Oxygen effect in the radiolysis of proteins

Radiolysis of myoglobin was carried out under air and under nitrogen in phosphate buffer at pH 5 and 7. The radiation products were separated by SDS-polyacrylamide gel electrophoresis and by HPL gel chromatography with guanidine.HCl. Under nitrogen the main reaction is the aggregation caused by covalent cross-links. Under air the radiolysis leads to peptide chain scission, which is not a random process, but produces specific protein fragments. The estimated molecular weights of these fragments gave further support to the assumption that the aminoacyl-proline peptide group is the preferential breaking site. In contrast to haemoglobin, myoglobin showed nearly no radiation-induced fragmentation under nitrogen.