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Kinetics, energetics, and electronic coupling of the primary electron transfer reactions in mutated reaction centers of Blastochloris viridis

MPG-Autoren
http://pubman.mpdl.mpg.de/cone/persons/resource/persons77759

Bibikova,  M.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons77899

Dohse,  B.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

http://pubman.mpdl.mpg.de/cone/persons/resource/persons78468

Oesterhelt,  D.
Oesterhelt, Dieter / Membrane Biochemistry, Max Planck Institute of Biochemistry, Max Planck Society;

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Zitation

Huppman, P., Arlt, T., Penzkofer, H., Schmidt, S., Bibikova, M., Dohse, B., et al. (2002). Kinetics, energetics, and electronic coupling of the primary electron transfer reactions in mutated reaction centers of Blastochloris viridis. Biophysical Journal, 82(6), 3186-3197.


Zitierlink: http://hdl.handle.net/11858/00-001M-0000-0010-6F1E-8
Zusammenfassung
Femtosecond spectroscopy in combination with site-directed mutagenesis has been used to study the dynamics of primary electron transfer in native and 12 mutated reaction centers of Blastochloris (B) (formerly called Rhodopseudomonas) viridis. The decay times of the first excited state P* vary at room temperature between of 0.6 and 50 ps, and at low temperatures between 0.25 and 90 ps. These changes in time constants are discussed within the scope of nonadiabatic electron transfer theory using different models: 1) If the mutation is assumed to predominantly influence the energetics of the primary electron transfer intermediates, the analysis of the room temperature data for the first electron transfer step to the intermediate P+BA- yields a reorganization energy lambda = 600 +/- 200 cm(- 1) and a free energy gap DeltaG ranging from -600 cm(-1) to 800 cm(-1). However, this analysis falls to describe the temperature dependence of the reaction rates. 2) A more realistic description of the temperature dependence of the primary electron transfer requires different values for the energetics and specific variations of the electronic coupling upon mutation. Apparently the mutations also lead to pronounced changes in the electronic coupling, which may even dominate the change in the reaction rate. One main message of the paper is that a simple relationship between mutation and a change in one reaction parameter cannot be given and that at the very least the electronic coupling is changed upon mutation.