Isolation and characterization of radiation-induced aliphatic peptide dimers.

alpha-Peptide radicals of L-Ala-L-Ala and tetra-L-Ala, formed from reaction with OH radicals, generated in H2O by ionizing radiation, were shown to give peptide dimers. These peptide dimers were separated and isolated by HPLC. On acid hydrolysis, all of the studied peptide dimers yielded alanine and 1,2-diamino-1,2-dimethyl succinic acid, which was characterized by gas chromatography-mass spectrometry as its TMS derivative. The described procedure is also suggested as a suitable method for isolation and characterization of amino acid dimers.