Picosecond fluorescence of reaction centres from <i>Rhodospirillum rubrum</i>

Abstract

The fluorescence kinetics of isolated Rhodospirillum rubrum reaction centres was studied. In the picosecond time range the decay was well approximated by two exponential components. The short‐lived component was observed only when P 870 was reduced and had a maximal amplitude at about 910 nm. Its lifetime was equal to 7 ± 2 ps both at room temperature and at 77 K. It is inferred that this fluorescence component is emitted by excited photochemically active P 870 before the formation of an intermediate radical‐pair state. The second, long‐lived component with a lifetime of about 100–200 ps was observed in a wider spectral range and had maxima at about 850 and 900 nm both under reducing and oxidizing conditions. The bulk of this luninescence seemed to be emitted either by photochemically inactive P 870 and/or by traces of antenna bacteriochlorophyll.