Radiolysis of N-acetyl amino acids as model compounds for radiation degradation of polypeptides

• Published in: Radiation physics and chemistry 1982, Vol.20 (5), p.351-358
• Main Authors: Wayne Garrett, R., Hill, David J.T., Ho, Sook-Ying, O'Donnell, James H., O'Sullivan, Paul W., Pomery, Peter J.
• Format: Article
• Language: English
• ISSN: 0146-5724
• DOI: 10.1016/0146-5724(82)90127-3

Radiation chemical yields of (i) the volatile radiolysis products and (ii) the trapped free radicals from the y-radiolysis of the N-acetyl derivatives of glycine, L-valine, L-phenylalanine and L-tyrosine in the polycrystalline state have been determined at room temperature (303 K). Carbon dioxide was found to be the major molecular product for all these compounds with G(CO 2) varying from 0.36 for N-acetyl-L-tyrosine to 8 for N-acetyl-L-valine. There was evidence for some scission of the N-C α bond, indicated by the production of acetamide and the corresponding aliphatic acid, but the determination reaction was found to be of much lesser importance than the decarboxylation reaction. A protective effect of the aromatic ring in N-acetyl-L-phenylalanine and in N-acetyl-L-tyrosine was indicated by the lower yields of volatile products for these compounds. The yields of trapped free radicals were found to vary with the nature of the amino acid side chain, increasing with chain length and chain branching. The radical yields were decreased by incorporation of an aromatic moiety in the side chain, this effect being greater for the tyrosyl side chain than for the phenyl side chain. The G(R·) values showed a good correlation with G(CO 2) indicating that a common reaction may be involved in radical production and carbon dioxide formation.