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Title: Intermolecular electronic interactions in the primary charge separation in bacterial photosynthesis

Abstract

In this paper the intermolecular overlap approximation is used to calculate the relative magnitudes of the electronic transfer integrals between the excited singlet state ({sup 1}P*) of the bacteriochlorophyll dimer (P) and the accessory bacteriochlorophyll (B) and between B{sup {minus}} and bacteriopheopytin (H), along the L and M subunits of the reaction center (RC) of Rps. viridis. The ratio of the electron-transfer integrals for B{sub L}{sup {minus}}H{sub L}{sup {minus}}B{sub L}H{sub L}{minus} and for B{sub M}{sup {minus}}H{sub M}{minus}B{sub M}H{sub M}{sup {minus}} was calculated to be 2.1 {plus minus} 0.5, which together with the value of 2.8 {plus minus} 0.7 for the ratio of the transfer integrals for {sup 1}P*B{sub L}-P{sup +}B{sub L}- and for {sup 1}P*B{sub M}-P{sup +}B{sub M}- results in the electronic contribution of 33 {plus minus} 16 to the ratio k{sub L}/k{sub m} of the rate constants k{sub L} and k{sub M} for the primary charge separation across the L and M branches of the RC, respectively. The asymmetry of the electronic coupling terms, which originates from the combination of the asymmetry in the charge distribution of {sup 1}P* and of structural asymmetry of the P-M and B-H arrangements across the L and M subunits, provides a major contributionmore » to the unidirectionality of the charge separation in bacterial photosynthesis. A significant contribution to the transfer integrals between adjacent pigments originates from nearby methyl groups through hyperconjugation. The ratio 6 {plus minus} 2 of the transfer integrals for {sup 1}P*B{sub L}-P{sup +}B{sub L}- and for B{sub L}-H{sub L}-B{sub L}H{sub L}- was utilized to estimate the energetic parameters required to ensure the dominance of the superexchange mediated unistep electron transfer {sup 1}P*BH {yields} P{sup +}BH{sup {minus}} over the thermally activated {sup 1}P*B {yields} P{sup +}B{sup {minus}} process. 31 refs., 6 figs., 2 tabs.« less

Authors:
; ; ; ;  [1]
  1. Freie Universitaet Berlin (West Germany)
Publication Date:
OSTI Identifier:
5448975
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society; (USA)
Additional Journal Information:
Journal Volume: 110:22; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; PHOTOSYNTHESIS; ELECTRON TRANSFER; BACTERIA; CHLOROPHYLL; EXPERIMENTAL DATA; CARBOXYLIC ACIDS; CHEMICAL REACTIONS; DATA; HETEROCYCLIC ACIDS; HETEROCYCLIC COMPOUNDS; INFORMATION; MICROORGANISMS; NUMERICAL DATA; ORGANIC ACIDS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; PHYTOCHROMES; PIGMENTS; PORPHYRINS; PROTEINS; SYNTHESIS; 140505* - Solar Energy Conversion- Photochemical, Photobiological, & Thermochemical Conversion- (1980-)

Citation Formats

Plato, M, Moebius, K, Michel-Beyerle, M E, Bixon, M, and Jortner, J. Intermolecular electronic interactions in the primary charge separation in bacterial photosynthesis. United States: N. p., 1988. Web. doi:10.1021/ja00230a002.
Plato, M, Moebius, K, Michel-Beyerle, M E, Bixon, M, & Jortner, J. Intermolecular electronic interactions in the primary charge separation in bacterial photosynthesis. United States. https://doi.org/10.1021/ja00230a002
Plato, M, Moebius, K, Michel-Beyerle, M E, Bixon, M, and Jortner, J. 1988. "Intermolecular electronic interactions in the primary charge separation in bacterial photosynthesis". United States. https://doi.org/10.1021/ja00230a002.
@article{osti_5448975,
title = {Intermolecular electronic interactions in the primary charge separation in bacterial photosynthesis},
author = {Plato, M and Moebius, K and Michel-Beyerle, M E and Bixon, M and Jortner, J},
abstractNote = {In this paper the intermolecular overlap approximation is used to calculate the relative magnitudes of the electronic transfer integrals between the excited singlet state ({sup 1}P*) of the bacteriochlorophyll dimer (P) and the accessory bacteriochlorophyll (B) and between B{sup {minus}} and bacteriopheopytin (H), along the L and M subunits of the reaction center (RC) of Rps. viridis. The ratio of the electron-transfer integrals for B{sub L}{sup {minus}}H{sub L}{sup {minus}}B{sub L}H{sub L}{minus} and for B{sub M}{sup {minus}}H{sub M}{minus}B{sub M}H{sub M}{sup {minus}} was calculated to be 2.1 {plus minus} 0.5, which together with the value of 2.8 {plus minus} 0.7 for the ratio of the transfer integrals for {sup 1}P*B{sub L}-P{sup +}B{sub L}- and for {sup 1}P*B{sub M}-P{sup +}B{sub M}- results in the electronic contribution of 33 {plus minus} 16 to the ratio k{sub L}/k{sub m} of the rate constants k{sub L} and k{sub M} for the primary charge separation across the L and M branches of the RC, respectively. The asymmetry of the electronic coupling terms, which originates from the combination of the asymmetry in the charge distribution of {sup 1}P* and of structural asymmetry of the P-M and B-H arrangements across the L and M subunits, provides a major contribution to the unidirectionality of the charge separation in bacterial photosynthesis. A significant contribution to the transfer integrals between adjacent pigments originates from nearby methyl groups through hyperconjugation. The ratio 6 {plus minus} 2 of the transfer integrals for {sup 1}P*B{sub L}-P{sup +}B{sub L}- and for B{sub L}-H{sub L}-B{sub L}H{sub L}- was utilized to estimate the energetic parameters required to ensure the dominance of the superexchange mediated unistep electron transfer {sup 1}P*BH {yields} P{sup +}BH{sup {minus}} over the thermally activated {sup 1}P*B {yields} P{sup +}B{sup {minus}} process. 31 refs., 6 figs., 2 tabs.},
doi = {10.1021/ja00230a002},
url = {https://www.osti.gov/biblio/5448975}, journal = {Journal of the American Chemical Society; (USA)},
issn = {0002-7863},
number = ,
volume = 110:22,
place = {United States},
year = {Wed Oct 26 00:00:00 EDT 1988},
month = {Wed Oct 26 00:00:00 EDT 1988}
}