The role of tocopherols in biomembrane lipid peroxidation.

The rate constants of elementary reactions of oxidation inhibition by tocopherols of different structures (peroxy radical destruction by antioxidant molecules, interaction of inhibitor radicals with one another and with oxidation substrate) are discussed. In contrast with most synthetic phenol antioxidants, tocopherols exhibit a high affinity to peroxy radicals (the rate constants for their reactions with these radicals are one or two orders of magnitude greater than those for reactions involving most synthetic phenols: they possess a fairly high stability of phenoxyl radicals formed and activity in the reaction of oxidation-chain transfer). The activity of tocopherol radicals in chain transfer reactions depends on their structure and manifests itself in a marked dependence of the extent of inhibition on oxidation conditions and the antioxidant concentration, up to an opposite effect.

[Radiosensitivity of coding and noncoding DNA sequences of various organisms].

Relationship between pyrimidine distribution patterns and radiosensitivity (Z) of DNA molecules of different species was derived by computer analysis of recurrence frequency of pyrimidine clusters. Blocking factors (beta) and Z for coding and non-coding DNA sequences of species from different taxonomic classes have been calculated within a new model. The radiosensitivity of coding DNA sequences practically does not vary whereas Z values were increased during evolution from simplest to higher organisms.