Photosynthesis Research

, Volume 65, Issue 3, pp 261–268

Kinetics of absorbance and anisotropy upon excited state relaxation in the reaction center core complex of a green sulfur bacterium

  • Sieglinde Neerken
  • Ying-Zhong Ma
  • Jochen Aschenbrücker
  • Kristiane A. Schmidt
  • Frank R. Nowak
  • Hjalmar P. Permentier
  • Thijs J. Aartsma
  • Tomas Gillbro
  • Jan Amesz
Article

DOI: 10.1023/A:1010647205220

Cite this article as:
Neerken, S., Ma, YZ., Aschenbrücker, J. et al. Photosynthesis Research (2000) 65: 261. doi:10.1023/A:1010647205220

Abstract

Properties of the excited states in reaction center core (RCC) complexes of the green sulfur bacterium Prosthecochloris aestuarii were studied by means of femtosecond time-resolved isotropic and anisotropic absorption difference spectroscopy at 275 K. Selective excitation of the different transitions of the complex resulted in the rapid establishment of a thermal equilibrium. At about 1 ps after excitation, the energy was located at the lowest energy transition, BChl a 835. Time constants varying between 0.26 and 0.46 ps were observed for the energy transfer steps leading to this equilibrium. These transfer steps were also reflected in changes in polarization. Our measurements indicate that downhill energy transfer towards excited BChl a 835 occurs via the energetically higher spectral forms BChl a 809 and BChl a 820. Low values of the anisotropy of about 0.07 were found in the ‘two-color’ measurements at 820 and 835 nm upon excitation at 800 nm, whereas the ‘one-color’ kinetics showed much higher anisotropies. Charge separation occurred with a time constant varying between 20 and 30 ps.

anisotropybacteriochlorophyll aexcited statesgreen sulfur bacteriareaction center

Copyright information

© Kluwer Academic Publishers 2000

Authors and Affiliations

  • Sieglinde Neerken
    • 1
  • Ying-Zhong Ma
    • 2
  • Jochen Aschenbrücker
    • 2
  • Kristiane A. Schmidt
    • 1
  • Frank R. Nowak
    • 1
  • Hjalmar P. Permentier
    • 1
  • Thijs J. Aartsma
    • 1
  • Tomas Gillbro
    • 2
  • Jan Amesz
    • 4
  1. 1.Department of Biophysics, Huygens LaboratoryLeiden UniversityLeidenThe Netherlands
  2. 2.Department of Physical ChemistryUmeå UniversityUmeåSweden
  3. 3.Department of ChemistryUniversity of California BerkeleyBerkeleyUSA
  4. 4.Department of Biophysics, Huygens LaboratoryLeiden UniversityLeidenThe Netherlands