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The damage caused by oxidative and glycative stress to cells accumulates on a daily basis and accelerates aging. Glutathione (GSH), a major antioxidant molecule in living organisms, plays a crucial role in detoxifying the stress-causing substances inherent in cells, such as H2O2 and methylglyoxal (MG), an important intermediate of advanced glycation end-products (AGEs). In this study, we focused on the enhanced antioxidant capacity of the selenium analog of GSH, i.e., selenoglutathione (GSeH), compared to GSH, and examined its effects on the detoxification of stress-causing substances and improvement in cell viability. In cell-free systems, GSeH (1 mM) generated in situ from GSeSeG in the presence of NADPH and glutathione reductase (GR) rapidly reduced more than 80% of 0.1 mM H2O2, indicating the significant glutathione peroxidase (GPx)-like antioxidant activity of GSeSeG. Similarly, around 50% of 0.5 mM MG was degraded by 0.5 mM GSeH within 30 min through a non-enzymatic mechanism. It was also found that GSeSeG (0.05–0.5 mM) showed glutathione S-transferase (GST)-like activity against 1-chloro-2,4-dinitrobenzene (CDNB), a model substance of oxidative stress-causing toxic materials in cells. Meanwhile, HeLa cells that had been pre-treated with GSeSeG exhibited increased viability against 1.2 mM H2O2 (at [GSeSeG] = 0.5–50 μM) and 4 mM MG (at [GSeSeG] = 3 μM), and the latter effect was maintained for two days. Thus, GSeSeG is a potential antioxidant and antiglycative stress agent for cells. [ABSTRACT FROM AUTHOR]

Sodium hypochlorite pentahydrate (NaClO·5H2O, 1) has recently been employed in organic synthesis as an oxidant for alcohols, sulfides, glycols, etc. In most of these reactions, however, reagent 1 functions just as a simple oxidant, and the variations of the reactions have not been well explored. In this study, we report another useful and fascinating reaction, in which reagent 1 functions as a green chlorinating reagent toward β,γ-unsaturated carboxylic acid (2). When substrate 2 was stirred at room temperature with 1 (2 eq) in acetonitrile for 1 h, α,β-unsaturated lactone (3) was obtained in moderate yields (up to 62%). The same reaction proceeded in various organic and aqueous solvents as well. When excess reagent 1 was employed, lactone 3 was further oxidized to the corresponding epoxide (4) for some cases. The conversion is initiated by electrophilic attack of HOCl to the C=C bond of 2 to generate a chloronium ion intermediate, which is cyclized to β-chlorolactone (5) and then 3 through the elimination of HCl. The usefulness of 1 as a chlorinating reagent was further demonstrated in the electrophilic substitution of activated aromatic compounds. [ABSTRACT FROM AUTHOR]

Weak nonbonded interaction between a divalent sulfur (S) atom and a main-chain carbonyl oxygen (O) atom are characterized in proteins. However, they have shown distinctly different directional propensities around the O atom from the S...O interactions in small organic compounds, although the linearity of the C-S...O or S-S...O atomic alignment was observed. The results suggested that S...O interactions may control protein structures to some extent and its unique directional properties can be applied to molecular design.

The oxidative regeneration pathways of two three-disulfide mutants of bovine pancreatic ribonuclease A lacking the 65-72 disulfide bond were investigated. Oxidized dithiothreitol was used as an oxidizing agent and 2-aminoethylmethanethiosulfonate as a thiol-blocking agent. Results show that the two mutants, Cys65 and Cys72, folded through the same pathway at a rate lower than that of the wild-type protein. It was also found that the removal of energetic factors causes deceleration of the regeneration of the three-disulfide mutants.

The strength of the nonbonded interaction between an unsymmetric amino nitrogen and the divalent selenium in seven 2-selenobenzylamine derivatives was determined via experimental and theoretical methods. The results, which showed a correlation between the strength of the Se...N interaction and the electrophilic reactivity of the selenium group, indicated the orbital interaction between the antibonding orbital of the Se-X bond and nitrogen lone pair as the cause of the observed phenomenon.

The X-ray structural characterization of an areneselenenyl chloride (ArSeCl), which is strongly stabilized by the intramolecular N...Se-Cl non-bonded interaction has been demonstrated. This interaction is the primary origin of the planar structure of ArSeCl which is also the case for Se-Cl bond. These indicated that the nature of the observed N...Se-Cl interaction is a three-centre-four-electron bond. The features of the electronic structure is discussed.

Mechanistic functions of the amino nitrogens situated at the active center of glutathione peroxidase (GPX), a selenium-containing enzyme, are examined. The model catalyst di-2-(N-cyclohexyl,N-(methylamino)methyl)phenyl diselenide acts exactly as GPX does in the induction catalytic cycle. H NMR spectroscopy revealed the presence of hypervalent Se-N bonding in the catalytic system.