Esr Studies of the Low Temperature Irradiation of Keratin and Its Component Amino Acids

The photoejection of electrons from the aromatic amino acids at 77°K by 290–340 nm radiation was found to involve both monophotonic and biphotonic processes. However, only monophotonic processes are involved when electrons are photoejected from cystine or cysteine. These electrons prefer to attach themselves to adjacent sulphur groups rather than the dielectric traps in the matrix, so that both anionic and cationic radicals are formed. In keratin at 77°K, the disulphide anion radicals are produced by both monophotonic and biphotonic mechanisms, indicating that the electrons captured by the disulphides are photo‐ejected from the aromatic amino acids. At room temperature the thiyl and aromatic radicals are produced only by monophotonic reactions.