Time‐resolved measurements of fluorescence from reaction centres of <i>Rhodopseudomonas sphaeroides</i> R26.1

Abstract

The fluorescence decay pattern of the emission from the ‘special pair’ in reaction centres from Rhodopseudomonas sphaeroides R26.1 was recorded with a time resolution of 1 ns. The decay kinetics were monitored in photochemically ‘open’ reaction centres and in reaction centres ‘closed’ either by chemical reduction of the ubiquinone or by prior removal of the ubiquinone. As previously noted with reaction centres from Rhodopseudomonas viridis three fluorescence decay phases have been resolved. The origin of these phases is described in terms of a model which assumes that some of the initial charge separation in the reaction centre occurs in the ‘M’ branch as well as in the ‘L’ branch and that putting a negative charge on the quinone electrostatically inhibits the forward rate of the charge separation.