Structural, dynamic, and energetic aspects of long-range electron transfer in photosynthetic reaction centers.
Intramolecular electron transfer within proteins plays an essential role in biological energy transduction. Electron donor and acceptor cofactors are bound in the protein matrix at specific locations, and protein-cofactor interactions as well as protein conformational changes can markedly influence the electron transfer rates. To assess these effects, we have investigated charge recombination from the primary quinone acceptor to the special pair bacteriochlorophyll dimer in wild-type reaction centers of Rhodobacter sphaeroides and four mutants with widely modified free energy gaps. After light-induced charge separation, the recombination kinetics were measured in the light- and dark-adapted forms of the protein from 10 to 300 K. The data were analyzed by using the spin-boson model, which allowed us to self-consistently determine the electronic coupling energy, the distribution of energy gaps, the spectral density of phonons, and the reorganization energy. The analysis revealed slow changes of the energy gap after charge separation. Interesting correlations of the control parameters governing electron transfer were found and related to structural and dynamic properties of the protein.
Kriegl
Jan M
JM
Department of Biophysics, University of Ulm, D-89069 Ulm, Germany.
Nienhaus
G Ulrich
GU
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D055592:Biophysical Phenomena; D001703:Biophysics; D004579:Electron Transport; D004734:Energy Metabolism; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000378:metabolism; D013053:Spectrophotometry; D013816:Thermodynamics
D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins