KINETICS OF THE PHOTO‐INDUCED EPR SIGNAL IN WHOLE‐CELL RHODOSPIRILLUM RUBRUM: EFFECTS OF LIGHT INTENSITY, DARK ADAPTATION, TEMPERATURE, AND MICROWAVE POWER

Abstract

Abstract— Kinetics of the bacteriochlorophyll (P870+) electron paramagnetic resonance signal photo‐induced at room temperature in whole‐cell Rhodospirillum rubrum exhibit transients which are strongly dependent upon the light‐dark history of the cells. This paper reports a study of these kinetics as a function of actinic light intensity, light‐dark history, temperature and applied microwave power. The simplest interpretation of the observed complexities in the kinetic curves is that the rate of formation and the rate of decay of P870+ are controlled by slow dark reactions of the electron‐transport chain, and that the rate‐controlling reaction is variable during the transition from a dark‐adapted to a steady state in the light. With this interpretation, it is possible to measure or to infer order‐of‐magnitude estimates of the lifetimes of some of the slow reactions. Copyright © 1974, Wiley Blackwell. All rights reserved