Spectral and kinetic effects accompanying the assembly of core complexes of Rhodobacter sphaeroides

Arvi Freiberg, Manoop Chenchiliyan, Margus Rätsep, Kõu Timpmann

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In the present work, spectral and kinetic changes accompanying the assembly of the light-harvesting 1 (LH1) complex with the reaction center (RC) complex into monomeric RC-LH1 and dimeric RC-LH1-PufX core complexes of the photosynthetic purple bacterium Rhodobacter sphaeroides are systematically studied over the temperature range of 4.5–300 K. The samples were interrogated with a combination of optical absorption, hole burning, fluorescence excitation, steady state and picosecond time resolved fluorescence spectroscopy. Fair additivity of the LH1 and RC absorption spectra suggests rather weak electronic coupling between them. A low-energy tail revealed at cryogenic temperatures in the absorption spectra of both monomeric and dimeric core complexes is proved to be due to the special pair of the RC. At selected excitation intensity and temperature, the fluorescence decay time of core complexes is shown to be a function of multiple factors, most importantly of the presence/absence of RCs, the supramolecular architecture (monomeric or dimeric) of the complexes, and whether the complexes were studied in a native membrane environment or in a detergent - purified state.

Original languageEnglish
Pages (from-to)1727-1733
Number of pages7
JournalBiochimica et Biophysica Acta - Bioenergetics
Issue number11
StatePublished - 1 Nov 2016
Externally publishedYes

Bibliographical note

Funding Information:
The authors are thankful to Prof. N. Hunter (Sheffield University) for kindly donating the samples for this research and Dr. Erko Jalviste for useful discussions. Partial financial support provided by the Estonian Research Council (grant IUT02-28 ), ESF DoRa 4 Program (grant NLOFY12523T), H2020-MSCA-RISE-2015 program (grant 690853), and Australian Research Council Discovery Project (grant DP150103137 ) is also greatly acknowledged.

Publisher Copyright:
© 2016 Elsevier B.V.


  • Excitation energy transfer
  • Exciton
  • Light-harvesting
  • Photosynthesis
  • Spectroscopy


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