@article {ISI:000244896900002, title = {Sulfur K-edge XAS as a probe of sulfur-centered radical intermediates.}, journal = {J. Am. Chem. Soc.}, volume = {129}, number = {11}, year = {2007}, month = {mar}, pages = {3034{\textendash}5}, abstract = {Sulfur K-edge XAS is used in the identification and characterization of sulfur based radicals obtained from UV irradiated glutathione. Ground state and time-dependent DFT calculations are used to identify thiyl (RS center dot) and perthiyl (RSS center dot) radical species.}, keywords = {DFT, Free Radicals, Free Radicals: analysis, Free Radicals: chemistry, GLUTATHIONE, Glutathione: chemistry, Oxidation-Reduction, PHOTOCHEMISTRY, SPECTROMETRY, SPECTROPHOTOMETRY, Sulfhydryl Compounds, Sulfhydryl Compounds: chemistry, SULFUR, sulfur redox, Sulfur: chemistry, ULTRAVIOLET, X-Ray Emission, X-Ray Emission: methods, XAS}, issn = {0002-7863}, doi = {10.1021/ja0676760}, url = {http://www.ncbi.nlm.nih.gov/pubmed/17319664}, author = {Martin-Diaconescu, Vlad and Kennepohl, Pierre} } @article {1112, title = {Chromatographic separation and identification of products from the reaction of dimethylarsinic acid with hydrogen sulfide}, journal = {Chemical Research in Toxicology}, volume = {18}, number = {12}, year = {2005}, note = {ISI Document Delivery No.: 004XYTimes Cited: 24Cited Reference Count: 44}, month = {Dec}, pages = {1821-1829}, type = {Article}, abstract = {The reaction of dimethylarsinic acid (DMA(V)) with hydrogen sulfide (H2S) is of biological significance and may be implicated in the overall toxicity and carcinogenicity of arsenic. The course of the reaction in aqueous phase was monitored, and an initial product, dimethylthioarsinic acid, was observed by using LC-ICP-MS and LC-ESI-MS. Dimethylarsinous acid was observed as a minor product. A second slower-forming product was identified, and the electrospray mass chromatograms for this species produced ions at m/z 275, 171, and 137 in positive mode. To aid in the identification of this slower-forming product, crystalline standards of sodium dimethyldithioarsinate and dimethylarsino dimethyldithioarsinate were prepared and re-characterized by using improved spectroscopic and structural analysis techniques. An aqueous solution of sodium dimethyldithioarsinate produced a single major chromatographic peak that matched the retention time (7.6 min) of the slower-forming product and contained similar molecular ions at m/z 275, 171, and 137 via LC-ESI-MS. The dimethylarsino dimethyldithioarsinate standard produced four aqueous phase species one of which coeluted with the slower forming product. This coeluting peak also produced the identical ESI-MS ions as the slower-forming product of DMA(V) + H2S. ESI-MS/MS experiments conducted on sodium dimethyldithioarsinate in deuterated water produced molecular ions at m/z 276, 173, and 137. Subsequent collisionally activated dissociation (CAD) experiments on m/z 276 did not produce a product ion at m/z 173. These data indicate that two different species are present in solution, while NMR data indicate that only dimethyldithioarsinic acid exists in aqueous solutions. This discrepancy was investigated by conducting NMR studies on the acidic solution of sodium dimethyldithioarsinate after taking this solution to dryness. The resolubilized solution produced a proton NMR signal characteristic of dimethylarsino dimethyldithioarsinate. Therefore, it was concluded that the ESI-MS ion at m/z 275 associated with the slowly forming second reaction product and the sodium dimethyldithioarsinate compound is a product of the ESI desolvation process.}, keywords = {CRYSTAL-STRUCTURE, DIMETHYLDITHIOARSINATE, GLUTATHIONE, METABOLITE, ORGANIC ARSENIC COMPOUNDS, RATS, REARRANGEMENT, TOXICITY, TRIMETHYLARSINE OXIDE, urine}, isbn = {0893-228X}, url = {://000234787200005}, author = {Fricke, M. W. and Zeller, M. and Sun, H. and Lai, V. W. M. and Cullen, W. R. and Shoemaker, J. A. and Witkowski, M. R. and Creed, J. T.} } @article {5225, title = {Reaction of human myoglobin and nitric oxide - Heme iron or protein sulfhydryl (S) nitrosation dependence on the absence or presence of oxygen}, journal = {Journal of Biological Chemistry}, volume = {276}, number = {6}, year = {2001}, note = {ISI Document Delivery No.: 401HBTimes Cited: 33Cited Reference Count: 58}, month = {Feb}, pages = {3991-3998}, type = {Article}, abstract = {The amino acid sequence of human myoglobin (Mb) is similar to other mammalian Mb except for a unique cysteine residue at position 110 (Cys(110)). Anaerobic treatment of ferrous forms of wild-type human Rib, the C110A variant of human Mb or horse heart Mb, with either authentic NO or chemically derived NO in vitro yields heme-NO complexes as detected by electron paramagnetic resonance spectroscopy (EPR). By contrast, no EPR-detectable heme-NO complex was observed from the aerobic reactions of NO and either the ferric or oxy-Mb forms of wild-type human or horse heart myoglobins, Mass analyses of wild-type human Mb treated aerobically with NO indicated a mass increase of similar to 30 atomic mass units (i.e,, NO/Mb = 1 mol/mol), Mass analyses of the corresponding apoprotein after heme removal showed that NO was associated with the apoprotein fraction. New electronic maxima were detected at A(333) nm (epsilon = 3665 +/- 90 mol(-1) cm(-1); mean +/- S.D.) and A(545) nm (epsilon = 44 +/- 3 mol(-1) cm(-1)) in solutions of S-nitrosated wild-type human Mb (similar to S-nitrosoglutathione), Importantly, the sulfhydryl S-H stretch vibration for Cys(110) measured by Fourier transform infrared (nu similar to 2552 cm(-1)) was absent for both holo- and apo- forms of the wild-type human protein after aerobic treatment of the protein with NO. Together, these data indicate that the reaction of wild-type human Mb and NO yields either heme-NO or a novel S-nitrosated protein dependent on the oxidation state of the heme iron and the presence or absence of dioxygen.}, keywords = {ELECTRON-SPIN-RESONANCE, GLUTATHIONE, HEMOGLOBIN, HUMAN SKELETAL-MUSCLE, METMYOGLOBIN, NITROSOTHIOLS, OXIDATION, RELAXING FACTOR, SMOOTH-MUSCLE, VASCULAR TONE}, isbn = {0021-9258}, url = {://000166921200038}, author = {Witting, P. K. and Douglas, D. J. and Mauk, A. G.} } @article {4942, title = {Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells}, journal = {Archives of Toxicology}, volume = {74}, number = {6}, year = {2000}, note = {ISI Document Delivery No.: 349ZATimes Cited: 358Cited Reference Count: 37}, month = {Aug}, pages = {289-299}, type = {Article}, abstract = {Biomethylation is considered a major detoxification pathway for inorganic arsenicals (iAs). According to the postulated metabolic scheme, the methylation of iAs yields methylated metabolites in which arsenic is present in both pentavalent and trivalent forms. Pentavalent mono- and dimethylated arsenicals are less acutely toxic than iAs. However, little is known about the toxicity of trivalent methylated species. In the work reported here the toxicities of iAs and trivalent and pentavalent methylated arsenicals were examined in cultured human cells derived from tissues that are considered a major site for iAs methylation (liver) or targets for carcinogenic effects associated with exposure to iAs (skin, urinary bladder, and lung). To characterize the role of methylation in the protection against toxicity of arsenicals, the capacities of cells to produce methylated metabolites were also examined. In addition to human cells, primary rat hepatocytes were used as methylating controls. Among the arsenicals examined, trivalent monomethylated species were the most cytotoxic in all cell types. Trivalent dimethylated arsenicals were at least as cytotoxic as trivalent iAs (arsenite) for most cell types. Pentavalent arsenicals were significantly less cytotoxic than their trivalent analogs. Among the cell types examined, primary rat hepatocytes exhibited the greatest methylation capacity for iAs followed by primary human hepatocytes, epidermal keratinocytes, and bronchial epithelial cells. Cells derived from human bladder did not methylate iAs. There was no apparent correlation between susceptibility of cells to arsenic toxicity and their capacity to methylate iAs. These results suggest that (1) trivalent methylated arsenicals, intermediary products of arsenic methylation, may significantly contribute to the adverse effects associated with exposure to iAs, and (2) high methylation capacity does not protect cells from the acute toxicity of trivalent arsenicals.}, keywords = {ARSENATE, arsenic, ARSENITE, BINDING, bladder, cell culture, CELLULAR UPTAKE, DIMETHYLARSINIC ACID, dimethylarsinous acid, DRINKING-WATER, ENZYMATIC METHYLATION, GLUTATHIONE, HEPATOCYTES, HUMAN, IN-VITRO METHYLATION, LIVER, lung, METABOLISM, methylarsonic acid, methylarsonous acid, METHYLATION, RABBIT LIVER, SKIN, TOXICITY}, isbn = {0340-5761}, url = {://000089074500001}, author = {Styblo, M. and Del Razo, L. M. and Vega, L. and Germolec, D. R. and LeCluyse, E. L. and Hamilton, G. A. and Reed, W. and Wang, C. and Cullen, W. R. and Thomas, D. J.} } @article {4552, title = {The separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid on the Hamilton PRP-X100 anion-exchange column}, journal = {Applied Organometallic Chemistry}, volume = {13}, number = {11}, year = {1999}, note = {ISI Document Delivery No.: 255DLTimes Cited: 24Cited Reference Count: 29}, month = {Nov}, pages = {837-843}, type = {Article}, abstract = {In order to separate the potential arsenite metabolites methylarsonous acid and dimethylarsinous acid from arsenite, arsenate, methylarsonic acid and dimethylarsinic acid, the pH-dependent retention behaviour of all six arsenic compounds was studied on a Hamilton PRP-X100 anion-exchange column with 30 mM phosphate buffers (pH 5, 6, 7, 8 and 9) containing 20\% (v/v) methanol as mobile phase and employing an inductively coupled plasma atomic emission spectrometer (ICP-AES) as the arsenic-specific detector. Baseline separation of dimethylarsinic acid, methylarsonous acid, methylarsonic acid, arsenate and dimethylarsinous acid was achieved with a 30 mmol dm(-3) phosphate buffer (pH 5)-methanol mixture (80:20, v/v) in 25 min. Arsenite is not baseline-separated from dimethylarsinic acid under these conditions, Copyright (C) 1999 John Wiley \& Sons, Ltd.}, keywords = {ARSENATE, ARSENITE, BEHAVIOR, DIMETHYLARSINIC ACID, dimethylarsinous acid, ENVIRONMENT, ENZYMATIC METHYLATION, GLUTATHIONE, HPLC-ICP-AES, LAKE-BIWA, METABOLISM, METHYLARSENICALS, methylarsonic acid, methylarsonous acid, SPECIATION, SPECTROMETRY}, isbn = {0268-2605}, url = {://000083654200005}, author = {Gailer, J. and Madden, S. and Cullen, W. R. and Denton, M. B.} }