Oxygen effect in the radiolysis of proteins. Part 2. Bovine serum albumin.

Radiolysis of bovine serum albumin under aerobic and anaerobic conditions was studied by SDS-polyacrylamide gel electrophoresis. After Coomassie Blue or Fast Green staining quantitative evaluations give information about the degradation processes of the protein. Under nitrogen the main reaction is the aggregation caused by covalent cross-links, which includes only a small portion of intermolecular S-S bridges. Under air the radiolysis leads to peptide chain scission, which is not a random process, but yields specific protein fragments. A mechanism for this fragmentation reaction is suggested. The radiation-induced broadening of the serum albumin peak is interpreted as being a result of intramolecular disulfide exchange. In contrast to lactate dehydrogenase the degradation of serum albumin is enhanced by oxygen, probably because of its low tryptophan content.