skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Exploring hyperfine interactions in spin-correlated radical pairs from photosynthetic proteins : high-frequency ENDOR and quantum beat oscillations.

Abstract

No abstract prepared.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC); FOR
OSTI Identifier:
914830
Report Number(s):
ANL/CHM/JA-57181
Journal ID: ISSN 0937-9347; APMREI; TRN: US200812%%284
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Appl. Magn. Reson.; Journal Volume: 31; Journal Issue: 1-2 ; 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
59 BASIC BIOLOGICAL SCIENCES; ENDOR; OSCILLATIONS; PROTEINS; RADICALS

Citation Formats

Poluektov, O. G., Utschig, L. M., Thurnauer, M. C., Kothe, G., Chemistry, and Univ. of Freiburg. Exploring hyperfine interactions in spin-correlated radical pairs from photosynthetic proteins : high-frequency ENDOR and quantum beat oscillations.. United States: N. p., 2007. Web. doi:10.1007/BF03166251.
Poluektov, O. G., Utschig, L. M., Thurnauer, M. C., Kothe, G., Chemistry, & Univ. of Freiburg. Exploring hyperfine interactions in spin-correlated radical pairs from photosynthetic proteins : high-frequency ENDOR and quantum beat oscillations.. United States. doi:10.1007/BF03166251.
Poluektov, O. G., Utschig, L. M., Thurnauer, M. C., Kothe, G., Chemistry, and Univ. of Freiburg. Mon . "Exploring hyperfine interactions in spin-correlated radical pairs from photosynthetic proteins : high-frequency ENDOR and quantum beat oscillations.". United States. doi:10.1007/BF03166251.
@article{osti_914830,
title = {Exploring hyperfine interactions in spin-correlated radical pairs from photosynthetic proteins : high-frequency ENDOR and quantum beat oscillations.},
author = {Poluektov, O. G. and Utschig, L. M. and Thurnauer, M. C. and Kothe, G. and Chemistry and Univ. of Freiburg},
abstractNote = {No abstract prepared.},
doi = {10.1007/BF03166251},
journal = {Appl. Magn. Reson.},
number = 1-2 ; 2007,
volume = 31,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • No abstract prepared.
  • A new phenomenon has been detected in the time-resolved electron-nuclear double resonance (ENDOR) spectra of the spin-correlated radical pairs in photosynthetic reaction center proteins. The observed effects result from both increased resolution and orientational selectivity provided by high magnetic field EPR and are manifest as specific, derivative-type lines in the ENDOR spectrum. Importantly, the positions and amplitudes of these lines contain information on the interaction of a particular nucleus with both correlated electron spins. Thus, spin density delocalization in the protein environment between the donor and acceptor in the SCRP can be revealed via SCRP ENDOR, providing a unique opportunitymore » to probe the electron-transfer pathways in natural and artificial photosynthetic assemblies.« less
  • The influence of anisotropic hyperfine interaction on transient nutation electron paramagnetic resonance (EPR) of light-induced spin-correlated radical pairs is studied theoretically. Expressions for the time evolution of the transient EPR signal during selective microwave excitation of single transitions are derived for a system comprised of a weakly coupled radical pair and one hyperfine-coupled nucleus with I=1/2. Zero-quantum electron coherence and single-quantum nuclear coherence are created as a result of the sudden light-induced generation of the radical pair state from a singlet-state precursor. Depending on the relative sizes of the nuclear Zeeman frequency and the secular and pseudo-secular parts of themore » hyperfine coupling, transitions between levels with different nuclear spin orientations are predicted to modulate the time-dependent EPR signal. These modulations are in addition to the well-known transient nutations and electron zero-quantum precessions. Our calculations provide insight into the mechanism of coherent nuclear modulations in the time-resolved EPR signals of doublets and radical pairs. Two distinct mechanisms of the modulations are presented for various microwave magnetic field strengths. The first modulation scheme arises from electron and nuclear coherences initiated by the laser excitation pulse and is {close_quotes}read out{open_quotes} by the weak microwave magnetic field. While the relative modulation depth of these oscillations with respect to the signal intensity is independent of the Rabi frequency, {omega}{sub 1}, the frequencies of this coherence phenomenon are modulated by the effective microwave amplitude and determined by the nuclear Zeeman interaction and hyperfine coupling constants as well as the electron-electron spin exchange and dipolar interactions between the two radical pair halves. In a second mechanism the modulations are both created and detected by the microwave radiation. (Abstract Truncated)« less
  • The magnetic-field-induced orientation of photosynthetic reaction centers has been studied by time-resolved D-band (130 GHz) electron paramagnetic resonance (EPR) of the secondary radical pair, P{sup +}{sub 700} A{sup -}{sub 1}, in plant photosystem I (PSI). Experiments have been performed for fresh and lyophilized whole cells of the deuterated cyanobacterium S. lividus. A computer fit of the angle-dependent D-band spectra, measured for two different sample orientations, provides the order parameter S{sub Z'Z'} of the symmetry axis, Z', of the susceptibility tensor, relative to the magnetic field. The positive sign of this order parameter indicates that membrane proteins are the major sourcemore » for the anisotropy of the diamagnetic susceptibility, {Delta}{chi}V. A value for {Delta}{chi}V has been extracted from the magnetic-field dependence of S{sub Z'Z'}. The value of {Delta}{chi}V = 5.7 x 10{sup -27} m{sup 3} is in good agreement with an estimate for the susceptibility anisotropy of a cyanobacterial cell. This demonstrates that whole cells are aligned in the magneto-orientation process. The combination of high-field EPR of a magnetically oriented sample with the analysis of quantum beat oscillations allows determination of the three-dimensional structure of P{sup +}{sub 700}A{sup -}{sub 1}in the photosynthetic membrane.« less