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[en] Complete text of publication follows. Plant derived resveratrol (trans-3,5,4'-trihydroxystilbene) possesses a broad spectrum of biological activities, one of them are very well known its antioxidative properties. Our work aims to provide kinetic data with regard to the reactivity of resveratrol with uninvestigated short-lived bioradicals, identified as mediators in oxidative lipid degradation processes. Radicals of our interest are alkoxyl radicals, well known propagators of the chain free radical reactions in lipids, and thiyl radicals which protect lipids from their degradation pathway, but at the same time cause the isomerization of the double bonds. In order to investigate these reactions of resveratrol laser flash photolysis was used. On the basis of competitive kinetics the rate constants were determined under pseudo-first order conditions in acetonitrile solutions at room temperature. Thiyl radicals were generated indirectly in solution containing 1-octadecanthiol and photosensitive benzophenone in acetonitrile using the light pulses at 347 nm from ruby laser. Tert-butoxyl radicals were generated directly by peroxide bond cleavage from di-tert-butyl peroxide in acetonitrile by light pulses of Nd:YAG at 355 nm, and ruby at 347 nm. Obtained rate constants for the reactions of resveratrol and radicals generated by laser flash photolysis will be summarized and compared with rare literature data for the rate constants of investigated reactions of resveratrol and other radicals generated by pulse radiolysis.
[en] Molecular invariants may be deduced in a very compact way through Grassman algebra. In this work, a generalized valence is defined for an atomic group; it reduces to the Known expressions for the case of an atom in a molecule. It is the same of the correlations between the fluctions of the atomic charges qc and qd (C belongs to the group and D does not) around their average values. Numerical results agree with chemical expectation. (author)
[pt]Invariantes moleculares podem ser deduzidos de uma forma muito compacta atraves de uma algebra de Grassmann. Neste trabalho, define-se uma valencia generalizada definida para um grupo atomico; ela se reduz as expressoes conhecidas para o caso de um atomo numa molecula. Ela e a soma das correlacoes entre as flutuacoes das cargas atomicas qc e qd (C pertence ao grupo e D nao) em torno de seus valores medios. Os resultados numericos estao de acordo com os valores quimicos. (author)
[en] Exposure of proteins to radicals in the presence of molecular oxygen results in side-chain oxidation and the formation of a range of side-chain oxidation products. A number of these materials have been used as markers of protein oxidation, including carbonyl groups formed on a range of side-chains. Recently, initial hydroxyl radical attack on a range of aliphatic side-chains (including Ala, Val, Leu, Asp residues), in the presence of molecular oxygen, has been shown to give rise to amino acid hydroperoxides and loss of the side-chain from the protein as a low-molecular-weight carbonyl compounds. These released carbonyls arise via the formation, and subsequent beta-scission, of alkoxyl radicals formed at the C-3 site. These carbonyls are not measured in most carbonyl assays and hence the extent of oxidative stress may be underestimated. We show in this study that the ratio of bound-to-released carbonyls is highly variable even when equivalent doses of oxidant are employed. Thus radiolytically-generated hydroxyl radicals give vastly different ratios of bound to released carbonyl products when compared to metal-ion/hydrogen peoxide systems, peroxyl radicals (derived from the thermolabile azo-compound AAPH) and hypochlorous acid. These studies therefore suggest that the absolute yield of carbonyl products detected on proteins cannot be compared between different oxidant systems, and a low level of protein-bound carbonyls does not always indicate a low level of oxidative stress
[en] An existing drift apparatus has been adapted to mobility measurements. Mobilities of C+/He, CH+/He, CH2+/He and CH3+/Ar, hitherto unknown or known with low accuracy only, have been determined over the E/N range of about 20 - 200 Td. (G.Q.)