Abstract: Photodamage and photooxidation mechanisms of bovine serumalbumin (BSA) as induced by UVradiation
and one-electron oxidation by SO4-· were investigated by 266 nm laser flash photolysis. BSA can be photoionized and photoexcited by 266 nm photons to give tryptophan (Trp)/NH+·, Trp/N· resulting from the rapid deprotonation of Trp/NH+·, and 3Trp*. Through intermolecular electron transfer between 3Trp* and tyrosine (Tyr), Tyr/O· was produced. In one-electron oxidation of BSA by SO4-· the apparent set up rate constants of Tyr and Trp radicals were calculated but intermolecular electron transfer was not observed. We propose that SO4-· oxidizes BSA by electron transfer to the Tyr and Trp of BSA with a rate constant of 1.51×10¹⁰ L·mol^-1·s^-1. This research provides an introductory theory to enable further study on the redox metabolic process of BSA.

Key words: Bovine serumalbumin, Photo-ionization, Photo-excitation, Electron transfer, One-electron oxidization