title: Excitation energy transfer and charge separation in photosystem II membranes revisited.
abstract: We have performed time-resolved fluorescence measurements on photosystem II (PSII) containing membranes (BBY particles) from spinach with open reaction centers. The decay kinetics can be fitted with two main decay components with an average decay time of 150 ps. Comparison with recent kinetic exciton annihilation data on the major light-harvesting complex of PSII (LHCII) suggests that excitation diffusion within the antenna contributes significantly to the overall charge separation time in PSII, which disagrees with previously proposed trap-limited models. To establish to which extent excitation diffusion contributes to the overall charge separation time, we propose a simple coarse-grained method, based on the supramolecular organization of PSII and LHCII in grana membranes, to model the energy migration and charge separation processes in PSII simultaneously in a transparent way. All simulations have in common that the charge separation is fast and nearly irreversible, corresponding to a significant drop in free energy upon primary charge separation, and that in PSII membranes energy migration imposes a larger kinetic barrier for the overall process than primary charge separation.
authors.affiliation: Wageningen University, Laboratory of Biophysics, 6700 ET Wageningen, The Netherlands.
authors.forename: Koen
authors.initials: K
authors.lastname: Broess
authors.forename: Gediminas
authors.initials: G
authors.lastname: Trinkunas
authors.forename: Chantal D
authors.initials: CD
authors.lastname: van der Weij-de Wit
authors.forename: Jan P
authors.initials: JP
authors.lastname: Dekker
authors.forename: Arie
authors.initials: A
authors.lastname: van Hoek
authors.forename: Herbert
authors.initials: H
authors.lastname: van Amerongen
mesh_terms: D002462:Cell Membrane / Q000737:chemistry* / Q000502:physiology* / Q000528:radiation effects; D003198:Computer Simulation; D004735:Energy Transfer / Q000187:drug effects / Q000502:physiology*; D008027:Light; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000502:physiology* / Q000528:radiation effects; D018724:Spinacia oleracea / Q000737:chemistry / Q000502:physiology / Q000528:radiation effects; D055672:Static Electricity
chemical_list: D045332:Photosystem II Protein Complex