title: Excitation Energy Transfer by Coherent and Incoherent Mechanisms in the Peridinin-Chlorophyll a Protein.
abstract: Excitation energy transfer from peridinin to chlorophyll (Chl) a is unusually efficient in the peridinin-chlorophyll a protein (PCP) from dinoflagellates. This enhanced performance is derived from the long intrinsic lifetime of 4.4 ps for the S2(11Bu+) state of peridinin in PCP, which arises from the electron-withdrawing properties of its carbonyl substituent. Results from heterodyne transient grating spectroscopy indicate that S2serves as the donor for two channels of energy transfer: a 30 fs process involving quantum coherence and delocalized peridinin-Chl states and an incoherent, 2.5 ps process initiated by dynamic exciton localization, which accompanies the formation of a conformationally distorted intermediate in 45 fs. The lifetime of the S2state is lengthened in PCP by its intramolecular charge-transfer character, which increases the system-bath coupling and slows the torsional motions that promote nonradiative decay to the S1(21Ag-) state.
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors.forename: Soumen
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Bishop
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors.forename: Jerome D
authors.initials: JD
authors.lastname: Roscioli
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3036, United States.
authors.forename: Amy M
authors.initials: AM
authors.lastname: LaFountain
authors.affiliation: Department of Chemistry, University of Connecticut , Storrs, Connecticut 06269-3036, United States.
authors.forename: Harry A
authors.initials: HA
authors.lastname: Frank
authors.affiliation: Department of Chemistry, Michigan State University , East Lansing, Michigan 48824-1322, United States.
authors.forename: Warren F
authors.identifier: http://orcid.org/0000-0002-7491-0264
authors.initials: WF
authors.lastname: Beck
mesh_terms: D002338:Carotenoids / Q000737:chemistry*; D002734:Chlorophyll / Q000031:analogs & derivatives* / Q000737:chemistry; D000077194:Chlorophyll A; D018360:Crystallography, X-Ray; D004141:Dinoflagellida / Q000737:chemistry; D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D008968:Molecular Conformation; D015800:Protozoan Proteins; D013205:Staphylococcal Protein A / Q000737:chemistry*
chemical_list: D045342:Light-Harvesting Protein Complexes; D015800:Protozoan Proteins; D013205:Staphylococcal Protein A; D002734:Chlorophyll; C085815:chlorophyll a'; C016040:peridinin; D002338:Carotenoids; D000077194:Chlorophyll A