title: Distortions of the Xanthophylls Caused by Interactions with Neighboring Pigments and the LHCII Protein Are Crucial for Studying Energy Transfer Pathways within the Complex.
abstract: It has been proposed that photoprotective non-photochemical quenching (NPQ) in higher plants arises from a conformational change in the antenna which alters pigment-pigment interactions. This brings about the formation of energy quenching "traps" that capture and dissipate excitation energy as heat. We have used the semiempirical AM1-CAS-CI method combined with the transition density cube (TDC) approach to model chlorophyll (Chl) to xanthophyll (Xanth) resonant Coulomb couplings in the crystal structure of LHCII. Due to its proposed role as the NPQ quenching site we have focused on lutein interactions and have explored how distortions to lutein conformation, as well as interpigment distances and relative orientations, affect this coupling. Our calculations indicate that distortions as well as Chl-lutein angle have a significant effect on coupling, whereas interpigment distances have a relatively minor effect. We therefore conclude that particular attention to the distortions of the Xanths should be given for calculation of energy transfer pathways and study of the NPQ mechanism.
authors.affiliation: The School of Biological and Chemical Sciences, Queen Mary's University of London , Mile End Road, London E1 4NS, England.
authors.forename: K F
authors.initials: KF
authors.lastname: Fox
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis , 1 Brookings Drive, Saint Louis, Missouri 63130-4899, United States.
authors.forename: William P
authors.initials: WP
authors.lastname: Bricker
authors.affiliation: Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis , 1 Brookings Drive, Saint Louis, Missouri 63130-4899, United States.
authors.forename: Cynthia
authors.initials: C
authors.lastname: Lo
authors.affiliation: The School of Biological and Chemical Sciences, Queen Mary's University of London , Mile End Road, London E1 4NS, England.
authors.forename: C D P
authors.initials: CD
authors.lastname: Duffy
mesh_terms: D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D010860:Pigments, Biological / Q000737:chemistry*; D024341:Xanthophylls / Q000737:chemistry*
chemical_list: D045342:Light-Harvesting Protein Complexes; D045332:Photosystem II Protein Complex; D010860:Pigments, Biological; D024341:Xanthophylls