Energy trapping and detrapping in reaction center mutants from Rhodobacter sphaeroides

Zivile Katiliene, Evaldas Katilius, Neal Woodbury

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16 Scopus citations


Time-resolved fluorescence of chromatophores isolated from strains of Rhodobactersphaeroides containing light harvesting complex I (LHI) and reaction center (RC) (no light harvesting complex II) was measured at several temperatures between 295 K and 10K. Measurements were performed to investigate energy trapping from LHI to the RC in RC mutants that have a P/ + midpoint potential either above or below wild-type (WT). Six different strains were investigated: WT + LHI, four mutants with altered RC P/ + midpoint potentials, and an LHI-only strain. In the mutants with the highest P/ + midpoint potentials, the electron transfer rate decreases significantly, and at low temperatures it is possible to directly observe energy transfer from LHI to the RC by detecting the fluorescence kinetics from both complexes. In all mutants, fluorescence kinetics are multiexponential. To explain this, RC + LHI fluorescence kinetics were analyzed using target analysis in which specific kinetic models were compared. The kinetics at all temperatures can be well described with a model which accounts for the energy transfer between LHI and the RC and also includes the relaxation of the charge separated state P+HA-, created in the RC as a result of the primary charge separation.

Original languageEnglish (US)
Pages (from-to)3240-3251
Number of pages12
JournalBiophysical journal
Issue number5
StatePublished - May 1 2003

ASJC Scopus subject areas

  • Biophysics


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