Darmstadt 2008 – scientific programme
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MO: Fachverband Molekülphysik
MO 16: Biomoleküle
MO 16.3: Poster
Tuesday, March 11, 2008, 14:00–19:00, Poster C1
Pigment-Pigment Interactions in Light-Harvesting Complexes Investigated by Nonlinear Laser Spectroscopy — •Alexander Betke1, Bernd Voigt1, Roger G. Hiller2, Maria Krikunova3, Heiko Lokstein4, and Ralf Menzel1 — 1Institut für Physik/Photonik, Universität Potsdam, Germany — 2Macquarie University, School of Biological Sciences, Australia — 3Institut für Experimentalphysik, Universität Hamburg, Germany — 4Institut für Biochemie und Biologie, Universität Potsdam, Germany
Two-photon fluorescence excitation- and nonlinear polarization spectroscopy in the frequency domain (NLPF) are sensitive methods to study pigment-pigment interactions in photosynthetic light-harvesting complexes (LHCs). Among the studied complexes are the peridinin-chlorophyll a - protein (PCP) and higher plant LHC II. Interactions between the peridinins and peridinin-chlorophyll interactions in PCP are resolved in the NLPF spectra. Excitonic interactions between the peridinins are revealed. Certain peridinin(s) show interaction between their "optically dark" S1 (21Ag−) or intramolecular charge-transfer state and chlorophyll a. Thus, these states are approximately isoenergetic. Two-photon absorption of zeaxanthin and violaxanthin in LHC II monitored by chlorophyll fluorescence shows spectral differences of their "optically dark" 21Ag− states. Specific changes in xanthophyll-chlorophyll interactions upon aggregation of LHC II are indicated by NLPF. These changes may underlay the chlorophyll-fluorescence quenching as the molecular basis of excess energy dissipation. Consequences for energy transfer in these complexes are discussed. Supported by the SFB 429.