- The reaction of hydrogen sulfide with disulfides: formation of a stable trisulfide and implications for biological systems
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Background and Purpose: The signalling associated with hydrogen sulfide (H2S) remains to be established, and recent studies have alluded to the possibility that H2S-derived species play important roles. Of particular interest are hydropersulfides (RSSH) and related polysulfides (RSSnR, n?>?1). This work elucidates the fundamental chemical relationship between these sulfur species as well as examines their biological effects. Experimental Approach: Using standard analytical techniques (1H-NMR and MS), the equilibrium reactions between H2S, disulfides (RSSR), RSSH, dialkyltrisulfides (RSSSR) and thiols (RSH) were examined. Their ability to protect cells from electrophilic and/or oxidative stress was also examined using cell culture. Key Results: H2S, RSSR, RSSH, RSSSR and RSH are all in a dynamic equilibrium. In a biological system, these species can exist simultaneously, and thus, it is difficult to discern which species is (are) the biological effector(s). Treatment of cells with the dialkyl trisulfide cysteine trisulfide (Cys-SSS-Cys) resulted in high intracellular levels of hydropersulfides and protection from electrophilic stress. Conclusions and Implications: In aqueous systems, the reaction between H2S and RSSR results in the formation of equilibria whereby H2S, RSH, RSSR, RSSH and RSSSR are present. In a biological system, any of these species can be responsible for the observed biological activity. These equilibrium species can also be generated via the reaction of RSH with RSSSR. Due to these equilibria, Cys-SSS-Cys can be a method for generating any of the other species. Importantly, HEK293T cells treated with Cys-SSS-Cys results in increased levels of hydropersulfides, allowing examination of the biological effects of RSSH. Linked Articles: This article is part of a themed section on Chemical Biology of Reactive Sulfur Species. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.4/issuetoc.
- Bianco, Christopher L,Toscano, John P,Akaike, Takaaki,Ida, Tomoaki,Nagy, Peter,Bogdandi, Virag,Kumagai, Yoshito,Henderson, Catherine F,Goddu, Robert N,Lin, Joseph,Fukuto, Jon M
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- Oxidation of L-cystine by 12-tungstocobaltate(III) in aqueous Perchlorate medium: A kinetic approach
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The oxidation reaction of L-cystine with 12-tungstocobaltate(III) (Co IIIW12O405- or Co IIIW5-) has been studied spectrophotometrically over the range 1.15 ≤ 103[H4L2+]T. ≤ 3.5; 2.0 ≤ pH ≤ 5.0; 25°C ≤ t ≤ 40°C and I = 0.3 mol dm-3 (NaClO4). Both the conjugate bases of L-cystine participate in the electron transfer reaction. The rate of the reaction has been found to increase with the increase in pH and [L-cystine]T. The reaction shows first order dependence both on [CoIIIW5-] and [L-cystine] T. The ΔH? (kJ mol-1) and ΔS? (J K-1 mol-1) for k1 and k2 paths are 16.9±2.0, 16.1±0.5 and-205±6, -204±1.5, respectively. Negative activation entropy is indicative of ordered transition state for the reaction. The product of the reaction has been found to be the cystinesulphoxide.
- Satpathy, Prasanna Kumar,Dash, Gobind Chandra,Mohanty, Prakash
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p. 1199 - 1203
(2009/03/11)
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- Homogeneous Aqueous Oxidation of Organic Molecules by OxoneR and Catalysis by a Water-Soluble Manganese Porphyrin Complex
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Peroxymonosulfate (KHSO5) oxidizes a wide variety of water-soluble organic molecules in aqueous solutions, and the reactions are generally more rapid in phosphate buffer (pH 6-7) than in pure water.A water-soluble porphyrin complex, meso-tetrakis(4-N-methylpyridyl)porphyrinatomanganese(III) chloride, catalyzes epoxidation and hydroxylation under neutral pH conditions.
- Zheng, Tu-Cai,Richardson, David E.
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p. 833 - 836
(2007/10/02)
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