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

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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.