title: Influence of phospholipid composition on self-assembly and energy-transfer efficiency in networks of light-harvesting 2 complexes.
abstract: In the photosynthetic membrane of purple bacteria networks of light-harvesting 2 (LH2) complexes capture the sunlight and transfer the excitation energy. In order to investigate the mutual relationship between the supramolecular organization of the pigment-protein complexes and their biological function, the LH2 complexes were reconstituted into three types of phospholipid membranes, consisting of L-α-phosphatidylglycerol (PG), L-α-phosphatidylcholine (PC), and L-α-phosphatidylethanolamine (PE)/PG/cardiolipin (CL). Atomic force microscopy (AFM) revealed that the type of phospholipids had a crucial influence on the clustering tendency of the LH2 complexes increased from PG over PC to PE/PG/CL, where the LH2 complexes formed large, densely packed clusters. Time-resolved spectroscopy uncovered a strong quenching of the LH2 fluorescence that is ascribed to singlet-singlet and singlet-triplet annihilation by an efficient energy transfer between the LH2 complexes in the artificial membrane systems. Quantitative analysis reveals that the intercomplex energy transfer efficiency varies strongly as a function of the morphology of the nanostructure, namely in the order PE/PG/CL > PC > PG, which is in line with the clustering tendency of LH2 observed by AFM. These results suggest a strong influence of the phospholipids on the self-assembly of LH2 complexes into networks and concomitantly on the intercomplex energy transfer efficiency.
authors.affiliation: Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan.
authors.forename: Ayumi
authors.initials: A
authors.lastname: Sumino
authors.forename: Takehisa
authors.initials: T
authors.lastname: Dewa
authors.forename: Tomoyasu
authors.initials: T
authors.lastname: Noji
authors.forename: Yuki
authors.initials: Y
authors.lastname: Nakano
authors.forename: Natsuko
authors.initials: N
authors.lastname: Watanabe
authors.forename: Richard
authors.initials: R
authors.lastname: Hildner
authors.forename: Nils
authors.initials: N
authors.lastname: Bösch
authors.forename: Jürgen
authors.initials: J
authors.lastname: Köhler
authors.forename: Mamoru
authors.initials: M
authors.lastname: Nango
mesh_terms: D004735:Energy Transfer; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry* / Q000378:metabolism; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D020560:Proteobacteria / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D045342:Light-Harvesting Protein Complexes; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols