Re-examination of primary radical pair recombination in Rp. viridis with Q(A) reduced

Charge recombination in the primary radical pair P+H- of the purple photosy nthetic bacterium Rp. viridis with pre-reduced secondary acceptor Q(A), has been studied by time-resolved photovoltage measurements and transient abso rption spectroscopy with a time resolution of 1 ns. The lifetime of P+H- wa s found to be 2.4-3 ns in intact membranes and similar to 5 ns in isolated reaction centers, in contrast to a lifetime of similar to 15 ns which has b een widely accepted in the literature for reaction centers. The origin of t he difference between lifetimes of P+H- in membranes and isolated reaction centers is discussed. (C) 1999 Elsevier Science B.V. All rights reserved.