The primary electron transfer has been investigated
by femtosecond time-resolved absorption spectroscopy
in two chemically modified reaction centers (RC) of
Rhodobacter sphaeroides, in which the monomeric bacteriochlorophylls
BA and BB have both been exchanged by 132-
hydroxybacteriochlorophyll a or [3-vinylJ-132-hydroxybacteriochlorophyll
a. The kinetics of the primary electron transfer
are not influenced by the 132-hydroxy modification. In RCs
containing [3-vinyl]-132-hydroxybacteriochlorophyll a the primary
rate is reduced by a factor of 10.