Femtosecond time-resolve fluorescence study of reaction center isolated from a purple bacteria Acidiphilium rubrum containing Zn-bacteriochlorophyll

Abstract

Photosynthetic Reaction center(RC) was purified from an acidophilic purple bacterium Acidiphilium rubrum that uses Zn-bacteriochlorophyll a as a major pigment. We measured femtosecond fluorescence kinetics by fluorescence upconversion to determine the electron transfer time from Zn-BChl dimer(P) to BPhe(H) in the purified RC. Accesary Zn-BChl(B) was excited by Ti-Safire laser at 815 nm of 180 fs width. The rise and decay of fluorescence from P were 160 fs and 3.3ps, respectively. The former represents the energy transfer from B to P, and the latter the electron transfer from P to H. The two time constants are almost equal to those in RC of R.sphaeroides that has typical Mg-BChl a type RC. Angles of dipole moment between B and P estimated by fluorescence depolarization was 32 degree. Energy transfer from LH1 to RC was estimated to be 42 ps by the fl photon counting.