A kinetic study of the production of light-induced ESR signals in Rhodospirillum rubrum chromatophores

Abstract

The rise kinetics of the light-induced ESR signal of Rhodospirillum rubrum chromatophores has been re-examined and the rise time of this signal has been found to be a function of bacteriochlorophyll concentration and of light intensity. At constant bacteriochlorophyll concentration the rate constant was found to be first order over a thousand-fold range of light intensities. The formation rate constant was found to be proportional to the light intensity (within experimental error). At the highest light intensity used (3.0 × 10 5 ergs cm −2 sec −1) the corrected characteristic time ( 1 k ) was found to be about 5 milliseconds. No evidence was found for an induction period within the resolving time of the instrumental system used. The experimental results presented here are consistent with the hypothesis that the light-induced ESR signal may originate from the primary photo-oxidant of bacterial photosynthesis.