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Effect of structural changes in Photosystem II supercomplexes on their fluorescence properties♣

A. ANDREEVA1,* , K. STOITCHKOVA1, S. ABAROVA1, M. BUSHEVA2

Affiliation

  1. Sofia University, Faculty of Physics, Department of Condensed Matter Physics, 5, J. Bourchier blvd., 1164 Sofia, Bulgaria
  2. Institute of Biophysics, Bulgarian Academy of Sciences, Acad. G. Bonchev str. bl.21, 1113 Sofia, Bulgaria

Abstract

Photosystem II is a multi-subunit pigment-protein complex embedded in the chloroplast thylakoid membranes. It consists of a large number of extrinsic and intrinsic proteins. In this report, the effect of the removal of extrinsic proteins of the oxygen-evolving complex, and several amino acids, from surface exposed polypeptides and/or small proteins on the efficiency of energy transfer and its regulation is investigated, by using chlorophyll a fluorescence at 77 K. The obtained results show that the two treatments have opposite effects on the photosystem II fluorescence. The removal of small surface exposed proteins enhances the total photosystem II fluorescence, influencing mainly the highly fluorescing trimeric outer antenna. The removal of extrinsic proteins of the oxygen-evolving complex results in a decrease in the total fluorescence intensity. The decrease is explained by a reduction of the distance from outer antenna to inner antenna CP43 and from outer antenna to proteins in the reaction center complex. This also diminishes the distances between chl a molecules and changes their mutual orientation, thus leading to possible concentration quenching of the chlorophyll fluorescence. For both treatments, the impact of the aggregation extent of outer antenna, controlled by the detergent concentration, is compared..

Keywords

Photosystem II, 77 K chlorophyll fluorescence, structural changes.

Submitted at: Nov. 5, 2008
Accepted at: Sept. 9, 2009

Citation

A. ANDREEVA, K. STOITCHKOVA, S. ABAROVA, M. BUSHEVA, Effect of structural changes in Photosystem II supercomplexes on their fluorescence properties♣, Journal of Optoelectronics and Advanced Materials Vol. 11, Iss. 9, pp. 1234-1237 (2009)