title: Energy level of P+B- with respect to P* found from recombination fluorescence measurements in pheophytin-modified reaction centres.
abstract: Recent studies of reaction centres from Rhodobacter sphaeroides (R-26), in which bacteriopheophytins a were replaced by plant pheophytins a, have shown that at low temperature the excited state of primary electron donor P* is converted to the state P+B-(A) (where B(A) is a bacteriochlorophyll a monomer in branch A) which has a long lifetime (about 600 ps [8]). This allows the direct measurement of the free energy difference between P* and P+B-(A) using the temperature dependence of the recombination fluorescence from P+B-(A). The data show that P+B-(A) is located below P* by 550+/-30 mV. Thus, the primary conversion of P* leads to the formation of P+B-(A) which is below P* in energy and is a real intermediate in electron transfer.
authors.affiliation: Belozerzky Institute of Physico-Chemical Biology, Moscow State University, Russia.
authors.forename: V A
authors.initials: VA
authors.lastname: Shuvalov
authors.forename: A G
authors.initials: AG
authors.lastname: Yakovlev
mesh_terms: D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D010674:Pheophytins / Q000378:metabolism / Q000494:pharmacology*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D012242:Rhodobacter sphaeroides / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods; D013816:Thermodynamics
chemical_list: D045342:Light-Harvesting Protein Complexes; D010674:Pheophytins; D045322:Photosynthetic Reaction Center Complex Proteins; C006678:bacteriopheophytin; C061694:pheophytin a