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Energy transfer in spectrally inhomogeneous light-harvesting pigment-protein complexes of purple bacteria

Hess, S. LU ; Åkesson, E. LU orcid ; Cogdell, R. J. ; Pullerits, T. LU and Sundström, V. LU (1995) In Biophysical Journal 69(6). p.2211-2225
Abstract

Energy transfer within the peripheral light-harvesting antenna of the purple bacteria Rhodobacter sphaeroides and Rhodopseudomonas palustris was studied by one- and two-color pump-probe absorption spectroscopy with approximately 100-fs tunable pulses at room temperature and at 77 K. The energy transfer from B800 to B850 occurs with a time constant of 0.7 +/- 0.05 ps at room temperature and 1.8 +/- 0.2 ps at 77 K and is similar in both species. Anisotropy measurements suggest a limited but fast B800 <--> B800 transfer time (tau approximately 0.3 ps). This is analyzed as incoherent hopping of the excitation in a system of spectrally inhomogeneous antenna pigment-protein complexes, by a master equation approach. The simulations show... (More)

Energy transfer within the peripheral light-harvesting antenna of the purple bacteria Rhodobacter sphaeroides and Rhodopseudomonas palustris was studied by one- and two-color pump-probe absorption spectroscopy with approximately 100-fs tunable pulses at room temperature and at 77 K. The energy transfer from B800 to B850 occurs with a time constant of 0.7 +/- 0.05 ps at room temperature and 1.8 +/- 0.2 ps at 77 K and is similar in both species. Anisotropy measurements suggest a limited but fast B800 <--> B800 transfer time (tau approximately 0.3 ps). This is analyzed as incoherent hopping of the excitation in a system of spectrally inhomogeneous antenna pigment-protein complexes, by a master equation approach. The simulations show that the measured B800 dynamics is well described as energy transfer with a characteristic average nearest-neighbor pairwise transfer time of 0.35 ps among approximately 10 Bchl molecules in a circular arrangement, in good agreement with the recent high-resolution structure of LH2. The possible presence of fast intramolecular relaxation processes within the Bchl a molecule was investigated by measurement of time-resolved difference absorption spectra and kinetics of Bchl a in solution and in low-temperature glasses. From these measurements it is concluded that fast transients observed at room temperature are due mainly to solvation processes, whereas at 77 K predominantly slower (> 10-ps) relaxation occurs.

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type
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publication status
published
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in
Biophysical Journal
volume
69
issue
6
pages
15 pages
publisher
Cell Press
external identifiers
  • pmid:8599629
  • scopus:0028834862
ISSN
0006-3495
DOI
10.1016/S0006-3495(95)80137-2
language
English
LU publication?
yes
id
c5042df1-8918-4684-b940-b667deaeae54
date added to LUP
2025-10-28 17:05:58
date last changed
2025-11-19 12:07:58
@article{c5042df1-8918-4684-b940-b667deaeae54,
  abstract     = {{<p>Energy transfer within the peripheral light-harvesting antenna of the purple bacteria Rhodobacter sphaeroides and Rhodopseudomonas palustris was studied by one- and two-color pump-probe absorption spectroscopy with approximately 100-fs tunable pulses at room temperature and at 77 K. The energy transfer from B800 to B850 occurs with a time constant of 0.7 +/- 0.05 ps at room temperature and 1.8 +/- 0.2 ps at 77 K and is similar in both species. Anisotropy measurements suggest a limited but fast B800 &lt;--&gt; B800 transfer time (tau approximately 0.3 ps). This is analyzed as incoherent hopping of the excitation in a system of spectrally inhomogeneous antenna pigment-protein complexes, by a master equation approach. The simulations show that the measured B800 dynamics is well described as energy transfer with a characteristic average nearest-neighbor pairwise transfer time of 0.35 ps among approximately 10 Bchl molecules in a circular arrangement, in good agreement with the recent high-resolution structure of LH2. The possible presence of fast intramolecular relaxation processes within the Bchl a molecule was investigated by measurement of time-resolved difference absorption spectra and kinetics of Bchl a in solution and in low-temperature glasses. From these measurements it is concluded that fast transients observed at room temperature are due mainly to solvation processes, whereas at 77 K predominantly slower (&gt; 10-ps) relaxation occurs.</p>}},
  author       = {{Hess, S. and Åkesson, E. and Cogdell, R. J. and Pullerits, T. and Sundström, V.}},
  issn         = {{0006-3495}},
  language     = {{eng}},
  number       = {{6}},
  pages        = {{2211--2225}},
  publisher    = {{Cell Press}},
  series       = {{Biophysical Journal}},
  title        = {{Energy transfer in spectrally inhomogeneous light-harvesting pigment-protein complexes of purple bacteria}},
  url          = {{http://dx.doi.org/10.1016/S0006-3495(95)80137-2}},
  doi          = {{10.1016/S0006-3495(95)80137-2}},
  volume       = {{69}},
  year         = {{1995}},
}