Tateki Hayashi

Novel Free Radicals Formed by the Amino-Carbonyl Reactions of Sugars with Amino Acids, Amines, and Proteins

Formation of novel free radicals in an early stage of the amino-carbonyl reactions of sugars with either amino acids,amines and some peptides were demonstrated by use of ESR spectroscopy. These radicals showed characteristic hyperfine ESR spectra and apparently differed from those observed in melanoidin. Formation of radicals of this type was faster at alkaline pH, but their signals were most stably observed in weakly acidic pH region and disappeared rapidly in other regions. The radicals developed even the mixtures were heated in open test tube but abolished rapidly by aeration. The results of reactions of various sugars or related carbonyl compounds with various amino compounds indicated that presence of sugar-like enedioi structure in the carbonyl compound and a primary amine group in the amino compound are necessary for the formation of the radical products, and that the spectral patterns were mainly influenced by the structure of amino compound, e.g. α-vs β-alanine, but not by the structure of sugar, except for three carbon aldehydes. Analyses of the hyperfine structures of ESR spectra lead to the assumption of the identity of the radical products as N,N’-disubstituted pyrazine radical derivatives. Formation of such free radicals was also investigated on some peptides and proteins.

Tris(2-deoxy-2-l-ascorbyl)amine: a novel compound related to a fairly stable free radical

Abstract Tri(2-deoxy-2-L-ascorbyl)amine ( 1 ), isolated as one of the new products of reaction of dehydroascorbic acid with an α-amino acid, produces by air oxidation a blue free radical species which is fairly stable in water.

Redox reaction of tri(2-deoxy-2-L-ascorbyl)amine. Formation of a persisting free radical species in water

Abstract Electrochemical studies showed that tri(2-deoxy-2- L -ascorbyl)amine ( 1 ), a new compound isolated as one of the products of reaction of dehydro- L -ascorbic acid with phenylalanine (with added L -ascorbic acid) in ethanol, is oxidized in aqueous solution in two reversible one-electron transfer steps, on mercury or platinum electrode. The first step occurs through the dianion, and its product is an unusually stable blue anion radical giving a characteristic ESR signal. The product of the second step of oxidation is labile and is slowly converted into the oxidized form of di(2-deoxy-2- L -ascorbyl)amine, presumably by hydrolysis with splitting of L -ascorbic acid.

On the Mechanism of Thymine Formation from Thymine Glycol by γ-irradiation in Aqueous System

SummaryTo elucidate the mechanism of the reverse reaction from thymine glycol to thymine in aqueous solution by γ-irradiation, the effects of oxygen, pH and various scavengers were studied. These results indicate that the reaction is due principally to hydrated electrons. This was also demonstrated by the reaction of thymine glycol with chemically-produced electrons. The rate constant of the reaction with hydrated electrons was estimated by the competition method. E.s.r. studies in ethylene glycol glass suggested the presence of the anion intermediate. A reaction mechanism involving disproportionate processes in thymine formation is proposed.