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PHOTOLYSIS AND PHOTO‐OXIDATION OF AMINO ACIDS AND PEPTIDES—III. EFFECT OF IONIZING RADIATION ON CYSTINE AND RELATED AMINO ACIDS
Author(s) -
Forbes W. F.,
Rivett D. E.,
Savige W. E.
Publication year - 1962
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1962.tb08082.x
Subject(s) - chemistry , amino acid , cystine , cysteic acid , cysteine , radical , ionizing radiation , irradiation , alanine , aqueous solution , lanthionine , radiolysis , photochemistry , organic chemistry , biochemistry , physics , nuclear physics , enzyme
Summary Irradiation of cystine (RSSR, R = NH 2 CH(COOH)CH 2 ‐ ‐ ), cysteine (RSH), S‐methycysteine (RSCH,) or lanthionine (RSR) in aqueous solution with ionizing radiation (X‐or y‐rays) yields products similar to those previously shown to be produced by ultraviolet light irradiation. The range and yields of products are affected by factors such as radiaion dosage, pH and the presence of air. Cystine readily yields products derived both from S‐S bond fission (e.g. cysteic acid) and from C‐S fission (e.g. alaninethiosulphuric acid (RSSO 3 H)). The initial products from cysteine are mainly cystine and alanine. With radiation doses up to 10 5 rad, S‐methylcysteine and lanthionine usually give low yields of the corresponding sulphoxides, but with higher doses (10 6‐ 10 7 rad) C‐S fission occurs yielding other amino acids such as alanine. On irradiation of the four amino acids in the solid state, ionizing radiation, unlike 2537Å light, effects only slight conversion to other amino acids. However electron spin resonance (ESR) spectra indicate that for cystine and cysteine similar trapped free radicals are obtained with both forms of electromagnetic radiation. The relative ease of S‐bond fission of these amino acids on irradiation in aqueous solution as compared with solid state irradiation is compatible with accepted views on indirect action of H, OH and OOH radicals.