Conformational Complexity in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum Revealed by Hole-Burning Spectroscopy
Journal Article
·
· Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory
- Kansas State Univ., Manhattan, KS (United States)
- Univ. of Glasgow, Scotland (United Kingdom)
This work discusses the protein conformational complexity of the B800–850 LH2 complexes from the purple sulfur bacterium Allochromatium vinosum, focusing on the spectral characteristics of the B850 chromophores. Low-temperature B850 absorption and the split B800 band shift blue and red, respectively, at elevated temperatures, revealing isosbestic points. The latter indicates the presence of two (unresolved) conformations of B850 bacteriochlorophylls (BChls), referred to as conformations 1 and 2, and two conformations of B800 BChls, denoted as B800R and B800B. The energy differences between average site energies of conformations 1 and 2, and B800R and B800B are similar (~200 cm–1), suggesting weak and strong hydrogen bonds linking two major subpopulations of BChls and the protein scaffolding. Although conformations 1 and 2 of the B850 chromophores, and B800R and B800B, exist in the ground state, selective excitation leads to 1 → 2 and B800R → B800B phototransformations. Different static inhomogeneous broadening is revealed for the lowest energy exciton states of B850 (fwhm ~195 cm–1) and B800R (fwhm ~140 cm–1). To describe the 5 K absorption spectrum and the above-mentioned conformations, we employ an exciton model with dichotomous protein conformation disorder. We show that both experimental data and the modeling study support a two-site model with strongly and weakly hydrogen-bonded B850 and B800 BChls, which under illumination undergo conformational changes, most likely caused by proton dynamics.
- Research Organization:
- Energy Frontier Research Centers (EFRC) (United States). Photosynthetic Antenna Research Center (PARC)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
- Grant/Contract Number:
- SC0001035
- OSTI ID:
- 1388891
- Journal Information:
- Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory, Journal Name: Journal of Physical Chemistry. A, Molecules, Spectroscopy, Kinetics, Environment, and General Theory Journal Issue: 23 Vol. 121; ISSN 1089-5639
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Contribution of low-temperature single-molecule techniques to structural issues of pigment–protein complexes from photosynthetic purple bacteria
|
journal | January 2018 |
Similar Records
On Light-Induced Photoconversion of B800 Bacteriochlorophylls in the LH2 Antenna of the Purple Sulfur Bacterium Allochromatium vinosum
Dichotomous Disorder versus Excitonic Splitting of the B800 Band of Allochromatium vinosum
Characterisation of the LH2 spectral variants produced by the photosynthetic purple sulphur bacterium Allochromatium vinosum
Journal Article
·
Mon Oct 09 20:00:00 EDT 2017
· Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
·
OSTI ID:1469903
Dichotomous Disorder versus Excitonic Splitting of the B800 Band of Allochromatium vinosum
Journal Article
·
Sun Jun 24 20:00:00 EDT 2018
· Journal of Physical Chemistry Letters
·
OSTI ID:1539331
Characterisation of the LH2 spectral variants produced by the photosynthetic purple sulphur bacterium Allochromatium vinosum
Journal Article
·
Sat Nov 01 00:00:00 EDT 2014
· Biochimica et Biophysica Acta - Bioenergetics
·
OSTI ID:1150020