Changing the site energy of per-614 in the Peridinin-chlorophyll a-protein does not alter its capability of chlorophyll triplet quenching |
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Authors: | Alessandro Agostini Jens Niklas Tim Schulte Marilena Di Valentin Marco Bortolus Eckhard Hofmann Wolfgang Lubitz Donatella Carbonera |
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Affiliation: | 1. Department of Chemical Sciences, University of Padova, via Marzolo 1, 35131 Padova, Italy;2. Biophysics, Department of Biology and Biotechnology, Ruhr-University Bochum, D-44780 Bochum, Germany;3. Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany |
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Abstract: | The peridinin–chlorophyll-a protein (PCP) is a water-soluble light harvesting protein of the dinoflagellate Amphidinium carterae, employing peridinin (Per) as the main carotenoid to fulfil light harvesting and photo-protective functions. Per molecules bound to the protein experience specific molecular surroundings which lead to different electronic and spectral properties. In the refolded N89?L variant PCP (N89?L-RFPCP) a significant part of the intensity on the long wavelength side of the absorption spectrum is shifted to shorter wavelengths due to a significant change in the Per-614 site energy. Since Per-614 has been shown to be the main chlorophyll (Chl) triplet quencher in the protein, and the relative geometry of pigments is not affected by the mutation as verified by X-ray crystallography, this variant is ideally suited to study the dependence of the triplet-triplet energy transfer (TTET) mechanism on the pigment site energy. By using a combination of Optically Detected Magnetic Resonance (ODMR), pulse Electron Paramagnetic Resonance (EPR) and Electron Nuclear DOuble Resonance (ENDOR) we found that PCP maintains the efficient Per-614-to-Chl-a TTET despite the change of Per-614 local energy. This shows the robustness of the photoprotective site, which is very important for the protection of the system. |
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Keywords: | PCP MFPCP main form PCP RFPCP refolded PCP Car carotenoid(s) Chl chlorophyll Per peridinin ZFS Zero Field Splitting EPR Electron Paramagnetic Resonance TTET triplet-triplet energy transfer ENDOR Electron Nuclear DOuble Resonance ODMR Optically Detected Magnetic Resonance T-S triplet minus singlet spectrum PCP Peridinin Carotenoid Triplet state Pulse EPR ENDOR ODMR |
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