Über die direkte Wirkung von Röntgenstrahlen auf Proteine, Peptide und Aminosäuren

Abstract

The primary effect of Roentgen rays (0.5 to 150 million r) on crystallized dry amino acids and peptides was investigated by chemical, biochemical and physico-chemical methods. The following reactions always recur: Amine formation as a result of decarboxylation; formation of an [alpha]-imino-or [alpha]-ketocarboxylic acid as a result of a dehydration in the [alpha]-, [beta]-position; formation of [beta]-, [gamma] -or [gamma]- [delta] -unsaturated [alpha]-aminocarboxylic acids or their [gamma]- or [delta] -lactones; breaking and cross-linking of aliphatic carbon chains. In peptides the same reactions occur as in amino acids, although in a different relation; here the radiochemical dehydration of a peptide linkage to an amino group leads to the formation of an energy-rich imino-acyl linkage which in the presence of water is immediately hydrolyzed. In long-chain peptides the end product was two fragments (also ammonia); one with an old amino-terminal and a new carboxyl-terminal amino acid, and the other with the old carboxyl-terminal amino acid and a keto group in place of an amino group on the other end. The ion yield for the formation of [alpha]-keto-acids from amino acids is related exponentially to the irradiation dose. The ion yield for the formation of pyruvic acid from serine is independent of the dose.