Document Detail

Tracking energy transfer between light harvesting complex 2 and 1 in photosynthetic membranes grown under high and low illumination.
MedLine Citation:
PMID:  22307601     Owner:  NLM     Status:  MEDLINE    
Energy transfer (ET) between B850 and B875 molecules in light harvesting complexes LH2 and LH1/RC (reaction center) complexes has been investigated in membranes of Rhodopseudomonas palustris grown under high- and low-light conditions. In these bacteria, illumination intensity during growth strongly affects the type of LH2 complexes synthesized, their optical spectra, and their amount of energetic disorder. We used a specially built femtosecond spectrometer, combining tunable narrowband pump with broadband white-light probe pulses, together with an analytical method based on derivative spectroscopy for disentangling the congested transient absorption spectra of LH1 and LH2 complexes. This procedure allows real-time tracking of the forward (LH2 → LH1) and backward (LH2←LH1) ET processes and unambiguous determination of the corresponding rate constants. In low-light grown samples, we measured lower ET rates in both directions with respect to high-light ones, which is explained by reduced spectral overlap between B850 and B875 due to partial redistribution of oscillator strength into a higher energetic exciton transition. We find that the low-light adaptation in R. palustris leads to a reduced elementary backward ET rate, in accordance with the low probability of two simultaneous excitations reaching the same LH1/RC complex under weak illumination. Our study suggests that backward ET is not just an inevitable consequence of vectorial ET with small energetic offsets, but is in fact actively managed by photosynthetic bacteria.
Larry Lüer; Vladimíra Moulisová; Sarah Henry; Dario Polli; Tatas H P Brotosudarmo; Sajjad Hoseinkhani; Daniele Brida; Guglielmo Lanzani; Giulio Cerullo; Richard J Cogdell
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2012-01-23
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  109     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2012 Jan 
Date Detail:
Created Date:  2012-02-06     Completed Date:  2012-03-30     Revised Date:  2013-06-26    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1473-8     Citation Subset:  IM    
Department of Nanoscience, Madrid Institute for Advanced Studies, 28049 Cantoblanco, Spain.
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MeSH Terms
Energy Transfer*
Light-Harvesting Protein Complexes / metabolism*
Grant Support
//Biotechnology and Biological Sciences Research Council
Reg. No./Substance:
0/Light-Harvesting Protein Complexes

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