title: Femtosecond transient absorption study of carotenoid to chlorophyll energy transfer in the light-harvesting complex II of photosystem II.
abstract: Singlet energy transfer between the carotenoids (Cars) and chlorophylls (Chls) in the light-harvesting complex II (LHC II) from higher plants has been studied using ultrafast transient absorption spectroscopy by exciting the Cars directly in the 475-515 nm wavelength range. LHC II trimers from Arabidopsis thaliana with well-defined Car compositions have been used. From HPLC, the wild type (WT) monomer contains two luteins (Ls), one neoxanthin (N), and a trace of violaxanthin (V) per 12 Chls. The ABA-3 mutant contains 1.4 Ls and 0.6 zeaxanthin (Z) per monomer. Though exploitation of the difference in Car constitution and exciting the WT at 475 and 490 nm, and the ABA-3 mutant at 490 and 515 nm, the different Car contributions to energy transfer have been probed. Evidence for energy transfer mainly from the Car to Chl b is observed in the WT. In the mutant, additional transfer from Car to Chl a correlates with the presence of Z. The results imply predominant energy transfer from the central Ls to Chl b which requires a modification of the currently accepted arrangement of Chl pigments in LHC II.
authors.affiliation: Max-Planck-Institut für Strahlenchemie, Mülheim an der Ruhr, Germany.
authors.forename: J P
authors.initials: JP
authors.lastname: Connelly
authors.forename: M G
authors.initials: MG
authors.lastname: Müller
authors.forename: R
authors.initials: R
authors.lastname: Bassi
authors.forename: R
authors.initials: R
authors.lastname: Croce
authors.forename: A R
authors.initials: AR
authors.lastname: Holzwarth
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D002338:Carotenoids / Q000032:analysis / Q000737:chemistry* / Q000378:metabolism; D002734:Chlorophyll / Q000737:chemistry* / Q000378:metabolism; D004735:Energy Transfer; D007700:Kinetics; D045342:Light-Harvesting Protein Complexes; D014975:Lutein / Q000032:analysis / Q000378:metabolism; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism; D045332:Photosystem II Protein Complex; D013053:Spectrophotometry; D013997:Time Factors; D024341:Xanthophylls; D019207:beta Carotene / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D024341:Xanthophylls; D019207:beta Carotene; D002734:Chlorophyll; D002338:Carotenoids; C005613:violaxanthin; C011947:neoxanthin; D014975:Lutein