Spectroscopy on the B850 band of individual light-harvesting 2 complexes of Rhodopseudomonas acidophila I. Experiments and Monte Carlo simulations

Citation
M. Ketelaars et al., Spectroscopy on the B850 band of individual light-harvesting 2 complexes of Rhodopseudomonas acidophila I. Experiments and Monte Carlo simulations, BIOPHYS J, 80(3), 2001, pp. 1591-1603
Citations number
49
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOPHYSICAL JOURNAL
ISSN journal
0006-3495 → ACNP
Volume
80
Issue
3
Year of publication
2001
Pages
1591 - 1603
Database
ISI
SICI code
0006-3495(200103)80:3<1591:SOTBBO>2.0.ZU;2-6
Abstract
The electronic structure of the circular aggregate of 18 bacteriochlorophyl l a (BChl a) molecules responsible for the B850 absorption hand of the ligh t-harvesting 2 (LH2) complex of the photosynthetic purple bacterium Rhodops eudomonas acidophila has been studied by measuring fluorescence-excitation spectra of individual complexes at 1.2 K. The spectra reveal several well-r esolved bands that are obscured in the single, broad B850 band observed in conventional absorption measurements on bulk samples. They are interpreted consistently in terms of the exciton model for the circular aggregate of BC hl a molecules. From the energy separation between the different exciton tr ansitions a reliable value of the intermolecular interaction is obtained. T he spectra of the individual complexes allow for a distinction between the intra- and the intercomplex disorder. In addition to the random disorder, a regular modulation of the interaction has to be assumed to account for all the features of the observed spectra. This modulation has a C-2 symmetry, which strongly suggests a structural deformation of the ring into an ellips e.