Acetic and Propionic Acid Production from γ-Irradiated Dry Proteins

Abstract

Acetic and propionic acid production from polyalanine, polyglycine, silk fibroin, and alpha-chymotrypsinogen A upon exposure in the solid state in vacuo to gamma rays has been determined by gas chromatography. The G values for the yield of propionic and acetic acid from alpha-chymotrypsinogen A are 0.21 and 0.19, respectively, and those from silk fibroin 0.7 and 0.7, respectively. This compares to the yield of acetic acid from polyglycine with a G value of 1.0 and the yield of propionic acid from polyalanine with a G value of 1.2. Comparison of these values on the basis of glycine and alanine content within the two proteins allows a closer correlation. The substantial yield of gamma ray-induced main-chain scissions (inferred from fatty acid production) in globular proteins and the absence of a decrease in molecular weight suggest the formation of intramolecular bonds by recombination of the long-lived radicals when the protein is dissolved after radiolysis.