Biochemistry (Moscow)

, Volume 82, Issue 8, pp 906–915 | Cite as

Femtosecond relaxation processes in Rhodobacter sphaeroides reaction centers

  • A. G. YakovlevEmail author
  • V. A. Shuvalov


Energy relaxation was studied with difference femtosecond spectroscopy in reaction centers of the YM210L mutant of the purple photosynthetic bacterium Rhodobacter sphaeroides at low temperature (90 K). A dynamical long-wavelength shift of stimulated emission of the excited state of the bacteriochlorophyll dimer P was found, which starts simultaneously with P* formation and is accompanied by a change in the spectral shape of this emission. The characteristic value of this shift was about 30 nm, and the characteristic time about 200 fs. Difference kinetics ΔA measured at fixed wavelengths demonstrate the femtosecond shift of the P* stimulated emission appearing as a dependence of these kinetics on wavelength. We found that the reported long-wavelength shift can be explained in terms of electron-vibrational relaxation of the P* excited state with time constants of vibrational and electronic relaxation of 100 and 50 fs, respectively. Alternative mechanisms of the dynamical shift of the P* stimulated emission spectrum are also discussed in terms of energy redistribution between vibrational modes or coherent excitation of the modes.


photosynthesis reaction center energy relaxation charge separation difference spectroscopy 



absorption change (illumination minus darkness)

BA and BB

monomeric bacteriochlorophylls in A and B chains, respectively

HA and HB

bacteriopheophytins in A and B chains, respectively


bacteriochlorophyll dimer

PA and PB

bacteriochlorophyll molecules that make up P

QA and QB

primary and secondary quinones, respectively


reaction center




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© Pleiades Publishing, Ltd. 2017

Authors and Affiliations

  1. 1.Belozersky Institute of Physico-Chemical BiologyLomonosov Moscow State UniversityMoscowRussia
  2. 2.Institute of Basic Biological ProblemsRussian Academy of SciencesPushchino, Moscow RegionRussia

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