Photooxidase Activity of Heated Chromatophores of Rhodospirillum rubrum

Abstract

A validation was sought of the photooxidase assay using reduced indophenol by comparing the effect of mild heat treatments on both the absorption spectrum and the photooxidase activity of the chromatophore of Rhodospirillum rubrum (Esmarch) Molisch strain 1. The mild heat treatments of the chromatophore caused a more rapid decline in the rate of photooxidation of reduced indophenol than a destruction of the far-red absorption band of bacteriochlorophyll. This indicated that such photooxidations were not simply a passage of electrons from the reduced indophenol to the nascent photooxidized bacteriochlorophyll as other heat-labile factors were also necessary for the photooxidation of the reduced indophenol. The rates of these photooxidations on a bacteriochlorophyll basis were comparable to the rates of the photoreduction of exogenous DPN. It is suggested that such photooxidations are valid measurements for the oxidant in bacterial photosynthesis.