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Proceedings Paper

Laser fluorescence spectroscopy of the light harvesting complex II in different aggregation states
Author(s): Atanaska Andreeva; Bilyana Vapirova; Mira Busheva
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Paper Abstract

In order to elucidate the molecular mechanism of the non-photochemical quenching of the excess light energy – quenching of excited chlorophyll a singlet states, low-temperature (77 K) steady-state laser fluorescence emission spectroscopy was applied to the main chlorophyll a/b protein light harvesting complex of photosystem II in different aggregation states. The aggregation of the complexes led to the quenching of the chlorophyll a fluorescence, as in the process of non-photochemical quenching. The quenching is concomitant with a strong broadening of the emission spectra and an appearance of a new emission band red shifted compared to the emission spectrum of the trimeric forms of the light harvesting complex of photosystem II. The aggregation state of the complexes was varied by changing the concentrations of the used detergent n-dodecyl &bgr;-D-maltoside. The low-temperature chlorophyll a emission spectra of the light harvesting complex of photosystem II were excited by laser line at 488 nm of an argon laser. Spectra were decomposed into the bands attributed to the trimeric and aggregated forms of the light harvesting complex of photosystem II. Based on the analysis of the obtained data and the new structure of light harvesting complex of photosystem II, a model describing quantitatively the quenching of the chlorophyll a fluorescence in the light harvesting complex of photosystem II in different aggregation states is proposed. The model revealed that upon aggregation besides the changes in the relative absorption of small and large aggregates, the amount of quenchers, most probably chl a dimers, and the rate constant for energy transfer to them are also changed.

Paper Details

Date Published: 5 March 2007
PDF: 5 pages
Proc. SPIE 6604, 14th International School on Quantum Electronics: Laser Physics and Applications, 66042C (5 March 2007); doi: 10.1117/12.727721
Show Author Affiliations
Atanaska Andreeva, Sofia Univ. (Bulgaria)
Bilyana Vapirova, Sofia Univ. (Bulgaria)
Mira Busheva, Institute of Biophysics (Bulgaria)


Published in SPIE Proceedings Vol. 6604:
14th International School on Quantum Electronics: Laser Physics and Applications

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