Charge Separation in Photosynthetic Reaction Centers

Ivashin, N. V.; Källebring, Bruno; Larsson, Sven; Hansson, Örjan

doi:10.1021/jp981208y

Cited by 61 publications

(59 citation statements)

References 47 publications

(84 reference statements)

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“…8,[13][14][15] Here we have re-examined V for P/B A and P/B B using the coordinates of Rb. sphaeroides, at a resolution of 2.2 Å, 16 and of Rps.…”

Section: Introductionmentioning

confidence: 99%

“…The opinions vary from total neglect of the hyperconjugated group 22 to assigning to them the main contribution. 14 Also it is not clear whether hyperconjugated groups facilitate the MCs by extending the MOs 14 or the "hole transfer" through occupied hyperconjugated groups contributes negative components to the MC. 27 We assume that when the through-space atomic couplings are properly considered, the extension of the MOs is not necessary for having a reasonable estimate of the coupling.…”

Section: Introductionmentioning

confidence: 99%

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Asymmetric Electron Transfer in Reaction Centers of Purple Bacteria Strongly Depends on Different Electron Matrix Elements in the Active and Inactive Branches

and

Scherz

2000

J. Phys. Chem. B

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We have re-examined the contribution of electronic matrix elements (V 1 ) between the primary electron donor and the accessory bacteriochlorophylls in the active (A) and inactive (B) branches of bacterial reaction centers (RC) to the unidirectional light-induced electron transfer (ET) (a preliminary report was recently given by Kolbasov and Scherz in Photosynthesis: Mechanisms and Effects; Garab, G., Ed.; Kluwer Academic Publishers: Dordrecht, 1998; Vol. II; pp 719-722). Our calculations showed that V 1 B 2 is probably smaller by 3 orders of magnitude than V 1 A 2 in Rb. sphaeroides and by at least 1 order of magnitude in Rps. Viridis. These phenomena reflect the quantum interference and mutual cancellation of the resonance integrals corresponding to different ET pathways between atoms of P and the accessory bacteriochlorophyll in the inactive branch.The calculated values of V and the corresponding ET rate constants for mutated RC further support this conclusion. Zhang and Friesner (Proc. Natl. Acad. Sci. U.S.A. 1998, 95, 13603-13605), using more elaborate calculations, showed that V 1 A /V 1 B for Rps. Viridis can reach a value of 14 for same reason, indicating that differences in the overlap matrix elements are key factors in the unidirectional electron flow in both organisms.

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“…8,[13][14][15] Here we have re-examined V for P/B A and P/B B using the coordinates of Rb. sphaeroides, at a resolution of 2.2 Å, 16 and of Rps.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Asymmetric Electron Transfer in Reaction Centers of Purple Bacteria Strongly Depends on Different Electron Matrix Elements in the Active and Inactive Branches

and

Scherz

2000

J. Phys. Chem. B

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“…59,60,61,62 The symmetry is already broken at the special pair with selective chargetransfer reactivity towards the L side and it has been suggested that the L side molecule has a less distorted macrocycle than the M side chromophore. 63,64 While other explanations have been brought forward, 65 there is structural evidence for multiple conformations in protein structures from site-directed mutants. 66 Resonance Raman and other vibrational techniques have been used to investigate this situation and have provided supporting information for structural flexibility of the chromophores.…”

Section: Chlorophyll Complexes In Photosynthesismentioning

confidence: 99%

61 The Structural Chemistry of Isolated Chlorophylls

Senge¹,

MacGowan²

2011

Handbook of Porphyrin Science

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“…From (19) follows the relation for determining the electronic transition matrix element (20); γ 0 , k 0 from Tables 1, 2 10.5 [74] INDO/S; for P * → B L 24 [16] From formula (2)…”

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confidence: 99%

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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Charge Separation in Photosynthetic Reaction Centers

Cited by 61 publications

References 47 publications

Asymmetric Electron Transfer in Reaction Centers of Purple Bacteria Strongly Depends on Different Electron Matrix Elements in the Active and Inactive Branches

Asymmetric Electron Transfer in Reaction Centers of Purple Bacteria Strongly Depends on Different Electron Matrix Elements in the Active and Inactive Branches

61 The Structural Chemistry of Isolated Chlorophylls

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

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