes. PMID:17166001

Hamann, Thomas W; Brunschwig, Bruce S; Lewis, Nathan S

2006-12-21

137

Resolution and characterization of helicate dimer and trimer complexes of 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane with copper(I).  

PubMed

Complexation of copper(I) with the binucleating ligand, 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane, mphenpr, result in formation of helical dimers, [Cu2(mphenpr)2](2+). The resolution of the enantiomeric forms of the dimers has been carried out with ?-[As(cat)3](-) as resolving agent and X-ray structures for two compounds, P-[Cu2(mphenpr)2](?-[As(cat)3])2 and P-[Cu2(mphenpr)2](?-[As(cat)3])2·4(CH3CN), are reported. The rate of racemization in poorly-coordinating solvents has been examined by (1)H NMR, and is slow. At saturating concentrations of [[Cu2(mphenpr)2](2+)] in acetonitrile, crystals of the helical trimeric complex [Cu3(mphenpr)3](ClO4)3 are obtained. The X-ray structure of the trimer is reported. This species has also been resolved. As with the helical dimer, racemization in poorly-coordinating solvents is slow, and circular dichroism and (1)H NMR spectra are reported. The absolute configuration of the resolved complex, P-[Cu3(mphenpr)3](?-[As(cat)3])3, has been determined by X-ray crystallography. PMID:23824074

Lemus, Luis; Guerrero, Juan; Costamagna, Juan; Lorca, Romina; Jara, Danilo H; Ferraudi, Guillermo; Oliver, Allen; Lappin, A Graham

2013-08-28

138

(+)-3-( sup 123 I)Iodo-MK-801: Synthesis and characterization of binding to the N-methyl-D-aspartate receptor complex  

SciTech Connect

Synthetic methods have been established for preparing high specific activity (+)-3-({sup 123}I)Iodo-MK-801 in high radiochemical yield. The binding of the radiotracer to rat cortical membranes has been examine to assess its potential use as an in vivo imaging agent for the N-methyl-D-aspartate (NMDA) receptor-ion channel complex. Under the conditions of the assay, specific (+)-3-({sup 123}I)Iodo-MK-801 binding to membrane homogenates represented greater than 95% of the total binding. Several structurally distinct, noncompetitive NMDA receptor antagonists inhibited binding with potencies in accordance with their reported inhibitory activity at the receptor complex. The concentration of ({plus minus})-3-Iodo-MK-801 required to inhibit 50% of (+)-3-({sup 123}I)Iodo-MK-801 binding (IC{sub 50}) was 3.4 nM when using a low ionic strength assay buffer and 5.5 nM in a physiological buffer. In a thoroughly washed membrane preparation, (+)-3-({sup 123}I)Iodo-MK-801 binding was enhanced by L-glutamate and glycine at concentrations known to activate the NMDA receptor. The results indicate that (+)-3-({sup 123}I)Iodo-MK-801 specifically labels the NMDA receptor complex in rat brain membranes and the retention of high affinity under near physiological assay conditions suggests that it may be useful as a SPECT imaging agent for the receptor in vivo.

Ransom, R.W.; Wai-si Eng; Burns, H.D.; Gibson, R.E.; Solomon, H.F. (Merck Sharp Dohme Research Labs., West Point, PA (USA))

1990-01-01

139

Homogeneous solvation controlled photoreduction of cobalt(III) complexes in aqueous 2-methyl-2-propanol solutions. Linear solvation energy relationship and cyclic voltammetric analyses  

NASA Astrophysics Data System (ADS)

The effect of solvent participation on the ligand-to-metal charge transfer (LMCT, L ? Co III) reduction of the of Co III(en) 2Br(RC 6H 4NH 2) 2+ where R = m-OCH 3, p-F, H, m-CH 3, p-CH 3,p-OC 2H 5 and p-OCH 3 were examined in aqueous 2-methyl-2-propanol (Bu tOH) solutions. The change in the reduction behavior of Co III centre was also examined through cyclic voltammetric studies. The observed reduction in quantum yield due to LMCT excitation can mainly be accounted using linear solvation energy relationship (LSER) comprising model correlation equations. These consist of empirical parameters such as Grunwald-Winstein's solvent ionizing power, Y, Dimroth-Richardt's solvent micro-polarity parameter, ETN, Gutmann's donor number, DN N, along with Kamlet-Taft's solvatochromic parameters (hydrogen bond acceptor acidity/basicity ?/ ? and solvent dipolarity/polarizability, ?*). The origin of solvent effect is found to be due to microscopic interaction between the solvent donor and the nitrogen-bound hydrogen of the ligand. Cyclic voltammograms show an irreversible reduction of Co III in DMF using Glassy Carbon Electrode, GCE, the redox peaks for the aniline complexes appear at -0.20 and 0.525 V. Irradiation of the complexes with UV light ( ? = 254 nm) in binary mixtures produce Co IIaq and the concentration of this species are highly dependent on xalc ( xalc = mole fraction of alcohol). The observed quantum yield (log ?Co(II)) is found to be linearly related to mole fraction of organic co-solvent added in the mixture, therefore, log ?Co(II) = 26.41 × 10 -2 when x2 = 0.0094 and 43.75 × 10 -2 when x2 = 0.076 for a typical complex Co III(en) 2Br( p-OCH 3C 6H 4NH 2) 2+ in aqueous 2-methyl-2-propanol at 300 K. Cyclic voltammetry and LSER analyses illustrate the variation of reduction property of Co(III) by the aryl ligand and homogeneous solvation of the excited state of the complex Co III(en) 2Br(RC 6H 4NH 2) 2+ in H 2O/Bu tOH mixtures.

Anbalagan, K.; Lydia, I. Sharmila

2008-03-01

140

Generation of a genomic tiling array of the human Major Histocompatibility Complex (MHC) and its application for DNA methylation analysis  

Microsoft Academic Search

BACKGROUND: The major histocompatibility complex (MHC) is essential for human immunity and is highly associated with common diseases, including cancer. While the genetics of the MHC has been studied intensively for many decades, very little is known about the epigenetics of this most polymorphic and disease-associated region of the genome. METHODS: To facilitate comprehensive epigenetic analyses of this region, we

Eleni M Tomazou; Vardhman K Rakyan; Gregory Lefebvre; Robert Andrews; Peter Ellis; David K Jackson; Cordelia Langford; Matthew D Francis; Liselotte Bäckdahl; Marcos Miretti; Penny Coggill; Diego Ottaviani; Denise Sheer; Adele Murrell; Stephan Beck

2008-01-01

141

Complex formation reactions of palladium(II)-1,3-diaminopropane with various biologically relevant ligands. Kinetics of hydrolysis of glycine methyl ester through complex formation  

Microsoft Academic Search

The interaction of [Pd(DAP)(H2O)2]2+ (DAP = 1,3-diaminopropane) with some selected bio-relevant ligands, containing different functional groups, were investigated.\\u000a The ligands used are dicarboxylic acids, amino acids, peptides and DNA constituents. Stoichiometry and stability constants\\u000a of the complexes formed are reported at 25°C and 0.1 M ionic strength. The results show the formation of 1:1 complexes with\\u000a amino acids and dicarboxylic

Ahmed A. El-Sherif; Mohamed M. Shoukry; Ramadan M. El-Bahnasawy; Dalia M. Ahmed

2010-01-01

142

Novel Square Arrangements in Tetranuclear and Octanuclear Iron(III) Complexes with Asymmetric Iron Environments Created by the Unsymmetric Bridging Ligand N,N,N'-Tris((N-methyl)-2-benzimidazolylmethyl)-N'-methyl-1,3-diamino-2-propanol.  

PubMed

The synthesis and characterization of novel tetranuclear and octanuclear iron(III) complexes with structures based on a nearly square arrangement of four iron ions are reported. Reaction of ferric nitrate, sodium acetate, and the unsymmetrical binucleating ligand HBMDP, where HBMDP is N,N,N'-tris((N-methyl)-2-benzimidazolylmethyl)-N'-methyl-1,3-diamino-2-propanol, in acetone/water yields the tetranuclear iron complex [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](4+), which exhibits coordination number asymmetry. The structure of [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](NO(3))(3)(OH).12H(2)O has been determined by single-crystal X-ray diffraction. Each (&mgr;-BMDP) ligand spans two iron(III) ions and causes these ions to become structurally distinct. Within this binuclear unit one iron atom is five-coordinate with distorted square pyramidal geometry and an N(2)O(3) donor set, while the other iron is six-coordinate with distorted octahedral geometry and an N(3)O(3) donor set. Two of these binuclear units are linked through a pair of oxo and acetato bridges to form the centrosymmetric tetranuclear complex. The coordinatively nonequivalent iron atoms exhibit distinct Mössbauer spectroscopic parameters and produce a pair of doublets at 80 K. The iron(III) centers are coupled antiferromagnetically with a room-temperature moment of 1.9 &mgr;(B) per iron with J = -103.3 cm(-)(1), zJ' = -105.9 cm(-)(1). The properties of the unsymmetric cation [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](4+) are similar to those observed for binuclear iron proteins with comparable coordinative inequivalence. Efforts to increase the solubility of [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](4+) by metathesis with sodium tetrafluoroborate resulted in the isolation of crystals of a new octanuclear iron species, [Fe(8)(&mgr;-O)(4)(&mgr;-BMDP)(4)(OH)(4)(&mgr;-OAc)(4)](BF(4))(3)(OH).2CH(3)CN.8H(2)O( )()(2), which has also been characterized by single-crystal X-ray diffraction. The asymmetric unit consists of an Fe(2)(&mgr;-O)(&mgr;-BMDP)(&mgr;-OAc)(OH) group which is externally bridged via the oxo ions to form a molecular square with four of the eight iron ions at the corners. Both iron sites are six-coordinate with distorted octahedral geometry. One has an N(2)O(4) donor set; the other has an N(3)O(3) donor set. PMID:11670809

Satcher, Joe H.; Olmstead, Marilyn M.; Droege, Michael W.; Parkin, Sean R.; Noll, Bruce C.; May, Leopold; Balch, Alan L.

1998-12-28

143

Poly(methyl methacrylate) microchip affinity capillary gel electrophoresis of aptamer-protein complexes for the analysis of thrombin in plasma.  

PubMed

Thrombin generation in blood serves as an important marker for various hemostasis-related diseases and conditions. Analytical techniques currently utilized for determining the thrombin potential of patients rely primarily on the enzymatic activity of thrombin. Microfluidic-based ACE using fluorescently labeled aptamers as affinity probes could provide a simple and efficient technique for the real-time analysis of thrombin levels in plasma. In this study, aptamers were used for the analysis of thrombin by affinity microchip CGE. The CGE used a poly(methyl methacrylate) (PMMA) microfluidic device for the sorting of the affinity complexes with a linear polyacrylamide (LPA) serving as the sieving matrix. Due to the fact that the assay was run under nonequilibrium electrophoresis conditions, the presence of the sieving gel was found to stabilize the affinity complex, providing improved electrophoretic performance compared to free-solution electrophoresis. Two fluorescently labeled aptamer affinity probes, HD1 and HD22, which bind to exosites I and II, respectively, of thrombin were investigated. With an electric field strength of 300 V/cm, two well-resolved peaks corresponding to free aptamer and the thrombin-aptamer complex were obtained in less than 1 min of separation time with a run-to-run and chip-to-chip reproducibility (RSD) of migration times <10% using both aptamers. HD22 affinity assays of thrombin produced baseline-resolved peaks with favorable efficiency due to its higher binding affinity, whereas HD1 assays showed poorer resolution of the free aptamer and complex peaks. HD22 was used in determining the level of thrombin in human plasma. Assays were performed directly on plasma that was diluted to 10% v/v. Thrombin was successfully analyzed by microchip CGE at a concentration level of 543.5 nM for the human plasma sample. PMID:18702051

Obubuafo, Anne; Balamurugan, Subramanian; Shadpour, Hamed; Spivak, David; McCarley, Robin L; Soper, Steven A

2008-08-01

144

Enzyme inhibitor studies reveal complex control of methyl-D-erythritol 4-phosphate (MEP) pathway enzyme expression in Catharanthus roseus.  

PubMed

In Catharanthus roseus, the monoterpene moiety exerts a strong flux control for monoterpene indole alkaloid (MIA) formation. Monoterpene synthesis depends on the methyl-D-erythritol 4-phosphate (MEP) pathway. Here, we have explored the regulation of this pathway in response to developmental and environmental cues and in response to specific enzyme inhibitors. For the MEP pathway entry enzyme 1-deoxy-D-xylulose 5-phosphate synthase (DXS), a new (type I) DXS isoform, CrDXS1, has been cloned, which, in contrast to previous reports on type II CrDXS, was not transcriptionally activated by the transcription factor ORCA3. Regulation of the MEP pathway in response to metabolic perturbations has been explored using the enzyme inhibitors clomazone (precursor of 5-ketochlomazone, inhibitor of DXS) and fosmidomycin (inhibitor of deoxyxylulose 5-phosphate reductoisomerase (DXR)), respectively. Young leaves of non-flowering plants were exposed to both inhibitors, adopting a non-invasive in vivo technique. Transcripts and proteins of DXS (3 isoforms), DXR, and hydroxymethylbutenyl diphosphate synthase (HDS) were monitored, and protein stability was followed in isolated chloroplasts. Transcripts for DXS1 were repressed by both inhibitors, whereas transcripts for DXS2A&B, DXR and HDS increased after clomazone treatment but were barely affected by fosmidomycin treatment. DXS protein accumulated in response to both inhibitors, whereas DXR and HDS proteins were less affected. Fosmidomycin-induced accumulation of DXS protein indicated substantial posttranscriptional regulation. Furthermore, fosmidomycin effectively protected DXR against degradation in planta and in isolated chloroplasts. Thus our results suggest that DXR protein stability may be affected by substrate binding. In summary, the present results provide novel insight into the regulation of DXS expression in C. roseus in response to MEP-pathway perturbation. PMID:23650515

Han, Mei; Heppel, Simon C; Su, Tao; Bogs, Jochen; Zu, Yuangang; An, Zhigang; Rausch, Thomas

2013-01-01

145

Enzyme Inhibitor Studies Reveal Complex Control of Methyl-D-Erythritol 4-Phosphate (MEP) Pathway Enzyme Expression in Catharanthus roseus  

PubMed Central

In Catharanthus roseus, the monoterpene moiety exerts a strong flux control for monoterpene indole alkaloid (MIA) formation. Monoterpene synthesis depends on the methyl-D-erythritol 4-phosphate (MEP) pathway. Here, we have explored the regulation of this pathway in response to developmental and environmental cues and in response to specific enzyme inhibitors. For the MEP pathway entry enzyme 1-deoxy-D-xylulose 5-phosphate synthase (DXS), a new (type I) DXS isoform, CrDXS1, has been cloned, which, in contrast to previous reports on type II CrDXS, was not transcriptionally activated by the transcription factor ORCA3. Regulation of the MEP pathway in response to metabolic perturbations has been explored using the enzyme inhibitors clomazone (precursor of 5-ketochlomazone, inhibitor of DXS) and fosmidomycin (inhibitor of deoxyxylulose 5-phosphate reductoisomerase (DXR)), respectively. Young leaves of non-flowering plants were exposed to both inhibitors, adopting a non-invasive in vivo technique. Transcripts and proteins of DXS (3 isoforms), DXR, and hydroxymethylbutenyl diphosphate synthase (HDS) were monitored, and protein stability was followed in isolated chloroplasts. Transcripts for DXS1 were repressed by both inhibitors, whereas transcripts for DXS2A&B, DXR and HDS increased after clomazone treatment but were barely affected by fosmidomycin treatment. DXS protein accumulated in response to both inhibitors, whereas DXR and HDS proteins were less affected. Fosmidomycin-induced accumulation of DXS protein indicated substantial posttranscriptional regulation. Furthermore, fosmidomycin effectively protected DXR against degradation in planta and in isolated chloroplasts. Thus our results suggest that DXR protein stability may be affected by substrate binding. In summary, the present results provide novel insight into the regulation of DXS expression in C. roseus in response to MEP-pathway perturbation.

Han, Mei; Heppel, Simon C.; Su, Tao; Bogs, Jochen; Zu, Yuangang; An, Zhigang; Rausch, Thomas

2013-01-01

146

Synthesis and crystal structure of a dinuclear yttrium(III)- (lanthanide(III)-) copper(II) complex with an unusual 2-methyl-2,4,6-tris(trifluoromethyl)-1,3-dioxane-4,6-diolato ligand  

SciTech Connect

A dinuclear Ln[sup III]-Cu[sup II] complex with an unusual 2-methyl-2,4,6-tris(trifluoromethyl)-1,3-dioxane-4,6-diolato ligand has been synthesized and characterized structurally. The 1,3-dioxane-4,6-diolato ligand is the product of cycloaddition of 1,1,1-trifluoro-2,2-propanediol to a hexafluoroacetylacetonato ligand promoted by the metal complex.

Wang, S.; Pang, Z.; Smith, K.D.L. (Univ. of Windsor, Ontario (Canada))

1993-11-10

147

An H3K36 methylation engaging Tudor motif of polycomb-like proteins mediates PRC2 complex targeting  

PubMed Central

SUMMARY Polycomb repressive complex 2 (PRC2) regulates pluripotency, differentiation and tumorigenesis through catalysis of histone H3 lysine 27 trimethylation (H3K27me3) on chromatin. However, the mechanisms that underlie PRC2 recruitment and spreading on chromatin remain unclear. Here we report that histone H3 lysine 36 trimethylation (H3K36me3)-binding activity is harbored in the Tudor motifs of PRC2-associated polycomblike (PCL) proteins PHF1/PCL1 and PHF19/PCL3. Ectopically expressed PHF1 induced Tudor-dependent stabilization of PRC2 complexes on bulk chromatin and mediated spreading of PRC2 and H3K27me3 into H3K36me3-containing chromatin regions. In murine pluripotent stem cells, we identified coexistence of H3K36me3, H3K27me3, and PHF19/PCL3 at a subset of ‘poised’ developmental genes, and demonstrated that PHF19/PCL3 Tudor function is required for optimal H3K27me3 and repression of these loci. Collectively, our data suggest that PCL recognition of H3K36me3 promotes intrusion of PRC2 complexes into active chromatin regions to promote gene silencing and modulate the chromatin landscape during development.

Cai, Ling; Rothbart, Scott B.; Lu, Rui; Xu, Bowen; Chen, Wei-Yi; Tripathy, Ashutosh; Rockowitz, Shira; Zheng, Deyou; Patel, Dinshaw J; Allis, C. David; Strahl, Brian D.; Song, Jikui; Wang, Gang Greg

2012-01-01

148

Photobehaviour of methyl-pyridinium and quinolinium iodide derivatives, free and complexed with DNA. A case of bisintercalation.  

PubMed

Excited state dynamics of four azinium salts were studied in buffered water and in the presence of salmon testes DNA. Complexation with DNA changes the photobehaviour of the free ligands lowering the photoreactivity and emission in favor of internal conversion. The interaction of these four dyes with DNA was studied with different techniques with the aim to establish the affinity and the type of binding between the ligands and DNA. The results from spectrophotometric and fluorimetric titrations provided evidence of a strong interaction between the azinium salts and the polynucleotide, with a binding constant of about 10(6) M(-1), making them interesting for therapeutical applications. Dichroic measurements allowed us to determine the possible modes of binding for each complex. Short living excited states of the free dyes were detected and characterized by ultrafast absorption spectroscopy. A further decrease of transient lifetimes was observed upon interaction with DNA. The bicationic pyridinium iodide was found to act as a bisintercalative agent, potentially increasing the cytotoxicity with low dose and less collateral effects. PMID:24740459

Mazzoli, Alessandra; Carlotti, Benedetta; Consiglio, Giuseppe; Fortuna, Cosimo G; Miolo, Giorgia; Spalletti, Anna

2014-05-21

149

Methyl chloroform  

SciTech Connect

Methyl chloroform is identified as a Class 1 ozone-depleting substance under Title VI of the CAA Amendments. On Nov. 30, 1993, EPA ordered the phaseout of Class 1 ozone-depleting substances -- chlorofluorocarbons (CFCs), halons, carbon tetrachloride and methyl chloroform -- by Jan. 1, 1996. Methyl chloroform and other Class 1 substances may be used after the dead-line if sources can be found through recycling or existing inventories. Methyl chloroform is listed as a hazardous air pollutant under CAA. It also is a SARA Title III, Sec. 313 compound with a reportable quantity of 1,000 pounds. OSHA and the American Conference of Government Industrial Hygienists have set 350 ppm as the time-weighted average airborne exposure level for methyl chloroform. NIOSH lists its immediately dangerous to life or health'' concentration as 1,000 parts per million. DOT identifies the substance as a hazardous material, Class 6.1 (poison).

Wray, T.K.

1994-04-01

150

A STUDY OF FUNDAMENTAL REACTION PATHWAYS FOR TRANSITION METAL ALKYL COMPLEXES. I. THE REACTION OF A NICKEL METHYL COMPLEX WITH ALKYNES. II. THE MECHANISM OF ALDEHYDE FORMATION IN THE REACTION OF A MOLYBDENUM HYDRIDE WITH MOLYBDENUM ALKYLS  

SciTech Connect

I. This study reports the rapid reaction under mild conditions of internal or terminal alkynes with methyl (acetyl~ acetonato) (triphenylphosphine) nickel (1) in either aromatic or ether solvents. In all cases vinylnickel products 2 are formed by insertion of the alkyne into the nickel=methyl bond. These complexes may be converted into a variety of organic products (e.g. alkenes, esters, vinyl halides) by treatment with appropriate reagents. Unsymmetrical alkynes give selectively the one regioisomer with the sterically largest substituent next to the nickel atom. In order to investigate the stereochemistry of the initial insertion, a x-ray diffraction study of the reaction of 1 with diphenylacetylene was carried out. This showed that the vinylnickel complex formed by overall trans insertion was the product of the reaction. Furthermore, subsequent slow isomerization of this complex, to a mixture of it and the corresponding cis isomer, demonstrated that this trans addition product is the kinetic product of the reaction. In studies with other alkynes, the product of trans addition was not always exclusively (or even predominantly) formed, but the ratio of the stereoisomers formed kinetically was substantially different from the thermodynamic ratio. Isotope labeling, added phosphine, and other experiments have allowed us to conclude that the mechanism of this reaction does involve initial cis addition. However, a coordinatively unsaturated vinylnickel complex is initially formed which can undergo rapid, phosphine-catalyzed cis-trans isomerization in competition with its conversion to the isolable phosphine-substituted kinetic reaction products. II. The reaction of CpMo(CO){sub 3}H (1a) with CpMo(CO){sub 3}R (2, R= CH{sub 3}, C{sub 2}H{sub 5}) at 50{degrees} C in THF gives the aldehyde RCHO and the dimers [CpMo(CO){sub 3}]{sub 2} (3a) and [CpMo(CO){sub 2}]{sub 2} (4a). Labeling one of the reactants with a methylcyclopentadienyl ligand it was possible to show that the mixed dimers MeCpMo(CO){sub 3}-(CO){sub 3}MoCp (3b) and MeCpMo(CO){sub 2}{triple_bond}(CO){sub 2}MoCp (4b) are the predominant kinetic products of the reaction. Additionally labeling the carbonyl ligands of 1a with {sup 13}CO led to the conclusion that all three of the carbonyl ligands in 1a end up in the tetracarbonyl dimers 4a if the reaction is carried out under a continuous purge of argon Trapping studies failed to find any evidence for the intermediacy of either [CpMo(CO){sub 3}]{sup -} or [CpMo(CO){sub 3}]{sup +} in this reaction. A mechanism is proposed that involves the initial migration of the alkyl ligand in 2 to CO forming an unsaturated acyl complex which reacts with 1a to give a binuclear complex containing a three center-two electron Mo-H-Mo bond. This complex then selectively looses a carbonyl from the acyl molybdenum, migrates the hydride to that same metal, and forms a metal-metal bond. This binuclear complex with the hydride and acyl ligands on one metal reductively eliminates aldehyde, and migrates a carbonyl ligand, to give 4a directly. The other product 3a is formed by addition of two molecules of free CO to 4a.

Huggins, John Mitchell

1980-06-01

151

KB-R7943, an inhibitor of the reverse Na+/Ca2+ exchanger, blocks N-methyl-D-aspartate receptor and inhibits mitochondrial complex I  

PubMed Central

BACKGROUND AND PURPOSE An isothiourea derivative (2-[2-[4-(4-nitrobenzyloxy)phenyl]ethyl]isothiourea methane sulfonate (KB-R7943), a widely used inhibitor of the reverse Na+/Ca2+ exchanger (NCXrev), was instrumental in establishing the role of NCXrev in glutamate-induced Ca2+ deregulation in neurons. Here, the effects of KB-R7943 on N-methyl-D-aspartate (NMDA) receptors and mitochondrial complex I were tested. EXPERIMENTAL APPROACH Fluorescence microscopy, electrophysiological patch-clamp techniques and cellular respirometry with Seahorse XF24 analyzer were used with cultured hippocampal neurons; membrane potential imaging, respirometry and Ca2+ flux measurements were made in isolated rat brain mitochondria. KEY RESULTS KB-R7943 inhibited NCXrev with IC50= 5.7 ± 2.1 µM, blocked NMDAR-mediated ion currents, and inhibited NMDA-induced increase in cytosolic Ca2+ with IC50= 13.4 ± 3.6 µM but accelerated calcium deregulation and mitochondrial depolarization in glutamate-treated neurons. KB-R7943 depolarized mitochondria in a Ca2+-independent manner. Stimulation of NMDA receptors caused NAD(P)H oxidation that was coupled or uncoupled from ATP synthesis depending on the presence of Ca2+ in the bath solution. KB-R7943, or rotenone, increased NAD(P)H autofluorescence under resting conditions and suppressed NAD(P)H oxidation following glutamate application. KB-R7943 inhibited 2,4-dinitrophenol-stimulated respiration of cultured neurons with IC50= 11.4 ± 2.4 µM. With isolated brain mitochondria, KB-R7943 inhibited respiration, depolarized organelles and suppressed Ca2+ uptake when mitochondria oxidized complex I substrates but was ineffective when mitochondria were supplied with succinate, a complex II substrate. CONCLUSIONS AND IMPLICATIONS KB-R7943, in addition to NCXrev, blocked NMDA receptors in cultured hippocampal neurons and inhibited complex I in the mitochondrial respiratory chain. These findings are critical for the correct interpretation of experimental results obtained with KB-R7943 and a better understanding of its neuroprotective action.

Brustovetsky, Tatiana; Brittain, Matthew K; Sheets, Patrick L; Cummins, Theodore R; Pinelis, Vsevolod; Brustovetsky, Nickolay

2011-01-01

152

The MIRA method for DNA methylation analysis  

PubMed Central

DNA methylation patterns are often altered in human cancer and aberrant methylation is considered a hallmark of malignant transformation. Several methods have been developed for the characterization of gene-specific and genome-wide DNA methylation patterns. In this chapter, we describe the methylated-CpG island recovery assay (MIRA), which is based on the high affinity of the MBD2b/MBD3L1 complex for double-stranded CpG-methylated DNA. MIRA has been used in combination with microarray platforms to map DNA methylation patterns across the human genome.

Rauch, Tibor A.; Pfeifer, Gerd P.

2010-01-01

153

Infrared spectra of the CH3-MX, CH2=MHX, and CH[triple bond]MH2X- complexes formed by reaction of methyl halides with laser-ablated group 5 metal atoms.  

PubMed

Reactions of group 5 metal atoms and methyl halides give carbon-metal single, double, and triple bonded complexes that are identified from matrix IR spectra and vibrational frequencies computed by DFT. Two different pairs of complexes are prepared in reactions of methyl fluoride with laser-ablated vanadium and tantalum atoms. The two vanadium complexes (CH(3)-VF and CH(2)=VHF) are persistently photoreversible and show a kinetic isotope effect on the yield of CD(2)=VDF. Identification of CH(2)=TaHF and CH[triple bond]TaH(2)F(-), along with the similar anionic Nb complex, suggests that the anionic methylidyne complex is a general property of the heavy group 5 metals. Reactions of Nb and Ta with CH(3)Cl and CH(3)Br have also been carried out to understand the ligand effects on the calculated structures and the vibrational characteristics. The methylidene complexes become more distorted with increasing halogen size, while the calculated C=M bond lengths and stretching frequencies decrease and increase, respectively. The anionic methylidyne complexes are less favored with increasing halogen size. Infrared spectra show a dramatic increase of the Ta methylidenes upon annealing, suggesting that the formation of CH(3)-TaX and its conversion to CH(2)=TaHX require essentially no activation energy. PMID:16913680

Cho, Han-Gook; Andrews, Lester

2006-08-24

154

Evaluating the identity and diiron core transformations of a (?-oxo)diiron(III) complex supported by electron-rich tris(pyridyl-2-methyl)amine ligands.  

PubMed

The composition of a (?-oxo)diiron(III) complex coordinated by tris[(3,5-dimethyl-4-methoxy)pyridyl-2-methyl]amine (R(3)TPA) ligands was investigated. Characterization using a variety of spectroscopic methods and X-ray crystallography indicated that the reaction of iron(III) perchlorate, sodium hydroxide, and R(3)TPA affords [Fe(2)(?-O)(?-OH)(R(3)TPA)(2)](ClO(4))(3) (2) rather than the previously reported species [Fe(2)(?-O)(OH)(H(2)O)(R(3)TPA)(2)](ClO(4))(3) (1). Facile conversion of the (?-oxo)(?-hydroxo)diiron(III) core of 2 to the (?-oxo)(hydroxo)(aqua)diiron(III) core of 1 occurs in the presence of water and at low temperature. When 2 is exposed to wet acetonitrile at room temperature, the CH(3)CN adduct is hydrolyzed to CH(3)COO(-), which forms the compound [Fe(2)(?-O)(?-CH(3)COO)(R(3)TPA)(2)](ClO(4))(3) (10). The identity of 10 was confirmed by comparison of its spectroscopic properties with those of an independently prepared sample. To evaluate whether or not 1 and 2 are capable of generating the diiron(IV) species [Fe(2)(?-O)(OH)(O)(R(3)TPA)(2)](3+) (4), which has previously been generated as a synthetic model for high-valent diiron protein oxygenated intermediates, studies were performed to investigate their reactivity with hydrogen peroxide. Because 2 reacts rapidly with hydrogen peroxide in CH(3)CN but not in CH(3)CN/H(2)O, conditions that favor conversion to 1, complex 1 is not a likely precursor to 4. Compound 4 also forms in the reaction of 2 with H(2)O(2) in solvents lacking a nitrile, suggesting that hydrolysis of CH(3)CN is not involved in the H(2)O(2) activation reaction. These findings shed light on the formation of several diiron complexes of electron-rich R(3)TPA ligands and elaborate on conditions required to generate synthetic models of diiron(IV) protein intermediates with this ligand framework. PMID:22264120

Do, Loi H; Xue, Genqiang; Que, Lawrence; Lippard, Stephen J

2012-02-20

155

A Novel Type Half-Unit Schiff Base Ligand, 3-[o-Aminophenyliminomethyl]-4Hydroxy6Methyl2-(1H)-Quinolone and its Metal Complexes. Part IV  

Microsoft Academic Search

A novel half-unit Schiff base ligand derived from 6-methyl-3-formyl-4-hydroxy-2-(1H)-quinolone and o-phenylenediamine was prepared. The Schiff base acts as a monobasic ligand. Metal complexes of the type [MLX]2, M = Cu(II), Ni(II) or Fe(III); X = Cl or OAc were obtained by the reaction of metal acetates or chlorides with the ligand, with the ligand behaving as a terdentate. However, the

Saied M. E. Khalil; Ali Taha; Faten S. M. Abd El-Hameed

1997-01-01

156

Stabilities of lead(II) complexes formed in aqueous solution with methyl thiophosphate (MeOPS 2- ), uridine 5'- O -thiomonophosphate (UMPS 2- ) or adenosine 5'- O -thiomonophosphate (AMPS 2- )  

Microsoft Academic Search

The acidity constants of twofold protonated methyl thiophosphate (MeOPS2-) and of monoprotonated uridine 5'-O-thiomonophosphate (UMPS2-) have been determined in aqueous solution (25 °C; I = 0.1 M, NaNO3) by potentiometric pH titration. The stability constants of their 1:1 complexes formed with Pb2+, i.e. Pb(MeOPS) and Pb(UMPS), have also been measured. The results show that replacement of a phosphate oxygen by

Carla P. Da Costa; Danuta Krajewska; Andrzej Okruszek; Wojciech J. Stec; Helmut Sigel

2002-01-01

157

One trinuclear copper(II) complex derived from a new Schiff base ligand based on the dianion of 4-chloro-6-(hydroxymethyl)-2-((3-aminopropylimino)methyl)-phenol: Synthesis, structure, spectroscopic and magnetic properties  

Microsoft Academic Search

A linear trinuclear copper(II) complex (1), prepared from a new Schiff base ligand, namely the dianion of 4-chloro-6-(hydroxymethyl)-2-((3-aminopropylimino)methyl)-phenol, was synthesized and characterized in this paper. The X-ray structural study reveals that the geometry of the central Cu2 ion is elongated octahedral and that of the two side Cu(II) ions is distorted square pyramidal. The magnetic susceptibility measurements from 2 to

Juechao Jiang; Zhaolian Chu; Wei Huang

2009-01-01

158

Thermodynamics of substituted pyrazolone IX: potentiometric, spectrophotometric and conductometeric studies of 4-(4-chlorophenylazo)-3-methyl-1-[2-hydroxy-3-morphilinopropane 1-yl]-2-pyrazolin-5-one and its metal complexes  

NASA Astrophysics Data System (ADS)

The dissociation constants of 4-(4-chlorophenylazo)-3-methyl-l-[2-hydroxy-3-morphilinopropane-1-yl]-2-pyrazolin-5-one (CAMP) has been determined potentiometrically in 0.1 M KCl and 40% (v/v) ethanol-water mixture. The stepwise stability constants of the formed complexes of Mn 2+, Co 2+, Ni 2+, Cu 2+, Zn 2+, La 3+, Ce 3+ and UO 22+ with CAMP have been determined. The stability of the formed complexes were found as follows: UO22+> Ce3+> La3+> Mn2+< Co2+< Ni2+< Cu2+> Zn2+The thermodynamic parameters (? G, ? H and ? S) for CAMP and its complexes were evaluated and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavourable. The formation of the complexes have been found to be spontaneous, exothermic or endothermic (depending on the metal) and entropically favourable. The stoichiometries of these complexes were determined spectrophotometrically and conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes.

El-Bindary, A. A.; El-Sonbati, A. Z.; El-Mosalamy, E. H.; El-Santawy, E. M.

2001-10-01

159

Crystal structure of phosphoserine aminotransferase from Escherichia coli at 2.3 A resolution: comparison of the unligated enzyme and a complex with alpha-methyl-l-glutamate.  

PubMed

Phosphoserine aminotransferase (PSAT; EC 2.6.1.52), a member of subgroup IV of the aminotransferases, catalyses the conversion of 3-phosphohydroxypyruvate to l-phosphoserine. The crystal structure of PSAT from Escherichia coli has been solved in space group P212121 using MIRAS phases in combination with density modification and was refined to an R-factor of 17.5% (Rfree=20.1 %) at 2.3 A resolution. In addition, the structure of PSAT in complex with alpha-methyl-l-glutamate (AMG) has been refined to an R-factor of 18.5% (Rfree=25.1%) at 2.8 A resolution. Each subunit (361 residues) of the PSAT homodimer is composed of a large pyridoxal-5'-phosphate binding domain (residues 16-268), consisting of a seven-stranded mainly parallel beta-sheet, two additional beta-strands and seven alpha-helices, and a small C-terminal domain, which incorporates a five-stranded beta-sheet and two alpha-helices. A three-dimensional structural comparison to four other vitamin B6-dependent enzymes reveals that three alpha-helices of the large domain, as well as an N-terminal domain (subgroup II) or subdomain (subgroup I) are absent in PSAT. Its only 15 N-terminal residues form a single beta-strand, which participates in the beta-sheet of the C-terminal domain. The cofactor is bound through an aldimine linkage to Lys198 in the active site. In the PSAT-AMG complex Ser9 and Arg335 bind the AMG alpha-carboxylate group while His41, Arg42 and His328 are involved in binding the AMG side-chain. Arg77 binds the AMG side-chain indirectly through a solvent molecule and is expected to position itself during catalysis between the PLP phosphate group and the substrate side-chain. Comparison of the active sites of PSAT and aspartate aminotransferase suggests a similar catalytic mechanism, except for the transaldimination step, since in PSAT the Schiff base is protonated. Correlation of the PSAT crystal structure to a published profile sequence analysis of all subgroup IV members allows active site modelling of nifs and the proposal of a likely molecular reaction mechanism. PMID:10024454

Hester, G; Stark, W; Moser, M; Kallen, J; Markovi?-Housley, Z; Jansonius, J N

1999-02-26

160

Magnetic, spectroscopic and X-ray crystallographic structural studies on copper(II) complexes of tridentate NNS Schiff base ligands formed from 2-acetylpyrazine and S-methyl- and S-benzyldithiocarbazates  

Microsoft Academic Search

New copper(II) complexes of general empirical formula, [Cu(NNS)X] (NNS=anionic forms of the 2-acetylpyrazine Schiff bases of S-methyl- and S-benzyldithiocarbazate, Hapsme and Hapsbz) and X=Cl?, Br?, NCS? and NO3? have been synthesized and characterized. X-ray crystal structures of the free ligand, Hapsbz and the complexes, [Cu(apsbz)(NO3)]?, [Cu(apsme)(NCS)]2 and [Cu(apsme)Cl]2 have been determined. In the solid state, the Schiff base, Hapsbz remains

Malai Haniti S. A. Hamid; Mohammad Akbar Ali; Aminul Huq Mirza; Paul V. Bernhardt; Boujemaa Moubaraki; Keith S. Murray

2009-01-01

161

Sterically hindered complexes of platinum(II) with planar heterocyclic nitrogen donors. A novel complex with 1-methyl-cytosine has a spectrum of activity different from cisplatin and is able of overcoming acquired cisplatin resistance.  

PubMed

A very interesting series of water soluble platinum compounds violating some of the classical structure-activity relationships, but still showing antitumor activity, was reported by Hollis and collaborators some 25 years ago [L.S. Hollis, A.R. Amundsenm, E.W. Stern. J. Med. Chem. 32 (1989) 128-136]. The compounds, having formula [PtClA(2)L](+) (A(2)=two monodentate or a bidentate amine, L=a secondary or tertiary amine or a N-donor heterocycle), were characterized by a positive charge and three non-labile N-donor ligands. We have extended the investigation to analogous compounds in which 2,9-dimethyl-1,10-phenanthroline has taken the place of the A(2) ligand(s) and L is 2-picoline (1), 6-amino-2-picoline (2), or 1-methyl-cytosine (3). The X-ray analysis of 2 has revealed a bow-like distortion of the phenanthroline plane, a sloping of the phenanthroline plane with respect to the coordination plane, and an overall shielding of the metallic core by the ortho substituents of the phenanthroline and pyridine ligands. In vitro grow inhibition assays have been performed on the most water soluble complex 3. The results indicate that this complex is characterized by a potent growth inhibitory activity with mean IC(50) value (in a panel of 11 human tumor cell lines) of 1.1 microM to be compared with a mean value of 3.8 microM for cisplatin. The same compound also appears to completely overcome the acquired cisplatin resistance stemming from reduced uptake or a multifocal mechanism, thus pointing to a mechanism of action distinctly different from that of cisplatin. PMID:16959321

Margiotta, Nicola; Natile, Giovanni; Capitelli, Francesco; Fanizzi, Francesco P; Boccarelli, Angelina; De Rinaldis, Pietro; Giordano, Domenico; Coluccia, Mauro

2006-11-01

162

Tin(IV) and organotin(IV) complexes containing mono or bidentate N-donor ligands—IV. 2-methyl-, 2-isopropyl- and 4-methyl-imidazole derivatives: synthesis, characterization and behaviour in solution  

Microsoft Academic Search

The interaction between 4-methyl-, 2-methyl- and 2-isopropyl-imidazole, L1, L2 and L3 respectively (L in general), and several tin(IV) and organotin(IV) acceptors in diethyl ether, acetonitrile, dichloromethane or chloroform, gives 1:1 [(L1)(C6H5)3SnCl] · 1\\/3H2O, [(L3)(C6H5)3SnCl], [(L3)(CH3)3SnCl] and [(L3)(6H5)2SnCl2] · (H2O), 2:1 [(L)2RnSnX4?n] · zH2O (L = L1, R = Me, n = 1, 2 or 3, X = Cl, z =

Claudio Pettinari; Maura Pellei; Fabio Marchetti; Carlo Santini; Michele Miliani

1998-01-01

163

Crosstalk between NSL Histone Acetyltransferase and MLL/SET Complexes: NSL Complex Functions in Promoting Histone H3K4 Di-Methylation Activity by MLL/SET Complexes  

PubMed Central

hMOF (MYST1), a histone acetyltransferase (HAT), forms at least two distinct multiprotein complexes in human cells. The male specific lethal (MSL) HAT complex plays a key role in dosage compensation in Drosophila and is responsible for histone H4K16ac in vivo. We and others previously described a second hMOF-containing HAT complex, the non-specific lethal (NSL) HAT complex. The NSL complex has a broader substrate specificity, can acetylate H4 on K16, K5, and K8. The WD (tryptophan-aspartate) repeat domain 5 (WDR5) and host cell factor 1 (HCF1) are shared among members of the MLL/SET (mixed-lineage leukemia/set-domain containing) family of histone H3K4 methyltransferase complexes. The presence of these shared subunits raises the possibility that there are functional links between these complexes and the histone modifications they catalyze; however, the degree to which NSL and MLL/SET influence one another's activities remains unclear. Here, we present evidence from biochemical assays and knockdown/overexpression approaches arguing that the NSL HAT promotes histone H3K4me2 by MLL/SET complexes by an acetylation-dependent mechanism. In genomic experiments, we identified a set of genes including ANKRD2, that are affected by knockdown of both NSL and MLL/SET subunits, suggested they are co-regulated by NSL and MLL/SET complexes. In ChIP assays, we observe that depletion of the NSL subunits hMOF or NSL1 resulted in a significant reduction of both H4K16ac and H3K4me2 in the vicinity of the ANKRD2 transcriptional start site proximal region. However, depletion of RbBP5 (a core component of MLL/SET complexes) only reduced H3K4me2 marks, but not H4K16ac in the same region of ANKRD2, consistent with the idea that NSL acts upstream of MLL/SET to regulate H3K4me2 at certain promoters, suggesting coordination between NSL and MLL/SET complexes is involved in transcriptional regulation of certain genes. Taken together, our results suggest a crosstalk between the NSL and MLL/SET complexes in cells.

Wang, Fei; Liu, Da; Ding, Jian; Yang, Yang; Conaway, Joan W.; Conaway, Ronald C.; Cao, Lingling; Wu, Donglu; Wu, Min; Cai, Yong; Jin, Jingji

2013-01-01

164

DNA interaction studies of cobalt (II) mixed-ligand complexes containing dimethyl-1, 10-phenanthroline and dipyrido[3,2-a:2',3'-c]phenazine: the role of methyl substitutions on the mode of binding.  

PubMed

Two cobalt (II) complexes containing a dipyrido[3,2-a:2',3'-c]phenazine (dppz) base with the general formulation [Co(dppz)(dmp)(2)]Cl(2), where dmp is 4,7-dimethyl-1,10-phenanthroline ligand (4,7-dmp) (1) and 2,9-dimethyl-1,10-phenanthroline ligand (2,9-dmp) (2) were synthesized and characterized. Binding interactions of these complexes with calf thymus DNA were investigated by emission, absorption, circular dichroism, and viscosity studies, and the effects of the positions of methyl substitutions in phenanthroline coligands were investigated. The DNA binding constants obtained from the absorption spectral titrations decrease in the order of 1?>?2, which is consistent with the trend in apparent emission enhancement of the complexes on binding to calf thymus DNA. These observations were supported by circular dichroism spectroscopy and viscosity measurements and reveal that DNA binding affinity of the complexes depends on the position of methyl groups on the phenanthroline ligands. PMID:21345129

Shahabadi, Nahid; Kashanian, Soheila; Mahdavi, Maryam

2011-07-01

165

Synthesis, spectral characterization and antioxidant activity studies of a bidentate Schiff base, 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its Cd(II), Cu(II), Ni(II) and Zn(II) complexes  

NASA Astrophysics Data System (ADS)

A new Schiff base bidentate ligand (L), 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its metal (Cu(II), Cd(II), Ni(II) and Zn(II)) complexes with general stoichiometry [M(L)2X2] (where X = Cl) were synthesized. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, ESR spectral analyses, and molar conductance studies. The molar conductance data revealed that all the metal chelates are non-electrolytes. IR spectra showed that ligand (L) is coordinated to the metal ions in a bidentate manner with N and O donor sites of the azomethine-N, and carbonyl-O. ESR and UV-Vis spectral data showed that the geometrical structure of the complexes are Orthorhombic. Furthermore, the antioxidant activity of the ligand and its complexes was determined by hydroxyl radical scavenging, DPPH, NO, reducing power methods in vitro. The obtained IC50 value of the DPPH activity for the copper complex (IC50 = 66.4 ?m) was higher than other compounds. Microbial assay of the above complexes against Staphylococcus aureus, Escherichia coli, Rhizocotonia bataticola and Alternaria alternata showed that copper complex exhibited higher activity than the other complexes.

Harinath, Y.; Harikishore Kumar Reddy, D.; Naresh Kumar, B.; Apparao, Ch.; Seshaiah, K.

2013-01-01

166

Synthesis, characterization and catalytic properties of diorganotin derivatives. Crystal and molecular structure of the first complex of 2-(2-methyl-3-nitroanilino)benzoic acid of 1,2:3,4-di-?2-2-(2-methyl-3-nitroanilino)benzoato- O, O-1,3-bis-2-(2-methyl-3-nitroanilino)benzoato- O-1,2,4:2,3,4-di-?3-oxo-tetrakis[di-methyltin(IV)  

Microsoft Academic Search

The complexes [Me2(MNAB)SnOSn(MNAB)Me2]2 (2) and [Me2Sn(MNAB)2] (3), where HMNAB is 2-(2-methyl-3-nitroanilino)benzoic acid, (1), have been prepared and structurally characterized by means of vibrational, 1H and 13C NMR spectroscopies. The crystal structure of [Me2(MNAB)SnOSn(MNAB)Me2]2 has been determined by X-ray crystallography. Three distannoxane rings are present to the dimeric tetraorganodistannoxane of planar ladder arrangement. The structure is centro-symmetric and features a central

Vaso N. Dokorou; Dimitra Kovala-Demertzi; Maria Louloudi; Anca Silvestru; Mavroudis A. Demertzis

2008-01-01

167

Spectral characterization, molecular modeling and antimicrobial studies on hydrazone metal complexes of 5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6(3H)dione and S-methyl dithiocarbazate.  

PubMed

Metal complexes of copper(II), nickel(II), cobalt(II), oxovanadium(IV), chromium(III) and cadmium(II) with a new bridged ONS dibasic tridentate hydrazone (H2L) derived from 5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6(3H)-dione with S-methyl dithiocarbazate have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, spectral (infrared, electronic, mass, 1H NMR and ESR) studies as well as thermal gravimetric analysis (TGA). The synthesized complexes have dimeric structures with the general formula [ML(NO3)m(H2O)x]2·nH2O·zMeOH, L=dianion of the hydrazone, m=0-1, x=0-2, n=0-4 and z=0-1. The metal complexes exhibited square planar, tetrahedral and octahedral geometrical arrangements, the molar conductivity data indicates that all complexes are neutral. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition stages of some complexes. Structural parameters of the ligand and its metal complexes have been theoretically computed on the basis of semiempirical PM3 level and the results were correlated with their experimental data. Antibacterial activities of the free ligand and its metal complexes were screened against various organisms. PMID:24810030

Taha, Ali; Emara, Adel A A; Mashaly, Mahmoud M; Adly, Omima M I

2014-09-15

168

Spectral characterization, molecular modeling and antimicrobial studies on hydrazone metal complexes of 5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6(3H)dione and S-methyl dithiocarbazate  

NASA Astrophysics Data System (ADS)

Metal complexes of copper(II), nickel(II), cobalt(II), oxovanadium(IV), chromium(III) and cadmium(II) with a new bridged ONS dibasic tridentate hydrazone (H2L) derived from 5-acetyl-4-hydroxy-2H-1,3-thiazine-2,6(3H)-dione with S-methyl dithiocarbazate have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibility measurements, spectral (infrared, electronic, mass, 1H NMR and ESR) studies as well as thermal gravimetric analysis (TGA). The synthesized complexes have dimeric structures with the general formula [ML(NO3)m(H2O)x]2·nH2O·zMeOH, L = dianion of the hydrazone, m = 0-1, x = 0-2, n = 0-4 and z = 0-1. The metal complexes exhibited square planar, tetrahedral and octahedral geometrical arrangements, the molar conductivity data indicates that all complexes are neutral. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition stages of some complexes. Structural parameters of the ligand and its metal complexes have been theoretically computed on the basis of semiempirical PM3 level and the results were correlated with their experimental data. Antibacterial activities of the free ligand and its metal complexes were screened against various organisms.

Taha, Ali; Emara, Adel A. A.; Mashaly, Mahmoud M.; Adly, Omima M. I.

2014-09-01

169

Stereospecific ligands and their complexes. Part XVII. Synthesis and characterization of ethylenediamine-N,N?-di-S,S-2-(3-methyl)butanoic acid and its platinum(IV) complex with bromido ligands. Crystal structure of s-cis-[PtBr2(S,S-eddv)]·H2O  

NASA Astrophysics Data System (ADS)

The synthesis of novel platinum(IV) complex of formula [PtBr2(S,S-eddv)]·H2O (S,S-eddv = ethylenediamine-N,N?-di-S,S-2-(3-methyl)butanoate ion) is reported. The complex has been obtained by direct reaction of potassium-hexabromidoplatinate(IV) with neutralized ethylenediamine-N,N?-di-S,S-2-(3-methyl)butanoic acid (H2-S,S-eddv). The ligand and complex were characterized by elemental analysis, infrared, 1H and 13C NMR spectroscopy. The spectroscopically predicted geometrical configuration of the obtained complex was confirmed by X-ray analyses of the crystal structure of the s-cis-[PtBr2(S,S-eddv)]·H2O. The asymmetric unit of the complex contains three crystallographically independent s-cis-[PtBr2(S,S-eddv)] and water molecules. The Pt(IV) atom in each complex molecule exhibits a distorted octahedral coordination geometry, built up by two cis-coordinated bromido ligands and one cis-N,N? and trans-O,O? coordinated S,S-eddv ligand (configuration index: OC-6-33). In the crystal structure, intermolecular N–H⋯O hydrogen bonds are found between the complex and water molecules.

Stojkovi?, Danijela Lj.; Jevti?, Verica V.; Radi?, Gordana P.; Poto??ák, Ivan; Trifunovi?, Sre?ko R.

2014-05-01

170

fullRecord:"self methylate" "self methylated" "self methylates" "self methylating" "self methylation" sulfomethylate sulfomethylated sulfomethylates sulfomethylating sulfomethylation phthalocyaninato phthalocyanine phthalocyanines tetrabenzoporphyrazine  

EPA Pesticide Factsheets

Did you mean: fullRecord:"self methylate" "self methylated" "self methylates" "self methylating" "self methylation" sulfomethylate sulfomethylated sulfomethylates sulfomethylating sulfomethylation phthalocyaninato phthalocyanine phthalocyanines tetrabenzoporphyrazine ?

171

Synthesis, crystal structure and properties of Zn(II) and Cd(II) complexes with 2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydro-1H-imidazol-2-yl)nicotinic acid ligand  

Microsoft Academic Search

Two novel complexes, namely [Cd(L)2] (1) and [Zn(L)2(H2O)2] (2) have been synthesized (HL=2-(4-isopropyl-4-methyl-5-oxo-4,5-dihydro-1H-imidazol-2-yl)nicotinic acid), which are characterized by elemental analysis, infrared spectrum and X-ray crystal diffraction. While strong hydrogen bonds play central roles in the formation of the 3D structure, the combined influence of the weak interactions such as C–H?O bonds, carbonyl?? and C–H?? interactions are also evident in the

Feilong Hu; Xianhong Yin; Yan Mi; Shanshan Zhang; Weiqiang Luo; Yue Zhuang

2010-01-01

172

Constrained photophysics of partially and fully encapsulated charge transfer probe (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester inside cyclodextrin nano-cavities: Evidence of cyclodextrins cavity dependent complex stoichiometry  

NASA Astrophysics Data System (ADS)

The polarity sensitive intra-molecular charge transfer (ICT) emission from (E)-3-(4-Methylaminophenyl) acrylic acid methyl ester (MAPAME) is found to show distinct changes once introduced into the nano-cavities of cyclodextrins in aqueous environment. Movement of the molecule from the more polar aqueous environment to the less polar, hydrophobic cyclodextrin interior is marked by the blue shift of the CT emission band with simultaneous fluorescence intensity enhancement. The emission spectral changes on complexation with the ?- and ?-CD show different stoichiometries as observed from the Benesi-Hildebrand plots. Fluorescence anisotropy and lifetime measurements were performed to probe the different behaviors of MAPAME in aqueous ?- and ?-CD solutions.

Ghosh, Shalini; Jana, Sankar; Guchhait, Nikhil

2011-12-01

173

SYNTHESIS AND SPECTRAL STUDIES OF TRI AND DIORGANOTIN(IV) COMPLEXES WITH 5-BENZOYL-?-METHYL-2-THIOPHENEACETIC ACID: CRYSTAL STRUCTURE OF [(CH3)3Sn(C14H11O3S)  

Microsoft Academic Search

A series of tri- and diorganotin(IV) complexes of the general formula R4?nSnLn (where R=CH3, C4H9, C6H6, C7H7, n=1, 2 and HL=5-benzoyl-?-methyl-2-thiopheneacetic acid) have been sythesized by the reaction of tri- and diorganotin- (IV) chloride(s) with the silver salt of the ligand in CHCl3 solution. All of the compounds have been characterized by IR, conductance measurement, multinuclear (H, C, Sn) NMR,

Fiaz Ahmad; Masood Parvez; Saqib Ali; M. Mazhar; Arshad Munir

2002-01-01

174

Synthesis and biodistribution of new oxo and nitrido 99mTc complexes with asymmetrical potentially dianionic or trianionic tetradentate SNNO ligands derived from methyl-2-aminocyclopentene-1-dithiocarboxylic acid.  

PubMed

In this work, 10 new asymmetrical tetradentate SNNO ligands were prepared by reaction of the amine function of methyl 2-[(beta-aminoethyl)amino]cyclopentene-1-dithiocarboxylate with various bifunctional substituents bearing hydroxyl/ketone and hydroxyl/aldehyde functional groups and with diethyl oxalate. 99mTc labeling efficiency was optimized by adjusting temperature and pH conditions. Seven nitrido and two oxo 99mTc complexes were isolated. Six of them proved to be stable near physiological conditions. Biodistribution studies in the rat showed a significant heart uptake for four of them and strong kidney and liver uptake for the other two. PMID:9466364

Belhadj-Tahar, H; Ouhayoun, E; Cros, G; Darbieu, M H; Tafani, J A; Fabre, J; Esquerre, J P; Coulais, Y

1998-01-01

175

Complex methyl groups dynamics in [(CH3)4P]3Sb2Br9 (PBA) from low to high temperatures by proton spin-lattice relaxation and narrowing of proton NMR spectrum.  

PubMed

Molecular dynamics of a polycrystalline sample of [(CH(3))(4)P](3)Sb(2)Br(9) (PBA) has been studied on the basis of the T(1) (24.7 MHz) relaxation time measurement, the proton second moment of NMR and the earlier published T(1) (90 MHz) relaxation times. The study was performed in a wide range of temperatures (30-337 K). The tunnel splitting omega(T) of the methyl groups was estimated as of low frequency (from kHz to few MHz). The proton spin pairs of the methyl group are known to perform a complex internal motion being a resultant of four components. Three of them involve mass transportation over and through the potential barrier and are characterized by the correlation times tau(3) and tau(T)of the jumps over the barrier and tunnel jumps in the threefold potential of the methyl group and tau(iso) the correlation time of isotropic rotation of the whole TMP cation. For tau(3) and tau(iso) the Arrhenius temperature dependence was assumed, while for tau(T)--the Schrödinger one. The fourth motion causes fluctuations of the tunnel splitting frequency, omega(T), and it is related to the lifetime of the methyl spin at the energy level. The correlation function for this fourth motion (tau(omega) correlation time) has been proposed by Müller-Warmuth et al. In this paper a formula for the correlation function and spectral density of the complex motion made of the above-mentioned four components was derived and used in interpretation of the T(1) relaxation time. The second moment of proton NMR line at temperatures below 50K is four times lower than its value for the rigid structure. The three components of the internal motion characterized by tau(T), tau(H), and tau(iso) were proved to reduce the second moment of the NMR line. The tunnel jumps of the methyl group reduce M(2) at almost 0K, the classical jumps over the barrier reduce M(2) in the vicinity of 50K, while the isotropic motion near 150K. Results of the study on the dynamics of CH(3) groups of TMP cation based on the second moment measurements were correlated with those based on T(1) time measurements. PMID:19853419

Latanowicz, L; Medycki, W; Jakubas, R

2009-11-01

176

Crystal Structure of Silkworm Bombyx mori JHBP in Complex With 2-Methyl-2,4-Pentanediol: Plasticity of JH-Binding Pocket and Ligand-Induced Conformational Change of the Second Cavity in JHBP  

PubMed Central

Juvenile hormones (JHs) control a diversity of crucial life events in insects. In Lepidoptera which major agricultural pests belong to, JH signaling is critically controlled by a species-specific high-affinity, low molecular weight JH-binding protein (JHBP) in hemolymph, which transports JH from the site of its synthesis to target tissues. Hence, JHBP is expected to be an excellent target for the development of novel specific insect growth regulators (IGRs) and insecticides. A better understanding of the structural biology of JHBP should pave the way for the structure-based drug design of such compounds. Here, we report the crystal structure of the silkworm Bombyx mori JHBP in complex with two molecules of 2-methyl-2,4-pentanediol (MPD), one molecule (MPD1) bound in the JH-binding pocket while the other (MPD2) in a second cavity. Detailed comparison with the apo-JHBP and JHBP-JH II complex structures previously reported by us led to a number of intriguing findings. First, the JH-binding pocket changes its size in a ligand-dependent manner due to flexibility of the gate ?1 helix. Second, MPD1 mimics interactions of the epoxide moiety of JH previously observed in the JHBP-JH complex, and MPD can compete with JH in binding to the JH-binding pocket. We also confirmed that methoprene, which has an MPD-like structure, inhibits the complex formation between JHBP and JH while the unepoxydated JH III (methyl farnesoate) does not. These findings may open the door to the development of novel IGRs targeted against JHBP. Third, binding of MPD to the second cavity of JHBP induces significant conformational changes accompanied with a cavity expansion. This finding, together with MPD2-JHBP interaction mechanism identified in the JHBP-MPD complex, should provide important guidance in the search for the natural ligand of the second cavity.

Fujimoto, Zui; Suzuki, Rintaro; Shiotsuki, Takahiro; Tsuchiya, Wataru; Tase, Akira; Momma, Mitsuru; Yamazaki, Toshimasa

2013-01-01

177

Crystal structure of silkworm Bombyx mori JHBP in complex with 2-methyl-2,4-pentanediol: plasticity of JH-binding pocket and ligand-induced conformational change of the second cavity in JHBP.  

PubMed

Juvenile hormones (JHs) control a diversity of crucial life events in insects. In Lepidoptera which major agricultural pests belong to, JH signaling is critically controlled by a species-specific high-affinity, low molecular weight JH-binding protein (JHBP) in hemolymph, which transports JH from the site of its synthesis to target tissues. Hence, JHBP is expected to be an excellent target for the development of novel specific insect growth regulators (IGRs) and insecticides. A better understanding of the structural biology of JHBP should pave the way for the structure-based drug design of such compounds. Here, we report the crystal structure of the silkworm Bombyx mori JHBP in complex with two molecules of 2-methyl-2,4-pentanediol (MPD), one molecule (MPD1) bound in the JH-binding pocket while the other (MPD2) in a second cavity. Detailed comparison with the apo-JHBP and JHBP-JH II complex structures previously reported by us led to a number of intriguing findings. First, the JH-binding pocket changes its size in a ligand-dependent manner due to flexibility of the gate ?1 helix. Second, MPD1 mimics interactions of the epoxide moiety of JH previously observed in the JHBP-JH complex, and MPD can compete with JH in binding to the JH-binding pocket. We also confirmed that methoprene, which has an MPD-like structure, inhibits the complex formation between JHBP and JH while the unepoxydated JH III (methyl farnesoate) does not. These findings may open the door to the development of novel IGRs targeted against JHBP. Third, binding of MPD to the second cavity of JHBP induces significant conformational changes accompanied with a cavity expansion. This finding, together with MPD2-JHBP interaction mechanism identified in the JHBP-MPD complex, should provide important guidance in the search for the natural ligand of the second cavity. PMID:23437107

Fujimoto, Zui; Suzuki, Rintaro; Shiotsuki, Takahiro; Tsuchiya, Wataru; Tase, Akira; Momma, Mitsuru; Yamazaki, Toshimasa

2013-01-01

178

Automethylation Activities within the Mixed Lineage Leukemia-1 (MLL1) Core Complex Reveal Evidence Supporting a "Two-active Site" Model for Multiple Histone H3 Lysine 4 Methylation*  

PubMed Central

The mixed lineage leukemia-1 (MLL1) core complex predominantly catalyzes mono- and dimethylation of histone H3 at lysine 4 (H3K4) and is frequently altered in aggressive acute leukemias. The molecular mechanisms that account for conversion of mono- to dimethyl H3K4 (H3K4me1,2) are not well understood. In this investigation, we report that the suppressor of variegation, enhancer of zeste, trithorax (SET) domains from human MLL1 and Drosophila Trithorax undergo robust intramolecular automethylation reactions at an evolutionarily conserved cysteine residue in the active site, which is inhibited by unmodified histone H3. The location of the automethylation in the SET-I subdomain indicates that the MLL1 SET domain possesses significantly more conformational plasticity in solution than suggested by its crystal structure. We also report that MLL1 methylates Ash2L in the absence of histone H3, but only when assembled within a complex with WDR5 and RbBP5, suggesting a restraint for the architectural arrangement of subunits within the complex. Using MLL1 and Ash2L automethylation reactions as probes for histone binding, we observed that both automethylation reactions are significantly inhibited by stoichiometric amounts of unmethylated histone H3, but not by histones previously mono-, di-, or trimethylated at H3K4. These results suggest that the H3K4me1 intermediate does not significantly bind to the MLL1 SET domain during the dimethylation reaction. Consistent with this hypothesis, we demonstrate that the MLL1 core complex assembled with a catalytically inactive SET domain variant preferentially catalyzes H3K4 dimethylation using the H3K4me1 substrate. Taken together, these results are consistent with a “two-active site” model for multiple H3K4 methylation by the MLL1 core complex.

Patel, Anamika; Vought, Valarie E.; Swatkoski, Stephen; Viggiano, Susan; Howard, Benny; Dharmarajan, Venkatasubramanian; Monteith, Kelsey E.; Kupakuwana, Gillian; Namitz, Kevin E.; Shinsky, Stephen A.; Cotter, Robert J.; Cosgrove, Michael S.

2014-01-01

179

Thermodynamics of substituted pyrazolone IX: potentiometric, spectrophotometric and conductometeric studies of 4-(4-chlorophenylazo)-3-methyl-1-[2-hydroxy-3-morphilinopropane 1-yl]-2-pyrazolin-5-one and its metal complexes.  

PubMed

The dissociation constants of 4-(4-chlorophenylazo)-3-methyl-1-[2-hydroxy-3-morphilinopropane-1-yl]-2-pyrazolin-5-one (CAMP) has been determined potentiometrically in 0.1 M KCl and 40% (v/v) ethanol-water mixture. The stepwise stability constants of the formed complexes of Mn2+, Co2+, Ni2+, Cu2+, Zn2+, La3+, Ce3+ and UO(2)2+, with CAMP have been determined. The stability of the formed complexes were found as follows: UO(2)2+ > Ce3+ > La3+ > Mn2+ < Co2+ < Ni2+ < Cu+ > Zn2+. The thermodynamic parameters (deltaG, deltaH and deltaS) for CAMP and its complexes were evaluated and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavourable. The formation of the complexes have been found to be spontaneous, exothermic or endothermic (depending on the metal) and entropically favourable. The stoichiometries of these complexes were determined spectrophotometrically and conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes. PMID:11767830

El-Bindary, A A; El-Sonbati, A Z; El-Mosalamy, E H; El-Santawy, E M

2001-10-01

180

Synthesis, characterization and studies on DNA-binding of a new Cu(II) complex with N1,N8-bis(l-methyl-4-nitropyrrole-2-carbonyl)triethylenetetramine.  

PubMed

A new Cu(II) complex of CuLCl(2) (here, L=N(1),N(8)-bis(1-methyl-4-nitropyrrole-2- carbonyl)triethylenetetramine) had been synthesized and characterized. The structure of the complex was investigated with density functional theory (DFT) calculations. DNA-binding of the Cu(II) complex and its effects on tumor cell viability were firstly studied. The interactions between the complex and calf thymus DNA had been investigated using UV spectra, fluorescent spectra, viscosity and CV (cyclic voltammetry). The cleavage reaction on plasmid DNA has been monitored by agarose gel electrophoresis. The experimental results show that the mode of binding of the complex to DNA is classical intercalation and the complex can cleave pBR322 DNA. The effects of the CuL on cell viability were tested using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) dye assay and the results indicate that the CuL had certain effect on cancer cells. PMID:17010441

Zhou, Cheng-Yong; Zhao, Jing; Wu, Yan-Bo; Yin, Cai-Xia; Pin, Yang

2007-01-01

181

New rhodium(III) and ruthenium(II) water-soluble complexes with 3,5-diaza-1-methyl-1-azonia-7-phosphatricyclo[3.3.1.1(3,7)]decane.  

PubMed

The new water-soluble phosphine complexes of rhodium(III), [RhI(4)(mtpa)(2)]I (1), and ruthenium(II), [RuI(4)(mtpa)(2)].2H(2)O (2) and [RuI(2)(mtpa)(3)(H(2)O)]I(3).2H(2)O (3) (mtpa = 3,5-diaza-1-methyl-1-azonia-7-phosphatricyclo[3.3.1.1(3,7)]decane cation), have been prepared in the reactions of RhCl(3).3H(2)O and RuCl(3).3H(2)O in water in the presence of phosphine and potassium iodide. Properties and reactivity of the complexes have been investigated using (1)H and (31)P NMR and IR spectroscopies. The complexes have also been structurally characterized by single crystal X-ray diffraction studies. The compounds [RhI(4)(mtpa)(2)]I and [RuI(4)(mtpa)(2)].2H(2)O are zwitterionic octahedral complexes. The compounds were tested as catalysts for two-phase hydroformylation of 1-hexene and hydrogenation of cinnamaldehyde. Complex 1 is a selective catalyst for reduction of the C=C bond while complexes 2 and 3 selectively hydrogenate the C=O bond. PMID:12739973

Smole?ski, Piotr; Pruchnik, Florian P; Ciunik, Zbigniew; Lis, Tadeusz

2003-05-19

182

Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2  

PubMed Central

Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films.

Onwudiwe, Damian C.; Ajibade, Peter A.

2011-01-01

183

Self-assembly of three Cd(II) complexes: From 0-D to 1-D and 2-D structures based on 1-((benzotriazol-1-yl)methyl)-1- H-1,3-imidazole ligand and different anions  

NASA Astrophysics Data System (ADS)

Three new complexes with the formulas [Cd(bmi) 2I 2] ( 1), [Cd(bmi) 2(Cl) 2] n ( 2) and [Cd(bmi) 2(SCN) 2] n ( 3) have been obtained through the self-assembly of an unsymmetrical ligand 1-((benzotriazol-1-yl)methyl)-1- H-1,3-imidazole (bmi) with Cd(II) salts at room temperature. Single crystal X-ray diffraction determination shows that complex 1 possesses mononuclear structure, complex 2 displays 1-D chain structure constructed by chloride bridging Cd(II) ions, and complex 3 exhibits 2-D grid network structure. In complexes 1 and 2, the unsymmetrical bmi ligands coordinate to metal ions as monodentate mode with the N atom from imidazole ring in preference to the N atom from benzotriazol ring. While in complex 3, bmi ligands coordinate to metal ions as ? 2-bridging mode with N atoms from imidazole and benzotriazol rings simultaneously. Additionally, their fluorescent properties also have been determined.

Duan, Likun; Ding, Yanan; Meng, Xiangru; Li, Weiqiang; Hou, Hongwei; Fan, Yaoting

2010-06-01

184

Mono and BiNuclear Metal Complexes of Schiff-Base Hydrazone (ONN) Derived from o-Hydroxyacetophenone and 2Amino4Hydrazino6Methyl Pyrimidine  

Microsoft Academic Search

A tridentate ONN donor Schiff-base hydrazone ligand, H2L, was synthesized by the condensation of 2-amino-4-hydrazino-6-methyl pyrimidine with o-hydroxyacetophenone. The structure of the ligand was elucidated by IR and H NMR spectra which indicated the presence of three different coordinating groups, the oxygen atom of the phenolic OH group, the nitrogen atom of the azomethine, C=N, group and one of the

Saied M. E. Khalil; H. S. Seleem; B. A. El-Shetary; M. Shebl

2002-01-01

185

The influence of counter ion and ligand methyl substitution on the solid-state structures and photophysical properties of mercury(II) complexes with (E)-N-(pyridin-2-ylmethylidene)arylamines.  

PubMed

Ten neutral monomeric, dimeric and polymeric mercury(II) complexes of compositions HgX(2)L (3, 8), [HgX(2)L](2) (1, 2, 4-6 and 7), [Hg(NO(3))(2)L](n) (9) and {[Hg(N(3))(2)L](2)}(n) (10) where X = chloride, bromide, iodide, nitrate and azide, and L = (E)-N-(pyridin-2-ylmethylidene)arylamine, are described. Compounds 1-10 were characterized by elemental analyses, and IR and (1)H NMR spectroscopic studies. The solution-state photophysical properties of the complexes are highly dependent on the anions as seen in the fluorescence emission features. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Iodide gives discrete monomeric complexes, chloride and bromide generate binuclear complexes formed through Hg-X-Hg bridges, while nitrate and azide lead to 1D coordination polymers. The significant differences in the observed aggregation patterns of the compounds indicate that the anions exert a substantial influence on the formation of the compounds. A further influence upon supramolecular aggregation is the presence of methyl substituents in L(3) and L(4), which generally enhances the probability of forming supramolecular ?? interactions involving the five-membered C(2)N(2)Hg chelate rings in their crystal structures. PMID:23172550

Basu Baul, Tushar S; Kundu, Sajal; Mitra, Sivaprasad; Höpfl, Herbert; Tiekink, Edward R T; Linden, Anthony

2013-02-01

186

Ternary copper(II) complexes involving 2-(aminomethyl)-benzimidazole and some bio-relevant ligands. Equilibrium studies and kinetics of hydrolysis for glycine methyl ester under complex formation  

Microsoft Academic Search

Formation equilibria of copper(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Cu(AMBI)L (L=amino acid, amide, dicarboxylic acid or DNA constituents) have been investigated. Ternary complexes of amino acids or amides are formed by a simultaneous mechanism. Amino acids form the complex Cu(AMBI)L, whereas amides form two complex species Cu(AMBI)L and Cu(AMBI)(LH?1). The ternary complexes of copper(II) with AMBI and

Ahmed A. El-Sherif; Mohamed M. Shoukry

2007-01-01

187

Oxidation of methyl formylstearate with molecular oxygen  

Microsoft Academic Search

Methyl formylstearate, containing soluble rhodium complex from rhodium-catalyzed hydroformylation of methyl oleate, is oxidized\\u000a in an emulsion to methyl carboxystearate. The reaction is carried out in a closed system at 20–25 C in the presence of either\\u000a air or oxygen (1–3 atm). Conversion to methyl carboxystearate is 87–89% in 2–3 hr; when catalytic amounts of calcium acetate\\u000a are present, 93–95%

J. P. Friedrich

1976-01-01

188

Analytical Methodologies for Detection of Gamma-valerolactone, Delta-valerolactone, Acephate, and Azinphos Methyl and their Associated Metabolites in Complex Biological Matrices  

SciTech Connect

Non-invasive biomonitoring for chemicals of interest in law enforcement and similar monitoring of pesticides together with their metabolites can not only save money but can lead to faster medical attention for individuals exposed to these chemicals. This study describes methods developed for the analysis of gamma-valerolactone (GVL), delta-valerolactone (DVL), acephate, and azinphos methyl in saliva and serum. Liquid chromatography/mass spectrometry (LC/MS) operated in the negative ion mode and in the positive ion mode and gas chromatography/mass spectrometry (GC/MS) were used to analyze GVL and DVL. Although both analytical techniques worked well, lower detection limits were obtained with GC/MS. The lactones and their corresponding sodium salts were spiked into both saliva and serum. The lactones were isolated from saliva or serum using newly developed extraction techniques and then subsequently analyzed using GC/MS. The sodium salts of the lactones are nonvolatile and require derivatization prior to analysis by this method. N-methyl-N-(t-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) was ultimately selected as the reagent for derivatization because the acidic conditions required for reactions with diazomethane caused the salts to undergo intramolecular cyclization to the corresponding lactones. In vitro studies were conducted using rat liver microsomes to determine other metabolites associated with these compounds. Azinphos methyl and acephate are classified as organophosphate pesticides, and are known to be cholinesterase inhibitors in humans and insects, causing neurotoxicity. For this reason they have both exposure and environmental impact implications. These compounds were spiked into serum and saliva and prepared for analysis by GC/MS. Continuation of this research would include analysis by GC/MS under positive ion mode to determine the parent ions of the unknown metabolites. Further research is planned through an in vivo analysis of the lactones and pesticides. These methodologies could be extended for further analysis of other similar compounds as well as chemical and biological warfare agents.

Zink, Erika M.; Clark, Ryan J.; Grant, Karen E.; Campbell, James A.; Hoppe, Eric W.

2005-01-01

189

Cigarette smoking and DNA methylation  

PubMed Central

DNA methylation is the most studied epigenetic modification, capable of controlling gene expression in the contexts of normal traits or diseases. It is highly dynamic during early embryogenesis and remains relatively stable throughout life, and such patterns are intricately related to human development. DNA methylation is a quantitative trait determined by a complex interplay of genetic and environmental factors. Genetic variants at a specific locus can influence both regional and distant DNA methylation. The environment can have varying effects on DNA methylation depending on when the exposure occurs, such as during prenatal life or during adulthood. In particular, cigarette smoking in the context of both current smoking and prenatal exposure is a strong modifier of DNA methylation. Epigenome-wide association studies have uncovered candidate genes associated with cigarette smoking that have biologically relevant functions in the etiology of smoking-related diseases. As such, DNA methylation is a potential mechanistic link between current smoking and cancer, as well as prenatal cigarette-smoke exposure and the development of adult chronic diseases.

Lee, Ken W. K.; Pausova, Zdenka

2013-01-01

190

Methylated DNA immunoprecipitation genome-wide analysis.  

PubMed

DNA methylation is an important and potentially heritable component of the epigenetic machinery that has a major role in the control of gene expression and can be deregulated in many diseases. This modification of genomic DNA can be assessed using the methylated DNA immunoprecipitation (MeDIP) method, based on the quantification of methylated DNA fragments enriched using an antibody specific for methyl-cytosines.The relationship between the enrichment level and the real DNA methylation status is complex, and only a few methods have been developed to evaluate MeDIP enrichment measures to estimate the absolute or relative number of methyl-cytosines in a given sample. Two such methods are MEDME and BATMAN. This chapter focuses on the description and use of the former with a brief discussion of the latter. PMID:21913075

Pelizzola, Mattia; Molinaro, Annette

2011-01-01

191

Novel square arrangements in tetranuclear and octanuclear iron(III) complexes with asymmetric iron environments created by the unsymmetric bridging ligand N,N,N{prime}-tris((N-methyl)-2-benzimidazolylmethyl)-N{prime}-methyl-1,3-diamino-2-propanol  

SciTech Connect

The synthesis and characterization of novel tetranuclear and octanuclear iron(III) complexes with structures based on a nearly square arrangement of four iron ions are reported. Reaction of ferric nitrate, sodium acetate, and the unsymmetrical binucleating ligand HBMDP, where HBMDP is N,N,N{prime}-tris((N-methyl)-2-benzimidazolylmethyl)-N{prime}-methyl-1,3-diamino-2-propanol, in acetone/water yields the tetranuclear iron complex [Fe{sub 4}({mu}-O){sub 2}({mu}-BMDP){sub 2}-({mu}-OAc){sub 2}]{sup 4+}, which exhibits coordination number asymmetry. The structure of [Fe{sub 4}({mu}-O){sub 2}({mu}-BMDP){sub 2}({mu}-OAc){sub 2}](NO{sub 3}){sub 3}(OH){center_dot}12H{sub 2}O has been determined by single-crystal X-ray diffraction. Each ({mu}-BMDP) ligand spans two iron(III) ions and causes these ions to become structurally distinct. Within this binuclear unit one iron atom is five-coordinate with distorted square pyramidal geometry and an N{sub 2}O{sub 3} donor set, while the other iron is six-coordinate with distorted octahedral geometry and an N{sub 3}O{sub 3} donor set. Two of these binuclear units are linked through a pair of oxo and acetato bridges to form the centrosymmetric tetranuclear complex. Efforts to increase the solubility of [Fe{sub 4}({mu}-O){sub 2}({mu}-BMDP){sub 2}({mu}-OAc){sub 2}]{sup 4+} by metathesis with sodium tetrafluoroborate resulted in the isolation of crystals of a new octanuclear iron species, which has also been characterized by single-crystal X-ray diffraction.

Satcher, J.H. Jr.; Parkin, S.R. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States); [Univ. of California, Davis, CA (United States). Dept. of Chemistry; Olmstead, M.M.; Noll, B.C.; Balch, A.L. [Univ. of California, Davis, CA (United States). Dept. of Chemistry] [Univ. of California, Davis, CA (United States). Dept. of Chemistry; Droege, M.W. [Lawrence Livermore National Lab., CA (United States)] [Lawrence Livermore National Lab., CA (United States); May, L. [Catholic Univ. of America, Washington, DC (United States)] [Catholic Univ. of America, Washington, DC (United States)

1998-12-28

192

Effect of persistence length on binding of DNA to polyions and overcharging of their intermolecular complexes in aqueous and in 1-methyl-3-octyl imidazolium chloride ionic liquid solutions.  

PubMed

The effect of persistence length on the intermolecular binding of DNA (200 bp, persistence length l(p) = 50 nm, polyanion) with three proteins, gelatin B (GB) (l(p) = 2 nm, polyampholyte chain), bovine serum albumin (BSA) (l(p) = 7 nm, polyampholyte colloid), gelatin A (GA) (l(p) = 10 nm, polyampholyte chain), and a polysaccharide chitosan (l(p) = 17 nm, polycation), was investigated in aqueous and in 1-methyl-3-octyl imidazolium chloride ionic liquid ([C8mim][Cl]) solutions. In DNA-GB and DNA-BSA solutions complexation primarily arises from surface patch binding whereas DNA-chitosan and DNA-GA binding was predominantly governed by electrostatic forces. These occurred at well defined pH values: (i) at pHc associative interactions ensued and soluble complexes were formed, (ii) at pH? soluble complexes coalesced to give rise to liquid-liquid phase separation (coacervation) and (iii) at pH(prep) formation of large insoluble complexes drove the solution towards liquid-solid phase separation. A universal phase diagram encapsulating the aforesaid interactions can be made using the persistence length of polyion as an independent variable. DNA formed overcharged intermolecular complexes with all these polyions when the polyion concentration was more than the concentration required to produce charge neutralized complexes (disproportionate binding). In IL solutions maximum binding occurred when 0.075 < [IL] < 0.10% (w/v) and the effect of overcharging was substantially screened. The extent of overcharge was a monotonous increasing function of the polyion persistence length. Results clearly revealed that DNA-polyion binding was hierarchical in polyion concentration and persistence length. Overcharging of the DNA-polyion complex was found to be ubiquitous for the polyions used in the present study. PMID:23775068

Rawat, Kamla; Pathak, Jyotsana; Bohidar, H B

2013-08-01

193

Structural rearrangement in the formation of jet-cooled complexes of chiral (S)-1,2,3,4-tetrahydro-3-isoquinolinemethanol with methyl lactate: chirality effect in conformer selection.  

PubMed

The jet-cooled complexes between the two enantiomers of methyl lactate (ML) and (S)-1,2,3,4-tetrahydro-3-isoquinolinemethanol (THIQM) are studied by double resonance spectroscopy combined with ab initio calculations. Both diastereomer complexes exist in different isomers, involving either direct addition of THIQM on ML with no structural rearrangement of the subunits or formation of very stable structures involving multiple intermolecular hydrogen bonds and extensive deformation of the subunits. Competition between these two processes and its dependence upon chirality are discussed. It is shown that the most stable form of the chromophore (THIQMI with an OH···N hydrogen bond) prefers to directly stick to ML to form the addition complex whereas the second conformer (THIQMII with NH···O hydrogen bond) rearranges to form a strongly bound structure. The two structures are formed for the homochiral as well the heterochiral complex, however with different relative abundance. This shows an enantioselective binding preference of ML for one of the conformers of the chromophore. PMID:23496094

Mahjoub, Ahmed; Le Barbu-Debus, Katia; Zehnacker, Anne

2013-04-11

194

Synthesis, characterization, and theoretical studies of Co(II) and Cu(II) complexes of 1-[(5-mercapto-[1,3,4]thiadiazol-2-ylimino)-methyl]-naphthalen-2-ol and its interaction with Cu nanoparticles  

NASA Astrophysics Data System (ADS)

The electronic absorption spectra of Schiff base namely 1-[(5-mercapto-[1,3,4]thiadiazol-2-ylimino)-methyl]-naphthalen-2-ol (H 2L) was studied in organic solvents of different polarity as well as in universal buffer solutions of varying pH values at room temperature; the pK a values were calculated. The effect of Co(II) and Cu(II) ions on the electronic absorption spectra of H 2L was also assigned and the stability constants of the complexes were calculated. The stoichiometry of the metal complexes was determined spectrophotometrically. Solid Co(II) and Cu(II) complexes with H 2L have been synthesized and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility measurements, IR, electronic as well as ESR spectral studies. The thermal decomposition of the metal complexes was studied by TGA and DTA techniques. The thermo-kinetic parameters; activation energy, pre-exponential factor and entropy of activation were estimated. The interaction between the Schiff base under investigation and the copper nanoparticles in the ground and excited state was considered. The fluorescence quenching rate constant of Schiff base by Cu nanoparticles has a large value.

El-Wakiel, Nadia; El-Sayed, Yusif; Gaber, Mohamed

2011-08-01

195

Synthesis, Characterization, and Biological Activity of N1-Methyl-2-(1H-1,2,3-Benzotriazol-1-y1)-3-Oxobutan- ethioamide Complexes with Some Divalent Metal (II) Ions  

PubMed Central

A new series of Zn2+, Cu2+, Ni2+, and Co2+ complexes of N1-methyl-2-(1H-1,2,3-benzotriazol-1-yl)-3-oxobutanethioamide (MBOBT), HL, has been synthesized and characterized by different spectral and magnetic measurements and elemental analysis. IR spectral data indicates that (MBOBT) exists only in the thione form in the solid state while 13C NMR spectrum indicates its existence in thione and thiole tautomeric forms. The IR spectra of all complexes indicate that (MBOBT) acts as a monobasic bidentate ligand coordinating to the metal(II) ions via the keto-oxygen and thiolato-sulphur atoms. The electronic spectral studies showed that (MBOBT) bonded to all metal ions through sulphur and nitrogen atoms based on the positions and intensity of their charge transfer bands. Furthermore, the spectra reflect four coordinate tetrahedral zinc(II), tetragonally distorted copper(II), square planar nickel(II), and cobalt(II) complexes. Thermal decomposition study of the complexes was monitored by TG and DTG analyses under N2 atmosphere. The decomposition course and steps were analyzed and the activation parameters of the nonisothermal decomposition are determined. The isolated metal chelates have been screened for their antimicrobial activities and the findings have been reported and discussed in relation to their structures.

Al-Awadi, Nouria A.; Shuaib, Nadia M.; Abbas, Alaa; El-Sherif, Ahmed A.; El-Dissouky, Ali; Al-Saleh, Esmaeil

2008-01-01

196

Methyl radical addition to methyl ethyl ketone  

Microsoft Academic Search

From relative rates of acetone formation in the azomethane sensitized decomposition of methyl ethyl ketone at 290 °C, log10(k\\/cm3mol?1s?1)=5.3±0.4 for the methyl radical addition to methyl ethyl ketone has been determined.

H. Knoll

1981-01-01

197

Catalysis of methyl acetate formation from methanol alone by ({mu}{sup 5}-C{sub 5}H{sub 5})(PPh{sub 3}){sub 2}RuX (X=Cl, SnCl{sub 3}, SnF{sub 3}): High activity for the SnF{sub 3} complex  

SciTech Connect

The authors have recently shown that the Ru(II)-Sn(II) bimetallic complex can catalyze the unprecedented one-step formation of acetic acid (or methyl acetate) with methanol used as the sole source. It was suggested that the reaction consists of sequential processes of methanol {r_arrow} formaldehyde (methyl){r_arrow}methyl formate {r_arrow} acetic acid (methyl acetate). While the Ru(II) complexes capable of catalyzing the dehydrogenation of methanol into methyl formate are known, this catalyst system is unique because of its extra ability to isomerize methyl formate to acetic acid without a CO atmosphere (usually high pressure) or an iodide promoter (often corrosive to reaction apparatus). In this communication, the authors examine the cyclopentadienyl bis(triphenylphosphine) ruthenium(II) auxilliary in view of its well defined geometry and configurational stability, and demonstrate that combination with the SnF{sub 3} ligand gives quite high catalytic ability compared to the conventional SnCl{sub 3} ligand. 12 refs., 1 fig.

Einaga, Hisahiro; Yamakawa, Tetsu; Shinoda, Sumio [Univ. of Tokyo (Japan)

1994-12-31

198

Equilibrium and 1 H NMR Kinetic Study of the Reactions of Dichlorido [S-Methyl-L-Cysteine(N,S)]Platinum(II) Complex with Some Relevant Biomolecules  

Microsoft Academic Search

The formation equilibria of the [Pt(SMC)(H2O)2]+ complex with some biologically relevant ligands such as L-methionine (L-met) and glutathione (GSH) were studied. The stoichiometry\\u000a and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species\\u000a has been evaluated as a function of pH. The reaction between [PtCl2(SMC)] and guanosine-5?-monophosphate (5?-GMP) was studied by 1H

Tanja Soldatovi?; Predrag ?anovi?; Radivoje Nikoli?; Ratomir Jeli?; Živadin D. Bugar?i?

2009-01-01

199

NMR-spectroscopic and solid-state investigations of cometal-free asymmetric conjugate addition: a dinuclear paracyclophaneimine zinc methyl complex.  

PubMed

We present herein the first indications for dimeric structures in cometal-free asymmetric conjugate addition reactions of dialkylzinc reagents with aldehydes. These are revealed by nonlinear effect (NLE) studies. A monomer-dimer equilibrium can be assumed which explains the increase of the ee value in the product over time. Also, DOSY NMR spectroscopic measurements indicate the existence of the catalyst as [LZnEt](n) complexes in solution. Additionally, the first X-ray structure of a zinc complex with a [2.2]paracyclophane ligand was determined. The structures of the zinc complexes are supported by DFT calculations of monomeric and dimeric species. PMID:20806920

Ay, S; Ziegert, R E; Zhang, H; Nieger, M; Rissanen, K; Fink, K; Kubas, A; Gschwind, R M; Bräse, S

2010-09-22

200

Novel light-conversion hybrids of SBA-16 functionalized with rare earth (Eu3+, Nd3+, Yb3+) complexes of modified 2-methyl-9-hydroxyphenalenone and 1,10-phenanthroline  

NASA Astrophysics Data System (ADS)

Novel rare earth complex-functionalized mesoporous SBA-16-type hybrid materials are synthesized by the co-condensation of modified 2-methyl-9-hydroxyphenalenone (MHPOSi), from modified 3-(triethoxysilyl)-propyl isocyanate (TEPIC), and tetraethoxysilane (TEOS) in the presence of Pluronic F127 as a template. These inorganic-organic mesoporous hybrids are characterized by FT-IR spectra, small-angle X-ray diffraction (SAXRD), N2 adsorption-desorption measurements, thermal analysis and spectroscopy. Their photophysical properties, which show novel light conversion properties, are discussed in detail. The Eu3+ hybrid system shows ultraviolet excitation and visible emission, and the Nd+ and Yb3+ hybrids exhibit visible excitation and NIR emission.

Gu, Yan-Jing; Yan, Bing; Qiao, Xiao-Fei

2013-03-01

201

A DFT/TD DFT study of the structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion  

NASA Astrophysics Data System (ADS)

The structure and spectroscopic properties of 5-methyl-2-(8-quinolinyl)benzoxazole and its complexes with Zn(II) ion were studied using a DFT and TD DFT methods with def2-TZVP basis set. It was shown that the type of functional used (B3-LYP or pbe0) implemented in TURBOMOLE package does not have essential influence on the geometry (small differences in bond length, valence and dihedral angles) of studied compounds in both ground and excited states. However, significant differences were obtained for the position of vertical absorption and emission transition but not for the oscillator strength of transition. Application of pbe0 functional seems to reproduce better the experimental spectrum.

Guzow, Katarzyna; Milewska, Magda; Czaplewski, Cezary; Wiczk, Wies?aw

2010-02-01

202

Whole genome methylation profiling by immunoprecipitation of methylated DNA.  

PubMed

I provide a protocol for DNA methylation profiling based on immunoprecipitation of methylated DNA using commercially available monoclonal antibodies that specifically recognize 5-methylcytosine. Quantification of the level of enrichment of the resulting DNA enables DNA methylation to be assayed for any genomic locus, including entire chromosomes or genomes if appropriate microarray or high-throughput sequencing platforms are used. In previous studies (1, 2), I have used hybridization to oligonucleotide arrays from Roche Nimblegen Inc, which allow any genomic region of interest to be interrogated, dependent on the array design. For example, using modern tiling arrays comprising millions of oligonucleotide probes, several complete human chromosomes can be assayed at densities of one probe per 100 bp or greater, sufficient to yield high-quality data. However, other methods such as quantitative real-time PCR or high-throughput sequencing can be used, giving either measurement of methylation at a single locus or across the entire genome, respectively. While the data produced by single locus assays is relatively simple to analyze and interpret, global assays such as microarrays or high-throughput sequencing require more complex statistical approaches in order to effectively identify regions of differential methylation, and a brief outline of some approaches is given. PMID:22907491

Sharp, Andrew J

2012-01-01

203

Gadolinium complex of tris[(3-hydroxy-1-methyl-2-oxo-1,2-didehydropyridine-4-carboxamido) ethyl]-amine. A new class of gadolinium magnetic resonance relaxation agents  

Microsoft Academic Search

Complexes of gadolinium(III) have proven to be especially effective MRI contrast agents; Gd{sup 3+} (S = 7\\/2) is unique in having the highest isotropic magnetic moment. The injection of gram quantities of potentially toxic metal cations requires that the complexes be stable to in vivo transmetalation, particularly with the competing calcium(II) ion in high concentration, while relaxivity is dependent on

Jide Xu; Sonya J. Franklin; D. W. Jr. Whiscuhunt; Kenneth N. Raymond

1995-01-01

204

Establishment of histone H3 methylation on the inactive X chromosome requires transient recruitment of Eed-Enx1 polycomb group complexes  

Microsoft Academic Search

Previous studies have implicated the Eed-Enx1 Polycomb group complex in the maintenance of imprinted X inactivation in the trophectoderm lineage in mouse. Here we show that recruitment of Eed-Enx1 to the inactive X chromosome (Xi) also occurs in random X inactivation in the embryo proper. Localization of Eed-Enx1 complexes to Xi occurs very early, at the onset of Xist expression,

Jose Silva; Winifred Mak; Ilona Zvetkova; Ruth Appanah; Tatyana B Nesterova; Zoe Webster; Antoine H. F. M Peters; Thomas Jenuwein; Arie P Otte; Neil Brockdorff

2003-01-01

205

Simultaneous determination of Mn2+ and Fe3+ as 4,4'[(4-cholorophenyl)methylene] bis(3-methyl-1-phenyl-1H-pyrazol-5-ol) complexes in some foods, vegetable and water samples by artificial neural networks.  

PubMed

A simple and sensitive spectrophotometric method to the simultaneous determination of Mn(2+) and Fe(3+) in foods, vegetable and water sample with the aid of artificial neural networks (ANNs) is described. It relies on the complexation of analytes with recently synthesised bis pyrazol base ligand as 4,4'[(4-cholorophenyl)methylene] bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)(CMBPP). The analytical data show that the ratio of ligand to metal in metal complexes is 1:1 and 1:2 for Fe(3+) and Mn(2+), respectively. It was found that the complexation reactions are completed at pH 6.7 and 5 min after mixing. The results showed that Mn(2+) and Fe(3+) could be determined simultaneously in the range of 0.20-7.5 and 0.30-9.0 mgl(-1), respectively. The analytical characteristics of the method such as the detection limit and the relative standard error predictions were calculated. The data obtained from synthetic mixtures of the metal ions were processed by radial basis function networks (RBFNs) and feed forward neural networks (FFNNs). The optimal conditions of the neural networks were obtained by adjusting various parameters by trial-and-error. Under the working conditions, the proposed methods were successfully applied to the simultaneous determination of elements in different water, tablet, rice, tea leaves, tomato, cabbage and lettuce samples. PMID:23411205

Abbasi-Tarighat, Maryam; Shahbazi, Elahe; Niknam, Khodabakhsh

2013-06-01

206

Well-defined iron complexes as efficient catalysts for "green" atom-transfer radical polymerization of styrene, methyl methacrylate, and butyl acrylate with low catalyst loadings and catalyst recycling.  

PubMed

Environmentally friendly iron(II) catalysts for atom-transfer radical polymerization (ATRP) were synthesized by careful selection of the nitrogen substituents of N,N,N-trialkylated-1,4,9-triazacyclononane (R3 TACN) ligands. Two types of structures were confirmed by crystallography: "[(R3 TACN)FeX2 ]" complexes with relatively small R groups have ionic and dinuclear structures including a [(R3 TACN)Fe(?-X)3 Fe(R3 TACN)](+) moiety, whereas those with more bulky R groups are neutral and mononuclear. The twelve [(R3 TACN)FeX2 ]n complexes that were synthesized were subjected to bulk ATRP of styrene, methyl methacrylate (MMA), and butyl acrylate (BA). Among the iron complexes examined, [{(cyclopentyl)3 TACN}FeBr2 ] (4?b) was the best catalyst for the well-controlled ATRP of all three monomers. This species allowed easy catalyst separation and recycling, a lowering of the catalyst concentration needed for the reaction, and the absence of additional reducing reagents. The lowest catalyst loading was accomplished in the ATRP of MMA with 4?b (59?ppm of Fe based on the charged monomer). Catalyst recycling in ATRP with low catalyst loadings was also successful. The ATRP of styrene with 4?b (117?ppm Fe atom) was followed by precipitation from methanol to give polystyrene that contained residual iron below the calculated detection limit (0.28?ppm). Mechanisms that involve equilibria between the multinuclear and mononuclear species were also examined. PMID:24664500

Nakanishi, So-Ichiro; Kawamura, Mitsunobu; Kai, Hidetomo; Jin, Ren-Hua; Sunada, Yusuke; Nagashima, Hideo

2014-05-01

207

Synthesis, characterization and biological activities of 2-((E)-(benzo[d][1,3]dioxol-6-ylimino)methyl)-6-ethoxyphenol and its metal complexes  

NASA Astrophysics Data System (ADS)

Metal complexes of Zn(II), Cd(II), Ni(II), Cu(II), and Fe(III) have been synthesized from the Schiff base ligand derived by the condensation of 3,4-(methylenedioxy)aniline and 3-ethoxy salicylaldehyde. The compounds have been characterized by using elemental analysis, molar conductance, IR, UV-Visible, 1H NMR, 13C NMR, mass spectra and thermal analysis (TG/DTA). The elemental analysis suggests the stoichiometry to be 1:1 (metal:ligand). The IR, 1H NMR, 13C NMR and UV-Visible spectral data suggest that the ligand coordinate to the metal atom by imino nitrogen and phenolic oxygen as bidentate manner. The mass spectral data also strengthen the formation of the metal complexes. The thermal behaviors of the complexes prove the presence of lattice as well as coordinated water molecules in the complexes. The in vitro biological screening effects of the synthesized compounds are tested against five bacterial species and three fungal species by well diffusion method. Antioxidant activities have also been performed for all the compounds. Metal complexes show more pronounced biological activity than the free ligand.

Sundararajan, M. L.; Anandakumaran, J.; Jeyakumar, T.

208

Mononuclear Ni(III)-alkyl complexes (alkyl = Me and Et): relevance to the acetyl-CoA synthase and methyl-CoM reductase.  

PubMed

Mononuclear, distorted trigonal bipyramidal [PPN][Ni(III)(R)(P(C(6)H(3)-3-SiMe(3)-2-S)(3))] (R = Me (1); R = Et (2)) were prepared by reaction of [PPN][Ni(III)Cl(P(C(6)H(3)-3-SiMe(3)-2-S)(3))] and CH(3)MgCl/C(2)H(5)MgCl, individually. EPR, SQUID studies as well as DFT computations reveal that the Ni(III) in 1 has a low-spin d(7) electronic configuration in a distorted trigonal bipyramidal ligand field. The Ni-C bond lengths of 1.994(3) A in 1 and 2.015(3) A in 2 are comparable to that in the Ni(III)-methyl state of MCR (approximately 2.04 A) (Sarangi, R.; Dey, M.; Ragsdale, S. W. Biochemistry 2009, 48, 3146). Under a CO atmosphere, CO triggers homolytic cleavage of the Ni(III)-CH(3) bond in 1 to produce Ni(II)-thiolate carbonyl [PPN][Ni(II)(CO)(P(C(6)H(3)-3-SiMe(3)-2-S)(3))] (3). Additionally, protonation of 1 with phenylthiol generates Ni(III)-thiolate [PPN][Ni(III)(SPh)(P(C(6)H(3)-3-SiMe(3)-2-S)(3))] (4). PMID:20568755

Lee, Chien-Ming; Chen, Chien-Hong; Liao, Fu-Xing; Hu, Ching-Han; Lee, Gene-Hsiang

2010-07-14

209

Methylation Patterns of Immunoglobulin Genes in Lymphoid Cells: Correlation of Expression and Differentiation with Undermethylation  

Microsoft Academic Search

Different states of eukaryotic gene expression are often correlated with different levels of methylation of DNA sequences containing structural genes and their flanking regions. To assess the potential role of DNA methylation in the expression of immunoglobulin genes, which require complex rearrangements prior to expression, methylation patterns were examined in cell lines representing different stages of lymphocyte maturation. Methylation of

Ursula Storb; Benjamin Arp

1983-01-01

210

Enzymatic methylation of the Mycobacterium tuberculosis heparin-binding haemagglutinin.  

PubMed

Heparin-binding haemagglutinin (HBHA) is an important Mycobacterium tuberculosis virulence factor. It displays a complex methylation pattern in its C-terminal, functional domain, which protects this domain against proteolysis. Here, it is shown that HBHA methylation is catalysed by mycobacterial enzymes and a radio-enzymatic and a nonradioactive enzyme assay are described, based on the recognition of methylated HBHA by monoclonal antibodies. MS analysis of in vitro methylated HBHA shows a complex methylation pattern similar to that of naturally methylated HBHA. Using recombinant hybrid molecules as acceptor substrates, it was found that the N-terminal domain of HBHA is not required for recognition by the HBHA-methyltransferase(s), although it is required for in vivo methylation. PMID:17263844

Host, Hélène; Drobecq, Hervé; Locht, Camille; Menozzi, Franco D

2007-03-01

211

A complex study of 5-amino-3-methyl-4-[2-(5-amino-1,3,4-oxadiazolo)]-isoxazole monohydrate: A new low-molecular-weight immune response modifier  

NASA Astrophysics Data System (ADS)

A new potential lead structure with immunological activity, 5-amino-3-methyl-4-[2-(5-amino-1,3,4-oxadiazolo)]-isoxazole monohydrate, was synthesized. A detailed description of synthesis is presented together with X-ray structural analysis. In vitro assays showed that the compound had a potent immunosuppressive activity. Next, Density Functional Theory (DFT) was employed to shed a light on molecular properties of the investigated isoxazole derivative. The molecular modeling part included geometric as well as electronic structure descriptions: (i) the conformational analysis was performed to localize the most appropriate conformation; (ii) the coordination energy and Basis Set Superposition Error (BSSE) were estimated for the complex of the isoxazole derivative interacting with water molecule; (iii) the potential energy distribution was used to assign molecular vibrations, and NBO population analysis served to describe the electronic structure; (iv) the electrostatic potential map was generated to provide the graphical presentation of regions exposed for intermolecular interactions. The contacts between the water molecule and the nitrogen atom of the isoxazole ring edge were present in the solid phase. On the other hand, the theoretical DFT prediction was that the oxygen atom of the edge should form a more stable complex with the water molecule.

Ryng, Stanis?aw; Zimecki, Micha?; Jezierska-Mazzarello, Aneta; Panek, Jaros?aw J.; M?czy?ski, Marcin; G?owiak, Tadeusz; Sawka-Dobrowolska, Wanda; Koll, Aleksander

2011-07-01

212

Lanthanide complexes containing 5-methyl-1,2,4-triazolo[1,5-a] pyrimidin-7(4H)-one and their therapeutic potential to fight leishmaniasis and Chagas disease.  

PubMed

In the last years, numerous and significant advances in lanthanide coordination chemistry have been achieved. The unique chemical nature of these metal ions which is conferred by their f-electrons has led to a wide range of coordination compounds with interesting structural, physical and also biological properties. Consequently, lanthanide complexes have found applications mainly in catalysis, gas adsorption, photochemistry and as diagnostic tools. However, research on their therapeutic potential and the understanding of their mechanism of action is still taking its first steps, and there is a distinct lack of research in the parasitology field. In the present work, we describe the synthesis and physical properties of seven new lanthanide complexes with the anionic form of the bioactive ligand 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO), namely [Ln(mtpO)3(H2O)6]·9H2O (Ln=La(III), Nd(III), Eu(III), Gd(III), Tb(III), Dy(III) and Er(III)). In addition, results on the in vitro antiproliferative activity against Leishmania spp. and Trypanosoma cruzi are described. The high activity of the new compounds against parasite proliferation and their low cytotoxicity against reference host cell lines show a great potential of this type of compounds to become a new generation of highly effective and non-toxic antiparasitic agents to fight the so considered neglected diseases leishmaniasis and Chagas disease. PMID:24861807

Caballero, Ana B; Rodríguez-Diéguez, Antonio; Salas, Juan M; Sánchez-Moreno, Manuel; Marín, Clotilde; Ramírez-Macías, Inmaculada; Santamaría-Díaz, Noelia; Gutiérrez-Sánchez, Ramón

2014-09-01

213

Syntheses of monomeric (. eta. sup 5 -pentamethylcyclopentadienyl)platinum(IV) methyl and bromo complexes and of (hydrotris(3,5-dimethyl-1-pyrazolyl)borato)trimethylplatinum  

SciTech Connect

The reaction of Cp*MgCl{center dot}THF (Cp* = C{sub 5}Me{sub 5}) with 1 equiv of PtMe{sub 3}I and PtMe{sub 2}Br{sub 2} produces Cp*PtMe{sub 3} (1) and Cp*PtMe{sub 2}Br (2), respectively. Reaction of 2 with Br{sub 2} produces Cp*PtMeBr{sub 2} (3) in good yield. The structures of 2 and 3 have been determined by x-ray crystallography, and the crystal structure data are reported. Complex 2 crystallizes in the monoclinic space group, P2{sub 1}/m, and complex 3 crystallizes in the monoclinic space group, P2{sub 1}/m. The molecules reside on mirror planes and are monomeric pseudotetrahedral Pt(IV) complexes with piano stool type geometries and {eta}{sup 5}-Cp* groups. Both molecules have Br atoms on the mirror. This leads to a disorder of the Me and the second Br positions in complex 3. The average Pt-C(Cp*) bond length is 2.25 (7) {angstrom} in 2 and 2.22 (4) {angstrom} in 3. The Pt-C(Me) and Pt-Br bond lengths in 2 are 2.07 (2) and 2.498 (2) {angstrom}, respectively. The ordered Pt-Br bond length in 3 is 2.496 (2) {angstrom}. Treatment of 1 with halogens results in the cleavage of the Pt-Cp* bond. The reaction of PtMe{sub 3}I with KTp* (Tp* = (HB(3,5-dimethylpyrazolyl){sub 3}){sup {minus}}) in thf gives Tp*PtMe{sub 3} (4) in almost quantitative yield. The reaction of 4 with Br{sub 2} brominates the 4-position of the pyrazolyl ring only. 28 refs., 2 figs., 5 tabs.

Roth, S.; Ramamoorthy, V.; Sharp, P.R. (Univ. of Missouri, Columbia (USA))

1990-09-05

214

DNA-gelatin complex coacervation, UCST and first-order phase transition of coacervate to anisotropic ion gel in 1-methyl-3-octylimidazolium chloride ionic liquid solutions.  

PubMed

Study of kinetics of complex coacervation occurring in aqueous 1-octyl-3-methylimidazolium chloride ionic liquid solution of low charge density polypeptide (gelatin A) and 200 base pair DNA, and thermally activated coacervate into anisotropic gel transition, is reported here. Associative interaction between DNA and gelatin A (GA) having charge ratio (DNA:GA = 16:1) and persistence length ratio (5:1) was studied at fixed DNA (0.005% (w/v)) and varying GA concentration (C(GA) = 0-0.25% (w/v)). The interaction profile was found to be strongly hierarchical and revealed three distinct binding regions: (i) Region I showed DNA-condensation (primary binding) for C(GA) < 0.10% (w/v), the DNA ? potential decrease from -80 to -5 mV (95%) (partial charge neutralization), and a size decrease by ?60%. (ii) Region II (0.10 < C(GA) < 0.15% (w/v)) indicated secondary binding, a 4-fold turbidity increase, a ? potential decrease from -5 to 0 mV (complete charge neutralization), which resulted in the appearance of soluble complexes and initiation of coacervation. (iii) Region III (0.15 < C(GA) < 0.25% (w/v)) revealed growth of insoluble complexes followed by precipitation. The hydration of coacervate was found to be protein concentration specific in Raman studies. The binding profile of DNA-GA complex with IL concentration revealed optimum IL concentration (=0.05% (w/v)) was required to maximize the interactions. Small angle neutron scattering (SANS) data of coacervates gave static structure factor profiles, I(q) versus wave vector q, that were remarkably similar and invariant of protein concentration. This data could be split into two distinct regions: (i) for 0.0173 < q < 0.0353 Å(-1), I(q) ~ q(-?) with ? = 1.35-1.67, and (ii) for 0.0353 < q < 0.35 Å(-1), I(q) = I(0)/(1 + q(2)?(2)). The correlation length found was ? = 2 ± 0.1 nm independent of protein concentration. The viscoelastic length (?8 nm) was found to have value close to the persistence length of the protein (?10 nm). Rheology data indicated that the coacervate phase resided close to the gelation state of the protein. Thus, on a heating-cooling cycle (heating to 50 °C followed by cooling to 20 °C), the heterogeneous coacervate exhibited an irreversible first-order phase transition to an anisotropic ion gel. This established a coacervate-ion gel phase diagram having a well-defined UCST. PMID:23194173

Rawat, Kamla; Aswal, V K; Bohidar, H B

2012-12-27

215

Methyl Cellulose Nitrate.  

National Technical Information Service (NTIS)

Methyl cellulose nitrate was prepared by nitration of methyl cellulose with 98% nitric acid dissolved in methylene chloride and, in 98% nitric acid without a solvent. With both procedures nitration is apparently complete within fifteen minutes. The hetero...

J. Bobinski Y. P. Carignan

1967-01-01

216

DNA methylation in insects  

Microsoft Academic Search

Cytosine DNA methylation has been demonstrated in numerous eukaryotic organisms and has been shown to play an important role in human disease. The func- tion of DNA methylation has been studied extensively in vertebrates, but establishing its primary role has proved difficult and controversial. Analysing methyl- ation in insects has indicated an apparent functional diversity that seems to argue against

L. M. Field; F. Lyko; M. Mandrioli; G. Prantera

2004-01-01

217

Comparative study on methyl- and ethylmercury-induced toxicity in C6 glioma cells and the potential role of LAT-1 in mediating mercurial-thiol complexes uptake.  

PubMed

Various forms of mercury possess different rates of absorption, metabolism and excretion, and consequently, toxicity. Methylmercury (MeHg) is a highly neurotoxic organic mercurial. Human exposure is mostly due to ingestion of contaminated fish. Ethylmercury (EtHg), another organic mercury compound, has received significant toxicological attention due to its presence in thimerosal-containing vaccines. This study was designed to compare the toxicities induced by MeHg and EtHg, as well as by their complexes with cysteine (MeHg-S-Cys and EtHg-S-Cys) in the C6 rat glioma cell line. MeHg and EtHg caused significant (p<0.0001) decreases in cellular viability when cells were treated during 30min with each mercurial following by a washing period of 24h (EC50 values of 4.83 and 5.05?M, respectively). Significant cytotoxicity (p<0.0001) was also observed when cells were treated under the same conditions with MeHg-S-Cys and EtHg-S-Cys, but the respective EC50 values were significantly increased (11.2 and 9.37?M). l-Methionine, a substrate for the l-type neutral amino acid carrier transport (LAT) system, significantly protected against the toxicities induced by both complexes (MeHg-S-Cys and EtHg-S-Cys). However, no protective effects of l-methionine were observed against MeHg and EtHg toxicities. Corroborating these findings, l-methionine significantly decreased mercurial uptake when cells were exposed to MeHg-S-Cys (p=0.028) and EtHg-S-Cys (p=0.023), but not to MeHg and EtHg. These results indicate that the uptake of MeHg-S-Cys and EtHg-S-Cys into C6 cells is mediated, at least in part, through the LAT system, but MeHg and EtHg enter C6 cells by mechanisms other than LAT system. PMID:23727015

Zimmermann, Luciana T; Santos, Danúbia B; Naime, Aline A; Leal, Rodrigo B; Dórea, José G; Barbosa, Fernando; Aschner, Michael; Rocha, João Batista T; Farina, Marcelo

2013-09-01

218

5-Hydroxytryptamine 5HT2C Receptors Form a Protein Complex with N-Methyl-d-aspartate GluN2A Subunits and Activate Phosphorylation of Src Protein to Modulate Motoneuronal Depolarization*  

PubMed Central

N-Methyl-d-aspartate (NMDA)-gated ion channels are known to play a critical role in motoneuron depolarization, but the molecular mechanisms modulating NMDA activation in the spinal cord are not well understood. This study demonstrates that activated 5HT2C receptors enhance NMDA depolarizations recorded electrophysiologically from motoneurons. Pharmacological studies indicate involvement of Src tyrosine kinase mediates 5HT2C facilitation of NMDA. RT-PCR analysis revealed edited forms of 5HT2C were present in mammalian spinal cord, indicating the availability of G-protein-independent isoforms. Spinal cord neurons treated with the 5HT2C agonist MK 212 showed increased SrcTyr-416 phosphorylation in a dose-dependent manner thus verifying that Src is activated after treatment. In addition, 5HT2C antagonists and tyrosine kinase inhibitors blocked 5HT2C-mediated SrcTyr-416 phosphorylation and also enhanced NMDA-induced motoneuron depolarization. Co-immunoprecipitation of synaptosomal fractions showed that GluN2A, 5HT2C receptors, and Src tyrosine kinase form protein associations in synaptosomes. Moreover, immunohistochemical analysis demonstrated GluN2A and 5HT2C receptors co-localize on the processes of spinal neurons. These findings reveal that a distinct multiprotein complex links 5-hydroxytryptamine-activated intracellular signaling events with NMDA-mediated functional activity.

Bigford, Gregory E.; Chaudhry, Nauman S.; Keane, Robert W.; Holohean, Alice M.

2012-01-01

219

Synthesis and structural analysis of (imido)vanadium(V) complexes containing chelate (anilido)methyl-imine ligands: ligand effect in ethylene dimerization.  

PubMed

A series of (imido)vanadium dichlorido complexes containing chelate anionic donor ligands of the type, VCl2(L)(NR) [R = 1-adamantyl (Ad), L = 2-(2,6-Me2C6H3)NCH2(C9H6N) (2), 8-(2,6-Me2C6H3)NCH2(C9H6N) (3); L = 2-(2,6-R'2C6H3)NCH2(C5H4N), R = 2-MeC6H4, R' = Me (4a), (i)Pr (4b); L = 2-(2,6-Me2C6H3)NCH2(C5H4N), R = 4-MeC6H4 (5), 3,5-Me2C6H3 (6)], have been prepared and identified. The reactions with ethylene by 2,3 in the presence of methylaluminoxane (MAO) afforded a mixture of high molecular weight polyethylene and oligomers. Reactions with ethylene by VCl2[2-(2,6-R'2C6H3)NCH2(C5H4N)](NAd) (1a,b), 4-6 afforded 1-butene with high selectivities (>92%), and the activities by 4a,b are at the same level as those in 1a,b. The activities by 5,6 were lower than 4a,b and were at the same level of that by VCl2[2-(2,6-Me2C6H3)NCH2(C5H4N)](NPh). These results thus suggest that both the chelate anionic donor and the imido ligands play a role for both the activity and the selectivity. PMID:23418852

Nomura, Kotohiro; Igarashi, Atsushi; Katao, Shohei; Zhang, Wenjuan; Sun, Wen-Hua

2013-03-01

220

Palladium(II) and platinum(II) organometallic complexes with 4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine. Antitumor activity of the platinum compounds.  

PubMed

Palladium and platinum complexes with HmtpO (where HmtpO=4,7-dihydro-5-methyl-7-oxo[1,2,4]triazolo[1,5-a]pyrimidine, an analogue of the natural occurring nucleobase hypoxanthine) of the types [M(dmba)(PPh3)(HmtpO)]ClO4[dmba=N,C-chelating 2-(dimethylaminomethyl)phenyl; M=Pd or Pt], [Pd(N-N)(C6F5)(HmtpO)]ClO4[N-N=2,2'-bipyridine (bpy), 4,4'-dimethyl-2,2'-bipyridine (Me2bpy), or N, N, N', N'-tetramethylethylenediamine (tmeda)] and cis-[M(C6F5)2(HmtpO)2] (M=Pd or Pt) (head-to-head atropisomer in the solid state) have been obtained. Pd(II) and Pt(II) complexes with the anion of HmtpO of the types [Pd(tmeda)(C6F5)(mtpO)], [Pd(dmba)(micro-mtpO)] 2, and [NBu4]2[M(C6F5)2(micro-mtpO)]2(M=Pd or Pt) have been prepared starting from the corresponding hydroxometal complexes. Complexes containing simultaneously both the neutral HmtpO ligand and the anionic mtpO of the type [NBu4][M(C6F5)2(HmtpO)(mtpO)] (M=Pd or Pt) have been also obtained. In these mtpO-HmtpO metal complexes, for the first time, prototropic exchange is observed between the two heterocyclic ligands. The crystal structures of [Pd(dmba)(PPh 3)(HmtpO)]+, cis-[Pt(C6F5)2(HmtpO)2].acetone, [Pd(C6F5)(tmeda)(mtpO)].2H2O, [Pd(dmba)(micro-mtpO)]2, [NBu4]2[Pd(C6F5)2(micro-mtpO)]2.CH2Cl2.toluene, [NBu4]2[Pt(C6F5)2(micro-mtpO)](2).0.5(toluene), and [NBu4][Pt(C6F5)2(mtpO)(HmtpO)] have been established by X-ray diffraction. Values of IC50 were calculated for the new platinum complexes cis-[Pt(C6F5)2(HmtpO)2] and [Pt(dmba)(PPh3)(HmtpO)]ClO4 against a panel of human tumor cell lines representative of ovarian (A2780 and A2780 cisR), lung (NCI-H460), and breast cancers (T47D). At 48 h incubation time, both complexes were about 8-fold more active than cisplatin in T47D and show very low resistance factors against an A2780 cell line, which has acquired resistance to cisplatin. The DNA adduct formation of cis-[Pt(C6F5)2(HmtpO)2] and [Pt(dmba)(PPh3)(HmtpO)]ClO4 was followed by circular dichroism and electrophoretic mobility. Atomic force microscopy images of the modifications caused by these platinum complexes on plasmid DNA pB R322 were also obtained. PMID:18447329

Ruiz, José; Villa, María Dolores; Cutillas, Natalia; López, Gregorio; de Haro, Concepción; Bautista, Delia; Moreno, Virtudes; Valencia, Laura

2008-06-01

221

Structural Basis for Methyl Transfer by a Radical SAM Enzyme  

SciTech Connect

The radical S-adenosyl-l-methionine (SAM) enzymes RlmN and Cfr methylate 23S ribosomal RNA, modifying the C2 or C8 position of adenosine 2503. The methyl groups are installed by a two-step sequence involving initial methylation of a conserved Cys residue (RlmN Cys{sup 355}) by SAM. Methyl transfer to the substrate requires reductive cleavage of a second equivalent of SAM. Crystal structures of RlmN and RlmN with SAM show that a single molecule of SAM coordinates the [4Fe-4S] cluster. Residue Cys{sup 355} is S-methylated and located proximal to the SAM methyl group, suggesting the SAM that is involved in the initial methyl transfer binds at the same site. Thus, RlmN accomplishes its complex reaction with structural economy, harnessing the two most important reactivities of SAM within a single site.

Boal, Amie K.; Grove, Tyler L.; McLaughlin, Monica I.; Yennawar, Neela H.; Booker, Squire J.; Rosenzweig, Amy C. (NWU); (Penn)

2011-09-16

222

Structural basis for Klf4 recognition of methylated DNA  

PubMed Central

Transcription factor Krüppel-like factor 4 (Klf4), one of the factors directing cellular reprogramming, recognizes the CpG dinucleotide (whether methylated or unmodified) within a specific G/C-rich sequence. The binding affinity of the mouse Klf4 DNA-binding domain for methylated DNA is only slightly stronger than that for an unmodified oligonucleotide. The structure of the C-terminal three Krüppel-like zinc fingers (ZnFs) of mouse Klf4, in complex with fully methylated DNA, was determined at 1.85 Å resolution. An arginine and a glutamate interact with the methyl group. By comparison with two other recently characterized structures of ZnF protein complexes with methylated DNA, we propose a common principle of recognition of methylated CpG by C2H2 ZnF proteins, which involves a spatially conserved Arg–Glu pair.

Liu, Yiwei; Olanrewaju, Yusuf Olatunde; Zheng, Yu; Hashimoto, Hideharu; Blumenthal, Robert M.; Zhang, Xing; Cheng, Xiaodong

2014-01-01

223

Organometallic benzylidene anilines: donor-acceptor features in NCN-pincer Pt(ii) complexes with a 4-(E)-[(4-R-phenyl)imino]methyl substituent.  

PubMed

A series of organometallic 4,4'-substituted benzylidene aniline complexes 4-ClPt-3,5-(CH2NMe2)2C6H2CH[double bond, length as m-dash]NC6H4R'-4', abbreviated as PtCl[NCN(CH[double bond, length as m-dash]NC6H4R'-4')-4], with R' = NMe2, Me, H, Cl, CN (, respectively), was synthesized via a Schiff-base condensation reaction involving reaction of PtCl[NCN(CH[double bond, length as m-dash]O)-4] () with the appropriate 4-R'-substituted aniline derivative () in toluene. The resulting arylplatinum(ii) products were obtained in 75-88% yield. Notably, product was also obtained in 68% yield from a reaction in the solid state by grinding solid with aniline . The structures of , , and in the solid state (single crystal X-ray diffraction) showed a non-planar geometry, in particular for compound . The electronic interaction between the donor benzylidene fragment PtCl(NCN-CH) and the para-R' aniline substituent through the azomethine bridge was studied with NMR and UV/Vis spectroscopy. Linear correlations were found between the azomethine (1)H, the (195)Pt NMR and various (13)C NMR chemical shifts, and the substituent parameters ?F and ?R of R' at the aniline site. In common with organic benzylidene anilines, the azomethine (1)H NMR chemical shift showed anomalous substituent behavior. The (195)Pt NMR chemical shift of the platinum center can be used as a probe for the electronic properties of the delocalized ?-system of the benzylidene aniline framework, to which it is connected. The dual substituent parameter treatment of the azomethine (13)C NMR shift gave important insight into the unique behaviour of the Pt-pincer group as a substituent. Inductively, it is a very strong electron-withdrawing group, whereas mesomerically it behaves like a very strong electron donating group. PMID:25007011

Batema, Guido D; Lutz, Martin; Spek, Anthony L; van Walree, Cornelis A; van Klink, Gerard P M; van Koten, Gerard

2014-07-22

224

Methylating agents and DNA repair responses: methylated bases and sources of strand breaks  

PubMed Central

The chemical methylating agents methylmethane sulfonate (MMS) and N-methyl-N?-nitro-N-nitrosoguanidine (MNNG) have been used for decades as classical DNA damaging agents. These agents have been utilized to uncover and explore pathways of DNA repair, DNA damage response, and mutagenesis. MMS and MNNG modify DNA by adding methyl groups to a number of nucleophilic sites on the DNA bases, although MNNG produces a greater percentage of O-methyl adducts. There has been substantial progress elucidating direct reversal proteins that remove methyl groups and base excision repair (BER), which removes and replaces methylated bases. Direct reversal proteins and BER thus counteract the toxic, mutagenic and clastogenic effects of methylating agents. Despite recent progress, the complexity of DNA damage responses to methylating agents is still being discovered. In particular, there is growing understanding of pathways such as homologous recombination, lesion bypass, and mismatch repair that react when the response of direct reversal proteins and BER is insufficient. Furthermore, the importance of proper balance within the steps in BER has been uncovered with the knowledge that DNA structural intermediates during BER are deleterious. A number of issues complicate elucidating the downstream responses when direct reversal is insufficient or BER is imbalanced. These include inter-species differences, cell-type specific differences within mammals and between cancer cell lines, and the type of methyl damage or BER intermediate encountered. MMS also carries a misleading reputation of being a ‘radiomimetic,’ i.e., capable of directly producing strand breaks. This review focuses on the DNA methyl damage caused by MMS and MNNG for each site of potential methylation to summarize what is known about the repair of such damage and the downstream responses and consequences if not repaired.

Wyatt, Michael D.; Pittman, Douglas L.

2008-01-01

225

DNA Methylation Profiling Identifies CG Methylation Clusters in Arabidopsis Genes  

Microsoft Academic Search

Cytosine DNA methylation in vertebrates is widespread, but methylation in plants is found almost exclusively at transposable elements and repetitive DNA [1]. Within regions of methylation, methylcytosines are typically found in CG, CNG, and asymmetric contexts. CG sites are maintained by a plant homolog of mammalian Dnmt1 acting on hemi-methylated DNA after replication. Methylation of CNG and asymmetric sites appears

Robert K. Tran; Jorja G. Henikoff; Daniel Zilberman; Renata F. Ditt; Steven E. Jacobsen; Steven Henikoff

2005-01-01

226

A preference of histone H1 for methylated DNA.  

PubMed Central

We have identified a clear preference of histone H1 for CpG-methylated DNA, irrespective of DNA sequence. The conditions under which this preference is observed allowed cooperative binding of H1; the H1-DNA complexes formed were shown earlier to be 'tramlines' of two DNA duplexes bridged by an array of H1 molecules, and multiples of these. The preference for methylated DNA is clear in sedimentation assays, which also show that the preference is greater with increased methylation level, and in gel retardation assays with an oligonucleotide containing a single methyl-CpG pair; it is shared by the globular domain which also binds cooperatively to DNA. A small intrinsic preference of H1 for methylated DNA is also apparent in Southwestern assays where the immobilized H1 presumably cannot bind cooperatively. Methylated DNA in H1-DNA complexes was partially protected (relative to unmethylated DNA) against digestion by MspI but not by enzymes whose cutting sites were not methylated, consistent with a direct interaction of H1 with methylated nucleotides; this was also true of GH1-DNA complexes. H1 variants (spH1 and H5) from transcriptionally repressed nuclei have a stronger preference than H1 for methylated DNA, suggesting that this may be relevant to the stabilization of chromatin higher order structure and transcriptional repression. Images

McArthur, M; Thomas, J O

1996-01-01

227

Orchestration of DNA Methylation  

Microsoft Academic Search

DNA methylation plays an important role in gene regulation. In order to gain a better understanding of the rules governing\\u000a this epigenetic modification, we have used microarray technology to map DNA methylation in the human genome. This analysis\\u000a has helped decipher the DNA sequences involved in setting up the basic global methylation pattern in the early embryo and\\u000a has revealed

Howard Cedar

2008-01-01

228

DNA methylation in insects.  

PubMed

Cytosine DNA methylation has been demonstrated in numerous eukaryotic organisms and has been shown to play an important role in human disease. The function of DNA methylation has been studied extensively in vertebrates, but establishing its primary role has proved difficult and controversial. Analysing methylation in insects has indicated an apparent functional diversity that seems to argue against a strict functional conservation. To investigate this hypothesis, we here assess the data reported in four different insect species in which DNA methylation has been analysed more thoroughly: the fruit fly Drosophila melanogaster, the cabbage moth Mamestra brassicae, the peach-potato aphid Myzus persicae and the mealybug Planococcus citri. PMID:15056357

Field, L M; Lyko, F; Mandrioli, M; Prantera, G

2004-04-01

229

Aberrant DNA methylation and drug resistance of tumor cells.  

PubMed

Drug resistance is one of the major obstacles limiting the success of cancer chemotherapy. The underlying mechanisms are complex. In recent years, the contribution of epigenetic changes to drug resistance has drawn increasing attention. DNA methylation is an important epigenetic modification that plays an important role in regulating gene expression and maintaining genome stability. Primary or acquired resistance of tumor cells is usually accompanied by aberrant DNA methylation. Accumulating evidence has shown that aberrant DNA methylation is involved in drug resistance of tumor cells. In this review, we briefly review the relationship between DNA methylation and drug resistance of tumor cells as well as the underlying mechanisms. PMID:24846990

Xinxin, Si; Yujie, Sun

2014-05-20

230

DNA methylation and cancer  

Microsoft Academic Search

There is tremendous ferment in the field of epigenetics as the relationships between chromatin structure and DNA methylation patterns become clearer. Central to this activity is the realization that the ‘histone code’, which involves the post-translational modification of histones and which has important ramifications for chromatin structure, may be linked to the DNA cytosine methylation pattern. New discoveries have suggested

Peter A Jones

2002-01-01

231

Mutation of a Single CTCF Target Site within the H19 Imprinting Control Region Leads to Loss of Igf2 Imprinting and Complex Patterns of De Novo Methylation upon Maternal Inheritance  

Microsoft Academic Search

The differentially methylated imprinting control region (ICR) region upstream of the H19 gene regulates allelic Igf2 expression by means of a methylation-sensitive chromatin insulator function. We have previously shown that maternal inheritance of mutated (three of the four) target sites for the 11-zinc finger protein CTCF leads to loss of Igf2 imprinting. Here we show that a mutation in only

Vinod Pant; Sreenivasulu Kurukuti; Elena Pugacheva; Shaharum Shamsuddin; Piero Mariano; Rainer Renkawitz; Elena Klenova; Victor Lobanenkov; Rolf Ohlsson

2004-01-01

232

[Accidental methyl alcohol poisoning].  

PubMed

An accidental poisoning due to drinking methyl alcohol in Chaoyang county is reported, analysing the accident. The poison came from the "retail white spirit" which was contaminated with methyl alcohol. Twenty-nine persons drank the wine, fourteen of them died, two of them became blind. After drinking this "retail white spirit" the drinkers showed symptoms of vertigo, headache, weakness, vomiting, night sweat, dyspnea and blurring of vision etc. within 6-120 hours. On examining the remaining spirit, we found the content of methyl alcohol to be between 16.6 and 40.69 g/100 ml. Some of the patients' urine and blood also contained methyl alcohol. We reckoned that each one of the twenty patients had taken more than 27 g of methyl alcohol and each of the ten dead drank more than 40 ml of the alcohol. PMID:2253526

Xiao, J H

1990-05-01

233

Cytosine methylation profiling of cancer cell lines.  

PubMed

DNA-methylation changes in human cancer are complex and vary between the different types of cancer. Capturing this epigenetic variability in an atlas of DNA-methylation changes will be beneficial for basic research as well as translational medicine. Hypothesis-free approaches that interrogate methylation patterns genome-wide have already generated promising results. However, these methods are still limited by their quantitative accuracy and the number of CpG sites that can be assessed individually. Here, we use a unique approach to measure quantitative methylation patterns in a set of >400 candidate genes. In this high-resolution study, we employed a cell-line model consisting of 59 cancer cell lines provided by the National Cancer Institute and six healthy control tissues for discovery of methylation differences in cancer-related genes. To assess the effect of cell culturing, we validated the results from colon cancer cell lines by using clinical colon cancer specimens. Our results show that a large proportion of genes (78 of 400 genes) are epigenetically altered in cancer. Although most genes show methylation changes in only one tumor type (35 genes), we also found a set of genes that changed in many different forms of cancer (seven genes). This dataset can easily be expanded to develop a more comprehensive and ultimately complete map of quantitative methylation changes. Our methylation data also provide an ideal starting point for further translational research where the results can be combined with existing large-scale datasets to develop an approach that integrates epigenetic, transcriptional, and mutational findings. PMID:18353987

Ehrich, Mathias; Turner, Julia; Gibbs, Peter; Lipton, Lara; Giovanneti, Mara; Cantor, Charles; van den Boom, Dirk

2008-03-25

234

Cytosine methylation profiling of cancer cell lines  

PubMed Central

DNA-methylation changes in human cancer are complex and vary between the different types of cancer. Capturing this epigenetic variability in an atlas of DNA-methylation changes will be beneficial for basic research as well as translational medicine. Hypothesis-free approaches that interrogate methylation patterns genome-wide have already generated promising results. However, these methods are still limited by their quantitative accuracy and the number of CpG sites that can be assessed individually. Here, we use a unique approach to measure quantitative methylation patterns in a set of >400 candidate genes. In this high-resolution study, we employed a cell-line model consisting of 59 cancer cell lines provided by the National Cancer Institute and six healthy control tissues for discovery of methylation differences in cancer-related genes. To assess the effect of cell culturing, we validated the results from colon cancer cell lines by using clinical colon cancer specimens. Our results show that a large proportion of genes (78 of 400 genes) are epigenetically altered in cancer. Although most genes show methylation changes in only one tumor type (35 genes), we also found a set of genes that changed in many different forms of cancer (seven genes). This dataset can easily be expanded to develop a more comprehensive and ultimately complete map of quantitative methylation changes. Our methylation data also provide an ideal starting point for further translational research where the results can be combined with existing large-scale datasets to develop an approach that integrates epigenetic, transcriptional, and mutational findings.

Ehrich, Mathias; Turner, Julia; Gibbs, Peter; Lipton, Lara; Giovanneti, Mara; Cantor, Charles; van den Boom, Dirk

2008-01-01

235

Inter-individual variation of DNA methylation and its implications for large-scale epigenome mapping  

Microsoft Academic Search

Genomic DNA methylation profiles exhibit substan- tial variation within the human population, with important functional implications for gene regula- tion. So far little is known about the characteristics and determinants of DNA methylation variation among healthy individuals. We performed bioinfor- matic analysis of high-resolution methylation pro- files from multiple individuals, uncovering complex patterns of inter-individual variation that are strongly correlated

Christoph Bock; Jörn Walter; Martina Paulsen; Thomas Lengauer

2008-01-01

236

Profile analysis and prediction of tissue-specific CpG island methylation classes  

Microsoft Academic Search

BACKGROUND: The computational prediction of DNA methylation has become an important topic in the recent years due to its role in the epigenetic control of normal and cancer-related processes. While previous prediction approaches focused merely on differences between methylated and unmethylated DNA sequences, recent experimental results have shown the presence of much more complex patterns of methylation across tissues and

Christopher Previti; Oscar Harari; Igor Zwir; Coral Del Val

2009-01-01

237

A new approach to primer design for the control of PCR bias in methylation studies  

Microsoft Academic Search

Primer design for PCR-based methylation analysis following bisulfite conversion of DNA is considerably more complex than primer design for regular PCR. The choice of the optimal primer set is critical to the performance and correct interpretation of the results. Most methodologies in methylation analysis utilize primers that theoretically amplify methylated and unmethylated templates at the same time. The proportional amplification

Tomasz K Wojdacz; Lise Lotte Hansen; Alexander Dobrovic

2008-01-01

238

Complexation of Ln(III) and Ca(II) Cations with 3,4-Dicarboxyinulin and Model Compounds: Methyl 3,4-Dicarboxy-alpha-D-fructofuranoside and 3,4-Dicarboxynystose, As Studied by Multinuclear Magnetic Resonance Spectroscopy and Potentiometry.  

PubMed

Complexes of Ln(III) and Ca(II) cations with 3,4-dicarboxyinulin (DCI) and model compounds, methyl 3,4-dicarboxy-alpha-D-fructofuranoside (DCF) and 3,4-dicarboxynystose (DCN) were studied using multinuclear magnetic resonance spectroscopy and potentiometric methods. Complexes of the model compounds with Ln(III) ions provided a feasible way in which to study complexation phenomena of the dicarboxyinulin/Ca(II) system using NMR techniques. Information on complex geometry was derived from the effect of Ln(III) ions on chemical shifts and longitudinal relaxation rates. Metal-ligand stoichiometries of 1:2 and 1:1, in which the ligand coordination was tridentate as well as tetradentate, were found. Potentiometric measurements carried out with Ca(II) yielded information on the stoichiometry as well as the cooperativity of metal ion binding by the ligands. PMID:11666765

Johnson, Louise; Verraest, Dorine L.; Besemer, Arie C.; van Bekkum, Herman; Peters, Joop A.

1996-09-11

239

Recognition of methylated DNA through methyl-CpG binding domain proteins  

PubMed Central

DNA methylation is a key regulatory control route in epigenetics, involving gene silencing and chromosome inactivation. It has been recognized that methyl-CpG binding domain (MBD) proteins play an important role in interpreting the genetic information encoded by methylated DNA (mDNA). Although the function of MBD proteins has attracted considerable attention and is well characterized, the mechanism underlying mDNA recognition by MBD proteins is still poorly understood. In this article, we demonstrate that the methyl-CpG dinucleotides are recognized at the MBD–mDNA interface by two MBD arginines through an interplay of hydrogen bonding and cation-? interaction. Through molecular dynamics and quantum-chemistry calculations we investigate the methyl-cytosine recognition process and demonstrate that methylation enhances MBD–mDNA binding by increasing the hydrophobic interfacial area and by strengthening the interaction between mDNA and MBD proteins. Free-energy perturbation calculations also show that methylation yields favorable contribution to the binding free energy for MBD–mDNA complex.

Zou, Xueqing; Ma, Wen; Solov'yov, Ilia A.; Chipot, Christophe; Schulten, Klaus

2012-01-01

240

Genomics of CpG Methylation in Developing and Developed Zebrafish  

PubMed Central

DNA methylation is a dynamic process through which specific chromatin modifications can be stably transmitted from parent to daughter cells. A large body of work has suggested that DNA methylation influences gene expression by silencing gene promoters. However, these conclusions were drawn from data focused mostly on promoter regions. Regarding the entire genome, it is unclear how methylation and gene transcription patterns are related during vertebrate development. To identify the genome-wide distribution of CpG methylation, we created series of high-resolution methylome maps of Danio rerio embryos during development and in mature, differentiated tissues. We found that embryonic and terminal tissues have unique methylation signatures in CpG islands and repetitive sequences. Fully differentiated tissues have increased CpG and LTR methylation and decreased SINE methylation relative to embryonic tissues. Unsupervised clustering analyses reveal that the embryonic and terminal tissues can be classified solely by their methylation patterning. Novel analyses also identify a previously undescribed genome-wide exon methylation signature. We also compared whole genome methylation with genome-wide mRNA expression levels using publicly available RNA-seq datasets. These comparisons revealed previously unrecognized relationships between gene expression, alternative splicing, and exon methylation. Surprisingly, we found that exonic methylation is a better predictor of mRNA expression level than promoter methylation. We also found that transcriptionally skipped exons have significantly less methylation than retained exons. Our integrative analyses reveal highly complex interplay between gene expression, alternative splicing, development, and methylation patterning in zebrafish.

McGaughey, David M.; Abaan, Hatice Ozel; Miller, Ryan M.; Kropp, Peter A.; Brody, Lawrence C.

2014-01-01

241

Tri-methyl-phospho-nium trans-tetra-chlorido-bis-(tri-methyl-phosphane-?P)iridate(III).  

PubMed

The title compound, [HP(CH3)3][IrCl4{(H3C)3P}2], consists of a tri-methyl-phospho-nium cation and a tetra-chlorido-bis-(tri-methyl-phosphane)iridate(III) anion. The anion has an octa-hedral arrangement of ligands, with the tri-methyl-phosphane groups occupying trans positions. The Ir(III) atom sits on an inversion center with one P(CH3)3 ligand and two chloride ligands in the asymmetric unit. The tri-methyl-phospho-nium cation is disordered about a twofold rotation axis. The title compound is the first structurally characterized tetra-chlorido-bis-(phosphane)iridate complex. PMID:24764937

Berg, Michael A; Davidson, Jesse; Merola, Joseph S

2014-03-01

242

Tri-methyl-phospho-nium trans-tetra-chlorido-bis-(tri-methyl-phosphane-?P)iridate(III)  

PubMed Central

The title compound, [HP(CH3)3][IrCl4{(H3C)3P}2], consists of a tri­methyl­phospho­nium cation and a tetra­chlorido­bis­(tri­methyl­phosphane)iridate(III) anion. The anion has an octa­hedral arrangement of ligands, with the tri­methyl­phosphane groups occupying trans positions. The IrIII atom sits on an inversion center with one P(CH3)3 ligand and two chloride ligands in the asymmetric unit. The tri­methyl­phospho­nium cation is disordered about a twofold rotation axis. The title compound is the first structurally characterized tetra­chlorido­bis­(phosphane)iridate complex.

Berg, Michael A.; Davidson, Jesse; Merola, Joseph S.

2014-01-01

243

Light-regulated transcription of genes encoding peridinin chlorophyll a proteins and the major intrinsic light-harvesting complex proteins in the dinoflagellate amphidinium carterae hulburt (Dinophycae). Changes In cytosine methylation accompany photoadaptation  

PubMed

In the dinoflagellate Amphidinium carterae, photoadaptation involves changes in the transcription of genes encoding both of the major classes of light-harvesting proteins, the peridinin chlorophyll a proteins (PCPs) and the major a/c-containing intrinsic light-harvesting proteins (LHCs). PCP and LHC transcript levels were increased up to 86- and 6-fold higher, respectively, under low-light conditions relative to cells grown at high illumination. These increases in transcript abundance were accompanied by decreases in the extent of methylation of CpG and CpNpG motifs within or near PCP- and LHC-coding regions. Cytosine methylation levels in A. carterae are therefore nonstatic and may vary with environmental conditions in a manner suggestive of involvement in the regulation of gene expression. However, chemically induced undermethylation was insufficient in activating transcription, because treatment with two methylation inhibitors had no effect on PCP mRNA or protein levels. Regulation of gene activity through changes in DNA methylation has traditionally been assumed to be restricted to higher eukaryotes (deuterostomes and green plants); however, the atypically large genomes of dinoflagellates may have generated the requirement for systems of this type in a relatively "primitive" organism. Dinoflagellates may therefore provide a unique perspective on the evolution of eukaryotic DNA-methylation systems. PMID:9576788

ten Lohuis MR; Miller

1998-05-01

244

Synthesis, Characterization, and Crystal Structure of a (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Hexapyridine Ligand, 1,2-Bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane. The First Example of a Discrete (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) Complex with a Dinucleating Ligand.  

PubMed

A mononucleating tripyridine ligand, 2-(bis(2-pyridyl)methyl)-6-methylpyridine (L(1)), and a dinucleating hexapyridine ligand, 1,2-bis[2-(bis(2-pyridyl)methyl)-6-pyridyl]ethane (L(2)), have been prepared. The reaction of a carbanion of 2,6-lutidine with 2-bromopyridine affords L(1) which is converted to L(2) quantitatively by treating with tert-butyllithium and 1,2-dibromoethane. (&mgr;-Oxo)bis(&mgr;-acetato)diiron(III) complexes [Fe(2)(O)(OAc)(2)(L(1))(2)](ClO(4))(2) (1) and [Fe(2)(O)(OAc)(2)L(2)](ClO(4))(2) (2) have been synthesized and characterized by means of infrared, UV/vis, mass, and Mössbauer spectroscopies and by measuring magnetic susceptibility and cyclic voltammograms. All the spectral data are consistent with the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure in both 1 and 2. A relatively strong molecular ion peak at m/z 865 corresponding to [{Fe(2)O(OAc)(2)L(2)}(ClO(4))](+) in a FAB mass spectrum of 2 suggests the stabilization of the (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) core structure by L(2) in a solution state. The compound 2.DMF.2-PrOH.H(2)O, chemical formula C(44)Cl(2)Fe(2)H(51)N(7)O(16), crystallizes in the monoclinic space group C2/c with a = 22.034(6) Å, b = 12.595(5) Å, c = 20.651(7) Å, beta = 121.49(2) degrees, and Z = 4. The cation has 2-fold symmetry with the bridging oxygen atom on the 2-fold axis: Fe-(&mgr;-O) = 1.782(5) Å, Fe-O-Fe = 123.6(6) degrees, and Fe.Fe = 3.142(3) Å. The diiron(III) core structure of 2 seems to be stabilized by encapsulation of the ligand. Compound 2 is the first example of a discrete (&mgr;-oxo)bis(&mgr;-acetato)diiron(III) complex with a dinucleating ligand. PMID:11666701

Kodera, Masahito; Shimakoshi, Hisashi; Nishimura, Masato; Okawa, Hisashi; Iijima, Seiichiro; Kano, Koji

1996-08-14

245

Employment of methyl 2-pyridyl ketone oxime in manganese non-carboxylate chemistry: Mn(II)(2)Mn(IV) and Mn(II)(2)Mn(III)(6) complexes.  

PubMed

The employment of the anion of methyl 2-pyridyl ketone oxime (mpko(-)) as a tridentate chelating/bridging ligand in manganese chemistry is described. The inorganic anion (Br(-), ClO(4)(-)) used in the reaction affects the identity of the product. The reaction of MnBr(2) and one equivalent of mpkoH in the presence of a base affords [Mn(3)(OMe)(2)(mpko)(4)Br(2)] (3), which is mixed-valence (2Mn(II), Mn(IV)). The central Mn(IV) atom in each of the two, crystallographically independent, centrosymmetric molecules is coordinated by four oximate oxygen atoms belonging to the eta(1):eta(1):eta(1):mu mpko(-) ligands, and two eta(1):mu MeO(-) groups, while six coordination at each terminal Mn(II) atom is completed by four nitrogen atoms belonging to the 'chelating' part of two mpko(-) ligands, and one Br(-) ion. The Mn(II) atoms have trigonal prismatic coordination geometry. The reaction of Mn(ClO(4))(2).6H(2)O, mpkoH and OH(-) (1:2:1) in MeOH gives [Mn(8)O(4)(OMe)(mpko)(9)(mpkoH)](ClO(4))(4) (4), which is also mixed-valence (2Mn(II), 6Mn(III)) and possesses the novel [Mn(8)(mu(3)-O)(4)(mu-OMe)(mu-OR'')(2)](11+) core. The latter possesses a U-shaped sequence of four fused {Mn(II)Mn(III)(2)(mu(3)-O)}(6+) triangular units, with a Mn(III)-Mn(III) edge being shared between the central triangles. Variable-temperature, solid-state dc and ac magnetic susceptibility studies were carried out on complexes 3 and 4 . The dc susceptibility data for 3 in the 5.0-300 K range have been fit to a model with two J values, revealing weak ferromagnetic Mn(II)Mn(IV) (J = +3.4 cm(-1)) and Mn(II)Mn(II) (J' = +0.3 cm(-1)) exchange interactions. Fitting of the magnetization vs. H/T data by matrix diagonalization and including only axial anisotropy (ZFS, D) gave ground state spin (S) and D values of S = 13/2, D = +0.17 cm(-1) for and S = 3, D = -0.09 cm(-1) for 4 . The combined work demonstrates the usefulness of mpko(-) in the preparation of interesting Mn clusters, without requiring the co-presence of carboxylate ligands. PMID:19173083

Stoumpos, Constantinos C; Stamatatos, Theocharis C; Sartzi, Harikleia; Roubeau, Olivier; Tasiopoulos, Anastasios J; Nastopoulos, Vassilios; Teat, Simon J; Christou, George; Perlepes, Spyros P

2009-02-14

246

Lysine methylation goes global.  

PubMed

The process of post-translational covalent modifications of proteins represents a transcription-independent regulatory mechanism allowing rapid alteration of protein activity and function in response to various intra- and extracellular stimuli. Lysine methylation (KM) was deemed to be a constant covalent mark, providing long-term signaling, including the histone-dependent mechanism for transcriptional memory. Only recently has it become apparent that lysine methylation, similar to other covalent modifications, is transient and can be dynamically regulated by an opposing activity, de-methylation. These discoveries accelerated a systematic search for other nonhistone substrates of lysine methylation, especially among transcription factors. Recent findings suggest that KM affects gene expression not only at the level of chromatin, but also by modifying transcription factors. PMID:16760670

Morgunkova, Anna; Barlev, Nick A

2006-06-01

247

Methylations: a radical mechanism.  

PubMed

On the basis of labeling experiments, Grove et al. (2011) have shown how an electrophilic carbon (from an RNA adenosine) can be methylated by S-adenosylmethionine-dependent methyltransferases though an original radical mechanism. PMID:21609836

Fontecave, Marc

2011-05-27

248

ENZYMOLOGY OF ARSENIC METHYLATION  

EPA Science Inventory

Enzymology of Arsenic Methylation David J. Thomas, Pharmacokinetics Branch, Experimental Toxicology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park...

249

DNA Methylation and Cancer  

Microsoft Academic Search

\\u000a DNA methylation acts in concert with other epigenetic mechanisms to regulate normal gene expression and facilitate chromatin\\u000a organization within cells. Aberrant DNA methylation patterns are acquired during carcinogenic transformation; such events\\u000a are often accompanied by alterations in chromatin structure at gene regulatory regions. The expression pattern of any given\\u000a gene is achieved by interacting epigenetic mechanisms. First, the insertion of

Phillippa C. Taberlay; Peter A. Jones

250

DNA methylation changes in inflammatory bowel disease  

PubMed Central

The cause of inflammatory bowel disease, encompassing Crohn’s disease and ulcerative colitis, remains a mystery but evidence is accumulating that complex interactions between the genetic background and the gut microbiota of the host and environmental factors associated with rapid industrialization and westernized life styles may underlie its pathogenesis. Recent epigenetic studies have suggested that interactions between environment and host DNA may play a leading role in the phenotypical expression of both diseases, explaining amongst others the differences in disease expression in monozygotic twins. DNA methylation is the most studied epigenetic modification and during the last decade its correlation to IBD pathogenesis has been well established. Genes from different molecular pathways have been studied but till now there is no standardized database of methylated genes in IBD. Thus, a thorough and in depth study of DNA methylation, its potential relation to IBD and its interaction with the available pharmaceutical armamentarium is of great interest.

Karatzas, Pantelis S.; Gazouli, Maria; Safioleas, Michael; Mantzaris, Gerasimos J.

2014-01-01

251

Methylation-specific PCR.  

PubMed

Defining DNA methylation patterns in the genome has become essential for understanding diverse biological processes including the regulation of gene expression, imprinted genes, and X chromosome inactivation and how these patterns are deregulated in human diseases. Methylation-specific (MS)-PCR is a useful tool for qualitative DNA methylation analysis with multiple advantages, including ease of design and execution, sensitivity in the ability to detect small quantities of methylated DNA, and the ability to rapidly screen a large number of samples without the need for purchase of expensive laboratory equipment. This assay requires modification of the genomic DNA by sodium bisulfite and two independent primer sets for PCR amplification, one pair designed to recognize the methylated and the other pair the unmethylated versions of the bisulfite-modified sequence. The amplicons are visualized using ethidium bromide staining following agarose gel electrophoresis. Amplicons of the expected size produced from either primer pair are indicative of the presence of DNA in the original sample with the respective methylation status. PMID:23913210

Huang, Zhiqing; Bassil, Christopher F; Murphy, Susan K

2013-01-01

252

DNA methylation and differentiation.  

PubMed Central

The methylation of specific cytosine residues in DNA has been implicated in regulating gene expression and facilitating functional specialization of cellular phenotypes. Generally, the demethylation of certain CpG sites correlates with transcriptional activation of genes. 5-Azacytidine is an inhibitor of DNA methylation and has been widely used as a potent activator of suppressed genetic information. Treatment of cells with 5-azacytidine results in profound phenotypic alterations. The drug-induced hypomethylation of DNA apparently perturbs DNA-protein interactions that may consequently alter transcriptional activity and cell determination. The inhibitory effect of cytosine methylation may be exerted via altered DNA-protein interactions specifically or may be transduced by a change in the conformation of chromatin. Recent studies have demonstrated that cytosine methylation also plays a central role in parental imprinting, which in turn determines the differential expression of maternal and paternal genomes during embryogenesis. In other words, methylation is the mechanism whereby the embryo retains memory of the gametic origin of each component of genetic information. A memory of this type would probably persist during DNA replication and cell division as methylation patterns are stable and heritable.

Michalowsky, L A; Jones, P A

1989-01-01

253

Cation-? interactions of methylated ammonium ions: A quantum mechanical study.  

PubMed

Cation-? interactions of methylated ammonium ions play a key role in a broad range of biochemical systems. These include methyl-lysine binding proteins which bind to methylated sites on histone proteins, lysine demethylase enzymes which demethylate these sites, and neurotransmitter receptor complexes which bind choline-derived ligands. Recognition in these systems is achieved through an 'aromatic cage' motif in the binding site. Here we use high-level quantum mechanical calculations to address how cation-? interactions of methylated ammonium ions are modulated by a change in methylation state and interaction geometry. We survey methyl-lysine and choline-derived complexes in the Protein Databank to validate our results against available structural data. A quantitative description of cation-? interactions of methylated ammonium systems is critical to structure-based efforts to target methyl-lysine binding proteins and demethylase enzymes in the treatment of unregulated transcriptional control, and neurotransmitter receptors in the treatment of neurological disease. It is our hope that our work will serve as a benchmark for the development of physical chemistry based force fields that can accurately model the contribution of cation-? interactions to binding and specificity in these systems. Proteins 2014; 82:1494-1502. © 2014 Wiley Periodicals, Inc. PMID:24464782

Rapp, Chaya; Goldberger, Elizabeth; Tishbi, Nasim; Kirshenbaum, Rachel

2014-07-01

254

Global DNA Methylation of Ischemic Stroke Subtypes  

PubMed Central

Ischemic stroke (IS), a heterogeneous multifactorial disorder, is among the leading causes of mortality and long-term disability in the western world. Epidemiological data provides evidence for a genetic component to the disease, but its epigenetic involvement is still largely unknown. Epigenetic mechanisms, such as DNA methylation, change over time and may be associated with aging processes and with modulation of the risk of various pathologies, such as cardiovascular disease and stroke. We analyzed 2 independent cohorts of IS patients. Global DNA methylation was measured by luminometric methylation assay (LUMA) of DNA blood samples. Univariate and multivariate regression analyses were used to assess the methylation differences between the 3 most common IS subtypes, large-artery atherosclerosis (LAA), small-artery disease (SAD), and cardio-aortic embolism (CE). A total of 485 IS patients from 2 independent hospital cohorts (n?=?281 and n?=?204) were included, distributed across 3 IS subtypes: LAA (78/281, 59/204), SAD (97/281, 53/204), and CE (106/281, 89/204). In univariate analyses, no statistical differences in LUMA levels were observed between the 3 etiologies in either cohort. Multivariate analysis, adjusted by age, sex, hyperlipidemia, and smoking habit, confirmed the lack of differences in methylation levels between the analyzed IS subtypes in both cohorts. Despite differences in pathogenesis, our results showed no global methylation differences between LAA, SAD, and CE subtypes of IS. Further work is required to establish whether the epigenetic mechanism of methylation might play a role in this complex disease.

Soriano-Tarraga, Carolina; Jimenez-Conde, Jordi; Giralt-Steinhauer, Eva; Mola, Marina; Ois, Angel; Rodriguez-Campello, Ana; Cuadrado-Godia, Elisa; Fernandez-Cadenas, Israel; Carrera, Caty; Montaner, Joan; Elosua, Roberto; Roquer, Jaume

2014-01-01

255

Paramutation of the r1 locus of maize is associated with increased cytosine methylation.  

PubMed Central

In paramutation two alleles of a gene interact so that one of the alleles is epigenetically silenced. The silenced state is then genetically transmissible for many generations. The large (220 kbp) multigenic complex R-r is paramutable: its level of expression is changed during paramutation. R-r was found to exhibit increases in its level of cytosine methylation (C-methylation) following paramutation. These C-methylation changes are localized to the 5' portions of the two genes in the complex that are most sensitive to paramutation. These methylation changes flank a small region called sigma that is thought to have been derived from a transposon named doppia. A mutant derivative of R-r that has a deletion of the sigma region fails to become methylated under conditions in which R-r is heavily methylated. This suggests that the presence of sigma sequences at the locus is required for the methylation changes that are observed following paramutation.

Walker, E L

1998-01-01

256

Abiotic Formation of Methyl Halides in the Terrestrial Environment  

NASA Astrophysics Data System (ADS)

Methyl chloride and methyl bromide are the most abundant chlorine and bromine containing organic compounds in the atmosphere. Since both compounds have relatively long tropospheric lifetimes they can effectively transport halogen atoms from the Earth's surface, where they are released, to the stratosphere and following photolytic oxidation form reactive halogen gases that lead to the chemical destruction of ozone. Methyl chloride and methyl bromide account for more than 20% of the ozone-depleting halogens delivered to the stratosphere and are predicted to grow in importance as the chlorine contribution to the stratosphere from anthropogenic CFCs decline. Today methyl chloride and methyl bromide originate mainly from natural sources with only a minor fraction considered to be of anthropogenic origin. However, until as recently as 2000 most of the methyl chloride and methyl bromide input to the atmosphere was considered to originate from the oceans, but investigations in recent years have clearly demonstrated that terrestrial sources such as biomass burning, wood-rotting fungi, coastal salt marshes, tropical vegetation and organic matter degradation must dominate the atmospheric budgets of these trace gases. However, many uncertainties still exist regarding strengths of both sources and sinks, as well as the mechanisms of formation of these naturally occurring halogenated gases. A better understanding of the atmospheric budget of both methyl chloride and methyl bromide is therefore required for reliable prediction of future ozone depletion. Biotic and abiotic methylation processes of chloride and bromide ion are considered to be the dominant pathways of formation of these methyl halides in nature. In this presentation I will focus on abiotic formation processes in the terrestrial environment and the potential parameters that control their emissions. Recent advances in our understanding of the abiotic formation pathway of methyl halides will be discussed. This will include a consideration on how stable isotope studies assisted advancements in this subject area. For example, it has been shown that the methoxyl groups of lignin and pectin which together constitute the bulk of the C1 plant pool have a carbon isotope signature significantly depleted in 13C. Plant-derived C1 volatile organic compounds (VOCs) are also highly depleted in 13C compared with Cn+1 VOCs. These observations suggest that the plant methoxyl pool is the predominant source of methyl halides released from senescent and dead plant litter. The distinct 13C depletion of plant methoxyl groups and naturally produced methyl halides may provide a helpful tool in constraining complex environmental processes and therefore improve our understanding of the global cycles of atmospheric methyl halides.

Keppler, F.

2011-12-01

257

Spectroscopic and biological studies of new binuclear metal complexes of a tridentate ONS hydrazone ligand derived from 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 4,6-diacetylresorcinol.  

PubMed

The binuclear hydrazone, H2L, ligand derived from 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 4,6-diacetylresorcinol, in the molar ratio 2:1, and its copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II), cerium(III), iron(III), oxovanadium(IV) and dioxouranium(VI) complexes have been synthesized. Structures of the ligand and its metal complexes were characterized by elemental analyses, spectral (infrared, electronic, mass, (1)H NMR and ESR) data, magnetic susceptibility, molar conductivity measurements and thermal gravimetric analysis (TGA). The ligand acts as dibasic with two ONS tridentate sites. The bonding sites are the azomethine nitrogen, phenolate oxygen and sulfur atoms. The metal complexes exhibit different geometrical arrangements such as square planer, tetrahedral and octahedral. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The ligand and its metal complexes showed antimicrobial activity towards Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus). Structural parameters of the ligand and its metal complexes were theoretically computed on the basis of semiempirical PM3 level, and the results were correlated with their experimental data. PMID:24858350

Adly, Omima M I; Emara, Adel A A

2014-11-11

258

Spectroscopic and biological studies of new binuclear metal complexes of a tridentate ONS hydrazone ligand derived from 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 4,6-diacetylresorcinol  

NASA Astrophysics Data System (ADS)

The binuclear hydrazone, H2L, ligand derived from 4-amino-6-methyl-3-thioxo-3,4-dihydro-1,2,4-triazin-5(2H)-one and 4,6-diacetylresorcinol, in the molar ratio 2:1, and its copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II), cerium(III), iron(III), oxovanadium(IV) and dioxouranium(VI) complexes have been synthesized. Structures of the ligand and its metal complexes were characterized by elemental analyses, spectral (infrared, electronic, mass, 1H NMR and ESR) data, magnetic susceptibility, molar conductivity measurements and thermal gravimetric analysis (TGA). The ligand acts as dibasic with two ONS tridentate sites. The bonding sites are the azomethine nitrogen, phenolate oxygen and sulfur atoms. The metal complexes exhibit different geometrical arrangements such as square planer, tetrahedral and octahedral. The Coats-Redfern equation was used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The ligand and its metal complexes showed antimicrobial activity towards Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Salmonella typhimurium and Escherichia coli), yeast (Candida albicans) and fungus (Aspergillus fumigatus). Structural parameters of the ligand and its metal complexes were theoretically computed on the basis of semiempirical PM3 level, and the results were correlated with their experimental data.

Adly, Omima M. I.; Emara, Adel A. A.

2014-11-01

259

2,5-Bis[4-methyl-3-(pyridin-3-yl)phenyl]-1,3,4-oxadiazole and its one-dimensional polymeric complex with ZnCl2.  

PubMed

2,5-Bis[4-methyl-3-(pyridin-3-yl)phenyl]-1,3,4-oxadiazole (L), C26H20N4O, forms one-dimensional chains via two types of intermolecular ?-? interactions. In catena-poly[[dichloridozinc(II)]-?-2,5-bis[4-methyl-3-(pyridin-3-yl)phenyl]-1,3,4-oxadiazole], [ZnCl2(C26H20N4O)]n, synthesized by the combination of L with ZnCl2, the Zn(II) centres are coordinated by two Cl atoms and two N atoms from two L ligands. [ZnCl2L]n forms one-dimensional P (plus) and M (minus) helical chains, where the L ligand has different directions of twist. The helical chains stack together via interchain ?-? and C-H···? interactions. PMID:24096495

Hou, Shan; Liu, Qi-Kui; Li, Yan-An; Ma, Jian-Ping; Dong, Yu-Bin

2013-10-01

260

Predominant expression of nuclear activator protein-1 complex with DNA binding activity following systemic administration of N-methyl- d-aspartate in dentate granule cells of murine hippocampus  

Microsoft Academic Search

The systemic administration of N-methyl-d-aspartate (100mg\\/kg, i.p.) resulted in preferential but transient expression of the transcription factor activator protein-1 in the granule cell layers of the dentate gyrus in the murine hippocampus by maximally 700% 1h later, without markedly affecting that in the pyramidal cell layers of the CA1 and CA3 subfields for 4h. The potentiation was completely prevented by

Y. Yoneda; K. Ogita; Y. Azuma; N. Kuramoto; T. Manabe; T. Kitayama

1999-01-01

261

Geometry of binding of the benzamidine- and arginine-based inhibitors N alpha-(2-naphthyl-sulphonyl-glycyl)-DL-p-amidinophenylalanyl-pipe ridine (NAPAP) and (2R,4R)-4-methyl-1-[N alpha-(3-methyl-1,2,3,4-tetrahydro-8- quinolinesulphonyl)-L-arginyl]-2-piperidine carboxylic acid (MQPA) to human alpha-thrombin. X-ray crystallographic determination of the NAPAP-trypsin complex and modeling of NAPAP-thrombin and MQPA-thrombin.  

PubMed

The X-ray crystal structure of the trypsin complex formed with N alpha-(2-naphthyl-sulphonyl-glycyl)-DL-p-amidinophenylalanyl-piper idine (NAPAP) was determined with X-ray data to 0.18-nm resolution and crystallographically refined. NAPAP binds into the active site of trypsin in a quite compact form: the p-amidinophenylalanine moiety of the D-stereoisomer binds into the specificity pocket; the glycyl group is hydrogen bonded with Gly216; the naphthyl group stands perpendicular to the indole moiety of Trp215; the piperidine ring is tightly packed between this naphthyl moiety and His57; in consequence the carboxy-terminal amido bond of NAPAP is located in such a way that it is not susceptible to the active-site Ser195. NAPAP and (2R,4R)-4-methyl-1-[N alpha-(3-methyl-1,2,3,4-tetrahydro-8- quinolinesulphonyl)-L-arginyl]-2-piperidine carboxylic acid (MQPA) [Matzusaki, T., Sasaki, C., Okumura, C. & Umeyama (1989) J. Biochem. (Tokyo) 105, 949-952] were transferred in their trypsin-binding conformations to human alpha-thrombin [Bode, W., Mayr, I., Baumann, U., Huber, R., Stone, S. R. & Hofsteenge, J. (1989) EMBO J. 8. 3467 - 3475] and energy minimized. Both synthetic inhibitors fit perfectly into the much more restricted active site of thrombin. The accommodation of the S-aryl moieties in the 'aryl-binding site' and of the piperidine rings in the S2 subsite of thrombin are particularly favorable. The preference of thrombin for distinctly substituted piperidine derivatives and its generally higher (compared with trypsin) affinity for benzamidine and arginine-based inhibitors can be accounted for by these thrombin inhibitor models. PMID:2226434

Bode, W; Turk, D; Stürzebecher, J

1990-10-01

262

4-(Di-methyl-amino)-pyridinium trichlorido[4-(di-methyl-amino)-pyridine-?N]cobaltate(II)  

PubMed Central

In the anion of the title compound, (C7H11N2)[CoCl3(C7H10N2)], the CoII ion is coordinated by one N atom from a 4-(di­methyl­amino)­pyridine (DMAP) ligand and three Cl atoms, forming a CoNCl3 polyhedron with a distorted tetra­hedral geometry. In the crystal, cations and anions are linked via weak N—H?Cl and C—H?Cl hydrogen bonds. Double layers of complex anions stack along the b- axis direction, which alternate with double layers of 4-(di­methyl­amino)-pyridinium cations.

Guenifa, Fatiha; Hadjadj, Nasreddine; Zeghouan, Ouahida; Bendjeddou, Lamia; Merazig, Hocine

2013-01-01

263

Predicting DNA methylation level across human tissues  

PubMed Central

Differences in methylation across tissues are critical to cell differentiation and are key to understanding the role of epigenetics in complex diseases. In this investigation, we found that locus-specific methylation differences between tissues are highly consistent across individuals. We developed a novel statistical model to predict locus-specific methylation in target tissue based on methylation in surrogate tissue. The method was evaluated in publicly available data and in two studies using the latest IlluminaBeadChips: a childhood asthma study with methylation measured in both peripheral blood leukocytes (PBL) and lymphoblastoid cell lines; and a study of postoperative atrial fibrillation with methylation in PBL, atrium and artery. We found that our method can greatly improve accuracy of cross-tissue prediction at CpG sites that are variable in the target tissue [R2 increases from 0.38 (original R2 between tissues) to 0.89 for PBL-to-artery prediction; from 0.39 to 0.95 for PBL-to-atrium; and from 0.81 to 0.98 for lymphoblastoid cell line-to-PBL based on cross-validation, and confirmed using cross-study prediction]. An extended model with multiple CpGs further improved performance. Our results suggest that large-scale epidemiology studies using easy-to-access surrogate tissues (e.g. blood) could be recalibrated to improve understanding of epigenetics in hard-to-access tissues (e.g. atrium) and might enable non-invasive disease screening using epigenetic profiles.

Ma, Baoshan; Wilker, Elissa H.; Willis-Owen, Saffron A. G.; Byun, Hyang-Min; Wong, Kenny C. C.; Motta, Valeria; Baccarelli, Andrea A.; Schwartz, Joel; Cookson, William O. C. M.; Khabbaz, Kamal; Mittleman, Murray A.; Moffatt, Miriam F.; Liang, Liming

2014-01-01

264

Lung cancer: From single-gene methylation to methylome profiling  

Microsoft Academic Search

DNA methylation as part of the epigenetic gene-silencing complex is a universal occurring change in lung cancer. Numerous\\u000a studies investigated methylation of specific genes in primary tumors, in serum or plasma samples, and in specimens from the\\u000a aerodigestive tract epithelium of lung cancer patients. In most studies, single genes or small numbers of genes were analyzed.\\u000a Moreover, it has been

Gerwin Heller; Christoph C. Zielinski; Sabine Zöchbauer-Müller

2010-01-01

265

Trans-chromosomal methylation.  

PubMed

The epigenome plays a vital role in helping to maintain and regulate cell functions in all organisms. Alleles with differing epigenetic marks in the same nucleus do not function in isolation but can interact in trans to modify the epigenetic state of one or both alleles. This is particularly evident when two divergent epigenomes come together in a hybrid resulting in thousands of alterations to the methylome. These changes mainly involve the methylation patterns at one allele being changed to resemble the methylation patterns of the other allele, in processes we have termed trans-chromosomal methylation (TCM) and trans-chromosomal demethylation (TCdM). These processes are primarily modulated by siRNAs and the RNA directed DNA methylation pathway. Drawing from other examples of trans-allelic interactions, we describe the process of TCM and TCdM and the effect such changes can have on genome activity. Trans-allelic epigenetic interactions may be a common occurrence in many biological systems. PMID:22705969

Greaves, Ian; Groszmann, Michael; Dennis, Elizabeth S; Peacock, W James

2012-08-01

266

Trans-chromosomal methylation  

PubMed Central

The epigenome plays a vital role in helping to maintain and regulate cell functions in all organisms. Alleles with differing epigenetic marks in the same nucleus do not function in isolation but can interact in trans to modify the epigenetic state of one or both alleles. This is particularly evident when two divergent epigenomes come together in a hybrid resulting in thousands of alterations to the methylome. These changes mainly involve the methylation patterns at one allele being changed to resemble the methylation patterns of the other allele, in processes we have termed trans-chromosomal methylation (TCM) and trans-chromosomal demethylation (TCdM). These processes are primarily modulated by siRNAs and the RNA directed DNA methylation pathway. Drawing from other examples of trans-allelic interactions, we describe the process of TCM and TCdM and the effect such changes can have on genome activity. Trans-allelic epigenetic interactions may be a common occurrence in many biological systems.

Greaves, Ian; Groszmann, Michael; Dennis, Elizabeth S.; Peacock, W. James

2012-01-01

267

Methyl Bromide Poisoning  

PubMed Central

Seven cases of methyl bromide poisoning which occurred amongst workers engaged on a fumigation project are described. The methods adopted for investigation of the environmental situation are discussed and the measurement of blood bromide levels on random samples of workers is suggested as an index of the effectiveness of equipment and working methods.

Rathus, E. M.; Landy, P. J.

1961-01-01

268

RNA nucleotide methylation.  

PubMed

Methylation of RNA occurs at a variety of atoms, nucleotides, sequences and tertiary structures. Strongly related to other posttranscriptional modifications, methylation of different RNA species includes tRNA, rRNA, mRNA, tmRNA, snRNA, snoRNA, miRNA, and viral RNA. Different catalytic strategies are employed for RNA methylation by a variety of RNA-methyltransferases which fall into four superfamilies. This review outlines the different functions of methyl groups in RNA, including biophysical, biochemical and metabolic stabilization of RNA, quality control, resistance to antibiotics, mRNA reading frame maintenance, deciphering of normal and altered genetic code, selenocysteine incorporation, tRNA aminoacylation, ribotoxins, splicing, intracellular trafficking, immune response, and others. Connections to other fields including gene regulation, DNA repair, stress response, and possibly histone acetylation and exocytosis are pointed out. WIREs RNA 2011 2 611-631 DOI: 10.1002/wrna.79 For further resources related to this article, please visit the WIREs website. PMID:21823225

Motorin, Yuri; Helm, Mark

2011-01-01

269

DNA methylation and cancer therapy  

Microsoft Academic Search

Vertebrate DNA is modified by methyl moieties at the 5?-position of cytosine rings residing in the di-nucleotide sequence CpG. Approximately 80% of CpG dinucleotide sequences are methylated. The pattern of distribution of methylated CGs is cell-type specific and correlates with gene expression programming and chromatin structure. Three kinds of seemingly contradictory aberrations in DNA methylation are observed in cancer, global

Moshe Szyf

2003-01-01

270

Methylation profiles of genes utilizing newly developed CpG island methylation microarray on colorectal cancer patients  

PubMed Central

Aberrant methylation of DNA has been shown to play an important role in a variety of human cancers, developmental disorders and aging. Hence, aberrant methylation patterns in genes can be a molecular marker for such conditions. Therefore, a reliable but uncomplicated method to detect DNA methylation is preferred, not merely for research purposes but for daily clinical practice. To achieve these aims, we have established a precise system to identify DNA methylation patterns based on an oligonucleotide microarray technology. Our microarray method has an advantage over conventional methods and is unique because it allows the precise measurement of the methylation patterns within a target region. Our simple signal detection system depends on using an avidin–biotinylated peroxidase complex and does not require an expensive laser scanner or hazardous radioisotope. In this study, we applied our technique to detect promoter methylation status of O6-methylguanine-DNA methyltransferase (MGMT) gene. Our easy-handling technology provided reproducible and precise measurement of methylated CpGs in MGMT promoter and, thus, our method may bring about a potential evolution in the handling of a variety of high-throughput DNA methylation analyses for clinical purposes.

Kimura, Naoki; Nagasaka, Takeshi; Murakami, Jun; Sasamoto, Hiromi; Murakami, Masahiro; Tanaka, Noriaki; Matsubara, Nagahide

2005-01-01

271

Targeting DNA methylation in cancer  

Microsoft Academic Search

There is overwhelming evidence that DNA methylation patterns are altered in cancer. Methylation of CG-rich islands in regulatory regions of genes marks them for transcriptional silencing. Multiple genes, which confer selective advantage upon cancer cells such as tumor suppressors, adhesion molecules, inhibitors of angiogenesis and repair enzymes are silenced. In parallel, tumor cell genomes are globally less methylated than their

Moshe Szyf

2003-01-01

272

Histone methylation in transcriptional control  

Microsoft Academic Search

Over the past year or so, methylation of histones has come to be recognised as a major player in the regulation of gene activity. This notion follows the discovery of lysine and arginine methyltransferases and proteins that recognise the methyl-lysine ‘mark’ on histones. Methylated histones have been implicated in heterochromatic repression, promoter regulation and the propagation of a repressed state

Tony Kouzarides

2002-01-01

273

fullRecord:"self OR methylate" OR "sulfo OR methylated" OR "sulfo OR methylates" OR "sulfo OR methylating" OR "sulfo OR methylation" OR sulfomethylate OR sulfomethylated OR sulfomethylates OR sulfomethylating OR sulfomethylation  

EPA Pesticide Factsheets

Did you mean: fullRecord:"self OR methylate" OR "sulfo OR methylated" OR "sulfo OR methylates" OR "sulfo OR methylating" OR "sulfo OR methylation" OR sulfomethylate OR sulfomethylated OR sulfomethylates OR sulfomethylating OR sulfomethylation ?

274

Spectroscopic studies of the 1:1 complexes of 4-nitrophenyl[bis(ethylsulfonyl)]methane and phenyl[bis(ethylsulfonyl)]methane with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and 1,5,7-triazabicyclo[4.4.0]dec-5-ene  

NASA Astrophysics Data System (ADS)

The 1:1 complexes of 4-nitrophenyl[bis(diethylsulfonyl)]methane (CH1) and phenyl[bis(diethylsulfonyl)]methane (CH2) with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) have been synthesized and their structures have been studied using the FT-IR, 1H NMR and PM5 semiempirical methods. In all complexes a proton has been transferred from C-H acid to TBD or MTBD molecules to yield ionic pairs. On the basis of the FT-IR and 1H NMR studies of the MTBD complexes, in acetonitrile, the ions have been shown to be fully dissociated. In the case of TBD formation of non-cyclic hydrogen bonded structures have been proposed for the complex being partially dissociated. The calculated structure of the CH2-TBD complex has shown very high similarity to the structure in the solid state.

Huczy?ski, A.; Binkowska, I.; Jarczewski, A.; Brzezinski, B.

2007-09-01

275

Electrophysiological Study, Biodistribution in Mice, and Preliminary PET Evaluation in a Rhesus Monkey of 1Amino3-[ 18F]fluoromethyl-5-methyl-adamantane ( 18F-MEM): A Potential Radioligand for Mapping the NMDA-Receptor Complex  

Microsoft Academic Search

The effect of the fluorinated memantine derivative and NMDA receptor antagonist, 1-amino-3-fluoromethyl-5-methyl-adamantane (19F-MEM), at the NMDA receptor ion channel was studied by patch clamp recording. The results showed that 19F-MEM is a moderate NMDA receptor channel blocker. A procedure for the routine preparation of the 18F-labelled analog 18F-MEM has been developed using a two-step reaction sequence. This involves the no-carrier-added

Samuel Samnick; Simon Ametamey; Klaus L Leenders; Peter Vontobel; Guenter Quack; Chris G Parsons; Henrik Neu; Pius A Schubiger

1998-01-01

276

4,4?,4?Tris(N-carbazolyl)-triphenylamine interlayer in highly efficient phosphorescent organic light emitting diodes based on tris[4-methyl-2-2(4?-trimethylsilylphenyl)pyridine]iridium complex  

Microsoft Academic Search

We developed highly efficient yellowish-green emitting phosphorescent organic light emitting diodes based on tris[4-methyl-2-2(4?-trimethylsilylphenyl)pyridine] [Ir(msippy)3]. The device showed electroluminescence emission from the dopant emitter at 521nm with CIE color coordinates of (0.32, 0.62). We investigated the roll of 4,4?,4?-Tris(carbazol-9-yl)triphenylamine (TcTa) interlayer between hole transporting and emissive layers on the higher device performances using different hole transporting materials. TcTa interlayer in

K. Thangaraju; Jonghee Lee; Jeong-Ik Lee; Hye Yong Chu; Seul-Ong Kim; Min-Gi Shin; Yun-Hi Kim; Kwon Soon-Ki

2011-01-01

277

THE EPR SPECTRA OF TETRADENTATE SCHIFF BASE COMPLEXES OF COPPER II VI, N, N'BIS(SALICYLIDENE)-O-PHENYLENEDIIMINE AND 7-METHYL-N, N'BIS(SALICYLIDENE)-O-PHENYLENEDIIMINE  

Microsoft Academic Search

The EPR spectra of single crystals of Cu(II) doped N, N'-bis(salicylidene)-o-phenylenediimine Ni(II), (Ni(II)(sal)2 phen), and N, N'-bis(7-methyl salicylidene)-o-phenylenediimine Ni(II), (Ni(II)(7-me sal)2phen) have been studied. The usual doublet spin-Hamiltonian parameters have been found to be: Cu(II) doped Ni(II)(sal)2phen; gz = 2.192·0.002,gx = 2.049·0.004,gy = 2.041·0.004,Az = 201.7 × 10 cm,Ax = 36.4 × 10 cm, Ay = 31.4 × 10 cm,A

Michele I. Scullane; Harry C. Allen Jr

1978-01-01

278

DNA Methylation Screening and Analysis  

PubMed Central

DNA methylation is an epigenetic form of gene regulation that is universally important throughout the life course, especially during in utero and postnatal development. DNA methylation aids in cell cycle regulation and cellular differentiation processes. Previous studies have demonstrated that DNA methylation profiles may be altered by diet and the environment, and that these profiles are especially vulnerable during development. Thus, it is important to understand the role of DNA methylation in developmental governance and subsequent disease progression. A variety of molecular methods exist to assay for global, gene-specific, and epigenome-wide methylation. Here we describe these methods and discuss their relative strengths and limitations.

Sant, Karilyn E.; Nahar, Muna S.; Dolinoy, Dana C.

2013-01-01

279

Dynamic DNA methylation across diverse human cell lines and tissues.  

PubMed

As studies of DNA methylation increase in scope, it has become evident that methylation has a complex relationship with gene expression, plays an important role in defining cell types, and is disrupted in many diseases. We describe large-scale single-base resolution DNA methylation profiling on a diverse collection of 82 human cell lines and tissues using reduced representation bisulfite sequencing (RRBS). Analysis integrating RNA-seq and ChIP-seq data illuminates the functional role of this dynamic mark. Loci that are hypermethylated across cancer types are enriched for sites bound by NANOG in embryonic stem cells, which supports and expands the model of a stem/progenitor cell signature in cancer. CpGs that are hypomethylated across cancer types are concentrated in megabase-scale domains that occur near the telomeres and centromeres of chromosomes, are depleted of genes, and are enriched for cancer-specific EZH2 binding and H3K27me3 (repressive chromatin). In noncancer samples, there are cell-type specific methylation signatures preserved in primary cell lines and tissues as well as methylation differences induced by cell culture. The relationship between methylation and expression is context-dependent, and we find that CpG-rich enhancers bound by EP300 in the bodies of expressed genes are unmethylated despite the dense gene-body methylation surrounding them. Non-CpG cytosine methylation occurs in human somatic tissue, is particularly prevalent in brain tissue, and is reproducible across many individuals. This study provides an atlas of DNA methylation across diverse and well-characterized samples and enables new discoveries about DNA methylation and its role in gene regulation and disease. PMID:23325432

Varley, Katherine E; Gertz, Jason; Bowling, Kevin M; Parker, Stephanie L; Reddy, Timothy E; Pauli-Behn, Florencia; Cross, Marie K; Williams, Brian A; Stamatoyannopoulos, John A; Crawford, Gregory E; Absher, Devin M; Wold, Barbara J; Myers, Richard M

2013-03-01

280

Hydridomethyl iridium complex  

DOEpatents

A process for functionalizing methane comprising: (a) reacting methane with a hydridoalkyl metal complex of the formula: CpIr[P(R.sub.1).sub.3 ]H(R.sub.2) wherein Cp represents a cyclopentadienyl or alkylcyclopentadienyl radical having from 1 to 5 carbon atoms; Ir represents an iridium atom; P represents a phosphorus atom; R.sub.1 represents an alkyl group; R.sub.2 represents an alkyl group having at least two carbon atoms; and H represents a hydrogen atom, in the presence of a liquid alkane R.sub.3 H having at least three carbon atoms to form a hydridomethyl complex of the formula: CpIr[P(R.sub.1).sub.3 ]HMe where Me represents a methyl radical. (b) reacting said hydridomethyl complex with an organic halogenating agent such as a tetrahalomethane or a haloform of the formulas: CX'X"X'"X"" or CHX'X"X'"; wherein X', X", X"', and X"" represent halogens selected from bromine, iodine and chlorine, to halomethyl complex of step (a) having the formula: CpIr[P(R.sub.1).sub.3 ]MeX: (c) reacting said halomethyl complex with a mercuric halide of the formula HgX.sub.2 to form a methyl mercuric halide of the formula HgMeX; and (d) reacting said methyl mercuric halide with a molecular halogen of the formula X.sub.2 to form methyl halide.

Bergman, Robert G. (P.O. Box 7141, San Francisco, CA 94120-7141); Buchanan, J. Michael (P.O. Box 7141, San Francisco, CA 94120-7141); Stryker, Jeffrey M. (P.O. Box 7141, San Francisco, CA 94120-7141); Wax, Michael J. (P.O. Box 7141, San Francisco, CA 94120-7141)

1989-01-01

281

Methylation: lost in hydroxylation?  

PubMed Central

Methylation of histone tails is a key determinant in forming active and silent states of chromatin. Histone methylation was regarded as irreversible until the recent identification of a lysine-specific histone demethylase (LSD1), which acts specifically on mono- and dimethylated histone H3 lysine 4. Here, we propose that the fission yeast protein Epe1 is a putative histone demethylase that could act by oxidative demethylation. Epe1 modulates the stability of silent chromatin and contains a JmjC domain. The Epe1 protein can be modelled onto the structure of the 2-oxoglutarate-Fe(II)-dependent dioxygenase, factor inhibiting hypoxia inducible factor (FIH), which is a protein hydroxylase that also contains a JmjC domain. Thus, Epe1 and certain other chromatin-associated JmjC-domain proteins may be protein hydroxylases that catalyse a novel histone modification. Another intriguing possibility is that, by hydroxylating the methyl groups, Epe1 and certain other JmjC-domain proteins may be able to demethylate mono-, di- or trimethylated histones.

Trewick, Sarah C.; McLaughlin, Paul J.; Allshire, Robin C.

2005-01-01

282

Abiotic methylation of mercury in the aquatic environment.  

PubMed

Methylation of inorganic mercury in the aquatic environment has been considered to be largely the result of biological processes, primarily involving sulfate-reducing bacteria. However, these processes cannot account for all of the methylmercury that is formed naturally. A growing body of evidence suggests that chemical reactions represent another possible pathway for mercury methylation in the aquatic environment. In order to assess the abiotic contribution to mercury methylation in the water column, and specifically the conditions under which this contribution may be significant, the current state of knowledge about environmentally significant methylation reactions is reviewed. Results of our laboratory-based investigations of aqueous mercury reactions with some potential methyl donors, including MeCo(dmg)(2)(H2O), a simple model for methylcobalamin, various methyltin compounds and methyl iodide, are presented. In each reaction, the yield of methylmercury and the rate of methylation depend strongly on environmental factors such as pH, temperature, and the presence of complexing agents, especially chloride. PMID:16226793

Celo, Valbona; Lean, David R S; Scott, Susannah L

2006-09-01

283

Bisulfite methylation profiling of large genomes.  

PubMed

Bisulfite conversion of genomic DNA differentiates cytosines from 5-methylcytosines and, thus, identifies DNA methylation patterns at the single-base level. Here, we review recent developments incorporating high-throughput sequencing of bisulfite-converted DNA for target-specific analyses and genome-wide mapping of plant and mammalian methylomes. These developments include the analysis of human embryonic stem cell and fetal fibroblast methylomes at single-base resolution, which supports the presence of non-CG DNA methylation in wild-type embryonic stem cells and induced pluripotent stem cells. New developments in nanopore sequencing technologies may lead to directly detecting 5-methylcytosine independently of bisulfite conversion, but the current accuracy of this approach remains a limitation. Furthermore, recent investigations detecting 5-hydroxymethylcytosine within mammalian DNA may add yet another level of complexity to the epigenetic code of the methylome. PMID:22121871

Reinders, Jon; Paszkowski, Jerzy

2010-04-01

284

Methyl group tunnelling studies in calixarenes  

NASA Astrophysics Data System (ADS)

Inelastic neutron scattering has been used to study the tunnelling of methyl groups belonging to several guest molecules (toluene, p-xylene, ?-picoline) incarcerated in a host calixarene matrix. In all the cases investigated, the low temperature neutron spectra show a number of bands which may be interpreted as being due to transitions between tunnel-split librational states of the guest methyl groups. The main line occurs near 0.63meV, very close to the CH 3 quantum free rotor limit. In the toluence complex, the quantum regime persists at least up to 60 K. Effects of coupling between rotational and vibrational modes are discussed. Very subtle structural changes not revealed by diffraction measurements are suggested by the neutron spectroscopy results.

Caciuffo, R.; Amoretti, G.; Carlile, C. J.; Fillaux, F.; Francescangeli, O.; Prager, M.; Ugozzoli, F.

1994-10-01

285

Methylation Profiling Using Methylated DNA Immunoprecipitation and Tiling Array Hybridization  

PubMed Central

DNA methylation is an important epigenetic modification that regulates development and plays a role in the pathophysiology of many diseases. It is dynamically changed during germline development. Methylated DNA immunoprecipitation (MeDIP) is an efficient, cost-effective method for locus-specific and genome-wide analysis. Methylated DNA fragments are enriched by a 5-methylcytidine-recognizing antibody, therefore allowing the analysis of both CpG and non-CpG methylation. The enriched DNA fragments can be amplified and hybridized to tiling arrays covering CpG islands, promoters, or the entire genome. Comparison of different methylomes permits the discovery of differentially methylated regions that might be important in disease- or tissue-specific expression. Here, we describe an established MeDIP protocol and tiling array hybridization method for profiling methylation of testicular germ cells.

Cheung, Hoi-Hung; Lee, Tin-Lap; Rennert, Owen M.; Chan, Wai-Yee

2013-01-01

286

Cytosine methylation regulates oviposition in the pathogenic blood fluke Schistosoma mansoni  

Microsoft Academic Search

Similar to other metazoan pathogens, Schistosoma mansoni undergoes transcriptional and developmental regulation during its complex lifecycle and host interactions. DNA methylation as a mechanism to control these processes has, to date, been discounted in this parasite. Here we show the first evidence for cytosine methylation in the S. mansoni genome. Transcriptional coregulation of novel DNA methyltransferase (SmDnmt2) and methyl-CpG-binding domain

Kathrin K. Geyer; Carlos M. Rodríguez López; Iain W. Chalmers; Sabrina E. Munshi; Martha Truscott; James Heald; Mike J. Wilkinson; Karl F. Hoffmann

2011-01-01

287

Catalytic reaction of methyl diazoacetate with 1-methyl-2-alkenylpyrroles  

Microsoft Academic Search

1.The reaction of 1-methyl-2-alkenylpyrroles with methyl diazoacetate at 20–50°C in the presence of CuCl leads to the formation of both adducts of the carbene at the exocyclic double bond, namely, esters of (1-methyl-2-pyrrolyl)cyclopropanecarboxylic acids, and the products of the insertion of the carbene at the 5- and 4-C-H bonds of the pyrrole ring.2.The competitive reactions method was used to show

V. M. Shostakovskii; A. U. Musaev; A. E. Vasil'vitskii; A. M. Guliev; O. M. Nefedov

1989-01-01

288

Regulation of p53 activity through lysine methylation.  

PubMed

p53 is a tumour suppressor that regulates the cellular response to genotoxic stresses. p53 is a short-lived protein and its activity is regulated mostly by stabilization via different post-translational modifications. Here we report a novel mechanism of p53 regulation through lysine methylation by Set9 methyltransferase. Set9 specifically methylates p53 at one residue within the carboxyl-terminus regulatory region. Methylated p53 is restricted to the nucleus and the modification positively affects its stability. Set9 regulates the expression of p53 target genes in a manner dependent on the p53-methylation site. The crystal structure of a ternary complex of Set9 with a p53 peptide and the cofactor product S-adenosyl-l-homocysteine (AdoHcy) provides the molecular basis for recognition of p53 by this lysine methyltransferase. PMID:15525938

Chuikov, Sergei; Kurash, Julia K; Wilson, Jonathan R; Xiao, Bing; Justin, Neil; Ivanov, Gleb S; McKinney, Kristine; Tempst, Paul; Prives, Carol; Gamblin, Steven J; Barlev, Nickolai A; Reinberg, Danny

2004-11-18

289

O-Carbonyl-Assisted Alkaline Hydrolyses of Methyl Benzoates.  

National Technical Information Service (NTIS)

The rates of alkaline hydrolysis of methyl 6-methyl-2-benzoylbenzoate, methyl 6-methyl-2-acetylbenzoate, methyl 6-chloro-2-benzoylbenzoate, methyl 6-chloro-2-acetylbenzoate, and the 6-unsubstituted analogs have been measured. In each case the 6-substitute...

M. S. Newman A. L. Leegwater

1968-01-01

290

DNA methylation in mouse testes.  

PubMed

DNA methylation of retrotransposons and imprinted genes is accurately regulated in spermatogenesis. In particular, CpG methylation of long interspersed elements-1 (LINE1 or L1) and intracisternal A-particle (IAP) retrotransposons during spermatogenesis has been well characterized. CpG methylation of the regulatory regions of retrotransposons is acquired during embryonic testis development; however, reductions of DNA methylation in LINE1 and/or IAP and/or Rasgrf1, which is an imprinted gene, are observed in deficient mice of piRNA biogenesis concerning. Here, we describe two methods, bisulfite sequencing and Southern blotting using a methylation-sensitive restriction enzyme, for analysis of DNA methylation of LINE1, IAP, and imprinted genes in mouse testes. PMID:24178559

Kuramochi-Miyagawa, Satomi; Kita-Kojima, Kanako; Shiromoto, Yusuke; Ito, Daisuke; Koshima, Hirotaka; Nakano, Toru

2014-01-01

291

Different measures of "genome-wide" DNA methylation exhibit unique properties in placental and somatic tissues  

PubMed Central

DNA methylation of CpGs located in two types of repetitive elements—LINE1 (L1) and Alu—is used to assess “global” changes in DNA methylation in studies of human disease and environmental exposure. L1 and Alu contribute close to 30% of all base pairs in the human genome and transposition of repetitive elements is repressed through DNA methylation. Few studies have investigated whether repetitive element DNA methylation is associated with DNA methylation at other genomic regions, or the biological and technical factors that influence potential associations. Here, we assess L1 and Alu DNA methylation by Pyrosequencing of consensus sequences and using subsets of probes included in the Illumina Infinium HumanMethylation27 BeadChip array. We show that evolutionary age and assay method affect the assessment of repetitive element DNA methylation. Additionally, we compare Pyrosequencing results for repetitive elements to average DNA methylation of CpG islands, as assessed by array probes classified into strong, weak and non-islands. We demonstrate that each of these dispersed sequences exhibits different patterns of tissue-specific DNA methylation. Correlation of DNA methylation suggests an association between L1 and weak CpG island DNA methylation in some of the tissues examined. We caution, however, that L1, Alu and CpG island DNA methylation are distinct measures of dispersed DNA methylation and one should not be used in lieu of another. Analysis of DNA methylation data is complex and assays may be influenced by environment and pathology in different or complementary ways.

Price, E. Magda; Cotton, Allison M.; Penaherrera, Maria S.; McFadden, Deborah E.; Kobor, Michael S.; Robinson, Wendy

2012-01-01

292

Genomics of CpG methylation in developing and developed zebrafish.  

PubMed

DNA methylation is a dynamic process through which specific chromatin modifications can be stably transmitted from parent to daughter cells. A large body of work has suggested that DNA methylation influences gene expression by silencing gene promoters. However, these conclusions were drawn from data focused mostly on promoter regions. Regarding the entire genome, it is unclear how methylation and gene transcription patterns are related during vertebrate development. To identify the genome-wide distribution of CpG methylation, we created series of high-resolution methylome maps of Danio rerio embryos during development and in mature, differentiated tissues. We found that embryonic and terminal tissues have unique methylation signatures in CpG islands and repetitive sequences. Fully differentiated tissues have increased CpG and LTR methylation and decreased SINE methylation relative to embryonic tissues. Unsupervised clustering analyses reveal that the embryonic and terminal tissues can be classified solely by their methylation patterning. Novel analyses also identify a previously undescribed genome-wide exon methylation signature. We also compared whole genome methylation with genome-wide mRNA expression levels using publicly available RNA-seq datasets. These comparisons revealed previously unrecognized relationships between gene expression, alternative splicing, and exon methylation. Surprisingly, we found that exonic methylation is a better predictor of mRNA expression level than promoter methylation. We also found that transcriptionally skipped exons have significantly less methylation than retained exons. Our integrative analyses reveal highly complex interplay between gene expression, alternative splicing, development, and methylation patterning in zebrafish. PMID:24657902

McGaughey, David M; Abaan, Hatice Ozel; Miller, Ryan M; Kropp, Peter A; Brody, Lawrence C

2014-01-01

293

Electrochemical strategy for sensing DNA methylation and DNA methyltransferase activity.  

PubMed

The present work demonstrates a novel signal-off electrochemical method for the determination of DNA methylation and the assay of methyltransferase activity using the electroactive complex [Ru(NH3)6](3+) (RuHex) as a signal transducer. The assay exploits the electrostatic interactions between RuHex and DNA strands. Thiolated single strand DNA1 was firstly self-assembled on a gold electrode via Au-S bonding, followed by hybridization with single strand DNA2 to form double strand DNA containing specific recognition sequence of DNA adenine methylation MTase and methylation-responsive restriction endonuclease Dpn I. The double strand DNA may adsorb lots of electrochemical species ([Ru(NH3)6](3+)) via the electrostatic interaction, thus resulting in a high electrochemical signal. In the presence of DNA adenine methylation methyltransferase and S-adenosyl-l-methionine, the formed double strand DNA was methylated by DNA adenine methylation methyltransferase, then the double strand DNA can be cleaved by methylation-responsive restriction endonuclease Dpn I, leading to the dissociation of a large amount of signaling probes from the electrode. As a result, the adsorption amount of RuHex reduced, resulting in a decrease in electrochemical signal. Thus, a sensitive electrochemical method for detection of DNA methylation is proposed. The proposed method yielded a linear response to concentration of Dam MTase ranging from 0.25 to 10UmL(-1) with a detection limit of 0.18UmL(-1) (S/N=3), which might promise this method as a good candidate for monitoring DNA methylation in the future. PMID:23473252

Wang, Gang Lin; Zhou, Long Yin; Luo, Hong Qun; Li, Nian Bing

2013-03-20

294

Quantitative reconstruction of leukocyte subsets using DNA methylation  

PubMed Central

Background Cell lineage-specific DNA methylation patterns distinguish normal human leukocyte subsets and can be used to detect and quantify these subsets in peripheral blood. We have developed an approach that uses DNA methylation to simultaneously quantify multiple leukocyte subsets, enabling investigation of immune modulations in virtually any blood sample including archived samples previously precluded from such analysis. Here we assess the performance characteristics and validity of this approach. Results Using Illumina Infinium HumanMethylation27 and VeraCode GoldenGate Methylation Assay microarrays, we measure DNA methylation in leukocyte subsets purified from human whole blood and identify cell lineage-specific DNA methylation signatures that distinguish human T cells, B cells, NK cells, monocytes, eosinophils, basophils and neutrophils. We employ a bioinformatics-based approach to quantify these cell types in complex mixtures, including whole blood, using DNA methylation at as few as 20 CpG loci. A reconstruction experiment confirms that the approach could accurately measure the composition of mixtures of human blood leukocyte subsets. Applying the DNA methylation-based approach to quantify the cellular components of human whole blood, we verify its accuracy by direct comparison to gold standard immune quantification methods that utilize physical, optical and proteomic characteristics of the cells. We also demonstrate that the approach is not affected by storage of blood samples, even under conditions prohibiting the use of gold standard methods. Conclusions Cell mixture distributions within peripheral blood can be assessed accurately and reliably using DNA methylation. Thus, precise immune cell differential estimates can be reconstructed using only DNA rather than whole cells.

2014-01-01

295

Methylated genes in breast cancer  

PubMed Central

Background Hundreds of hypermethylated genes have been described in breast cancer, yet the nature and contribution of these genes in their methylated state to overall risk and prognosis is under-characterized in non-sporadic breast cancers. We therefore compared associations of DNA methylation with tumor stage, hormone/growth receptor status and clinical outcomes in a familial breast cancer cohort. Because few previous methylation studies have considered the oncogenic or tumor suppressor properties of their gene sets, this functional status was included as part of our correlative analysis. Results We found methylation of oncogenes was associated with better prognostic indicators, whereas tumor suppressor gene methylation was associated with a more severe phenotype in women that were either HER2+ or lymph node positive at diagnosis, and/or tended to recur or develop distant metastases. For example, the methylation of the tumor suppressor gene APC was strongly associated with a specific subset of tumors that were both ER+ and HER2+, while methylation of the TWIST oncogene was associated with breast cancers that did not metastasize. Methods This was a retrospective, hospital-based study of n = 99 archival breast tumors derived from women with a germline genetic BRCA1 or BRCA2 mutation and/or familial breast cancer history. DNA methylation was quantified from formalin fixed, paraffin embedded tumors using the established protocol of quantitative multiplex-methylation specific PCR (QM-MSP). Non-parametric statistics were used to analyze candidate gene methylation in association with clinical outcomes. Conclusion We report several novel, positive associations between percent methylation of the APC, RASSF1A, TWIST, ER?, CDH1 and Cyclin D2 genes and key variables such as tumor stage, hormone and growth receptor status, and a history of recurrent or metastatic disease. Our data suggest the potential utility of parsing gene methylation by functional status and breast tumor subtype.

Vang, Russell; Blackford, Amanda; Fackler, Mary Jo

2011-01-01

296

Antagonism between DNA and H3K27 Methylation at the Imprinted Rasgrf1 Locus  

PubMed Central

At the imprinted Rasgrf1 locus in mouse, a cis-acting sequence controls DNA methylation at a differentially methylated domain (DMD). While characterizing epigenetic marks over the DMD, we observed that DNA and H3K27 trimethylation are mutually exclusive, with DNA and H3K27 methylation limited to the paternal and maternal sequences, respectively. The mutual exclusion arises because one mark prevents placement of the other. We demonstrated this in five ways: using 5-azacytidine treatments and mutations at the endogenous locus that disrupt DNA methylation; using a transgenic model in which the maternal DMD inappropriately acquired DNA methylation; and by analyzing materials from cells and embryos lacking SUZ12 and YY1. SUZ12 is part of the PRC2 complex, which is needed for placing H3K27me3, and YY1 recruits PRC2 to sites of action. Results from each experimental system consistently demonstrated antagonism between H3K27me3 and DNA methylation. When DNA methylation was lost, H3K27me3 encroached into sites where it had not been before; inappropriate acquisition of DNA methylation excluded normal placement of H3K27me3, and loss of factors needed for H3K27 methylation enabled DNA methylation to appear where it had been excluded. These data reveal the previously unknown antagonism between H3K27 and DNA methylation and identify a means by which epigenetic states may change during disease and development.

McLean, Chelsea M.; Dokshin, Gregoriy A.; Persson, Jenna M.; Herman, Herry; Pasini, Diego; Miro, Xavier; Donohoe, Mary E.; Lee, Jeannie T.; Helin, Kristian; Soloway, Paul D.

2008-01-01

297

Interstellar methyl mercaptan  

NASA Technical Reports Server (NTRS)

Methyl mercaptan (CH3SH) has been identified in Sgr B2 from observations of six lines in its millimeter-wave spectrum. The CH3SH rotational temperature and column density in Sgr B2 are T(rot) = 9 plus or minus 3 K and N = 1.5 plus or minus 0.2 x 10 to the 14th per sq cm, respectively. The CH3SH/CH3OH ratio is apparently not greatly different from the cosmic S/O ratio.

Linke, R. A.; Frerking, M. A.; Thaddeus, P.

1979-01-01

298

Fluorine-induced chemiluminescence detection of biologically methylated tellurium, selenium, and sulfur compounds  

Microsoft Academic Search

The sensitive detection of volatile, methylated selenium and tellurium compounds based on capillary gas chromatography coupled to fluorine-induced chemiluminescence detection is described. The method requires no sample derivatization, and the detection limits for selenides and tellurides (low pg range) are the lowest reported to date. This technique can resolve and speciate complex mixtures of methylated tellurium, selenium, and sulfur gases

T. G. Chasteen; G. M. Silver; J. W. Birks; R. Fall

1990-01-01

299

Novel mixed ligand complexes of bioactive Schiff base (E)-4-(phenyl (phenylimino) methyl) benzene-1,3-diol and 2-aminophenol/2-aminobenzoic acid: Synthesis, spectral characterization, antimicrobial and nuclease studies  

NASA Astrophysics Data System (ADS)

A novel bidentate Schiff base ligand has been synthesized using 2,4-dihydroxybenzophenone and aniline. Its mixed ligand complexes of MAB type [M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); HA = Schiff base and B = 2-aminophenol/2-aminobenzoic acid] have been synthesized and characterized on the basis of spectral data UV-Vis, IR, 1H NMR, FAB-Mass, EPR, SEM and magnetic studies. All the complexes were soluble in DMF and DMSO. Elemental analysis and molar conductance values indicate that the complexes are non-electrolytes. HA binds with M(II) ions through azomethine and deprotonated phenolic group and B binds through the primary amine group and deprotonated phenolic/carboxylic groups. Using FAB-Mass the cleavage pattern of the ligand (HA) has been established. All the complexes adopt octahedral geometry around the metal ions. It has been confirmed with the help of UV-Vis, IR, 1H NMR and FAB-Mass spectral data. DNA binding activities of the complexes 1d and 2d are studied by UV-Vis spectroscopy and cleavage studies of Schiff base ligand and its complexes 1d and 2d have been by agarose gel electrophoresis method. In vitro biological activities of the free ligand (HA) and their metal complexes (1a-1e and 2a-2e) were screened against few bacteria, Escherichia coli, Staphylococcus saphyphiticus, Staphylococcus aureus, Pseudomonas aeruginosa and fungi Aspergillus niger, Enterobacter species, Candida albicans by well diffusion technique.

Subbaraj, P.; Ramu, A.; Raman, N.; Dharmaraja, J.

2014-01-01

300

Novel mixed ligand complexes of bioactive Schiff base (E)-4-(phenyl (phenylimino) methyl) benzene-1,3-diol and 2-aminophenol/2-aminobenzoic acid: synthesis, spectral characterization, antimicrobial and nuclease studies.  

PubMed

A novel bidentate Schiff base ligand has been synthesized using 2,4-dihydroxybenzophenone and aniline. Its mixed ligand complexes of MAB type [M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); HA=Schiff base and B=2-aminophenol/2-aminobenzoic acid] have been synthesized and characterized on the basis of spectral data UV-Vis, IR, (1)H NMR, FAB-Mass, EPR, SEM and magnetic studies. All the complexes were soluble in DMF and DMSO. Elemental analysis and molar conductance values indicate that the complexes are non-electrolytes. HA binds with M(II) ions through azomethine and deprotonated phenolic group and B binds through the primary amine group and deprotonated phenolic/carboxylic groups. Using FAB-Mass the cleavage pattern of the ligand (HA) has been established. All the complexes adopt octahedral geometry around the metal ions. It has been confirmed with the help of UV-Vis, IR, (1)H NMR and FAB-Mass spectral data. DNA binding activities of the complexes 1d and 2d are studied by UV-Vis spectroscopy and cleavage studies of Schiff base ligand and its complexes 1d and 2d have been by agarose gel electrophoresis method. In vitro biological activities of the free ligand (HA) and their metal complexes (1a-1e and 2a-2e) were screened against few bacteria, Escherichia coli, Staphylococcus saphyphiticus, Staphylococcus aureus, Pseudomonas aeruginosa and fungi Aspergillus niger, Enterobacter species, Candida albicans by well diffusion technique. PMID:23981416

Subbaraj, P; Ramu, A; Raman, N; Dharmaraja, J

2014-01-01

301

Crystal structure and vibrational spectra of 2-chloromethyl-5-hydroxy-4 H-pyran-4-one and 5-hydroxy-2-methyl-4 H-pyran-4-one as potential ligands for Fe(III) complexes  

NASA Astrophysics Data System (ADS)

The title compounds form octahedral bidentate complexes with iron(III). Both the ligands and the complexes exhibit biological activity. The complexes may form isomers of fac or mer configuration. To predict the complex configuration, the structures of chlorokojic acid and allomaltol were determined and their vibrational spectra were analysed. The structure of chlorokojic acid, C 6H 5ClO 3, was solved in the polar space group Pna2 1 (ITC No. 33) and that of allomaltol, C 6H 6O 3, in centrosymmetric space group P1¯ (ITC No. 2). The characteristic features of both structures are molecular ribbons but of different origin. In the case of chlorokojic acid, the ribbons are formed of molecules related by twofold screw axis and linked by H-bonds of O sbnd H⋯O type. In allomaltol, the ribbons are built of centrosymmetric dimers joined by the weak interactions of C sbnd H⋯O type. The normal modes of vibration have been calculated by means of the density functional theory method B3LYP and the 6-31+G ?? basis set. The results were used for the vibrational analysis of both compounds. The theoretical spectra are in agreement with the experimental ones. The detailed inspection of the results obtained led to conclusion that allomaltol should form fac complexes with iron(III) in analogy to kojic acid, whereas for chlorokojic acid the mer isomer might be expected.

Hryniewicz, Katarzyna; Stadnicka, Katarzyna; Pattek-Janczyk, Agnieszka

2009-02-01

302

Neural Tube Defects, Folic Acid and Methylation  

PubMed Central

Neural tube defects (NTDs) are common complex congenital malformations resulting from failure of the neural tube closure during embryogenesis. It is established that folic acid supplementation decreases the prevalence of NTDs, which has led to national public health policies regarding folic acid. To date, animal studies have not provided sufficient information to establish the metabolic and/or genomic mechanism(s) underlying human folic acid responsiveness in NTDs. However, several lines of evidence suggest that not only folates but also choline, B12 and methylation metabolisms are involved in NTDs. Decreased B12 vitamin and increased total choline or homocysteine in maternal blood have been shown to be associated with increased NTDs risk. Several polymorphisms of genes involved in these pathways have also been implicated in risk of development of NTDs. This raises the question whether supplementation with B12 vitamin, betaine or other methylation donors in addition to folic acid periconceptional supplementation will further reduce NTD risk. The objective of this article is to review the role of methylation metabolism in the onset of neural tube defects.

Imbard, Apolline; Benoist, Jean-Francois; Blom, Henk J.

2013-01-01

303

Synthesis, characterization and antitumor activity of polymeric copper(II) complexes with thiosemicarbazones of 3-methyl-5-oxo-1-phenyl-3-pyrazolin-4-carboxaldehyde and 5-oxo-3-phenyl-3-pyrazolin-4-carboxaldehyde.  

PubMed

New polymeric copper(II) complexes with two tridentate ONS thiosemicarbazone ligands containing substituted pyrazolone moiety were synthesized and characterized by means of spectroscopic, electrochemical and crystallographic techniques. While both ligands exist as different tautomers in the solid state and DMSO-d(6) solution, Cu(II) ion coordinates the ligands from the same tautomeric form with square-pyramidal geometry around each Cu atom. In the crystal structures, the copper(II) complex cation forms polymeric chains {[Cu(L)Cl](+)}(n) with a bridging chlorine atom. One of the complexes was found to have a significantly higher cytotoxic potential in comparison with cisplatin in inhibition of several cell lines (HL60, REH, C6, L929 and B16). The results obtained on the basis of flow cytometry indicated that apoptosis could be possible mechanism of cell death. PMID:21955843

Leovac, Vukadin M; Bogdanovi?, Goran A; Jovanovi?, Ljiljana S; Joksovi?, Ljubinka; Markovi?, Violeta; Joksovi?, Milan D; Den?i?, Sonja Misirli?; Isakovi?, An?elka; Markovi?, Ivanka; Heinemann, Frank W; Trifunovi?, Sre?ko; ?alovi?, Ivica

2011-11-01

304

Synthesis and structural characterization of molybdenum(VI) and iron(II) coordination compounds with S-alkyl-N-methyl-S-(2-pyridyl)sulfoximines and catalytic epoxidation activity of the molybdenum complexes.  

PubMed

Coordination compounds oxido(diperoxido)(S-butyl-N-methyl-S-(2-pyridyl)sulfoximine)molybdenum(VI), [MoO(O2)2{SO(NMe)(n)Bu(NC5H4)}] (5c), and bis{(dichlorido)(N,S-dimethyl-2-pyridylsulfoximine)iron(II)}, tetrahydrofuran solvate (1:1) (6), [FeCl2{SO(NMe)Me(NC5H4)}]2·THF are prepared from the free ligand 4 and molybdenum(VI) oxidediperoxide(dihydrate) and iron dichloride, respectively. The crystal structures reveal a trigonal bipyramid with the pyridine ring and the single oxygen on molybdenum in a trans arrangement for 5c and a planar ?(2)-Cl2Fe2 ring with trans-oriented exocyclic Cl atoms for 6 whereas the structures of the N,N-dicoordinated ligands are only little effected by the metals. Coordination compounds (5) efficiently catalyze the epoxidation of cyclooctene or of monosubstituted alkenes by tert-butyl hydroperoxide. PMID:24180337

Brussaard, Yvonne; Olbrich, Falk; Schaumann, Ernst

2013-11-18

305

Synthesis and cholinergic affinity of diastereomeric and enantiomeric isomers of 1-methyl-2-(2-methyl-1,3-dioxolan-4-yl)- pyrrolidine, 1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine and of Their iodomethylates  

Microsoft Academic Search

Four out of the eight possible stereoisomers of 1-methyl-2-(2-methyl-1,3-dioxolan-4-yl)pyrrolidine, 1-methyl-2-(2-methyl-1,3-oxathiolan-5-yl)pyrrolidine and the corresponding iodomethylates have been synthesised. They were formally derived from hybridisation of potent though unselective agonists studied before, such as 1,3-dioxolane 1 and 1,3-oxathiolane 2, with the structure of nicotine. It was expected that, by exalting the molecular complexity of the parent compounds, in particular through stereochemical complication

Silvia Dei; Cristina Bellucci; Michela Buccioni; Marta Ferraroni; Fulvio Gualtieri; Luca Guandalini; Dina Manetti; Rosanna Matucci; Maria Novella Romanelli; Serena Scapecchi; Elisabetta Teodori

2003-01-01

306

Erasing the methyl mark: histone demethylases at the center of cellular differentiation and disease  

PubMed Central

The enzymes catalyzing lysine and arginine methylation of histones are essential for maintaining transcriptional programs and determining cell fate and identity. Until recently, histone methylation was regarded irreversible. However, within the last few years, several families of histone demethylases erasing methyl marks associated with gene repression or activation have been identified, underscoring the plasticity and dynamic nature of histone methylation. Recent discoveries have revealed that histone demethylases take part in large multiprotein complexes synergizing with histone deacetylases, histone methyltransferases, and nuclear receptors to control developmental and transcriptional programs. Here we review the emerging biochemical and biological functions of the histone demethylases and discuss their potential involvement in human diseases, including cancer.

Cloos, Paul A.C.; Christensen, Jesper; Agger, Karl; Helin, Kristian

2008-01-01

307

DNA methylation and human disease  

Microsoft Academic Search

DNA methylation is a crucial epigenetic modification of the genome that is involved in regulating many cellular processes. These include embryonic development, transcription, chromatin structure, X chromosome inactivation, genomic imprinting and chromosome stability. Consistent with these important roles, a growing number of human diseases have been found to be associated with aberrant DNA methylation. The study of these diseases has

Keith D. Robertson

2005-01-01

308

Molecular Structure of Methyl benzoate  

NSDL National Science Digital Library

Methyl benzoate is used mainly as a perfume; it has a very pleasant smell and mixes well with scents of ylang ylang, musk, rose, and geranium. Methyl benzoate also acts as a solvent for cellulose esters, as a dying carrier, disinfectant additive, penetrating agent, and as a pesticide.

2002-10-11

309

DNA Methylation and Gene Function  

Microsoft Academic Search

In most higher organisms, DNA is modified after synthesis by the enzymatic conversion of many cytosine residues to 5-methylcytosine. For several years, control of gene activity by DNA methylation has been recognized as a logically attractive possibility, but experimental support has proved elusive. However, there is now reason to believe, from recent studies, that DNA methylation is a key element

Aharon Razin; Arthur D. Riggs

1980-01-01

310

DNA Methylation in the Malignant Transformation of Meningiomas  

PubMed Central

Meningiomas are central nervous system tumors that originate from the meningeal coverings of the brain and spinal cord. Most meningiomas are pathologically benign or atypical, but 3–5% display malignant features. Despite previous studies on benign and atypical meningiomas, the key molecular pathways involved in malignant transformation remain to be determined, as does the extent of epigenetic alteration in malignant meningiomas. In this study, we explored the landscape of DNA methylation in ten benign, five atypical and four malignant meningiomas. Compared to the benign tumors, the atypical and malignant meningiomas demonstrate increased global DNA hypomethylation. Clustering analysis readily separates malignant from atypical and benign tumors, implicating that DNA methylation patterns may serve as diagnostic biomarkers for malignancy. Genes with hypermethylated CpG islands in malignant meningiomas (such as HOXA6 and HOXA9) tend to coincide with the binding sites of polycomb repressive complexes (PRC) in early developmental stages. Most genes with hypermethylated CpG islands at promoters are suppressed in malignant and benign meningiomas, suggesting the switching of gene silencing machinery from PRC binding to DNA methylation in malignant meningiomas. One exception is the MAL2 gene that is highly expressed in benign group and silenced in malignant group, representing de novo gene silencing induced by DNA methylation. In summary, our results suggest that malignant meningiomas have distinct DNA methylation patterns compared to their benign and atypical counterparts, and that the differentially methylated genes may serve as diagnostic biomarkers or candidate causal genes for malignant transformation.

Gao, Fan; Shi, Lingling; Russin, Jonathan; Zeng, Liyun; Chang, Xiao; He, Shuhan; Chen, Thomas C.; Giannotta, Steven L.; Weisenberger, Daniel J.; Zada, Gabriel; Mack, William J.; Wang, Kai

2013-01-01

311

A Search for Methyl Acetate in Hot Cores  

NASA Astrophysics Data System (ADS)

We propose to search for methyl acetate, CH3COOCH3, in high mass hot cores. Methyl acetate is possibly synthesized through multiple reaction pathways from molecules previously detected in hot cores, most notably from acetic acid and methanol via esterification. Esterification, beyond the formation of methyl formate, has not yet been observed in the ISM. The project is already underway in nothern sources based on millimeter data from the Caltech Submillimeter Observatory (CSO). We hope to study the chemically rich southern source G327.3 (decl B1950=-54.49'15.6"), amongst others, using MOPRA and to search for acetic acid and methyl acetate. Observations are supported by laboratory studies of methyl acetate in the 3 mm and 1 mm and successful spectral fitting by the Blake group at Caltech. If detected, methyl acetate, consisting of 11 atoms, would be one of the larger complex organic molecules detected in the interstellar medium and could point to previously unconsidered reaction mechanisms.

Kelley, Matthew; Braakman, Rogier; Blake, Geoffrey

2006-10-01

312

Torsional motions in methyl glycolate  

NASA Astrophysics Data System (ADS)

Microwave spectra of the ground state and nine torsionally excited states and the far-infrared spectrum of methyl glycolate are reported and analyzed in terms of a flexible model involving the methyl and two skeletal torsional modes. The shifts of methyl torsional A-state rotational constants relative to the ground state observed for a series of torsionally excited states, the methyl torsional A- E splittings for the ground state and five torsionally excited states, and 10 observed skeletal torsional far-infrared transition frequencies have been used to derive three structural relaxation parameters and nine potential energy parameters. As an unexpected nonlocal interaction, a sizable coupling has been obtained between the methyl torsion and the torsion about the C?C bond, which changes the direction of the intramolecular hydrogen bond.

Meyer, R.; Caminati, W.; Hollenstein, H.

1989-09-01

313

Methods of DNA methylation detection  

NASA Technical Reports Server (NTRS)

The present invention provides for methods of DNA methylation detection. The present invention provides for methods of generating and detecting specific electronic signals that report the methylation status of targeted DNA molecules in biological samples.Two methods are described, direct and indirect detection of methylated DNA molecules in a nano transistor based device. In the direct detection, methylated target DNA molecules are captured on the sensing surface resulting in changes in the electrical properties of a nano transistor. These changes generate detectable electronic signals. In the indirect detection, antibody-DNA conjugates are used to identify methylated DNA molecules. RNA signal molecules are generated through an in vitro transcription process. These RNA molecules are captured on the sensing surface change the electrical properties of nano transistor thereby generating detectable electronic signals.

Maki, Wusi Chen (Inventor); Filanoski, Brian John (Inventor); Mishra, Nirankar (Inventor); Rastogi, Shiva (Inventor)

2010-01-01

314

Histone methylation in myelodysplastic syndromes  

PubMed Central

Histone methylation is a type of epigenetic modification that is critical for the regulation of gene expression. Numerous studies have demonstrated that abnormalities of this newly characterized epigenetic modification are involved in the development of multiple diseases, including cancer. There is also emerging evidence for a link between histone methylation and the pathogenesis of myeloid neoplasms, including myelodysplastic syndromes (MDS). This article provides an overview of recent progress in the studies of histone methylation in myeloid malignancies, with an emphasis on MDS. We cover each type of histone methylation modification and their regulatory mechanisms, as well as their abnormalities in MDS or potential connections to MDS. We also summarize the recent progress in the development of inhibitors targeting histone methylation and their applications as potential therapeutic agents.

Wei, Yue; Ganan-Gomez, Irene; Salazar-Dimicoli, Sophie; McCay, Sara L.; Garcia-Manero, Guillermo

2013-01-01

315

4,4'-, 5,5'-, and 6,6'-dimethyl-2,2'-bipyridyls: The structures, phase transitions, vibrations, and methyl group tunneling of their complexes with chloranilic acid  

NASA Astrophysics Data System (ADS)

The crystal and molecular structures of 4,4'- and 6,6'-dimethyl-2,2'-bipyridyl complexes with 2,5-dichloro-3,6-dihydroxy-p-benzoquinone (chloranilic acid, CLA) have been determined and compared with those of the complex with the 5,5'-derivative, which is known to possess interesting antiferroelectric properties. In the crystalline state, all three compounds form hydrogen bonded chains with N+-H...O- and O-H...N bridges on both sides of the bipyridyl constituent. The comparison of three derivatives indicates that the N+-H...O- hydrogen bonds are shortest for the 5,5'-dimethyl complex. The 4,4'- and 6,6'-derivatives do not show any ferroelectric feature. The 6,6'-one is, however, characterized by a continuous phase transition, revealed in the differential scanning calorimetry, dilatometric, and dielectric characteristics. The tunneling splitting measured by neutron backscattering in the energy range +/-30 ?eV for the neat dimethyl bipyridyls and their complexes with CLA indicates that the different splittings are primarily due to the crystal packing effect and that charge transfer between interacting compounds plays only a minor role.

Bator, G.; Sawka-Dobrowolska, W.; Sobczyk, L.; Grech, E.; Nowicka-Scheibe, J.; Pawlukoj?, A.; Wuttke, J.; Baran, J.; Owczarek, M.

2011-07-01

316

Methyl Halide Production by Fungi  

NASA Astrophysics Data System (ADS)

Methyl chloride (CH3Cl), methyl bromide (CH3Br) and methyl iodide (CH3I) are methyl halide gases that contribute significant amounts of halogen radicals to the atmosphere. In an effort to better understand the global budget of methyl halides and their impact on the atmosphere, we need to identify the natural sources in addition to the known anthropogenic sources of these compounds. We are investigating the role of fungi in the production of methyl halides in the soils and wetlands in southern New Hampshire, USA. Previous research has shown that wood decay fungi and ectomycorrhizal fungi, which are within a group of fungi called basidiomycetes, emit methyl halides. In our study, measurements of headspace gas extracted from flasks containing fungi grown in culture demonstrate that a variety of fungi, including basidiomycetes and non-basidiomycetes, emit methyl halides. Our research sites include four ecosystems: an agricultural field, a temperate forest, a fresh water wetland, and coastal salt marshes. We have collected and isolated fungi at each site by culturing tissue samples of fruiting bodies and plant material, by using wood baits, and from the direct culture of soil. We compared the rates of methyl halide emissions from the fungi in the four ecosystems. In addition, we measured emissions from previously assayed fungal isolates after reintroducing them to sterilized soils that were collected from their original environments. Fungal biomass was determined by substrate-induced respiration (SIR). The emission rate by the fungus was determined by a linear regression of the concentration of methyl halide in the sample headspace over time divided by the fungal biomass.

Dailey, G. D.; Varner, R. K.; Blanchard, R. O.; Sive, B. C.; Crill, P. M.

2005-12-01

317

Epigenome-wide inheritance of cytosine methylation variants in a recombinant inbred population  

PubMed Central

Cytosine DNA methylation is one avenue for passing information through cell divisions. Here, we present epigenomic analyses of soybean recombinant inbred lines (RILs) and their parents. Identification of differentially methylated regions (DMRs) revealed that DMRs mostly cosegregated with the genotype from which they were derived, but examples of the uncoupling of genotype and epigenotype were identified. Linkage mapping of methylation states assessed from whole-genome bisulfite sequencing of 83 RILs uncovered widespread evidence for local methylQTL. This epigenomics approach provides a comprehensive study of the patterns and heritability of methylation variants in a complex genetic population over multiple generations, paving the way for understanding how methylation variants contribute to phenotypic variation.

Schmitz, Robert J.; He, Yupeng; Valdes-Lopez, Oswaldo; Khan, Saad M.; Joshi, Trupti; Urich, Mark A.; Nery, Joseph R.; Diers, Brian; Xu, Dong; Stacey, Gary; Ecker, Joseph R.

2013-01-01

318

Accounting for Population Stratification in DNA Methylation Studies  

PubMed Central

DNA methylation is an important epigenetic mechanism that has been linked to complex disease and is of great interest to researchers as a potential link between genome, environment, and disease. As the scale of DNA methylation association studies approaches that of genome-wide association studies (GWAS), issues such as population stratification will need to be addressed. It is well-documented that failure to adjust for population stratification can lead to false positives in genetic association studies, but population stratification is often unaccounted for in DNA methylation studies. Here, we propose several approaches to correct for population stratification using principal components from different subsets of genome-wide methylation data. We first illustrate the potential for confounding due to population stratification by demonstrating widespread associations between DNA methylation and race in 388 individuals (365 African American and 23 Caucasian). We subsequently evaluate the performance of our principal-components approaches and other methods in adjusting for confounding due to population stratification. Our simulations show that 1) all of the methods considered are effective at removing inflation due to population stratification, and 2) maximum power can be obtained with SNP-based principal components, followed by methylation-based principal components, which out-perform both surrogate variable analysis and genomic control. Among our different approaches to computing methylation-based principal components, we find that principal components based on CpG sites chosen for their potential to proxy nearby SNPs can provide a powerful and computationally efficient approach to adjustment for population stratification in DNA methylation studies when genome-wide SNP data are unavailable.

Barfield, Richard T.; Almli, Lynn M.; Kilaru, Varun; Smith, Alicia K.; Mercer, Kristina B.; Duncan, Richard; Klengel, Torsten; Mehta, Divya; Binder, Elisabeth B.; Epstein, Michael P.; Ressler, Kerry J.; Conneely, Karen N.

2014-01-01

319

Synthesis, structural characterization, superoxide dismutase and antimicrobial activities studies of copper (II) complexes with 2-(E)-(2-(2-aminoethylamino) methyl)-4-bromophenol and (19E, 27E)-N1, N2-bis (phenyl (pyridine-2-yl)-methylene)-ethane-1, 2-diamine as ligands  

NASA Astrophysics Data System (ADS)

Three new copper (II) complexes, [Cu(L)(H2O)]ClO4 (1), [Cu(L1)(ClO4)]+ (2) and [Cu(L1)]2+ (3), where HL = 2-(E)-(2-(2-aminoethylamino)methyl)-4-bromophenol, L1 =(19E, 27E)-N1,N2-bis(phenyl(pyridine-2-yl)-methylene)-ethane-1, 2-diamine, have been synthesized and characterized by using various physic-chemical and spectroscopic methods. The solid-state structures of 1 and 2 were determined by single crystal X-ray crystallography. Infrared spectra, ligand field spectra and magnetic susceptibility measurements agree with the observed crystal structures. The molecular structure of copper complexes showed that the ligands occupies the basal plane of square pyramidal geometry with the H2O of 1 or the ClO4 of 2 occupying the remaining apical position. Complexes 1 and 2 crystallize in the monoclinic system of the space group P21/c, a = 10.5948(6)Å, b = 19.6164(11)Å, c = 8.6517(5)Å, ? = 90°, ? = 108.213(2)°, ? = 90° and Z = 4 for 1, a = 9.5019(3)Å, b = 11.3 801(3)Å, c = 25.3168(14)Å, ? = 90°, ? = 100.583(4)°, ? = 90°, and Z = 4 for 2. The synthesized Schiff base (HL/L1) was behaves as tetradentate ON3/N4 ligands with donor groups suitable placed for forming 2 or 3 five membered chelate rings. Copper (II) complexes display X-band EPR spectra in 100% DMSO at 77 K giving g|| > g? > 2.0023 indicating dx2-y2 ground state. The half-wave potential values for Cu (II)/Cu (I) redox couple obtained in the reaction of the copper (II) complexes with molecular oxygen and superoxide radical (O2-) electronegated in DMSO are in agreement with the SOD-like activity of the copper (II) complexes. In vitro antimicrobial activities of the complexes against the two bacteria (Escherichia coli, Salmonella typhi) and the two fungi (Penicillium, Aspergillus sp.) have been investigated comparing with the Schiff base ligands.

Choudhary, Mukesh; Patel, R. N.; Rawat, S. P.

2014-07-01

320

DNA methylation alterations exhibit intraindividual stability and interindividual heterogeneity in prostate cancer metastases.  

PubMed

Human cancers almost ubiquitously harbor epigenetic alterations. Although such alterations in epigenetic marks, including DNA methylation, are potentially heritable, they can also be dynamically altered. Given this potential for plasticity, the degree to which epigenetic changes can be subject to selection and act as drivers of neoplasia has been questioned. We carried out genome-scale analyses of DNA methylation alterations in lethal metastatic prostate cancer and created DNA methylation "cityscape" plots to visualize these complex data. We show that somatic DNA methylation alterations, despite showing marked interindividual heterogeneity among men with lethal metastatic prostate cancer, were maintained across all metastases within the same individual. The overall extent of maintenance in DNA methylation changes was comparable to that of genetic copy number alterations. Regions that were frequently hypermethylated across individuals were markedly enriched for cancer- and development/differentiation-related genes. Additionally, regions exhibiting high consistency of hypermethylation across metastases within individuals, even if variably hypermethylated across individuals, showed enrichment for cancer-related genes. Whereas some regions showed intraindividual metastatic tumor heterogeneity in promoter methylation, such methylation alterations were generally not correlated with gene expression. This was despite a general tendency for promoter methylation patterns to be strongly correlated with gene expression, particularly at regions that were variably methylated across individuals. These findings suggest that DNA methylation alterations have the potential for producing selectable driver events in carcinogenesis and disease progression and highlight the possibility of targeting such epigenome alterations for development of longitudinal markers and therapeutic strategies. PMID:23345608

Aryee, Martin J; Liu, Wennuan; Engelmann, Julia C; Nuhn, Philipp; Gurel, Meltem; Haffner, Michael C; Esopi, David; Irizarry, Rafael A; Getzenberg, Robert H; Nelson, William G; Luo, Jun; Xu, Jianfeng; Isaacs, William B; Bova, G Steven; Yegnasubramanian, Srinivasan

2013-01-23

321

Photodissociation of methyl chloride and methyl bromide in the atmosphere  

NASA Technical Reports Server (NTRS)

Methyl chloride (CH3Cl) and methyl bromide (CH3Br) have been suggested to be significant sources of the stratospheric halogens. The breakup of these compounds in the stratosphere by photodissociation or reaction with OH releases halogen atoms which catalytically destroy ozone. Experimental results are presented for ultraviolet photoabsorption cross sections of CH3Cl and CH3Br. Calculations are presented of loss rates for the methyl halides due to photodissociation and reaction with OH and of mixing ratios of these species in the stratosphere.

Robbins, D. E.

1976-01-01

322

Role of Histone H3 Lysine 27 Methylation in Polycomb-Group Silencing  

Microsoft Academic Search

Polycomb group (PcG) proteins play important roles in maintaining the silent state of HOX genes. Recent studies have implicated histone methylation in long-term gene silencing. However, a connection between PcG-mediated gene silencing and histone methylation has not been established. Here we report the purification and characterization of an EED-EZH2 complex, the human counterpart of the Drosophila ESC-E(Z) complex. We demonstrate

Ru Cao; Liangjun Wang; Hengbin Wang; Li Xia; Hediye Erdjument-Bromage; Paul Tempst; Richard S. Jones; Yi Zhang

2002-01-01

323

A rapid low temperature method for preparation of methyl esters of fatty acids  

Microsoft Academic Search

A rapid method for preparation of methyl esters of fatty acids in lipids has been accomplished by forming the sulfuric acid\\u000a complex of the lipid in ethyl ether at the temp of a dry ice-acetone bath. Decomposition of the complex with methanol results\\u000a in direct formation of methyl esters of the fatty acids. A comparison was made of gas liquid

Gertrude W. McGinnis; L. R. Dugan

1965-01-01

324

Synthesis, crystal structure and properties of the Cu II complex of a tetradentate imidazole-functionalized diazamesocyclic ligand, 1,4-bis( N-1-methylimidazol-2-yl-methyl)-1,4-diazacycloheptane  

NASA Astrophysics Data System (ADS)

A new potential tetradentate ligand, 1,4-bis( N-1-methylimidazol-2-ylmethyl)-1,4-diazacycloheptane ( L), together with its Cu II complex [Cu LCl]ClO 4 ( 1), has been reported. The crystal structure of 1, determined by single-crystal X-ray analysis, shows that it is in chiral P2 12 12 1 space group. The Cu II centre is penta-coordinated in square pyramidal geometry and the diazacycloheptane (DACH) ring adopts normal boat configuration. The most striking feature of this complex is the formation of a 3D network bridged through the C-H⋯Cl hydrogen bonds with the perchlorate anions in the cavities, and stabilized via ?- ? stacking interactions along the a-direction. The solution behaviour of 1 has been further investigated by UV/Vis and ESR techniques.

Du, Miao; Guo, Ya-Mei; Chen, Shen-Tan; Bu, Xian-He

2002-10-01

325

2-Amino-4-(piperidin-1-yl)-11H-pyrimido[4,5-b][1,5]benzodiazepin-6-ium chloride monohydrate and 2-amino-4-[methyl(2-methylphenyl)amino]-11H-pyrimido[4,5-b][1,5]benzodiazepin-6-ium chloride-benzene-1,2-diamine (1/1): complex sheets generated by multiple hydrogen bonds.  

PubMed

In each of 2-amino-4-(piperidin-1-yl)-11H-pyrimido[4,5-b][1,5]benzodiazepin-6-ium chloride monohydrate, C(16)H(19)N(6)(+).Cl(-).H(2)O, (I), and 2-amino-4-[methyl(2-methylphenyl)amino]-11H-pyrimido[4,5-b][1,5]benzodiazepin-6-ium chloride-benzene-1,2-diamine (1/1), C(19)H(19)N(6)(+).Cl(-).C(6)H(8)N(2), (II), the seven-membered ring in the cation adopts a boat conformation. The pyrimidine ring in (II) adopts a twist-boat conformation, but the corresponding ring in (I) is essentially planar. The amino groups of the benzene-1,2-diamine component of (II) are both pyramidal. The independent components of (I) are linked into complex sheets by a combination of N-H...O, N-H...N, N-H...Cl and O-H...Cl hydrogen bonds. In the crystal structure of (II), one N-H...N hydrogen bond and six independent N-H...Cl hydrogen bonds combine to link the components into complex sheets. PMID:20354298

Quiroga, Jairo; Trilleras, Jorge; Cobo, Justo; Glidewell, Christopher

2010-04-01

326

Synthesis and structure of the nickel(II) complex of 1,1,1-tris(((2-(methylthio)ethyl)thio)methyl)ethane, an all-sulfur ligand that promotes hexakis(thioether) coordination  

Microsoft Academic Search

Prompted by the potential analogy of thioethers to phosphines and by the occurrence of thioether coordination in blue copper proteins, they have recently been investigating the properties of homoleptic hexakis(thioether) complexes of transition-metal ions. Earlier work has shown that this new environment can be imposed on transition-metal ions by coordination to crown thioethers and that it induces unusual electronic structure

Celia M. Thorne; Simon C. Rawle; Gary A. Admans; Stephen R. Cooper

1986-01-01

327

Penta-aqua-(di-methyl-formamide)-cobalt(II) sulfate di-methyl-formamide monosolvate  

PubMed Central

The title compound, [Co(C3H7NO)(H2O)5]SO4·C3H7NO, contains five aqua ligands, a CoII atom, a sulfate ion and both a coordinating and a non-coordinating di­methyl­formamide (DMF) mol­ecule. The DMF solvent mol­ecule lies between the complex units, which are located along the b axis. The sulfate ion is for charge balance. The CoII atom has distorted octa­hedral coordination geometry, being ligated by five aqua ligands and the O atom of the DMF ligand. O—H?O hydrogen bonds between the aqua ligands and the sulfate anion and non-coordinating DMF molecule lead to the formation of a three-dimensional network. Since all constituents lie on a mirror plane, the H atoms of all methyl groups and of one of the aqua ligands are equally disordered over two positions.

Tas, Murat; Camur, Seval; Topal, Sevim

2013-01-01

328

DNA methylation and gene expression.  

PubMed

A large body of evidence demonstrates that DNA methylation plays a role in gene regulation in animal cells. Not only is there a correlation between gene transcription and undermethylation, but also transfection experiments clearly show that the presence of methyl moieties inhibits gene expression in vivo. Furthermore, gene activation can be induced by treatment of cells with 5-azacytidine, a potent demethylating agent. Methylation appears to influence gene expression by affecting the interactions with DNA of both chromatin proteins and specific transcription factors. Although methylation patterns are very stable in somatic cells, the early embryo is characterized by large alterations in DNA modification. New methodologies are now becoming available for studying methylation at this stage and in the germ line. During development, tissue-specific genes undergo demethylation in their tissue of expression. In tissue culture cells this process is highly specific and appears to involve an active mechanism which takes place in the absence of DNA replication. The X chromosome undergoes inactivation during development; this is accompanied by de novo methylation, which appears necessary to stably maintain its silent state. As opposed to the programmed changes in DNA methylation which occur in vivo, immortalized tissue culture cells demonstrate alterations in DNA modification which take place over a long time scale and which appear to be the result of selective pressures present during the growth of these cells in culture. PMID:1943996

Razin, A; Cedar, H

1991-09-01

329

Is there an attractive interaction between two methyl groups?  

NASA Astrophysics Data System (ADS)

A weak interaction was found between the two methyl groups in the complexes of XCH3-CH3BH2 (X = F, CN, NO2, HCO, and SOCH3), where the former methyl group acts as a Lewis acid and the latter one as a Lewis base. This directional interaction has small interaction energy, accompanied with some small changes in geometry and spectroscopy. Stronger Lewis acids FYH3 (Y = Si, Ge, and Sn) as well as Lewis bases CH3BeH and CH3MgH were compared. Dispersion energy is the major source of attraction and electrostatic contribution grows up to exceed dispersion energy for stronger interactions.

Zhuo, Hong-Ying; Jiang, Li-Xia; Li, Qing-Zhong; Li, Wen-Zuo; Cheng, Jian-Bo

2014-07-01

330

Synthesis, crystal structures, and biological evaluation of Cu(II) and Zn(II) complexes of 2-benzoylpyridine Schiff bases derived from S-methyl- and S-phenyldithiocarbazates  

Microsoft Academic Search

Two NNS tridentate Schiff base ligands of 2-benzoylpyridine S-methyldithiocarbazate (HL1) and 2-benzoylpyridine S-phenyldithiocarbazate (HL2) and their transition metal complexes [Cu2(L1)2(CH3COO)](ClO4) (1), [Zn2(L1)2(ClO4)2] (2), [Zn(L2)2](3) have been prepared and characterized by elemental analysis, IR, MS, NMR and single-crystal X-ray diffraction studies. In the solid state, each of two Schiff bases remains in its thione tautomeric form with the thione sulfur atom

Ming X. Li; Li Z. Zhang; Chun L. Chen; Jing Y. Niu; Bian S. Ji

331

Naturally occurring methyl salicylate glycosides.  

PubMed

As an important part of non steroids anti-inflammation drug (NSAIDs), salicylate has developed from natural substance salicylic acid to natrium salicylicum, to aspirin. Now, methyl salicylate glycoside, a new derivative of salicylic acid, is modified with a -COOH group integrated one methyl radical into formic ether, and a -OH linked with a monosaccharide, a disaccharide or a trisaccharide unit by glycosidic linkage. It has the similar pharmacological activities, anti-inflammatory, analgesic, antipyretic and antithrombotic as the previous salicylates' without resulting in serious side effects, particularly the gastrointestinal toxicity. Owing to the superiority of those significant bioactivities, methyl salicylate glycosides have became a hot research area in NSAIDs for several years. This paper compiles all 9 naturally occurring methyl salicylate glycosides, their distribution of the resource and pharmacological mechanism, which could contribute to the new drug discovery. PMID:24329991

Mao, Ping; Liu, Zizhen; Xie, Meng; Jiang, Rui; Liu, Weirui; Wang, Xiaohong; Meng, Shen; She, Gaimei

2014-01-01

332

DNA methylation analysis in human cancer  

PubMed Central

Chapter summary The functional impact of aberrant DNA methylation and the widespread alterations in DNA methylation in cancer development has led to the development of a variety of methods to characterize the DNA methylation patterns. This chapter will critique and describe the major approaches to analyzing DNA methylation.

O'Sullivan, Eileen; Goggins, Michael

2014-01-01

333

DNA methylation in breast and colorectal cancers  

Microsoft Academic Search

DNA methylation is one of several epigenetic changes observed in cells. Aberrant methylation of tumor suppressor genes, proto-oncogenes, and vital cell cycle genes has led many scientists to investigate the underlying cellular mechanisms of DNA methylation under normal and pathological conditions. Although DNA methylation is necessary for normal mammalian embryogenesis, both hypo- and hypermethylation of DNA are frequently observed in

Anshu Agrawal; Richard F Murphy; Devendra K Agrawal

2007-01-01

334

DNA Methylation, Cancer Susceptibility, and Nutrient Interactions  

Microsoft Academic Search

DNA methylation is an important epigenetic mechanism of transcriptional control. DNA methylation plays an essential role in maintaining cellular function, and changes in methylation patterns may contribute to the development of cancer. Aberrant methylation of DNA (global hypomethylation accompanied by region-specific hypermethylation) is frequently found in tumor cells. Global hypomethylation can result in chromosome instability, and hypermethylation has been associated

CINDY D. DAVIS; ERIC O. UTHUS

2004-01-01

335

A Common Mode of Recognition for Methylated CpG  

PubMed Central

Much is known about vertebrate DNA methylation, however it is not known how methylated CpG within particular sequences is recognized. Two recent structures of C2H2 zinc finger (ZnF) proteins, in complex with methylated DNA, reveal a common recognition mode for 5-methylcytosine (5mC) that involves a 5mC-Arg-G triad. In the two ZnF proteins, an arginine that precedes the first Zn-binding histidine (RH motif) can interact with 5mCpG or TpG dinucleotide. Among a family of >300 human KRAB (Krüppel-associated box) domain-containing ZnF proteins examined, two-thirds contain at least one ZnF that includes an RH motif. We propose that the RH-ZnF motifs provide specificity for 5mCpG, while the neighboring ZnF fingers recognize the surrounding DNA sequence context.

Liu, Yiwei; Zhang, Xing; Blumenthal, Robert M.; Cheng, Xiaodong

2013-01-01

336

Methylation of the flagellin of Salmonella typhimurium.  

PubMed

The methylation of endogenous proteins by Salmonella typhimurium SL 870 was investigated in cell-free extracts by using S-adenosylmethionine as methyl donor. Several lines of evidence are presented which suggest that one of the methylated products is the protein flagellin. Mutant strains of SL 870 (nml(-)fla(+) and nml(+)fla(-)) were also found to synthesize epsilon-N-methyl-lysine. It is proposed that S. typhimurium possesses at least two genes specifying different methylating enzymes. One gene product is a flagellin-specific methylating enzyme, whereas the other gene(s) codes for enzymes that methylate one or more other cell proteins. PMID:5541007

Tronick, S R; Martinez, R J

1971-01-01

337

Doubly pyrazolate-bridged dinuclear complexes of a highly constrained bis-terdentate ligand: observation of a [high spin-low spin] state for [Fe(II)2(PMAP)2][SbF6]2.2.25(C3H8O) (PMAP = 3,5-bis{[N-(2-pyridylmethyl)amino]-methyl}-1H-pyrazolate).  

PubMed

The bis-terdentate pyrazole-based ligand 3,5-bis{[N-(2-pyridylmethyl)amino]methyl}-1H-pyrazole (PMAPH) was synthesized from 3,5-(1H)-pyrazoledicarbaldehyde and 2 equiv of 2-(aminomethyl)pyridine, using sodium borohydride to reduce the imine intermediate. A family of dinuclear complexes [M(II/III)(2)(PMAP)(2)](X)(2/4) was prepared by 2:2:2 reactions of MX(2)/PMAPH/base, where M = Zn(II) and X = BF(4)(-); M = Cu(II) and X = ClO(4)(-), BF(4)(-), OAc(-), NO(3)(-); M = Ni(II), Fe(III) and X = ClO(4)(-), BF(4)(-); M = Fe(II) and X = SbF(6)(-). Single crystal X-ray structure determinations on four complexes: [Fe(III)(2)(PMAP)(2)](BF(4))(4).2MeCN, [Ni(II)(2)(PMAP)(2)](ClO(4))(2).2MeCN, [Cu(II)(2)(PMAP)(2)](BF(4))(2).2MeCN, and [Zn(II)(2)(PMAP)(2)](BF(4))(2).2MeCN confirmed a dinuclear doubly pyrazolate-bridged structure for each. The two metal centers in these complexes have similar N(6) distorted octahedral coordination spheres, with all donors provided by the two deprotonated PMAP(-) ligands. Magnetic measurements reveal intra-dinuclear antiferromagnetic interactions for both the M = Cu(II) and Ni(II) [M(2)(PMAP)(2)](BF(4))(4) complexes, with J/k(B) = -252(2) K and J/k(B) = -24.7(2) K (H = -2JS(M)S(M)), respectively. Interestingly magnetic measurements show that the complex [Fe(2)(II)(PMAP)(2)](SbF(6))(2).2.25(C(3)H(8)O) is in a mixed high spin (HS)-low spin (LS) spin state, [HS-LS], from 300 to 1.8 K, with no sign of spin crossover to a fully low spin form [LS-LS] even at 1.8 K. PMID:20394410

Noble, Andy; Olguín, Juan; Clérac, Rodolphe; Brooker, Sally

2010-05-17

338

Genome-wide DNA methylation analysis in cohesin mutant human cell lines.  

PubMed

The cohesin complex has recently been shown to be a key regulator of eukaryotic gene expression, although the mechanisms by which it exerts its effects are poorly understood. We have undertaken a genome-wide analysis of DNA methylation in cohesin-deficient cell lines from probands with Cornelia de Lange syndrome (CdLS). Heterozygous mutations in NIPBL, SMC1A and SMC3 genes account for ?65% of individuals with CdLS. SMC1A and SMC3 are subunits of the cohesin complex that controls sister chromatid cohesion, whereas NIPBL facilitates cohesin loading and unloading. We have examined the methylation status of 27 578 CpG dinucleotides in 72 CdLS and control samples. We have documented the DNA methylation pattern in human lymphoblastoid cell lines (LCLs) as well as identified specific differential DNA methylation in CdLS. Subgroups of CdLS probands and controls can be classified using selected CpG loci. The X chromosome was also found to have a unique DNA methylation pattern in CdLS. Cohesin preferentially binds to hypo-methylated DNA in control LCLs, whereas the differential DNA methylation alters cohesin binding in CdLS. Our results suggest that in addition to DNA methylation multiple mechanisms may be involved in transcriptional regulation in human cells and in the resultant gene misexpression in CdLS. PMID:20448023

Liu, Jinglan; Zhang, Zhe; Bando, Masashige; Itoh, Takehiko; Deardorff, Matthew A; Li, Jennifer R; Clark, Dinah; Kaur, Maninder; Tatsuro, Kondo; Kline, Antonie D; Chang, Celia; Vega, Hugo; Jackson, Laird G; Spinner, Nancy B; Shirahige, Katsuhiko; Krantz, Ian D

2010-09-01

339

Genome-wide DNA methylation analysis in cohesin mutant human cell lines  

PubMed Central

The cohesin complex has recently been shown to be a key regulator of eukaryotic gene expression, although the mechanisms by which it exerts its effects are poorly understood. We have undertaken a genome-wide analysis of DNA methylation in cohesin-deficient cell lines from probands with Cornelia de Lange syndrome (CdLS). Heterozygous mutations in NIPBL, SMC1A and SMC3 genes account for ?65% of individuals with CdLS. SMC1A and SMC3 are subunits of the cohesin complex that controls sister chromatid cohesion, whereas NIPBL facilitates cohesin loading and unloading. We have examined the methylation status of 27 578 CpG dinucleotides in 72 CdLS and control samples. We have documented the DNA methylation pattern in human lymphoblastoid cell lines (LCLs) as well as identified specific differential DNA methylation in CdLS. Subgroups of CdLS probands and controls can be classified using selected CpG loci. The X chromosome was also found to have a unique DNA methylation pattern in CdLS. Cohesin preferentially binds to hypo-methylated DNA in control LCLs, whereas the differential DNA methylation alters cohesin binding in CdLS. Our results suggest that in addition to DNA methylation multiple mechanisms may be involved in transcriptional regulation in human cells and in the resultant gene misexpression in CdLS.

Liu, Jinglan; Zhang, Zhe; Bando, Masashige; Itoh, Takehiko; Deardorff, Matthew A.; Li, Jennifer R.; Clark, Dinah; Kaur, Maninder; Tatsuro, Kondo; Kline, Antonie D.; Chang, Celia; Vega, Hugo; Jackson, Laird G.; Spinner, Nancy B.; Shirahige, Katsuhiko; Krantz, Ian D.

2010-01-01

340

Genome-Wide Methylated DNA Immunoprecipitation Analysis of Patients with Polycystic Ovary Syndrome  

PubMed Central

Polycystic ovary syndrome (PCOS) is a complex, heterogeneous disorder of uncertain etiology. Recent studies suggested that insulin resistance (IR) plays an important role in the development of PCOS. In the current study, we aimed to investigate the molecular mechanism of IR in PCOS. We employed genome-wide methylated DNA immunoprecipitation (MeDIP) analysis to characterize genes that are differentially methylated in PCOS patients vs. healthy controls. Besides, we also identified the differentially methylated genes between patients with PCOS-non-insulin resistance (PCOS-NIR) and PCOS-insulin resistance (PCOS-IR). A total of 79 genes were differentially methylated between PCOS-NIR vs. PCOS-IR patients, and 40 genes were differentially methylated in PCOS patients vs. healthy controls. We analyzed these differentially methylated genes by constructing regulatory networks and protein-protein interaction (PPI) networks. Further, Gene Ontology (GO) and pathway enrichment analysis were also performed to investigate the biological functions of networks. We identified multiple categories of genes that were differentially methylated between PCOS-NIR and PCOS-IR patients, or between PCOS patients and healthy controls. Significantly, GO categories of immune response were differentially methylated in PCOS-IR vs. PCOS-NIR. Further, genes in cancer pathways were also differentially methylated in PCOS-NIR vs. PCOS-IR patients or in PCOS patients vs. healthy controls. The results of this current study will help to further understand the mechanism of PCOS.

Shen, Hao-ran; Qiu, Li-hua; Zhang, Zhi-qing; Qin, Yuan-yuan; Cao, Cong; Di, Wen

2013-01-01

341

Genome-wide conserved consensus transcription factor binding motifs are hyper-methylated  

PubMed Central

Background DNA methylation can regulate gene expression by modulating the interaction between DNA and proteins or protein complexes. Conserved consensus motifs exist across the human genome ("predicted transcription factor binding sites": "predicted TFBS") but the large majority of these are proven by chromatin immunoprecipitation and high throughput sequencing (ChIP-seq) not to be biological transcription factor binding sites ("empirical TFBS"). We hypothesize that DNA methylation at conserved consensus motifs prevents promiscuous or disorderly transcription factor binding. Results Using genome-wide methylation maps of the human heart and sperm, we found that all conserved consensus motifs as well as the subset of those that reside outside CpG islands have an aggregate profile of hyper-methylation. In contrast, empirical TFBS with conserved consensus motifs have a profile of hypo-methylation. 40% of empirical TFBS with conserved consensus motifs resided in CpG islands whereas only 7% of all conserved consensus motifs were in CpG islands. Finally we further identified a minority subset of TF whose profiles are either hypo-methylated or neutral at their respective conserved consensus motifs implicating that these TF may be responsible for establishing or maintaining an un-methylated DNA state, or whose binding is not regulated by DNA methylation. Conclusions Our analysis supports the hypothesis that at least for a subset of TF, empirical binding to conserved consensus motifs genome-wide may be controlled by DNA methylation.

2010-01-01

342

CHH islands: de novo DNA methylation in near-gene chromatin regulation in maize.  

PubMed

Small RNA-mediated regulation of chromatin structure is an important means of suppressing unwanted genetic activity in diverse plants, fungi, and animals. In plants specifically, 24-nt siRNAs direct de novo methylation to repetitive DNA, both foreign and endogenous, in a process known as RNA-directed DNA methylation (RdDM). Many components of the de novo methylation machinery have been identified recently, including multiple RNA polymerases, but specific genetic features that trigger methylation remain poorly understood. By applying whole-genome bisulfite sequencing to maize, we found that transposons close to cellular genes (particularly within 1 kb of either a gene start or end) are strongly associated with de novo methylation, as evidenced both by 24-nt siRNAs and by methylation specifically in the CHH sequence context. In addition, we found that the major classes of transposons exhibited a gradient of CHH methylation determined by proximity to genes. Our results further indicate that intergenic chromatin in maize exists in two major forms that are distinguished based on proximity to genes-one form marked by dense CG and CHG methylation and lack of transcription, and one marked by CHH methylation and activity of multiple forms of RNA polymerase. The existence of the latter, which we call CHH islands, may have implications for how cellular gene expression could be coordinated with immediately adjacent transposon repression in a large genome with a complex organization of genes interspersed in a landscape of transposons. PMID:23269663

Gent, Jonathan I; Ellis, Nathanael A; Guo, Lin; Harkess, Alex E; Yao, Yingyin; Zhang, Xiaoyu; Dawe, R Kelly

2013-04-01

343

Corruption of the Intra-Gene DNA Methylation Architecture Is a Hallmark of Cancer  

PubMed Central

Epigenetic processes - including DNA methylation - are increasingly seen as having a fundamental role in chronic diseases like cancer. It is well known that methylation levels at particular genes or loci differ between normal and diseased tissue. Here we investigate whether the intra-gene methylation architecture is corrupted in cancer and whether the variability of levels of methylation of individual CpGs within a defined gene is able to discriminate cancerous from normal tissue, and is associated with heterogeneous tumour phenotype, as defined by gene expression. We analysed 270985 CpGs annotated to 18272 genes, in 3284 cancerous and 681 normal samples, corresponding to 14 different cancer types. In doing so, we found novel differences in intra-gene methylation pattern across phenotypes, particularly in those genes which are crucial for stem cell biology; our measures of intra-gene methylation architecture are a better determinant of phenotype than measures based on mean methylation level alone (K-S test in all 14 diseases tested). These per-gene methylation measures also represent a considerable reduction in complexity, compared to conventional per-CpG beta-values. Our findings strongly support the view that intra-gene methylation architecture has great clinical potential for the development of DNA-based cancer biomarkers.

Bartlett, Thomas E.; Zaikin, Alexey; Olhede, Sofia C.; West, James; Teschendorff, Andrew E.; Widschwendter, Martin

2013-01-01

344

Hafnocene catalysts for selective propylene oligomerization: efficient synthesis of 4-methyl-1-pentene by beta-methyl transfer.  

PubMed

A series of hafnocene complexes (eta5-C5Me4R1)(eta5-C5Me4R2)HfCl2 with [R1, R2] = [H, H] (1), [Me, H] (2), [Me, Me] (3), [Et, Me] (4), [(i)Pr, Me] (5), [SiMe(3), Me] (6), [(t)Bu, Me] (7), [(n)Bu, Me] (8), [(i)Bu, Me] (9), [Et, Et] (10), [(n)Bu, (n)Bu] (11), [(i)Bu, (i)Bu] (12) was tested as catalyst precursors for propylene oligomerization. Upon activation with methylaluminoxane or [Ph(3)C][B(C(6)F(5))(4)]/Al(i)Bu(3), complexes 2-4 and 8-12 catalyzed the dimerization of propylene to produce 4-methyl-1-pentene with selectivities ranging from 23.9 to 61.6 wt % in the product mixture. The selectivity was dependent on the nature of the substituents R(1) and R(2), with the highest value found for (eta5-C5Me4(i)Bu)2HfCl2 (12). Rapid deactivation was observed for 5-7, whereas (eta5-C5Me4H)2HfCl2 (1) polymerized propylene. 4-Methyl-1-pentene is proposed to form by repeated 1,2-insertion of propylene into the hafnocene methyl cation, followed by selective beta-methyl elimination. Detailed analysis of the byproduct distribution (isobutene, 1-pentene, 2-methyl-1-pentene, 2,4-dimethyl-1-pentene, 4-methyl-1-heptene, 4,6-dimethyl-1-heptene), determined by gas chromatography, was performed with the aid of a stochastic simulation involving rate constants for the propagation by insertion, beta-hydride elimination, and beta-methyl elimination. The rate of termination is dependent on the structure of the growing chain of the active species as well as on the bulkiness of the cyclopentadienyl ligands. The selectivity highly depends on the reaction conditions (pressure, temperature, concentration of methylaluminoxane). The rates of beta-methyl elimination leading to 4-methyl-1-pentene were proportional to propylene pressure for 2-4 and 8-10 but practically independent from propylene pressure for the sterically bulkier derivatives 11-12. PMID:17002399

Suzuki, Yasuhiko; Yasumoto, Takahiro; Mashima, Kazushi; Okuda, Jun

2006-10-01

345

Anticancer activity of methyl-substituted oxaliplatin analogs.  

PubMed

Oxaliplatin is successfully used in systemic cancer therapy. However, resistance development and severe adverse effects are limiting factors for curative cancer treatment with oxaliplatin. The purpose of this study was to comparatively investigate in vitro and in vivo anticancer properties as well as the adverse effects of two methyl-substituted enantiomerically pure oxaliplatin analogs [[(1R,2R,4R)-4-methyl-1,2-cyclohexanediamine] oxalatoplatinum(II) (KP1537), and [(1R,2R,4S)-4-methyl-1,2-cyclohexanediamine]oxalatoplatinum(II) (KP1691)] and to evaluate the impact of stereoisomerism. Although the novel oxaliplatin analogs demonstrated in multiple aspects activities comparable with those of the parental compound, several key differences were discovered. The analogs were characterized by reduced vulnerability to resistance mechanisms such as p53 mutations, reduced dependence on immunogenic cell death induction, and distinctly attenuated adverse effects including weight loss and cold hyperalgesia. Stereoisomerism of the substituted methyl group had a complex and in some aspects even contradictory impact on drug accumulation and anticancer activity both in vitro and in vivo. To summarize, methyl-substituted oxaliplatin analogs harbor improved therapeutic characteristics including significantly reduced adverse effects. Hence, they might be promising metal-based anticancer drug candidates for further (pre)clinical evaluation. PMID:22331606

Jungwirth, Ute; Xanthos, Dimitris N; Gojo, Johannes; Bytzek, Anna K; Körner, Wilfried; Heffeter, Petra; Abramkin, Sergey A; Jakupec, Michael A; Hartinger, Christian G; Windberger, Ursula; Galanski, Markus; Keppler, Bernhard K; Berger, Walter

2012-05-01

346

Tissue-specific dysregulation of DNA methylation in aging  

PubMed Central

SUMMARY The normal aging process is a complex phenomenon associated with physiological alterations in the function of cells and organs over time. Although an attractive candidate for mediating transcriptional dysregulation, the contribution of epigenetic dysregulation to these progressive changes in cellular physiology remains unclear. In this study, we employed the genome-wide HELP assay to define patterns of cytosine methylation throughout the rat genome, and the LUMA assay to measure global levels of DNA methylation in the same samples. We studied both liver and visceral adipose tissue, and demonstrated significant differences in DNA methylation with age at >5% of sites analyzed. Furthermore, we showed that epigenetic dysregulation with age is a highly tissue-dependent phenomenon. The most distinctive loci were located at intergenic sequences and conserved non-coding elements, and not at promoters nor at CG-dinucleotide dense loci. Despite this, we found that there was a subset of genes at which cytosine methylation and gene expression changes were concordant. Finally, we demonstrated that changes in methylation occur consistently near genes that are involved in metabolism and metabolic regulation, implicating their potential role in the pathogenesis of age-related diseases. We conclude that different patterns of epigenetic dysregulation occur in each tissue over time and may cause some of the physiological changes associated with normal aging.

Thompson, Reid F.; Atzmon, Gil; Gheorghe, Ciprian; Liang, Hong Qian; Lowes, Christina; Greally, John M.; Barzilai, Nir

2010-01-01

347

Increased DNA methylation of neuropsychiatric genes occurs in borderline personality disorder.  

PubMed

Borderline personality disorder (BPD) is a complex psychiatric disease of increasing importance. Epigenetic alterations are hallmarks for altered gene expression and could be involved in the etiology of BPD. In our study we analyzed DNA methylation patterns of 14 neuropsychiatric genes (COMT, DAT1, GABRA1, GNB3, GRIN2B, HTR1B, HTR2A, 5-HTT, MAOA, MAOB, NOS1, NR3C1, TPH1 and TH). DNA methylation was analyzed by bisulfite restriction analysis and pyrosequencing in whole blood samples of patients diagnosed with DSM-IV BPD and in controls. Aberrant methylation was not detectable using bisulfite restriction analysis, but a significantly increased methylation of HTR2A, NR3C1, MAOA, MAOB and soluble COMT (S-COMT) was revealed for BPD patients using pyrosequencing. For HTR2A the average methylation of four CpG sites was 0.8% higher in BPD patients compared to controls (p = 0.002). The average methylation of NR3C1 was 1.8% increased in BPD patients compared to controls (p = 0.0003) and was higher at 2 out of 8 CpGs (p ? 0.04). In females, an increased average methylation (1.5%) of MAOA was observed in BPD patients compared to controls (p = 0.046). A similar trend (1.4% higher methylation) was observed for MAOB in female BPD patients and increased methylation was significant for 1 out of 6 CpG sites. For S-COMT, a higher methylation of 2 out of 4 CpG sites was revealed in BPD patients (p ? 0.02). In summary, methylation signatures of several promoter regions were established and a significant increased average methylation (1.7%) occurred in blood samples of BPD patients (p < 0.0001). Our data suggest that aberrant epigenetic regulation of neuropsychiatric genes may contribute to the pathogenesis of BPD. PMID:22139575

Dammann, Gerhard; Teschler, Stefanie; Haag, Tanja; Altmüller, Franziska; Tuczek, Frederik; Dammann, Reinhard H

2011-12-01

348

Water Mediated Ligand Functional Group Cooperativity: The Contribution of a Methyl Group to Binding Affinity is Enhanced by a COO? Group Through Changes in the Structure and Thermo dynamics of the Hydration Waters of Ligand-Thermolysin Complexes  

PubMed Central

Ligand functional groups can modulate the contributions of one another to the ligand-protein binding thermodynamics, producing either positive or negative cooperativity. Data presented for four thermolysin phosphonamidate inhibitors demonstrate that the differential binding free energy and enthalpy caused by replacement of a H with a Me group, which binds in the well-hydrated S2? pocket, are more favorable in presence of a ligand carboxylate. The differential entropy is however less favorable. Dissection of these differential thermodynamic parameters, X-ray crystallography, and density-functional theory calculations suggest that these cooperativities are caused by variations in the thermodynamics of the complex hydration shell changes accompanying the H?Me replacement. Specifically, the COO? reduces both the enthalpic penalty and the entropic advantage of displacing water molecules from the S2? pocket, and causes a subsequent acquisition of a more enthalpically, less entropically, favorable water network. This study contributes to understanding the important role water plays in ligand-protein binding.

Nasief, Nader N; Tan, Hongwei; Kong, Jing; Hangauer, David

2012-01-01

349

The energetic and wave function properties of atomic, molecular, and solid state systems: Hydrogen ion and the lithium, neon, and phosphorus atoms; Boron trifluoride-ammonia molecular complex and methyl derivatives; Vanadium, chromium, and manganese ions and neutral manganese transition metal impurities in silicon  

NASA Astrophysics Data System (ADS)

The variational Hartree-Fock-Roothaan (HF) method with correlation corrections introduced through Many Body Perturbation Theory (MBPT) and the variational Density Functional Theory (DFT) have been investigated for atomic systems to provide insights into the strengths and weaknesses of each variational approach to solving the multicenter many-electron Hamiltonian. The HF+MBPT method, having been found to be more reliable and physically relevant from the atomic investigations, is used to investigate the electronic structures and associated properties of the BF3?NH3 molecular complex, and through cluster methods, the most likely locations of the transitional metal impurities V2+, Cr+, Mn2+ and Mn 0 in Silicon. Atomic systems are ideal for studying the effectiveness of different modern variational techniques such as HF+MBPT and DFT because of the depth of earlier investigations by rigorous techniques such as the Linked Cluster Many Body Perturbation Theory (LCMBPT). An in-depth comparison of the calculated energetic and magnetic hyperfine properties of carefully selected atomic systems with earlier calculated LCMBPT results and experiment will be presented. It will be shown that through varying the types of gaussians included in the basis sets used for these variational calculations one can illustrate the inherent assumptions and difficulties of the respective theories. These results coupled with a fundamental understanding of the respective theories leads to the conclusion that for a detailed quantitative investigation the HF+MBPT method is more physically intuitive and accurate, though not without its own deficiencies that should be addressed in the future. The BF3?NH3 molecular complex, along with its methyl derivatives BF3?NHx(CH3) 3-x (x=0,1,2) is investigated and relative covalency and instantaneous van der Waals contributions to the complexation bond are presented. The accuracy of the calculated results are tested by comparison of the calculated 19F* nuclear quadrupole interaction (NQI) coupling constants and asymmetry parameters with experiment. The complexation bonds are shown to have increasing van der Waals contributions with the addition of methyl groups to the ammonia. Finally investigations into the possible locations of the transition metal impurities V2+, Cr+, Mn2+, and Mn0 in a silicon lattice will be presented. Binding energies, geometry of the potential energy surface, and magnetic hyperfine calculations, as well as probability of formation will all be considered while differentiating between the possible Hexagonal Interstitial (Hi), Tetrahedral Interstitial (Ti), and Substitutional (S) locations in the silicon lattice. The Ti site will be shown to be the most likely location in the silicon lattice for all of the transition metal impurities investigated. The Substitutional site will be shown to be a stable location if a pre-existing vacancy exists in the silicon lattice.

Pink, Roger H.

350

40 CFR 721.6920 - Butyl acrylate, polymer with substituted methyl styrene, methyl methacrylate, and substituted...  

Code of Federal Regulations, 2010 CFR

...methyl methacrylate, and substituted silane. 721.6920 Section 721.6920 ...methyl methacrylate, and substituted silane. (a) Chemical substance and significant...methyl methacrylate, and substituted silane (PMN P-91-272) is subject to...

2010-07-01

351

Synthesis and characterization of rhenium(V) oxo complexes with N-[N-(3-diphenylphosphinopropionyl)glycyl]cysteine methyl ester. X-ray crystal structure of (ReO[Ph(2)P(CH(2))(2)C(O)-Gly-Cys-OMe(P,N,N,S)]).  

PubMed

The PN(2)S chelate N-[N-(3-diphenylphosphinopropionyl)glycyl]-S-tritylcysteine methyl ester [PN(2)S(Trt)-OMe] was synthesized and reacted with ReOCl(3)(PPh(3))(2) and Ph(4)P[ReOCl(4)]. The reactions of both tritylated and detritylated ligands with Re(V)O precursors gave two diastereomers, 9a and 9b, of the ReO(PN(2)S-OMe) complex. The two isomers, produced in a 1:1 molar ratio, are stable and do not interconvert. They were separated by reverse-phase HPLC and characterized by NMR, FT-IR, and UV-visible spectroscopy and electrospray mass spectrometry. X-ray analysis established for 9a the presence in the solid of the syn isomer. Compound 9a, C(21)H(23)N(2)O(5)PSRe, crystallized from warm acetonitrile in the triclinic space group Ponemacr;, a = 9.828(2) A, b = 11.163(2) A, c = 11.641(2) A, alpha = 106.48(3) degrees, beta = 109.06(3) degrees, gamma = 102.81(3) degrees, V = 1085.7(4) A(3), Z = 2. The PN(2)S coordination set is in the equatorial plane, and the complex shows a distorted square pyramidal coordination. The anti configuration assigned to 9b is consistent with all the available physicochemical data. Follow-up of the reaction of the detritylated ligand with Ph(4)P[ReOCl(4)] in ethanol or acetonitrile indicated that the phosphorus atom of the chelate binds first to the metal and that this bond acts as the driving force for coordination. PMID:12588125

Visentin, Roberta; Rossin, Raffaella; Giron, Maria Cecilia; Dolmella, Alessandro; Bandoli, Giuliano; Mazzi, Ulderico

2003-02-24

352

Alcohol, DNA Methylation, and Cancer  

PubMed Central

Cancer is one of the most significant diseases associated with chronic alcohol consumption, and chronic drinking is a strong risk factor for cancer, particularly of the upper aerodigestive tract, liver, colorectum, and breast. Several factors contribute to alcohol-induced cancer development (i.e., carcinogenesis), including the actions of acetaldehyde, the first and primary metabolite of ethanol, and oxidative stress. However, increasing evidence suggests that aberrant patterns of DNA methylation, an important epigenetic mechanism of transcriptional control, also could be part of the pathogenetic mechanisms that lead to alcohol-induced cancer development. The effects of alcohol on global and local DNA methylation patterns likely are mediated by its ability to interfere with the availability of the principal biological methyl donor, S-adenosylmethionine (SAMe), as well as pathways related to it. Several mechanisms may mediate the effects of alcohol on DNA methylation, including reduced folate levels and inhibition of key enzymes in one-carbon metabolism that ultimately lead to lower SAMe levels, as well as inhibition of activity and expression of enzymes involved in DNA methylation (i.e., DNA methyltransferases). Finally, variations (i.e., polymorphisms) of several genes involved in one-carbon metabolism also modulate the risk of alcohol-associated carcinogenesis.

Varela-Rey, Marta; Woodhoo, Ashwin; Martinez-Chantar, Maria-Luz; Mato, Jose M.; Lu, Shelly C.

2013-01-01

353

PCMdb: Pancreatic Cancer Methylation Database  

NASA Astrophysics Data System (ADS)

Pancreatic cancer is the fifth most aggressive malignancy and urgently requires new biomarkers to facilitate early detection. For providing impetus to the biomarker discovery, we have developed Pancreatic Cancer Methylation Database (PCMDB, http://crdd.osdd.net/raghava/pcmdb/), a comprehensive resource dedicated to methylation of genes in pancreatic cancer. Data was collected and compiled manually from published literature. PCMdb has 65907 entries for methylation status of 4342 unique genes. In PCMdb, data was compiled for both cancer cell lines (53565 entries for 88 cell lines) and cancer tissues (12342 entries for 3078 tissue samples). Among these entries, 47.22% entries reported a high level of methylation for the corresponding genes while 10.87% entries reported low level of methylation. PCMdb covers five major subtypes of pancreatic cancer; however, most of the entries were compiled for adenocarcinomas (88.38%) and mucinous neoplasms (5.76%). A user-friendly interface has been developed for data browsing, searching and analysis. We anticipate that PCMdb will be helpful for pancreatic cancer biomarker discovery.

Nagpal, Gandharva; Sharma, Minakshi; Kumar, Shailesh; Chaudhary, Kumardeep; Gupta, Sudheer; Gautam, Ankur; Raghava, Gajendra P. S.

2014-02-01

354

Histone methylation during neural development.  

PubMed

Post-translational modification of histone proteins, such as the methylation of lysine and arginine residues, influences the higher order of chromatin and leads to gene activation or silencing. Histone methyltransferases or demethylases actively add or remove various methylation marks in a cell-type-specific and context-dependent way. They are therefore important players in regulating the transcriptional program of a cell. Some control of the various cellular programs is necessary during the differentiation of stem cells along a specific lineage, when differentiation to alternative lineages needs to be suppressed. One example is the development of neurons from neural stem cells during neurogenesis. Neurogenesis is a highly organized process that requires the proper coordination of survival, proliferation, differentiation and migration signals. This holds true for both embryonic and neural stem cells that give rise to the various cell types of the central nervous system. The control of embryonic and neural stem cell self-renewal and differentiation is achieved by both extrinsic and intrinsic signals that regulate gene expression precisely. Recent advances in neuroscience support the importance of epigenetic modifications, such as the methylation and acetylation of histones, as an important intrinsic mechanism for the regulation of central nervous system development. This review summarizes our current knowledge of histone methylation processes during neural development and provides insights into the function of histone methylation enzymes and their role during central nervous system development. PMID:24817100

Roidl, Deborah; Hacker, Christine

2014-06-01

355

40 CFR 180.437 - Methyl 2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate and methyl 6-(4-isopropyl-4...  

Code of Federal Regulations, 2013 CFR

...4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p-toluate and methyl 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl...4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p -toluate and methyl 6-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl...4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)-p -toluate and methyl...

2013-07-01

356

Linking DNA methylation to the onset of human tubal ectopic pregnancy  

PubMed Central

Ectopic pregnancy is a common reproductive disorder of unknown etiology and is a leading cause of maternal and fetal mortality. Because of the asymptomatic nature of early tubal ectopic pregnancy and the lack of specific biomarkers for early diagnosis, a better understanding of the complex cellular and molecular interactions that contribute to tubal ectopic pregnancy is required. DNA methylation is the most studied epigenetic process in various tissues and cells, and the goal of this article is to provide a brief review of recent work describing the potential mechanisms of DNA methylation and the biological function of such methylation in normal intrauterine pregnancy. Further, novel findings from our laboratory highlight the possible role of DNA methylation in human Fallopian tube dysfunction and suggest a possible correlation between methylation of estrogen receptor ? in women and the occurrence of tubal ectopic pregnancies.

Wang, Lei; Feng, Yi; Zou, Shien; Brannstrom, Mats; He, Lin; Billig, Hakan; Shao, Ruijin

2013-01-01

357

Comparisons of Non-Gaussian Statistical Models in DNA Methylation Analysis  

PubMed Central

As a key regulatory mechanism of gene expression, DNA methylation patterns are widely altered in many complex genetic diseases, including cancer. DNA methylation is naturally quantified by bounded support data; therefore, it is non-Gaussian distributed. In order to capture such properties, we introduce some non-Gaussian statistical models to perform dimension reduction on DNA methylation data. Afterwards, non-Gaussian statistical model-based unsupervised clustering strategies are applied to cluster the data. Comparisons and analysis of different dimension reduction strategies and unsupervised clustering methods are presented. Experimental results show that the non-Gaussian statistical model-based methods are superior to the conventional Gaussian distribution-based method. They are meaningful tools for DNA methylation analysis. Moreover, among several non-Gaussian methods, the one that captures the bounded nature of DNA methylation data reveals the best clustering performance.

Ma, Zhanyu; Teschendorff, Andrew E.; Yu, Hong; Taghia, Jalil; Guo, Jun

2014-01-01

358

Exploring genome wide bisulfite sequencing for DNA methylation analysis in livestock: a technical assessment  

PubMed Central

Recent advances made in “omics” technologies are contributing to a revolution in livestock selection and breeding practices. Epigenetic mechanisms, including DNA methylation are important determinants for the control of gene expression in mammals. DNA methylation research will help our understanding of how environmental factors contribute to phenotypic variation of complex production and health traits. High-throughput sequencing is a vital tool for the comprehensive analysis of DNA methylation, and bisulfite-based strategies coupled with DNA sequencing allows for quantitative, site-specific methylation analysis at the genome level or genome wide. Reduced representation bisulfite sequencing (RRBS) and more recently whole genome bisulfite sequencing (WGBS) have proven to be effective techniques for studying DNA methylation in both humans and mice. Here we report the development of RRBS and WGBS for use in sheep, the first application of this technology in livestock species. Important technical issues associated with these methodologies including fragment size selection and sequence depth are examined and discussed.

Doherty, Rachael; Couldrey, Christine

2014-01-01

359

Comparisons of non-gaussian statistical models in DNA methylation analysis.  

PubMed

As a key regulatory mechanism of gene expression, DNA methylation patterns are widely altered in many complex genetic diseases, including cancer. DNA methylation is naturally quantified by bounded support data; therefore, it is non-Gaussian distributed. In order to capture such properties, we introduce some non-Gaussian statistical models to perform dimension reduction on DNA methylation data. Afterwards, non-Gaussian statistical model-based unsupervised clustering strategies are applied to cluster the data. Comparisons and analysis of different dimension reduction strategies and unsupervised clustering methods are presented. Experimental results show that the non-Gaussian statistical model-based methods are superior to the conventional Gaussian distribution-based method. They are meaningful tools for DNA methylation analysis. Moreover, among several non-Gaussian methods, the one that captures the bounded nature of DNA methylation data reveals the best clustering performance. PMID:24937687

Ma, Zhanyu; Teschendorff, Andrew E; Yu, Hong; Taghia, Jalil; Guo, Jun

2014-01-01

360

COPPER(II), NICKEL AND URANYL COMPLEXES OF SOME AMINO ACIDS  

Microsoft Academic Search

The formation constants of copper(II) and nickel complexes of ; hydroxyproline, asparagine and N,Ndimethylglycine have been obtained. The pK\\/; sub 2\\/ of asparagine and the formation constants of its complexes are independeut ; of the optical configanration. The nickel complexes of serine methyl ester and ; glycine methyl ester are equally stable, indicating that the serine ester ; coordinates to

N. C. Li; B. E. Doody; J. M. White

1958-01-01

361

DNA methylation and primary immune thrombocytopenia.  

PubMed

DNA methylation is a heritable, stable, and also reversible way of DNA modification; it can regulate gene expression without changing the nucleotide sequences. Because it takes part in regulation of immune responses, the loss of methylation homeostasis in immune cells will result in autoimmune disease by inducing aberrant gene expression. Primary immune thrombocytopenia (ITP) is an acquired autoimmune disease with many immune deficiencies. Recently, it was well documented that abnormal DNA methylation is also involved in the etiology of ITP. In this review, we elucidate the role of DNA methylation in autoimmune diseases by summarizing the DNA methylation-sensitive genes and the relationship between DNA methylation and ITP. PMID:23664508

Li, Huiyuan; Xuan, Min; Yang, Renchi

2013-01-01

362

Aryloxide anions can form outer sphere complexes with metals as electropositive as uranium.  

PubMed

A uranium complex containing an outer sphere aryloxide anion is formed by the proteolytic cleavage of the methyl group in the mono-methyl uranium metallocene, (C(5)Me(5))(2)[(i)PrNC(Me)N(i)Pr]UMe, by 2,6-di-tert-butyl-4-methyl phenol. PMID:20024222

Evans, William J; Walensky, Justin R; Ziller, Joseph W

2009-12-21

363

40 CFR 721.10121 - Poly[oxy(methyl-1,2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-, branched.  

Code of Federal Regulations, 2010 CFR

...2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-, branched...2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-, branched...2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-,...

2009-07-01

364

40 CFR 721.10121 - Poly[oxy(methyl-1,2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-, branched.  

Code of Federal Regulations, 2013 CFR

...2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-, branched...2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-, branched...2-ethanediyl)], .alpha.-methyl-.omega.-(4-nonylphenoxy)-,...

2013-07-01

365

Optical bio-sniffer for methyl mercaptan in halitosis  

Microsoft Academic Search

An optical bio-sniffer for methyl mercaptan (MM) one of major odorous chemicals in halitosis (bad breath) was constructed by immobilizing monoamine oxidase type A (MAO-A) onto a tip of a fiber optic oxygen sensor (od: 1.59mm) with an oxygen sensitive ruthenium organic complex (excitation: 470nm, fluorescent: 600nm). A flow cell for circulating buffer solution was applied to rinse and clean

Kohji Mitsubayashi; Takeshi Minamide; Kimio Otsuka; Hiroyuki Kudo; Hirokazu Saito

2006-01-01

366

Conformational properties of Methyl ?-maltoside and Methyl ?- and ?-cellobioside disaccharides  

PubMed Central

An investigation of the conformational properties of methyl ?-maltoside, methyl ?-cellobioside and methyl ?-cellobioside disaccharides, using NMR spectroscopy and molecular dynamics (MD) techniques, is presented. Emphasis is placed on validation of a recently presented force field for hexopyranose disaccharides followed by elucidation of the conformational properties of two different types of glycosidic linkages, ?-(1?4) and ?-(1?4). Both gas-phase and aqueous-phase simulations are performed to gain insight into the effect of solvent on the conformational properties. A number of transglycosidic J-coupling constants and proton-proton distances are calculated from the simulations and are used to identify the percent sampling of the three glycosidic conformations, syn, anti-? and anti-?, and, in turn, describe the flexibility around the glycosidic linkage. The results show the force field to be in overall good agreement with experiment, though some very small limitations are evident. Subsequently, a thorough hydrogen bonding analysis is performed to obtain insights into the conformational properties of the disaccharides. In methyl ?-maltoside competition between HO2?-O3 intramolecular hydrogen bonding and intermolecular hydrogen bonding of those groups with solvent lead to increased sampling of syn ?,? conformations and better agreement with NMR J-coupling constants. In methyl ? and ?-cellobioside, O5?-HO6 and HO2?-O3 hydrogen bonding interactions are in competition with intermolecular hydrogen bonding involving the solvent molecules. This competition leads to retention of the O5?-HO3 hydrogen bond and increased sampling of the syn region of the ?/? map. Moreover, glycosidic torsions are correlated to the intramolecular hydrogen bonding occurring in the molecules. The present results verify that in the ?-(1?4)-linkage intramolecular hydrogen bonding in the aqueous phase is due to the decreased ability of water to successfully compete for the O5? and HO3 hydrogen bonding moieties in contrast to that occurring between the O5? and HO6 atoms in this ?-(1?4)-linkage.

Hatcher, Elizabeth; Sawen, Elin; Widmalm, Goran; MacKerell, Alexander D.

2010-01-01

367

Transcription is required for establishment of germline methylation marks at imprinted genes  

PubMed Central

Genomic imprinting requires the differential marking by DNA methylation of genes in male and female gametes. In the female germline, acquisition of methylation imprint marks depends upon the de novo methyltransferase Dnmt3a and its cofactor Dnmt3L, but the reasons why specific sequences are targets for Dnmt3a and Dnmt3L are still poorly understood. Here, we investigate the role of transcription in establishing maternal germline methylation marks. We show that at the Gnas locus, truncating transcripts from the furthest upstream Nesp promoter disrupts oocyte-derived methylation of the differentially methylated regions (DMRs). Transcription through DMRs in oocytes is not restricted to this locus but occurs across the prospective DMRs at many other maternally marked imprinted domains, suggesting a common requirement for transcription events. The transcripts implicated here in gametic methylation are protein-coding, in contrast to the noncoding antisense transcripts involved in the monoallelic silencing of imprinted genes in somatic tissues, although they often initiate from alternative promoters in oocytes. We propose that transcription is a third essential component of the de novo methylation system, which includes optimal CpG spacing and histone modifications, and may be required to create or maintain open chromatin domains to allow the methylation complex access to its preferred targets.

Chotalia, Mita; Smallwood, Sebastien A.; Ruf, Nico; Dawson, Claire; Lucifero, Diana; Frontera, Marga; James, Katherine; Dean, Wendy; Kelsey, Gavin

2009-01-01

368

Genome-Wide DNA Methylation Patterns and Transcription Analysis in Sheep Muscle  

PubMed Central

DNA methylation plays a central role in regulating many aspects of growth and development in mammals through regulating gene expression. The development of next generation sequencing technologies have paved the way for genome-wide, high resolution analysis of DNA methylation landscapes using methodology known as reduced representation bisulfite sequencing (RRBS). While RRBS has proven to be effective in understanding DNA methylation landscapes in humans, mice, and rats, to date, few studies have utilised this powerful method for investigating DNA methylation in agricultural animals. Here we describe the utilisation of RRBS to investigate DNA methylation in sheep Longissimus dorsi muscles. RRBS analysis of ?1% of the genome from Longissimus dorsi muscles provided data of suitably high precision and accuracy for DNA methylation analysis, at all levels of resolution from genome-wide to individual nucleotides. Combining RRBS data with mRNAseq data allowed the sheep Longissimus dorsi muscle methylome to be compared with methylomes from other species. While some species differences were identified, many similarities were observed between DNA methylation patterns in sheep and other more commonly studied species. The RRBS data presented here highlights the complexity of epigenetic regulation of genes. However, the similarities observed across species are promising, in that knowledge gained from epigenetic studies in human and mice may be applied, with caution, to agricultural species. The ability to accurately measure DNA methylation in agricultural animals will contribute an additional layer of information to the genetic analyses currently being used to maximise production gains in these species.

Couldrey, Christine; Brauning, Rudiger; Bracegirdle, Jeremy; Maclean, Paul; Henderson, Harold V.; McEwan, John C.

2014-01-01

369

The functions of DNA methylation by CcrM in Caulobacter crescentus: a global approach  

PubMed Central

DNA methylation is involved in a diversity of processes in bacteria, including maintenance of genome integrity and regulation of gene expression. Here, using Caulobacter crescentus as a model, we exploit genome-wide experimental methods to uncover the functions of CcrM, a DNA methyltransferase conserved in most Alphaproteobacteria. Using single molecule sequencing, we provide evidence that most CcrM target motifs (GANTC) switch from a fully methylated to a hemi-methylated state when they are replicated, and back to a fully methylated state at the onset of cell division. We show that DNA methylation by CcrM is not required for the control of the initiation of chromosome replication or for DNA mismatch repair. By contrast, our transcriptome analysis shows that >10% of the genes are misexpressed in cells lacking or constitutively over-expressing CcrM. Strikingly, GANTC methylation is needed for the efficient transcription of dozens of genes that are essential for cell cycle progression, in particular for DNA metabolism and cell division. Many of them are controlled by promoters methylated by CcrM and co-regulated by other global cell cycle regulators, demonstrating an extensive cross talk between DNA methylation and the complex regulatory network that controls the cell cycle of C. crescentus and, presumably, of many other Alphaproteobacteria.

Gonzalez, Diego; Kozdon, Jennifer B.; McAdams, Harley H.; Shapiro, Lucy; Collier, Justine

2014-01-01

370

The functions of DNA methylation by CcrM in Caulobacter crescentus: a global approach.  

PubMed

DNA methylation is involved in a diversity of processes in bacteria, including maintenance of genome integrity and regulation of gene expression. Here, using Caulobacter crescentus as a model, we exploit genome-wide experimental methods to uncover the functions of CcrM, a DNA methyltransferase conserved in most Alphaproteobacteria. Using single molecule sequencing, we provide evidence that most CcrM target motifs (GANTC) switch from a fully methylated to a hemi-methylated state when they are replicated, and back to a fully methylated state at the onset of cell division. We show that DNA methylation by CcrM is not required for the control of the initiation of chromosome replication or for DNA mismatch repair. By contrast, our transcriptome analysis shows that >10% of the genes are misexpressed in cells lacking or constitutively over-expressing CcrM. Strikingly, GANTC methylation is needed for the efficient transcription of dozens of genes that are essential for cell cycle progression, in particular for DNA metabolism and cell division. Many of them are controlled by promoters methylated by CcrM and co-regulated by other global cell cycle regulators, demonstrating an extensive cross talk between DNA methylation and the complex regulatory network that controls the cell cycle of C. crescentus and, presumably, of many other Alphaproteobacteria. PMID:24398711

Gonzalez, Diego; Kozdon, Jennifer B; McAdams, Harley H; Shapiro, Lucy; Collier, Justine

2014-04-01

371

Role of Histone H3 Lysine 27 Methylation in X Inactivation  

Microsoft Academic Search

The Polycomb group (PcG) protein Eed is implicated in regulation of imprinted X-chromosome inactivation in extraembryonic cells but not of random X inactivation in embryonic cells. The Drosophila homolog of the Eed-Ezh2 PcG protein complex achieves gene silencing through methylation of histone H3 on lysine 27 (H3-K27), which suggests a role for H3-K27 methylation in imprinted X inactivation. Here we

Kathrin Plath; Jia Fang; Susanna K. Mlynarczyk-Evans; Ru Cao; Kathleen A. Worringer; Hengbin Wang; Cecile C. de la Cruz; Arie P. Otte; Barbara Panning; Yi Zhang

2003-01-01

372

Photo-sensitized oxidation of unsaturated fatty acid methyl esters. The identification of different pathways  

Microsoft Academic Search

and Summary  The photo-sensitized oxidation of methyl linolenate and methyl oleate was studied using erythrosine and riboflavin as sensitizers.\\u000a The complex mixtures of hydroperoxides obtained were analyzed for the proportion of conjugated products and, after reduction\\u000a to the corresponding mixtures of hydroxystearates, for the distribution of positional isomers. By comparing the mixtures with\\u000a that obtained from autoxidation, it was shown that

Henry W.-S. Chan

1977-01-01

373

Interindividual Concordance of Methylation Profiles in Human Genes for Tumor Necrosis Factors alpha and beta  

Microsoft Academic Search

The DNA in mammalian genomes is characterized by complex patterns of DNA methylation that reflect the states of all genetic activities of that genome. The modified nucleotide 5-methyldeoxycytidine (^5mdC) can affect the interactions of specific proteins with DNA sequence motifs. The most extensively studied effect of sequence-specific methylations is that of the long-term silencing of eukaryotic (mammalian) promoters. We have

Stefan Kochanek; Miklos Toth; Albrecht Dehmel; Doris Renz; Walter Doerfler

1990-01-01

374

75 FR 19272 - Thifensulfuron methyl; Pesticide Tolerances  

Federal Register 2010, 2011, 2012, 2013

...thifensulfuron methyl in or on safflower, seed. Interregional Research Project Number...2-thiophenecarboxylate), in or on safflower, seed at 0.05 parts per million (ppm...residues of thifensulfuron methyl on safflower seed at 0.05ppm. EPA's...

2010-04-14

375

Molecular Structure of Methyl Corylone  

NSDL National Science Digital Library

Methyl Corylone produces a taste and fragrance similar to Cyclotene. It is naturally found in coffee, tobacco and tobacco substitute cigarettes. This substance has a maple and caramel taste and as a flavor additive, it is recommended for caramel, maple, coffee and raisin.

2006-10-04

376

Toxicological Profile for Methyl Mercaptan.  

National Technical Information Service (NTIS)

The Statement was prepared to give information about methyl mercaptan and to emphasize the human health effects that may result from exposure to it. The Environmental Protection Agency (EPA) has identified 1,300 sites on its National Priorities List (NPL)...

1992-01-01

377

Ten members of the Arabidopsis gene family encoding methyl-CpG-binding domain proteins are transcriptionally active and at least one, AtMBD11 ,i s crucial for normal development  

Microsoft Academic Search

Animal proteins that contain a methyl-CpG-binding domain (MBD) are suggested to provide a link between DNA methylation, chromatin remodelling and gene silencing. However, some MBD proteins reside in chromatin remodelling complexes, but do not have specific affinity for methylated DNA. It has recently been shown that the Arabidopsis genome contains 12 putative genes encoding proteins with domains similar to MBD,

Anita Berg; Trine J. Meza; Mirela Mahic; Tage Thorstensen; Kjetil Kristiansen; Reidunn B. Aalen

2003-01-01

378

Structural adaptations in the interaction of EcoRI endonuclease with methylated GAATTC sites.  

PubMed Central

We have studied the interaction of EcoRI endonuclease with oligonucleotides containing GAATTC sites bearing one or two adenine-N6-methyl groups, which would be in steric conflict with key protein side chains involved in recognition and/or catalysis in the canonical complex. Single-strand methylation of either adenine produces small penalties in binding free energy (deltadeltaG0(S) approximately +1.4 kcal/mol), but elicits asymmetric structural adaptations in the complex, such that cleavage rate constants are strongly inhibited and unequal in the two DNA strands. The dependences of cleavage rate constants on the concentration of the Mg2+ cofactor are unaltered. When either adenine is methylated on both DNA strands, deltadeltaG0(S) (approximately +4 kcal/mol) is larger than the expected sum of the deltadeltaG0(S) values for the single-strand methylations, because the asymmetric adaptations cannot occur. Cleavage rate constants are reduced by 600 000-fold for the biologically relevant GAmATTC/CTTmAAG site, but the GmAATTC/CTTAmAG site forms only a non-specific complex that cannot be cleaved. These observations provide a detailed thermodynamic and kinetic explanation of how single-strand and double-strand methylation protect against endonuclease cleavage in vivo. We propose that non-additive effects on binding and structural 'adaptations' are important in understanding how DNA methylation modulates the biological activities of non-catalytic DNA binding proteins. Images

Jen-Jacobson, L; Engler, L E; Lesser, D R; Kurpiewski, M R; Yee, C; McVerry, B

1996-01-01

379

Changes in GE2270 antibiotic production in Planobispora rosea through modulation of methylation metabolism.  

PubMed

Thiazolylpeptide GE2270 is a potent antibiotic inhibiting protein synthesis in Gram-positive bacteria. It is produced as a complex of 10 related metabolites, differing mainly in the degree of methylation, by fermentation of the rare actinomycete Planobispora rosea ATCC 53773. Addition of vitamin B12 to the fermentation medium doubled total complex production and markedly changed the relative production of the various GE2270 metabolites, enhancing the biosynthesis of the more methylated component A. Among methylation inhibitors, the addition of sinefungin increased the amount of factor D2, which differs from component A in the lack of a methyl group. Since sinefungin is an S-adenosyl-L-methionine methyltransferase-specific inhibitor, these results indicate that the methylation step converting D2 into A involves an S-adenosyl-L-methionine methyltransferase. Simultaneous supplementation of vitamin B12 and sinefungin led to a twofold increase in D2 concentration, showing that vitamin B12, in addition to having an effect on the late methylation step, exerts a stimulating action on antibiotic backbone synthesis. This is possibly due to its role in an unusual pathway of serine synthesis peculiar to P. rosea metabolism. Finally, fermentation medium modifications were shown to be useful for the production of industrially valuable levels of components A or D2 in the GE2270 complex as starting points for the production of new interesting semi-synthetic antibiotics. PMID:12777492

Gastaldo, Luciano; Marinelli, Flavia

2003-06-01

380

ELUCIDATING THE PATHWAY FOR ARSENIC METHYLATION  

EPA Science Inventory

Enzymatically-catalyzed methylation of arsenic is part of a metabolic pathway that converts inorganic arsenic into methylated products. Hence, in humans chronically exposed to inorganic arsenic, methyl and dimethyl arsenic account for most of the arsenic that is excreted in the ...

381

DNA methylation in cancer and ageing  

Microsoft Academic Search

Epigenetic gene silencing through DNA methylation is now clearly thought to be one of the important steps in the mechanism underlying tumourigenesis. The methylation of several genes increases with age in normal tissues such as the colon. Methylation related to cancer and ageing may lead to new biomarkers and therapeutic concepts for cancer.

Yasuhito Yuasa

2002-01-01

382

Developmental regulation of neuronal genes by DNA methylation: environmental influences.  

PubMed

Steroid hormones have wide-ranging organizational, activational and protective actions in the brain. In particular, the organizational effects of early exposure to 17?-estradiol (E2) and glucocorticoids are essential for long-lasting behavioral and cognitive functions. Both steroid hormones mediate many of their actions through intracellular receptors that act as transcription factors. In the rodent cerebral cortex, estrogen receptor mRNA and protein expression are high early in postnatal life and declines dramatically as the animal approaches puberty. An understanding of the molecular mechanisms driving this developmental regulation of gene expression is critical for understanding the complex events that determine lasting brain physiology and prime the plasticity of neurons. Gene expression can be suppressed by the epigenetic modification of the promoter regions by DNA methylation that results in gene silencing. Indeed, the decrease in ER? mRNA expression in the cortex during development is accompanied by an increase in promoter methylation. Numerous environmental stimuli can alter the DNA methylation that occurs for ER?, glucocorticoid receptors, as well as many other critical genes involved in neuronal development. For example, maternal behavior toward pups can alter epigenetic regulation of ER? mRNA expression. Additionally perinatal stress and exposure to environmental estrogens can also have lasting effects on gene expression by modifying DNA methylation of these important genes. Taken together, there appears to be a critical window during development where, outside factors that alter epigenetic programming can have lasting effects on neuronal gene expression. PMID:23501000

Wilson, Melinda E; Sengoku, Tomoko

2013-10-01

383

Structural consequences of two methyl additions in the E. coli trp repressor L-tryptophan binding pocket  

SciTech Connect

The flexibility and specificity of the L-tryptophan corepressor binding pocket of E coli trp repressor are being investigated by high-resolution crystallographic examination of aporepressor/corepressor analog complexes. While addition of a methyl group on the corepressor indole (5-methyl-tryptophan) results in a small but measurable shift in the position of that functional group introduction of a methyl group on a nearby residue in the binding pocket (Val 58 {yields} Ile) leaves the indole position of L-tryptophan essentially unchanged. Careful alignment of these structures with aporepressor/L-tryptophan/operator-DNA complexes reveal why 5-methyltryptophan is a better corepressor than L-tryptophan.

Lawson, C.L.

1995-12-01

384

The superiority of asymmetric alkyl methyl carbonates  

SciTech Connect

The electrochemical behavior of graphite electrodes cycled galvanostatically versus Li metal in electrolyte solutions containing LiPF{sub 6}, LiC(SO{sub 2}CF{sub 3}){sub 3}, and LiN(SO{sub 2}C{sub 2}F{sub 5}){sub 2} in ethyl and methyl alkyl carbonates was studied. The solvents include ethyl methyl, ethyl propyl, methyl propyl, isopropyl methyl, and isopropyl ethyl carbonates. The use of asymmetric, aliphatic alkyl methyl carbonates is shown to be essential to achieve both high capacity and long cycle life with graphite electrodes in Li-ion batteries.

Ein-Eli, Y.; McDevitt, S.F.; Laura, R. [Covalent Associates, Inc., Woburn, MA (United States)

1998-01-01

385

Aberrant DNA methylation in human cancers.  

PubMed

DNA methylation, one of the best-characterized epigenetic modifications, plays essential roles in diseases, including human cancers. In recent years, our understanding on DNA methylation with human cancers has made significant progress, which was facilitated by stunning development in the analysis of the human methylome of multiple cancer types. In this review, recent developments in the characterization of aberrant DNA methylation involved in human cancers development were discussed with special emphasis on the mechanisms of aberrant DNA methylation in human cancers. We also summarize the recent treatment strategy for human cancers with de-methylation drugs. PMID:24337838

Li, Wen; Chen, Bi-feng

2013-12-01

386

Methods in DNA methylation profiling  

PubMed Central

Metastable and somatically heritable patterns of DNA methylation provide an important level of genomic regulation. In this article, we review methods for analyzing these genome-wide epigenetic patterns and offer a perspective on the ever-expanding literature, which we hope will be useful for investigators who are new to this area. The historical aspects that we cover will be helpful in interpreting this literature and we hope that our discussion of the newest analytical methods will stimulate future progress. We emphasize that no single approach can provide a complete view of the overall methylome, and that combinations of several modalities applied to the same sample set will give the clearest picture. Given the unexpected epigenomic patterns and new biological principles, as well as new disease markers, that have been uncovered in recent studies, it is likely that important discoveries will continue to be made using genome-wide DNA methylation profiling.

Zuo, Tao; Tycko, Benjamin; Liu, Ta-Ming; Lin, Huey-Jen L; Huang, Tim H-M

2010-01-01

387

Molecular Structure of Methyl Acrylate  

NSDL National Science Digital Library

Commercially available since 1944, methyl acrylate is a clear, colorless liquid with a sweet, fruity odor. This lachrymator often found in tobacco smoke, is used in the manufacturing of polymers, leather finishing, resins, textile, paper coatings, and plastic films. It is highly flammable and polymerizes explosively with exposure to light or heat. Inhibition by hydroquinone monomethyl ether, MEHQ, helps to prevent this problem. Because MEHQ functionality is reliant on oxygen, methyl acrylate must never be stored in an inert environment. Contact with skin will lead to severe deep burns, while ingestion or inhalation could lead to nausea, cough and abdominal pain. The liver, lungs, and kidneys are target organs for this compound, and medical attention should be sought immediately upon exposure.

2002-10-01

388

Silencing of human polycomb target genes is associated with methylation of histone H3 Lys 27  

Microsoft Academic Search

Polycomb group (PcG) complexes 2 and 3 are involved in transcriptional silencing. These complexes contain a histone lysine methyltransferase (HKMT) activity that targets different lysine residues on histones H1 or H3 in vitro. However, it is not known if these histones are methylation targets in vivo because the human PRC2\\/3 complexes have not been studied in the context of a

Antonis Kirmizis; Stephanie M. Bartley; Andrei Kuzmichev; Raphael Margueron; Danny Reinberg; Roland Green; Peggy J. Farnham

2004-01-01

389

Methyl and arylchalcogenolate complexes of cadmium in a sulfur rich coordination environment: syntheses and structural characterization of the tris(2-mercapto-1-tert-butylimidazolyl)hydroborato cadmium complexes [Tm(Bu(t))]CdMe, and [Tm(Bu(t))]CdEAr (E = O, S, Se, Te) and analysis of the bonding in chalcogenolate compounds.  

PubMed

A series of arylchalcogenolate complexes of cadmium supported by tris(2-mercapto-1-tert-butylimidazolyl)hydroborato ligation, namely [Tm(Bu(t))]CdEAr (EAr = OC(6)H(3)Ph(2), SPh, SePh, TePh), has been synthesized from [Tm(Bu(t))]CdMe; structural characterization by X-ray diffraction indicates that the variation in Cd-EAr bond lengths is similar to that of Zn-EAr and correlates closely with the covalent radius of the chalcogen, in marked contrast to the large variation in M-OAr and M-SAr bond lengths observed for other metals (Zr and Sm). PMID:16932812

Melnick, Jonathan G; Parkin, Gerard

2006-09-21

390

High-resolution mapping reveals a conserved, widespread, dynamic meiotically regulated mRNA methylation program  

PubMed Central

N6-methyladenosine (m6A) is the most ubiquitous mRNA base modification, but little is known about its precise location, temporal dynamics, and regulation. Here, we generated genomic maps of m6A sites in meiotic yeast transcripts at nearly single-nucleotide resolution, identifying 1,308 putatively methylated sites within 1,183 transcripts. We validated 8/8 methylation sites in different genes with direct genetic analysis, demonstrated that methylated sites are significantly conserved in a related species, and built a model that predicts methylated sites directly from sequence. Sites vary in their methylation profiles along a dense meiotic time-course, and are regulated both locally, via predictable methylatability of each site, and globally, through the core meiotic circuitry. The methyltransferase complex components localize to the yeast nucleolus, and this localization is essential for mRNA methylation. Our data illuminates a conserved, dynamically regulated methylation program in yeast meiosis, and provides an important resource for studying the function of this epitranscriptomic modification.

Schwartz, Schraga; Agarwala, Sudeep D.; Mumbach, Maxwell R.; Jovanovic, Marko; Mertins, Philipp; Shishkin, Alexander; Tabach, Yuval; Mikkelsen, Tarjei S; Satija, Rahul; Ruvkun, Gary; Carr, Steven A.; Lander, Eric S.; Fink, Gerald R.; Regev, Aviv

2014-01-01

391

Aberrant methylation of gene associated CpG sites occurs in borderline personality disorder.  

PubMed

Borderline personality disorder (BPD) is a complex psychiatric disease with an increased impact in the last years. While the diagnosis and therapy are well established, little is known on the pathogenesis of borderline personality disorder. Previously, a significant increase in DNA methylation of relevant neuropsychiatric genes in BPD patients has been reported. In our study we performed genome wide methylation analysis and revealed specific CpG sites that exhibited increased methylation in 24 female BPD patients compared to 11 female healthy controls. Bead chip technology and quantitative bisulfite pyrosequencing showed a significantly increased methylation at CpG sites of APBA2 (1.1 fold) and APBA3 (1.1 fold), KCNQ1 (1.5 fold), MCF2 (1.1 fold) and NINJ2 (1.2 fold) in BPD patients. For the CpG sites of GATA4 and HLCS an increase in DNA methylation was observed, but was only significant in the bead chip assay. Moreover genome wide methylation levels of blood samples of BPD patients and control samples are similar. In summary, our results show a significant 1.26 fold average increase in methylation at the analyzed gene associated CpG sites in the blood of BPD patients compared to controls samples (p<0.001). This data may provide new insights into epigenetic mechanisms underlying the pathogenesis of BPD. PMID:24367640

Teschler, Stefanie; Bartkuhn, Marek; Künzel, Natascha; Schmidt, Christian; Kiehl, Steffen; Dammann, Gerhard; Dammann, Reinhard

2013-01-01

392

Promoter methylation of leukemia inhibitory factor receptor gene in colorectal carcinoma.  

PubMed

Aberrant methylation of gene promoters and corresponding loss of gene expression plays a critical role in the initiation and progression of colorectal cancer. An IL-6-type cytokine receptor, leukemia inhibitory factor receptor (LIFR), is a component of cell-surface receptor complexes for multifunctional cytokines such as LIF. Herein, we report that LIFR is methylated in human colon cancer. LIFR promoter was methylated in primary tumor tissues with high frequency (65%, 52/80). Quantitative methylation-specific PCR (TaqMan-MSP) demonstrated differential promoter methylation of LIFR in primary colorectal cancer tissues as compared to normal colon tissues (5%, 4/80). LIFR methylation was not detectable in 13 normal colon mucosa samples obtained from patients without cancer. The mRNA expression of LIFR was significantly down-regulated in colon cancer tissues as compared to corresponding normal tissues. A strong expression of LIFR protein was observed in all non-malignant normal and adjacent normal colon mucosa tissues whereas down-regulated LIFR protein expression was observed in primary tumors. These results demonstrate that cancer-specific methylation and a specific decrease of LIFR expression are a common inactivation event in colon cancer development. PMID:21617854

Cho, Yong Gu; Chang, Xiaofei; Park, Il-Seok; Yamashita, Keishi; Shao, Chunbo; Ha, Patrick K; Pai, Sara I; Sidransky, David; Kim, Myoung Sook

2011-08-01

393

Dynamics of DNA methylation in recent human and great ape evolution.  

PubMed

DNA methylation is an epigenetic modification involved in regulatory processes such as cell differentiation during development, X-chromosome inactivation, genomic imprinting and susceptibility to complex disease. However, the dynamics of DNA methylation changes between humans and their closest relatives are still poorly understood. We performed a comparative analysis of CpG methylation patterns between 9 humans and 23 primate samples including all species of great apes (chimpanzee, bonobo, gorilla and orangutan) using Illumina Methylation450 bead arrays. Our analysis identified ?800 genes with significantly altered methylation patterns among the great apes, including ?170 genes with a methylation pattern unique to human. Some of these are known to be involved in developmental and neurological features, suggesting that epigenetic changes have been frequent during recent human and primate evolution. We identified a significant positive relationship between the rate of coding variation and alterations of methylation at the promoter level, indicative of co-occurrence between evolution of protein sequence and gene regulation. In contrast, and supporting the idea that many phenotypic differences between humans and great apes are not due to amino acid differences, our analysis also identified 184 genes that are perfectly conserved at protein level between human and chimpanzee, yet show significant epigenetic differences between these two species. We conclude that epigenetic alterations are an important force during primate evolution and have been under-explored in evolutionary comparative genomics. PMID:24039605

Hernando-Herraez, Irene; Prado-Martinez, Javier; Garg, Paras; Fernandez-Callejo, Marcos; Heyn, Holger; Hvilsom, Christina; Navarro, Arcadi; Esteller, Manel; Sharp, Andrew J; Marques-Bonet, Tomas

2013-01-01

394

Reprogramming DNA methylation in the mammalian life cycle: building and breaking epigenetic barriers  

PubMed Central

In mammalian development, epigenetic modifications, including DNA methylation patterns, play a crucial role in defining cell fate but also represent epigenetic barriers that restrict developmental potential. At two points in the life cycle, DNA methylation marks are reprogrammed on a global scale, concomitant with restoration of developmental potency. DNA methylation patterns are subsequently re-established with the commitment towards a distinct cell fate. This reprogramming of DNA methylation takes place firstly on fertilization in the zygote, and secondly in primordial germ cells (PGCs), which are the direct progenitors of sperm or oocyte. In each reprogramming window, a unique set of mechanisms regulates DNA methylation erasure and re-establishment. Recent advances have uncovered roles for the TET3 hydroxylase and passive demethylation, together with base excision repair (BER) and the elongator complex, in methylation erasure from the zygote. Deamination by AID, BER and passive demethylation have been implicated in reprogramming in PGCs, but the process in its entirety is still poorly understood. In this review, we discuss the dynamics of DNA methylation reprogramming in PGCs and the zygote, the mechanisms involved and the biological significance of these events. Advances in our understanding of such natural epigenetic reprogramming are beginning to aid enhancement of experimental reprogramming in which the role of potential mechanisms can be investigated in vitro. Conversely, insights into in vitro reprogramming techniques may aid our understanding of epigenetic reprogramming in the germline and supply important clues in reprogramming for therapies in regenerative medicine.

Seisenberger, Stefanie; Peat, Julian R.; Hore, Timothy A.; Santos, Fatima; Dean, Wendy; Reik, Wolf

2013-01-01

395

A sensitive microfluidic platform for a high throughput DNA methylation assay.  

PubMed

DNA methylation is an epigenetic modification essential for normal development and maintenance of somatic biological functions. DNA methylation provides heritable, long-term chromatin regulation and the aberrant methylation pattern is associated with complex diseases including cancer. Discovering novel therapeutic targets demands development of high-throughput, sensitive and inexpensive screening platforms for libraries of chemical or biological matter involved in DNA methylation establishment and maintenance. Here, we present a universal, high-throughput, microfluidic-based fluorometric assay for studying DNA methylation in vitro. The enzymatic activity of bacterial HPAII DNA methyltransferase and its kinetic properties are measured using the assay (K = 5.8 nM, K = 9.8 nM and Kcat = 0.04 s(-1)). Using the same platform, we then demonstrate a two-step approach for high-throughput in vitro identification and characterization of small molecule inhibitors of methylation. The approach is examined using known non-nucleoside inhibitors, SGI-1027 and RG108, for which we measured IC50 of 4.5 ?M and 87.5 nM, respectively. The dual role of the microfluidic-based methylation assay both for the quantitative characterization of enzymatic activity and high-throughput screening of non-nucleoside inhibitors coupled with quantitative characterization of the inhibition potential highlights the advantages of our system for epigenetic studies. PMID:24841578

Ronen, Maria; Avrahami, Dorit; Gerber, Doron

2014-07-01

396

DNA methylation in gastric cancer, related to Helicobacter pylori and Epstein-Barr virus.  

PubMed

Gastric cancer is a leading cause of cancer death worldwide, and significant effort has been focused on clarifying the pathology of gastric cancer. In particular, the development of genome-wide analysis tools has enabled the detection of genetic and epigenetic alterations in gastric cancer; for example, aberrant DNA methylation in gene promoter regions is thought to play a crucial role in gastric carcinogenesis. The etiological viewpoint is also essential for the study of gastric cancers, and two distinct pathogens, Helicobacter pylori (H. pylori) and Epstein-Barr virus (EBV), are known to participate in gastric carcinogenesis. Chronic inflammation of the gastric epithelium due to H. pylori infection induces aberrant polyclonal methylation that may lead to an increased risk of gastric cancer. In addition, EBV infection is known to cause extensive methylation, and EBV-positive gastric cancers display a high methylation epigenotype, in which aberrant methylation extends to not only Polycomb repressive complex (PRC)-target genes in embryonic stem cells but also non-PRC-target genes. Here, we review aberrant DNA methylation in gastric cancer and the association between methylation and infection with H. pylori and EBV. PMID:24744581

Matsusaka, Keisuke; Funata, Sayaka; Fukayama, Masashi; Kaneda, Atsushi

2014-04-14

397

Nitric Oxide Modifies Global Histone Methylation by Inhibiting Jumonji C Domain-containing Demethylases*?  

PubMed Central

Methylation of lysine residues on histone tails is an important epigenetic modification that is dynamically regulated through the combined effects of methyltransferases and demethylases. The Jumonji C domain Fe(II) ?-ketoglutarate family of proteins performs the majority of histone demethylation. We demonstrate that nitric oxide (•NO) directly inhibits the activity of the demethylase KDM3A by forming a nitrosyliron complex in the catalytic pocket. Exposing cells to either chemical or cellular sources of •NO resulted in a significant increase in dimethyl Lys-9 on histone 3 (H3K9me2), the preferred substrate for KDM3A. G9a, the primary methyltransferase acting on H3K9me2, was down-regulated in response to •NO, and changes in methylation state could not be accounted for by methylation in general. Furthermore, cellular iron sequestration via dinitrosyliron complex formation correlated with increased methylation. The mRNA of several histone demethylases and methyltransferases was also differentially regulated in response to •NO. Taken together, these data reveal three novel and distinct mechanisms whereby •NO can affect histone methylation as follows: direct inhibition of Jumonji C demethylase activity, reduction in iron cofactor availability, and regulation of expression of methyl-modifying enzymes. This model of •NO as an epigenetic modulator provides a novel explanation for nonclassical gene regulation by •NO.

Hickok, Jason R.; Vasudevan, Divya; Antholine, William E.; Thomas, Douglas D.

2013-01-01

398

Nitric oxide modifies global histone methylation by inhibiting Jumonji C domain-containing demethylases.  

PubMed

Methylation of lysine residues on histone tails is an important epigenetic modification that is dynamically regulated through the combined effects of methyltransferases and demethylases. The Jumonji C domain Fe(II) ?-ketoglutarate family of proteins performs the majority of histone demethylation. We demonstrate that nitric oxide ((•)NO) directly inhibits the activity of the demethylase KDM3A by forming a nitrosyliron complex in the catalytic pocket. Exposing cells to either chemical or cellular sources of (•)NO resulted in a significant increase in dimethyl Lys-9 on histone 3 (H3K9me2), the preferred substrate for KDM3A. G9a, the primary methyltransferase acting on H3K9me2, was down-regulated in response to (•)NO, and changes in methylation state could not be accounted for by methylation in general. Furthermore, cellular iron sequestration via dinitrosyliron complex formation correlated with increased methylation. The mRNA of several histone demethylases and methyltransferases was also differentially regulated in response to (•)NO. Taken together, these data reveal three novel and distinct mechanisms whereby (•)NO can affect histone methylation as follows: direct inhibition of Jumonji C demethylase activity, reduction in iron cofactor availability, and regulation of expression of methyl-modifying enzymes. This model of (•)NO as an epigenetic modulator provides a novel explanation for nonclassical gene regulation by (•)NO. PMID:23546878

Hickok, Jason R; Vasudevan, Divya; Antholine, William E; Thomas, Douglas D

2013-05-31

399

The Dynamics of DNA Methylation in Schizophrenia and Related Psychiatric Disorders  

PubMed Central

Major psychiatric disorders such as schizophrenia (SZ) and bipolar disorder (BP) with psychosis (BP+) express a complex symptomatology characterized by positive symptoms, negative symptoms, and cognitive impairment. Postmortem studies of human SZ and BP+ brains show considerable alterations in the transcriptome of a variety of cortical structures, including multiple mRNAs that are downregulated in both inhibitory GABAergic and excitatory pyramidal neurons compared with non-psychiatric subjects (NPS). Several reports show increased expression of DNA methyltransferases in telencephalic GABAergic neurons. Accumulating evidence suggests a critical role for altered DNA methylation processes in the pathogenesis of SZ and related psychiatric disorders. The establishment and maintenance of CpG site methylation is essential during central nervous system differentiation and this methylation has been implicated in synaptic plasticity, learning, and memory. Atypical hypermethylation of candidate gene promoters expressed in GABAergic neurons is associated with transcriptional downregulation of the corresponding mRNAs, including glutamic acid decarboxylase 67 (GAD67) and reelin (RELN). Recent reports indicate that the methylation status of promoter proximal CpG dinucleotides is in a dynamic balance between DNA methylation and DNA hydroxymethylation. Hydroxymethylation and subsequent DNA demethylation is more complex and involves additional proteins downstream of 5-hydroxymethylcytosine, including members of the base excision repair (BER) pathway. Recent advances in our understanding of altered CpG methylation, hydroxymethylation, and active DNA demethylation provide a framework for the identification of new targets, which may be exploited for the pharmacological intervention of the psychosis associated with SZ and possibly BP+.

Grayson, Dennis R; Guidotti, Alessandro

2013-01-01

400

Characterizing Genes with Distinct Methylation Patterns in the Context of Protein-Protein Interaction Network: Application to Human Brain Tissues  

PubMed Central

Background DNA methylation is an essential epigenetic mechanism involved in transcriptional control. However, how genes with different methylation patterns are assembled in the protein-protein interaction network (PPIN) remains a mystery. Results In the present study, we systematically dissected the characterization of genes with different methylation patterns in the PPIN. A negative association was detected between the methylation levels in the brain tissues and topological centralities. By focusing on two classes of genes with considerably different methylation levels in the brain tissues, namely the low methylated genes (LMGs) and high methylated genes (HMGs), we found that their organizing principles in the PPIN are distinct. The LMGs tend to be the center of the PPIN, and attacking them causes a more deleterious effect on the network integrity. Furthermore, the LMGs express their functions in a modular pattern and substantial differences in functions are observed between the two types of genes. The LMGs are enriched in the basic biological functions, such as binding activity and regulation of transcription. More importantly, cancer genes, especially recessive cancer genes, essential genes, and aging-related genes were all found more often in the LMGs. Additionally, our analysis presented that the intra-classes communications are enhanced, but inter-classes communications are repressed. Finally, a functional complementation was revealed between methylation and miRNA regulation in the human genome. Conclusions We have elucidated the assembling principles of genes with different methylation levels in the context of the PPIN, providing key insights into the complex epigenetic regulation mechanisms.

Zhao, Zheng; Li, Shengli; Bai, Jing; Wu, Aiwei; Jiang, Chunjie; Wang, Yuan; Su, Bin; Li, Xia

2013-01-01

401

Dynamics of Histone Lysine Methylation: Structures of Methyl Writers and Eraser  

PubMed Central

In Eukarya, the packaging of DNA into chromatin provides a barrier that allows for regulation of access to the genome. Chromatin is refractory to processes acting on DNA. ATP-dependent chromatin remodeling machines and histone-modify