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Various 2-substituted-1,3-dithiane oxides (1-oxide and 1,3-dioxide) have been metalated and reacted for the first time with a trialkylborane (trioctylborane). The 2-chloro-1,3-dioxide results in migration of an octyl group from boron to carbon with the displacement of chloride and gives nonanoic acid after oxidation, but there is no evidence for a second migration involving displacement of a sulfenate group. The reaction involving lithiation of the 2-methoxy-1-oxide results in two migrations, with the displacement of both the methoxy group and the thiolate unit of the dithiane ring, giving dioctyl ketone after oxidation, but the yield is low, primarily because thiophilic addition of the lithiating agent predominates over lithiation. Again, there is no evidence for the displacement of the sulfenate unit. However, the intermediate prior to oxidation can be treated with trifluoroacetic anhydride to induce a Pummerer rearrangement, and the presumed trifluoroacetoxyalkylthiolate group then acts as a novel leaving group and is displaced, resulting in trioctylmethanol on oxidation, but the yield is again very low. [ABSTRACT FROM AUTHOR]

The work considers direct and indirect electrochemical methods of activation of hydrogen sulfide in the reaction with cycloheptane. It is suggested to apply anodic (cathodic) activation and combined redox systems including the electrode and chemical substance (oxidant, mediator, and deprotonating agent) to enhance HS reactivity. It is shown that interaction between activated HS with cycloheptane results in the product of thiolation of the substrate and the further formation of dicycloheptyl sulfide, dicycloheptyl disulfide, dicycloheptyl trisulfide, and dicycloheptyl sulfoxide. The current efficiency of sulfur-containing compounds depends on the method of reagent activation and duration of the reaction. [ABSTRACT FROM AUTHOR]

Human microsomal glutathione transferase 2 (MGST2) is a trimeric integral membrane protein that belongs to the membrane-associated proteins in eicosanoid and glutathione metabolism (MAPEG) family. The mammalian MAPEG family consists of six members where four have been structurally determined. MGST2 activates glutathione to form a thiolate that is crucial for GSH peroxidase activity and GSH conjugation reactions with electrophilic substrates, such as 1-chloro-2,4-dinitrobenzene (CDNB). Several studies have shown that MGST2 is able to catalyze a GSH conjugation reaction with the epoxide LTA 4 forming the pro-inflammatory LTC 4 . Unlike its closest homologue leukotriene C 4 synthase (LTC4S), MGST2 appears to activate its substrate GSH using only one of the three potential active sites [Ahmad S, et al. (2013) Biochemistry . 52, 1755–1764]. In order to demonstrate and detail the mechanism of one-third of the sites reactivity of MGST2, we have determined the enzyme oligomeric state, by Blue native PAGE and Differential Scanning Calorimetry, as well as the stoichiometry of substrate and substrate analog inhibitor binding to MGST2, using equilibrium dialysis and Isothermal Titration Calorimetry, respectively. Global simulations were used to fit kinetic data to determine the catalytic mechanism of MGST2 with GSH and CDNB (1-chloro-2,4-dinitrobenzene) as substrates. The best fit was observed with 1/3 of the sites catalysis as compared with a simulation where all three sites were active. In contrast to LTC4S, MGST2 displays a 1/3 the sites reactivity, a mechanism shared with the more distant family member MGST1 and recently suggested also for microsomal prostaglandin E synthase-1. [ABSTRACT FROM AUTHOR]

Abstract: Intracellular generation of reactive oxygen species (ROS) is an inescapable consequence of aerobic metabolism. Although some of these oxygen-derived metabolites are well-documented mediators of cell and tissue damage, others have been shown to be crucial for cell survival and homeostasis. One ROS that has been identified as a major second messenger in redox signaling is hydrogen peroxide (H2O2). This small, membrane-permeable oxidant is produced transiently in physiological (nontoxic) amounts by a variety of different enzymes residing within different subcellular compartments and organelles. There is an accumulating literature demonstrating that the reversible, H2O2-mediated oxidation of different signaling proteins is an important posttranslational mechanism that regulates a number of different biological processes including cell proliferation, differentiation, motility and apoptosis. Although several, well-characterized methods have been developed to quantify the generation of extracellular H2O2, the ability to unequivocally detect and quantify this important signaling molecule within living cells has been relatively limited. Fortunately, a great deal of progress has been made over the past few years in developing H2O2-selective probes that are capable of detecting physiological levels of this signaling molecule. This overview presents a critical evaluation of the established as well as the more recently developed methods to detect and quantify extracellular and intracellular H2O2 produced by living cells. [Copyright &y& Elsevier]

RS- ion is called as thiolate anion and it is well stated in the literature that certain metals made complexes with thiolate anion, in order to prove this fact a study was design to check the affect of different concentrations of lithium carbonate on the status of thiolate anion by using UV-visible spectrophotometer. Results show that there is decrease in the concentration of thiolate anion with the increase in concentration of lithium ions showing the possibility of interaction between lithium ion and thiolate anion resulting in the formation of oligomeric Li-S-R. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) is an important second messenger in cellular signal transduction. H2O2-dependent signalling regulates many cellular processes, such as proliferation, differentiation, migration and apoptosis. Nevertheless, H2O2 is an oxidant and a major contributor to DNA damage, protein oxidation and lipid peroxidation, which can ultimately result in cell death and/or tumourigenesis. For this reason, cells have developed complex antioxidant systems to scavenge ROS. Recently, our laboratory identified the protein, annexin A2, as a novel cellular redox regulatory protein. Annexin A2 possesses a reactive cysteine residue (Cys-8) that is readily oxidized by H2O2 and subsequently reduced by the thioredoxin system, thereby enabling annexin A2 to participate in multiple redox cycles. Thus, a single molecule of annexin A2 can inactivate several molecules of H2O2. In this report, we will review the studies detailing the reactivity of annexin A2 thiols and the importance of these reactive cysteine(s) in regulating annexin A2 structure and function. We will also focus on the recent reports that establish novel functions for annexin A2, namely as a protein reductase and as a cellular redox regulatory protein. We will further discuss the importance of annexin A2 redox regulatory function in disease, with a particular focus on tumour progression. [ABSTRACT FROM AUTHOR]

Abstract: Cytochrome P450 was the first hemoprotein found to have a thiolate anion as the axial ligand of the heme. Several other heme–thiolate proteins, including nitric oxide synthase, were later found in animals, plants, and microorganisms. Both cytochrome P450 and nitric oxide synthase, two major members of the heme–thiolate protein family, catalyze monooxygenase reactions, but the physiological functions of other heme–thiolate proteins are apparently highly diverse. Chloroperoxidase of a mold, Caldaryomyces fumago, catalyzes a haloperoxidase reaction. CooA of a bacterium, Rhodospirillum rubrum, and heme-regulated eIF2α kinase of animals function as the sensors for carbon monoxide and nitric oxide, respectively, to elicit biological responses to these gases. The role of heme in the enzymatic activity of cystathionine β-synthase is still unknown. It is likely that more heme–thiolate proteins with diversified functions will be found in various organisms in the future. [Copyright &y& Elsevier]

Reactivity of 5-thioxylopyranosyl bromide and 1,5-dithioxylopyranoside towards thiolate anions. Reactivity of thiolate anion RS– 2′ (C6H5–S–) and 3′ (p-CH3–C6H4–S–) towards 5-thioxylopyranosyl bromide Xyl–Br yields to the corresponding 1,5-dithioxylopyranoside Xyl–SR 7 R = C6H5– and 8 R = p-CH3–C6H4, respectively. In the presence of 4′ (C6H5–CH2–S–) or 5′ (CH3–S–), the reaction gives the 5-thioxylopyranose 9. Anions 5′ and 4′ react with 1,5-dithioxylopyranoside 10 Xyl–SR′ (R′ = –C6H4–CO–C6H4–CN) to give sulphide derivative 11 (CH3–S–C6H4–CO–C6H4– CN) and 13 (C6H5–CH2–S–C6H4–CO–C6H4–CN), respectively, and the 1,5–dithioxylose 12. These differences in terms of reactivity could be explained by the nucleophilic behaviour of the formed thiolate anion. To cite this article: D. Brevet et al., C. R. Chimie 6 (2003). [Copyright &y& Elsevier]