Nuclear Wave Packet Motion between P* and P+BA- Potential Surfaces with a Subsequent Electron Transfer to HA in Bacterial Reaction Centers at 90 K. Electron Transfer Pathway

Yakovlev, A. G.; Shkuropatov, A. Ya.; Shuvalov, Vladimir V

doi:10.1021/bi020250n

Cited by 60 publications

(113 citation statements)

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“…Many authors, using different analysis methods, have concluded that the vibration with frequency 130-150 cm -1 initiates primary electron transfer in the reaction centers of purple bacteria [43][44][45][46][47][48][49][50][51][52][53][54][55][76][77][78]. From our model [17], it also follows that the h α mode with frequency 130-150 cm -1 corresponds to broadening of the P absorption band and controls primary electron transfer.…”

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confidence: 70%

“…It is characteristic that for reaction centers of Rb. sphaeroides in the P + B L − absorption band (1020 nm) and the H L bleaching band (760 nm), in the Fourier transformation of the kinetics the contribution of oscillations with frequency 32 cm -1 predominate, while in the P * stimulated emission band (935 nm) the frequency ≈130 cm -1 frequency dominates [48][49][50]. Domination of the frequency ≈30 cm -1 was also observed in detection of P + H L − absorption at 788 nm [46].…”

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confidence: 99%

“…Shuvalov et al [48][49][50][51][52][53][54] studied the coherence of vibrations in the reaction centers of purple bacteria, improving the accuracy of the determination of the oscillation frequencies as a result of shortening the duration of excitation. In studying the effect of deuteration of the reaction centers on oscillation of P * stimulated emission, induced by absorption of P + B L − and bleaching of H L for native and mutant reaction centers of Rb.…”

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confidence: 99%

“…Zinth et al [67] observed the frequency ≈150 cm -1 . Shuvalov et al [48][49][50][51][52][53][54], using a technique with higher time resolution, isolated frequencies in the range 130-150 cm -1 by Fourier transformation of the kinetics of stimulated emission. Analogous frequencies appear in the resonance Raman scattering spectra [77,78].…”

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confidence: 99%

“…As a result, the dipole HOH55 changes orientation in the chain by ≈90 o , ensuring practically irreversible electron transport from P * through B L to H L . Stabilization of the system, due to orientation of the dipole HOH55 along the force lines of the field created by the dipole P * , is accompanied by generation of the harmonics of the 32 cm -1 mode, which are studied in detail in [48][49][50][51][52][53][54]. The reason for the appearance of harmonics, in our opinion, involves the parametric interaction of the ≈130 cm -1 h α mode with the 32 cm -1 h µ mode, which characterizes rotational vibration of the dipole HOH55.…”

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confidence: 99%

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Model for primary electron transfer and coupling of electronic states at reaction centers of purple bacteria

Pavlovich

2006

J Appl Spectrosc

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A detailed derivation is presented for relations making it possible to describe the effect of temperature on the halfwidth of the P960 and P870 absorption bands and also on the electron transfer (ET) rate at reaction centers (RCs) of the purple bacteria Rps. viridis and Rb. sphaeroides. Primary electron transfer is considered as a resonant nonradiative transition between P * and P + B L − states (where P is a special pair, B L is an additional bacteriochlorophyll in the L branch of the reaction center). It has been shown that the vibrational h α mode with frequency 130-150 cm -1 controls primary electron transfer. It has been found that the matrix element of the electronic transition between the states P * and P + B L − is equal to 12.7 ± 0.9 and 12.0 ± 1.2 cm -1 for Rps.viridis and Rb. sphaeroides respectively. The mechanism is discussed for electron transport from P * and B L and then to bacteriopheophytin H L .Introduction. In bacterial photosynthesis, we can isolate two fundamentally important steps in conversion of solar energy (see, for example, [1][2][3][4][5][6][7][8]). The first step involves absorption of light by light-harvesting antennas LH2 and LH1 followed by transfer of excitation energy to the reaction center. The second step involves electron transport processes in the reaction center. In turn, it includes primary electron transfer from a special pair (P), which is a dimer of bacteriochlorophyll a or b (BChl) to bacteriopheophytin (H) with participation of additional BChl (B), and also secondary electron transfer from bacteriopheophytin to ubiquinone. As a result, rather stable charge separation occurs in the membrane, which controls the sequence of dark electrochemical processes.It is important that in the native forms of the reaction centers, the efficiency of charge separation reaches 100% [9]. For comparison, we note that the best types of semiconductor solar cells provide an efficiency <20% [10]. So persistent efforts have been applied to designing "molecular devices" which under artificial conditions would reproduce the highly efficient processes of conversion of excitation energy to electrical energy, like what occurs in bacterial photosynthesis. Specialists working in the field of storage and conversion of solar energy are especially interested in photosynthesis problems [6,8,11].The task of this work is narrower. It involves refining the theory of the effect of temperature on the spectra and rate of electron transfer (ET), and also developing a method for determining the matrix element for an electronic transition with electron transfer to the reaction center of purple bacteria.Theory of activationless electron transfer. The well-known theory of Bixon and Jortner [12] is based on ideas concerning the effect of polar modes in complex biological systems on the electron transfer rate k ET . According to [12]:

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