Photoelectron generation and transfer to cytochrome c studied by nanosecond transient absorption spectroscopy

Abstract

A reaction scheme is proposed and shown to be useful for time-resolved spectroscopy of cytochrome c reduction on the nanosecond timescale. It is based on photochemical generation of hydrated electrons from ferrocyanide by a pulsed UV laser and the reduction of cytochrome c by the hydrated electrons. The reaction scheme is such that the system nearly regenerates itself, and it can be modified for more complete regeneration. Results by two types of nanosecond transient absorption spectroscopy are presented. Both methods utilize pulses of the fourth harmonic, at 266 nm, from a Nd:YAG laser for the photolysis. One technique is based on a gated vidicon detector for identification of the transient species. The other uses a transient recorder for kinetic measurements at a higher time resolution. The observed results are in close agreement with those obtained by a kinetic analysis including all coupled reactions and using previously determined values of the quantum yields and rate constants. The approach utilizing photochemically generated hydrated electrons as reductants might be useful in several other systems for studies of transient states involved in redox transitions. © 1985 American Institute of Physics.