Charge-Transfer Character of the Low-Energy Chl a Qy Absorption Band in Aggregated Light Harvesting Complexes II
| Autor: | Ximao Feng, Michael Reus, Jun Li, Yiqun Yang, Adam Kell, Ryszard Jankowiak, Chen Lin, Alfred R. Holzwarth |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Quenching
Absorption spectroscopy Photosystem II Protein Conformation Chemistry Spectrum Analysis Light-Harvesting Protein Complexes Temperature Analytical chemistry Photosystem II Protein Complex Electrons Charge (physics) Photochemistry Surfaces Coatings and Films Light-harvesting complex Spinacia oleracea Absorption band Materials Chemistry Phonons Physical and Theoretical Chemistry Absorption (electromagnetic radiation) Spectroscopy |
| Zdroj: | The Journal of Physical Chemistry B. 118:6086-6091 |
| ISSN: | 1520-5207 1520-6106 |
| Popis: | One of the key functions of the major light harvesting complex II (LHCII) of higher plants is to protect Photosystem II from photodamage at excessive light conditions in a process called "non-photochemical quenching" (NPQ). Using hole-burning (HB) spectroscopy, we investigated the nature of the low-energy absorption band in aggregated LHCII complexes - which are highly quenched and have been established as a good in vitro model for NPQ. Nonresonant holes reveal that the lowest energy state (located near 683.3 nm) is red-shifted by ~4 nm and significantly broader (by a factor of 4) as compared to nonaggregated trimeric LHCII. Resonant holes burned in the low-energy wing of the absorption spectrum (685-710 nm) showed a high electron-phonon (el-ph) coupling strength with a Huang-Rhys factor S of 3-4. This finding combined with the very low HB efficiency in the long-wavelength absorption tail is consistent with a dominant charge-transfer (CT) character of the lowest energy transition(s) in aggregated LHCII. The value of S decreases at shorter wavelengths (685 nm), in agreement with previous studies (J. Pieper et al., J. Phys. Chem. B 1999, 103, 2422-2428), proving that the low-energy excitonic state is strongly mixed with the CT states. Our findings support the mechanistic model in which Chl-Chl CT states formed in aggregated LHCII are intermediates in the efficient excited state quenching process (M. G. Müller et al., Chem. Phys. Chem. 2010, 11, 1289-1296; Y. Miloslavina et al., FEBS Lett. 2008, 582, 3625-3631). |
| Databáze: | OpenAIRE |
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