Osnabrück 2002 – scientific programme
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SYBP: Biophotonik
SYBP 3: Einzelmolekülmethoden III
SYBP 3.4: Talk
Thursday, March 7, 2002, 17:30–17:45, HS 11/215
Single-molecule spectroscopy of LH3 complexes — •Jean-Manuel Segura1,2, Martijn Ketelaars1, Silke Oellerich1, Gerhard Magis1, Ward de Ruijter1, Jürgen Köhler3, and Thijs J. Aartsma1 — 1Huygens Laboratory, Department of Biophysics, Leiden University, The Netherlands — 2Laboratoire de chimie physique des polyméres et membranes, EPFL, 1015 Lausanne, Switzerland — 3Experimentalphysik IV, Universität Bayreuth, 95440 Bayreuth
Light-harvesting complexes are chlorophyll-binding proteins specialized in collecting and transferring light energy during photosynthesis. Single-molecule spectroscopy provides a wealth of information about the mechanisms of energy transfer inside these complexes. We have investigated the light-harvesting 3 (LH3) of purple bacteria, which is produced under certain growth conditions instead of the extensively studied LH2 complex. The structures of both complexes are very similar with the chlorophyll molecules arranged in two concentric rings, the outer ring absorbing light at 800nm, while the inner ring absorbs at 820nm (850 nm in LH2). The general pattern of energy delocalisation remains in LH3 similar to LH2 with a high delocalisation of the energy of excitonic character in the centre ring and a localization on 2-3 chromophores in the outer ring. Spectral diffusion is highly increased in LH3 inducing a broadening of the bands and interesting spectral dynamics. A large heterogeneity in the single-complex properties is observed reflected in a variety of excitonic patterns. These experiments provide valuable information about the relationships between spectroscopic properties and structure.