Damage to the amino acid residues in protein molecules during irradiation

The prediction of the original site of localization of damage (free valence) in protein components of the cell during irradiation seems important primarily for the search for a method of their effective radiation protection in the cell. Usually data on the reactivity of the biopolymer - amino acids - with respect to radiolysis products - free radicals - are used for this purpose. However, when a number of proteins are irradiated in aqueous solutions, noncorrespondence of the degree of damage to individual fragments of the macromolecules to what should have occurred according to the reactivity of individually irradiated amino acids is detected. It seemed advisable to determine the vulerability of individual amino acid residues in certain proteins, using ESR measurements for this purpose, namely, under conditions of low-temperature irradiation of the proteins, when the conversions of macroradicals are inhibited, to establish the major types of primary macroradicals according to the ESR spectra and to determine their partial yields. The authors analyzed the data of ESR measurements in 10% solutions of gelatin and total thymus histones, and dry wool keratin preparation, differing substantially in amino acid composition, irradiated at 77 K. Under these conditions the electron acts as the main reagent possessing mobility