USE OF LASER FLASH-PHOTOLYSIS TIME-RESOLVED SPECTROPHOTOMETRY TO INVESTIGATE INTERPROTEIN AND INTRAPROTEIN ELECTRON-TRANSFER MECHANISMS

A description is given of the methodology developed in our laboratory for the application of laser flash photolysis to the elucidation of th e kinetics and mechanism of electron transfer processes which occur in termolecularly between two protein molecules within a collisional comp lex, or intramolecularly between two redox centers within a single mul tisubunit or multidomain protein. This involves the use of flavin anal ogs, excited to their lowest triplet state by a laser flash, to initia te electron transfer. either by oxidation of a sacrificial donor follo wed by redox protein reduction via the flavin semiquinone, or by direc t oxidation of a reduced redox protein by the flavin triplet. Time-res olved spectrophotometry is used to follow the course of the sequence o f electron transfer events initiated by the laser flash. The applicati on of this methodology to the following systems is described: cytochro me c/cytochrome c peroxidase; ferredoxin/ferredoxin NADP-reductase; cy tochrome c/plastocyanin; flavocytochrome b2; and sulfite oxidase.