B(sub A) and B(sub B) absorbance perturbations induced by coherent nuclear motions in reaction centers from Rhodobacter sphaeroides upon 30-fs excitation of the primary donor

Article Abstract:

Native and B(sub B)-modified reaction centers from Rhodobacter sphaeroides R26 and of the mutant YM210W at 293 K using 30 fs excitation pulses at 865 nm showed subpicosecond oscillations in the B band. When compared with oscillations in stimulated emission, the (30 +/- 3) and (12 +/- 2) cm(super -1) modes in the 800 nm kinetics were found to be enhanced with regard to the broad structure around 150 cm(super -1) in all reaction centers (RCs). The maximal amplitude of both modes is observed in native and B(sub B)-modified RCs, while their minimal amplitude is noted in the YM210W mutant, where the rate of electron transfer is significantly reduced.

Electron transport, Electron donor-acceptor complexes, Nuclear excitation

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Magnetic field effects on the recombination kinetics of radical pairs

Article Abstract:

The effects of magnetic field on the recombination kinetics of radical pairs in zero field, in high field and with a static field jump shortly after formation by a pulse of light were investigated. The recombination kinetics were calculated within the framework of the radical pair mechanism, thus, treating nuclear spins in a semiclassical fashion. Experimental results showed that the form of the decay depends on the applied magnetic field strength and the rate of electron spin-lattice relaxation.

Magnetic fields, Radicals (Chemistry), Electron paramagnetic resonance, Nuclear spin

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Electrooptical properties of different redox states of native and modified reaction centers of Rhodobacter sphaeroides

Article Abstract:

The Stark spectra of selectively and nonselectively BPheo -> Pheo exchanged reaction centers were examined and contrasted with those of native reaction centers. It was observed that Pheo, when incorporated into the reaction center protein, has an almost pure second-derivative shaped Stark spectrum. This suggests that absorbance modifications are mostly due to the interaction between the electric field and the change in permanent electric dipole moment upon excitation.

Oxidation-reduction reaction, Oxidation-reduction reactions, Bacteria, Photosynthetic, Photosynthetic bacteria, Electrooptics, Electro-optics

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