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Sumino, Ayumi ; Dewa, Takehisa ; Noji, Tomoyasu ; Nakano, Yuki ; Watanabe, Natsuko ; Hildner, Richard ; Bösch, Nils ; Köhler, Jürgen ; Nango, Mamoru:
Influence of phospholipid composition on self-assembly and energy-transfer efficiency in networks of light-harvesting 2 complexes.
In: The Journal of Physical Chemistry B.
Bd. 117
(2013)
Heft 36
.
- S. 10395-10404.
ISSN 1520-5207
DOI: https://doi.org/10.1021/jp4047819
Volltext
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.