Comparative study of spectral flexibilities of bacterial
light-harvesting complexes: structural implications
Danielis Rutkauskas 1*, John Olsen 2, Andrew Gall 3, Richard N Cogdell 3, C N Hunter 4 and Rienk van Grondelle 5
1 Vrije Universiteit, Amsterdam
2 University of Sheffield
3 University of Glasgow
4 University of Sheffield Western Bank
5 Vrije Universiteit
* To whom correspondence should be addressed. E-mail: danielis{at}nat.vu.nl.
Submitted on October 12, 2005
Revised on November 16, 2005
Accepted on 16 December 2005
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Abstract |
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This paper presents a comparative study of the frequencies of spectral jumping of individual light-harvesting complexes of six different types: LH2 of Rhodopseudomonas acidophila, Rhodobacter sphaeroides, Rhodospirillum molischianum, LH1 of Rhodobacter sphaeroides, and two "domain swap mutants" of LH2 of Rhodobacter sphaeroides: PACLH1 and PACLH2mol, in which the a-polypeptide C-terminus is exchanged with the corresponding sequence from LH1 of Rhodobacter sphaeroides or LH2 of Rhodospirillum molischianum, respectively (Olsen et al. 2003). The quasi-stable states of fluorescence peak wavelength that were previously observed for the LH2 of Rhodopseudomonas acidophila were confirmed for other species. We also observed occurrences of extremely blue-shifted spectra, which were associated with reversible bleaching of one of the chromophore rings. Different jumping behaviour is observed for single complexes of different types investigated with the same equivalent excitation intensity. The differences in spectral diffusion is associated with subtle differences of the binding pocket of B850 pigments and the structural flexibility of the different types of complexes.
Key Words:
LH1, LH2, fluorescence, microscopic, photosynthetic, single molecule
