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Split EPR signals from photosystem II are modified by methanol, reflecting S state-dependent binding and alterations in the magnetic coupling in the CaMn4 cluster

Su, Ji Hu ; Havelius, Kajsa G.V. LU ; Mamedov, Fikret LU ; Ho, Felix M. and Styring, Stenbjörn LU (2006) In Biochemistry 45(24). p.7617-7627
Abstract

Methanol binds to the CaMn4 cluster in photosystem II (PSII). Here we report the methanol dependence of the split EPR signals originating from the magnetic interaction between the CaMn4 cluster and the Y Z· radical in PSII which are induced by illumination at 5 K. We found that the magnitudes of the "split S1" and "split S3" signals induced in the S1 and S 3 states of PSII centers, respectively, are diminished with an increase in the methanol concentration. The methanol concentrations at which half of the respective spectral changes had occurred ([MeOH]1/2) were 0.12 and 0.57%, respectively. By contrast, the "split S0" signal induced in... (More)

Methanol binds to the CaMn4 cluster in photosystem II (PSII). Here we report the methanol dependence of the split EPR signals originating from the magnetic interaction between the CaMn4 cluster and the Y Z· radical in PSII which are induced by illumination at 5 K. We found that the magnitudes of the "split S1" and "split S3" signals induced in the S1 and S 3 states of PSII centers, respectively, are diminished with an increase in the methanol concentration. The methanol concentrations at which half of the respective spectral changes had occurred ([MeOH]1/2) were 0.12 and 0.57%, respectively. By contrast, the "split S0" signal induced in the So state is broadened, and its amplitude is enhanced. [MeOH]1/2 for this change was found to be 0.54%. We discuss these observations with respect to the location and nature of the methanol binding site. Furthermore, by comparing this behavior with methanol effects reported for other EPR signals in the different S states, we propose that the observed methanol-dependent changes in the split S1 and split So EPR signals are caused by an increase in the extent of magnetic coupling within the cluster.

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author
; ; ; and
publishing date
type
Contribution to journal
publication status
published
in
Biochemistry
volume
45
issue
24
pages
11 pages
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:33745162889
  • pmid:16768457
ISSN
0006-2960
DOI
10.1021/bi060333u
language
English
LU publication?
no
id
cd3fea38-1eaf-46f4-bd0f-c61345b7283b
date added to LUP
2020-01-15 11:24:21
date last changed
2024-05-29 07:38:27
@article{cd3fea38-1eaf-46f4-bd0f-c61345b7283b,
  abstract     = {{<p>Methanol binds to the CaMn<sub>4</sub> cluster in photosystem II (PSII). Here we report the methanol dependence of the split EPR signals originating from the magnetic interaction between the CaMn<sub>4</sub> cluster and the Y <sub>Z</sub>· radical in PSII which are induced by illumination at 5 K. We found that the magnitudes of the "split S<sub>1</sub>" and "split S<sub>3</sub>" signals induced in the S<sub>1</sub> and S <sub>3</sub> states of PSII centers, respectively, are diminished with an increase in the methanol concentration. The methanol concentrations at which half of the respective spectral changes had occurred ([MeOH]<sub>1/2</sub>) were 0.12 and 0.57%, respectively. By contrast, the "split S<sub>0</sub>" signal induced in the So state is broadened, and its amplitude is enhanced. [MeOH]<sub>1/2</sub> for this change was found to be 0.54%. We discuss these observations with respect to the location and nature of the methanol binding site. Furthermore, by comparing this behavior with methanol effects reported for other EPR signals in the different S states, we propose that the observed methanol-dependent changes in the split S<sub>1</sub> and split So EPR signals are caused by an increase in the extent of magnetic coupling within the cluster.</p>}},
  author       = {{Su, Ji Hu and Havelius, Kajsa G.V. and Mamedov, Fikret and Ho, Felix M. and Styring, Stenbjörn}},
  issn         = {{0006-2960}},
  language     = {{eng}},
  month        = {{06}},
  number       = {{24}},
  pages        = {{7617--7627}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Biochemistry}},
  title        = {{Split EPR signals from photosystem II are modified by methanol, reflecting S state-dependent binding and alterations in the magnetic coupling in the CaMn<sub>4</sub> cluster}},
  url          = {{http://dx.doi.org/10.1021/bi060333u}},
  doi          = {{10.1021/bi060333u}},
  volume       = {{45}},
  year         = {{2006}},
}