Electron spin polarization in sequential electron transfer. An example from iron-containing photosynthetic bacterial reaction center proteins

Snyder, Seth W.; Morris, Andrea L.; Bondeson, S. R.; Norris, James R.; Thurnauer, Marion C.

doi:10.1021/ja00062a053

Cited by 24 publications

(18 citation statements)

References 4 publications

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“…The TREPR technique and ESP have also been powerful tools for the investigation of problems particularly of interest in the area of photosynthesis, for example, to provide direct evidence for a specific electron acceptor in photosystem I, [47] and elucidation of donor ± acceptor pairs in the bacterial photosynthetic reaction center. [48,53,54] A recent study in photosynthetic models has revealed structural information using a zinc porphyrin with a para arrangement of N,N,N',N'-tetraalkyl-para-phenylenediamine and naphthoquinone units. [49] Other studies dealing with the photosynthetic reaction center demonstrate that additional kinetics and structural information can be obtained by operating the EPR spectrometer at various frequencies.…”

Section: Other Applications Of the Trepr Technique And Espmentioning

confidence: 99%

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Turro

Kleinman

Karatekin

2000

Angew. Chem. Int. Ed.

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Most molecular and supramolecular organic photochemical reactions involve paramagnetic reactive intermediates (such as molecular triplet states, triplet radical pairs, and free radicals). In a number of cases these species are created with “anomalous” spin populations which are far from thermal equilibrium. Such paramagnetic species are said to be “spin polarized” and may be observed directly by time‐resolved electron paramagnetic resonance (TREPR). The TREPR technique can be applied to exploit spin polarization, which, in addition to providing an enormous signal to noise enhancement, also reveals the mechanisms involved in photochemical reactions. TREPR spectroscopy provides a means of tracking the reaction of radicals with molecules and the nonreactive interactions of radicals with other radicals in real time. The latter interactions provide a systematic investigation of supramolecular interactions of geminate radicals in micelles.

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Section: Other Applications Of the Trepr Technique And Espmentioning

confidence: 99%

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Turro

Kleinman

Karatekin

2000

Angew. Chem. Int. Ed.

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“…Under the assumption that RP1 has decayed essentially to zero, one can use infinity as the upper limit of the integration in Eq. (5). Thus, the density matrix of the secondary pair can be written in the form:…”

Section: Theoretical Description Of Consecutive Radical Pairsmentioning

confidence: 99%

“…However, for chemically modified bacterial reaction centres and in particular for the state P+FX in photosystem I (PSI) and heliobacteria, the lifetime of the precursor is long enough that its spin dynamics must be taken explicitly into account. The EPR spectra of sequential radical pairs have been studied by several authors [2][3][4][5][6][7][8][9][10]. Essentially all of these studies have dealt with the electron transfer step P+I --PQA in modified bacterial reaction centres in which the lifetime of P+I -is long enough that its spin dynamics must be considered but short enough that it is not observed directly.…”

Section: Introductionmentioning

confidence: 99%

Electron spin polarization in consecutive spin-correlated radical Pairs: Application to short-lived and long-lived precursors in type 1 photosynthetic reaction centres

et al. 1998

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An analytical treatment of the spin dynamics in sequential photoinduced correlated coupled radical pairs is presented and applied to the spectra of the states P'A, and P+Fx in type 1 photosynthetic reaction centres. Expressions for the spin polarized spectra are derived for the specific limiting cases of a very short-lived and very long-lived primary radical pair which correspond to the situation found in heliobacteria and photosystem I (PSI), respectively. The inhomogeneous linebroadening due to the unresolved hyperfine couplings is taken explicitly into account. It is shown that the density matrix of the secondary pair p2 can be written as the sum of two terms corresponding to (i) the part which is independent of the spin dynamics in the precursor, (ii) the additional spin polarization which is generated during the lifetime of the precursor and transferred to the secondary pair. The latter term contains two contributions which arise from the difference of the Zeeman interactions of the radicals in the primary pair and from the inhomogeneous line broadening. The predicted polarization patterns are compared to those established for chemically induced dynamic electron polarization (CIDEP) when uncoupled radicals are generated from a radical pair precursor. The expressions are then used to simulate the experimental spectra of the consecutive pairs PA and P'FX in PSI using parameters derived entirely from independent experimental data. Excellent agreement with the experimental results is obtained. The spectra of P'FX in heliobacteria at X-and Kband are also simulated and it is shown that the observed polarization patterns can be reproduced assuming direct electron transfer from A o to Fx with a time constant of r = 600 ps.

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“…[8][9][10][11][12][13]. At that time, the focus was on two experimentally observed limiting cases: a very shortlived and very long-lived p¡ radical pair.…”

Section: Introductionmentioning

confidence: 99%

Interpretation of multifrequency transient EPR spectra of the P 700 + A0Q K − state in photosystem I complexes with a sequential correlated radical pair model: Wild type versus A0 mutants

et al. 2003

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Transient electron paramagnetic resonance (TR-EPR) spectra of the electron-hole pair state P7+ooAoQ~, in photosystem I are numerically calculated. Parameter variation concems mainly the exchange integral J of the precursor spin pair state P~'ooAoQK and its lifetime r. A prominent emissive feature in the high-field region (PT+00 par O of the EPR spectrum tums out to be diminished with increasing lifetime r of the precursor pair state in the case of positive exchange coupling J > 0 (ferromagnetic type). Correspondingly, the emissive feature becomes more pronounced with increasing lifetime r in the case of negative exchange coupling J < 0 (antiferromagnetic type). These results can be used to interpret the changes in the pattem observed in TR-EPR spectra comparing wild-type and specific A 0 mutants. The central ligating amino acid residue to the A 0 chlorophyll cofactor is mutated from native methionine (M) to leucine (L) in either the PsaA or the PsaB branch. Changes are observed on[y for the A-side mutant: M688L(PsaA). They are consistent with the following parameters in the precursor pair P7+0~A~: J= 0.5+1.0 mT and r = 1.5+2 ns (as compared to r~ 0.05 ns in the wild type).

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Electron spin polarization in sequential electron transfer. An example from iron-containing photosynthetic bacterial reaction center proteins

Cited by 24 publications

References 4 publications

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Electron Spin Polarization and Time-Resolved Electron Paramagnetic Resonance: Applications to the Paradigms of Molecular and Supramolecular Photochemistry

Electron spin polarization in consecutive spin-correlated radical Pairs: Application to short-lived and long-lived precursors in type 1 photosynthetic reaction centres

Interpretation of multifrequency transient EPR spectra of the P 700 + A0Q K − state in photosystem I complexes with a sequential correlated radical pair model: Wild type versus A0 mutants

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