Analysis of dipolar and exchange interactions between manganese and tyrosine Z in the S2YZ . state of acetate-inhibited photosystem II via EPR spectral simulations at X- and Q-bands

K. V. Lakshmi, Sandra S. Eaton, Gareth R. Eaton, Harry A. Frank, Gary W Brudvig

Research output: Contribution to journalArticle

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Abstract

Upon room-temperature illumination, acetate-inhibited photosystem II membranes are known to exhibit a 240 G wide X-band (∼9.5 GHz) electron paramagnetic resonance (EPR) signal at 10 K. This EPR signal arises from an interaction between the S = 1/2 multiline S2 state of the tetranuclear manganese cluster and an oxidized tyrosine residue, YZ.. In the present study, the exchange and dipolar interactions between the two paramagnetic species are simulated at X- and Q-band (∼33 GHz) frequencies utilizing second-order perturbation theory. The positions and relative intensities of the hyperfine lines in the S = 1/2 S2 state multiline EPR signal of the noninteracting Mn4 cluster are accurately simulated by including g anisotropy and four sets of axially symmetric 55Mn hyperfine tensors. These parameters are then used to simulate the dipolar and exchange interactions giving rise to the interacting S2YZ . (formerly referred to as S3) EPR signal. Relative intensities of components of the S2YZ. EPR spectrum, at both X- and Q-band frequencies, are best reproduced with a dipolar coupling corresponding to an interspin distance of 7.7 Å and an exchange coupling (J) of -280 × 10-4 cm-1.

Original languageEnglish
Pages (from-to)8327-8335
Number of pages9
JournalJournal of Physical Chemistry B
Volume102
Issue number42
Publication statusPublished - Oct 15 1998

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Photosystem II Protein Complex
tyrosine
Exchange interactions
Manganese
Paramagnetic resonance
Tyrosine
manganese
acetates
electron paramagnetic resonance
Acetates
simulation
interactions
Exchange coupling
superhigh frequencies
Frequency bands
Tensors
Anisotropy
perturbation theory
Lighting
illumination

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Analysis of dipolar and exchange interactions between manganese and tyrosine Z in the S2YZ . state of acetate-inhibited photosystem II via EPR spectral simulations at X- and Q-bands. / Lakshmi, K. V.; Eaton, Sandra S.; Eaton, Gareth R.; Frank, Harry A.; Brudvig, Gary W.

In: Journal of Physical Chemistry B, Vol. 102, No. 42, 15.10.1998, p. 8327-8335.

Research output: Contribution to journalArticle

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abstract = "Upon room-temperature illumination, acetate-inhibited photosystem II membranes are known to exhibit a 240 G wide X-band (∼9.5 GHz) electron paramagnetic resonance (EPR) signal at 10 K. This EPR signal arises from an interaction between the S = 1/2 multiline S2 state of the tetranuclear manganese cluster and an oxidized tyrosine residue, YZ.. In the present study, the exchange and dipolar interactions between the two paramagnetic species are simulated at X- and Q-band (∼33 GHz) frequencies utilizing second-order perturbation theory. The positions and relative intensities of the hyperfine lines in the S = 1/2 S2 state multiline EPR signal of the noninteracting Mn4 cluster are accurately simulated by including g anisotropy and four sets of axially symmetric 55Mn hyperfine tensors. These parameters are then used to simulate the dipolar and exchange interactions giving rise to the interacting S2YZ . (formerly referred to as S3) EPR signal. Relative intensities of components of the S2YZ. EPR spectrum, at both X- and Q-band frequencies, are best reproduced with a dipolar coupling corresponding to an interspin distance of 7.7 {\AA} and an exchange coupling (J) of -280 × 10-4 cm-1.",
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