title: Initial electron donor and acceptor in isolated Photosystem II reaction centers identified with femtosecond mid-IR spectroscopy.
abstract: Despite the apparent similarity between the plant Photosystem II reaction center (RC) and its purple bacterial counterpart, we show in this work that the mechanism of charge separation is very different for the two photosynthetic RCs. By using femtosecond visible-pump-mid-infrared probe spectroscopy in the region of the chlorophyll ester and keto modes, between 1,775 and 1,585 cm(-1), with 150-fs time resolution, we show that the reduction of pheophytin occurs on a 0.6- to 0.8-ps time scale, whereas P+, the precursor state for water oxidation, is formed after approximately 6 ps. We conclude therefore that in the Photosystem II RC the primary charge separation occurs between the "accessory chlorophyll" Chl(D1) and the pheophytin on the so-called active branch.
authors.affiliation: Faculty of Sciences, Vrije Universiteit, 1081 HV, Amsterdam, The Netherlands. ml.groot@few.vu.nl
authors.forename: Marie Louise
authors.initials: ML
authors.lastname: Groot
authors.forename: Natalia P
authors.initials: NP
authors.lastname: Pawlowicz
authors.forename: Luuk J G W
authors.initials: LJ
authors.lastname: van Wilderen
authors.forename: Jacques
authors.initials: J
authors.lastname: Breton
authors.forename: Ivo H M
authors.initials: IH
authors.lastname: van Stokkum
authors.forename: Rienk
authors.initials: R
authors.lastname: van Grondelle
mesh_terms: D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D010084:Oxidation-Reduction; D010674:Pheophytins / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D013055:Spectrophotometry, Infrared / Q000295:instrumentation / Q000379:methods*; D018724:Spinacia oleracea; D013997:Time Factors
chemical_list: D010674:Pheophytins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll