Hystons, new quasi-particles, and electron transfer in bacterial photosynthesis

Pavlovich, V. S.

doi:10.1016/s1386-9477(02)00397-1

Cited by 2 publications

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“…Another way to describe the effect of temperature on the rate of electron transfer at the reaction centers of purple bacteria has been proposed in [17]. It was shown that polar modes modulate the frequency of the electronic transition ω and cause broadening of the electronic (exciton) absorption and emission bands.…”

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“…The first type correspond to vibrations which are accompanied by a change in the entropy of the system; the second type correspond to vibrations when the entropy of the system does not change (isentropic vibrational process). Using the golden rule of quantum mechanics [18,19], it has been found [17] that in the case of h µ modes, the rate constant for activationless electron transfer is…”

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confidence: 99%

“…The difference between relations (1), (3), and (4) is connected with the different interpretations of electron transfer processes. In the theory of Bixon and Jortner [12], electron transfer is considered as a reaction where the reaction coordinate is identified with the coordinate of motion for the harmonic oscillator x, while in the theory of hyston modes [17] it is considered as a resonance process at the transition frequency ω tr . It is important that formulas (3), (4), which have only two variable parameters k 0 and θ, describe well the experimental data obtained in [16,20] on the effect of temperature on the rate of primary and secondary electron transfer at reaction centers of purple bacteria.…”

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“…It is relevant to emphasize that the need to classify the polar modes as hyston h µ and pseudo-hyston h α is mainly due to the fundamental difference between the type of temperature dependence of the modulation broadening of the spectra: for the h µ modes, the broadening is proportional to coth 2 (θ/T) [17,60,61], while for the h α modes it is proportional to coth (θ/T) (13) [17,59]. Figure 1 shows the results of treatment of the experimental data for the halfwidth of the absorption spectra for reaction centers of Rps.…”

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confidence: 99%

“…This diagram is clear, but has a disadvantage since one-dimensional motion is Fig. 2 Schematic representation of the free energy potentials for activationless electron transfer from the excited Se state to a charge separation state CS (a) and the equivalent energy level diagram for the electronic ground state S g and the excited electronic state S e , broadened by the h α mode (b) [17]. The horizontal arrows (in the ground state and the excited state) indicate a reversible resonant transition from an S e state to a CS charge separation state at the frequency ω tr (left hand side of (8); spectral width of the transition γ ET ); the k ET arrows reflect electron transfer and stabilization of the system as a result of transition from an ETS state to an equilibrium * CS state (right-hand side of (8)).…”

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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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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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Photoinduced Self-Organization in “Semiconductor World”: Part I. from Protophotosynthesis to Protomembranes

Gradov,

Gradova

2023

Preprint

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This work is the first part of a series of papers on a comprehensive analysis of the processes of prebiotic self-organization and protophotosynthesis on the surface of semiconductor minerals and in systems of natural dispersed semiconductors. Comprehensive analysis within the framework of the "semiconductor world" concept allows integrating a variety of models on a single physical basis - from ZnS world and FeS world (based on inorganic semiconductors) to the PAH world and aromatic world (including organic semiconductors). Thus, we do not put forward a new alternative hypothesis of chemical evolution - a new "chemical world", but only integrate the evolutionary and geochemical criteria of different "chemical worlds" into a single "physical world", which gives one the opportunity to reconstruct and predict the directions of chemical evolution according to the uniform principles of physical chemistry. In the first part of this series we consider photoinduced self-organization and "photo-controlled" evolution of the early protobiological systems performing solar energy conversion on the surface of dispersed semiconductor minerals capable of (photo)catalyzing and photosensitizing prebiological processes. The latter include a transition from the elementary cycles of photocatalytic reactions on the surface of semiconductors to protophotometabolic cycles and protophotosynthesis, from photophysical processes on the surface of mineral semiconductors to photoinduced membrane potentials, from photocontrolled sorption on the surface of such minerals to the formation of photosensitive protomembranes and selection of photosynthetic structures. The evolutionary approach to the analysis of protobiological mechanisms and protobioenergetics within the framework of the "semiconductor world" concept provides a new approach to the study of the last common point of divergence of protobiological systems, where the emergence principles of different energy supply schemes (like the energy source-specific photoautotrophy and substrate-specific chemoautotrophy) merge at the physicochemical level. The proposed integrating scheme is consistent with most biological, geological, and physicochemical concepts, which ensures its complete cross-checking and internal consistency.

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Hystons, new quasi-particles, and electron transfer in bacterial photosynthesis

Cited by 2 publications

References 16 publications

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

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

Photoinduced Self-Organization in “Semiconductor World”: Part I. from Protophotosynthesis to Protomembranes

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