QM/MM dynamics of a Peridinin model in triplet state in three prototypical solvents |
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| Institution: | 1. Dipartimento di Scienze Fisiche e Chimiche, Università dell’Aquila, Via Vetoio 2, 67100, Coppito, L’Aquila, Italy;2. Sorbonne Universities, UPMC, Laboratoire de Réactivité de Surface UMR CNRS 7197, Tour 43-53, 3rd floor, 4 Pl. Jussieu, 75005, Paris, France;3. Service de Bioénergétique, Biologie Structurale et Mécanismes (SB2SM) CEA, iBiTec-S, Biochimie Biophysique et Biologie Structurale (B3S), I2BC, UMR 9198, F-91191 Gif-sur-Yvette, France;1. Department of Physics, SCE?Shamoon College of Engineering, Beer-Sheva 84100, Israel;2. Department of Physics, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel;3. Department of Medicine, University of Virginia, Charlottesville, VA 22901, USA;4. Surgery B Department, Soroka University Medical Center, Faculty of Health Sciences, Ben-Gurion University, Beer-Sheva 84101, Israel;1. Department of Neurobiology, Institute of Pharmacology, Polish Academy of Sciences, Sm?tna 12, 31-343 Kraków, Poland;2. Faculty of Foundry Engineering, AGH University of Science and Technology, ul. Reymonta 23, 30-059 Kraków, Poland;3. Institute of Nuclear Physics, Polish Academy of Science, 31-342 Krakow, Poland;4. Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060 Kraków, Poland;5. Department of Chemistry, Hankuk University of Foreign Studies, Yongin, Kyunggi-Do, 449-791, South Korea;1. Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland;2. Frank Laboratory of Neutron Physics, JINR, 141980 Dubna, Russia;1. Institute of Solid State Chemistry, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg, Russian Federation;2. Institute of Mathematics and Mechanics, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg, Russian Federation;3. Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, 620990 Ekaterinburg, Russian Federation |
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| Abstract: | Peridinin (Per) is a carbonyl-containing carotenoid playing a key role in light harvesting and photoprotection in dinoflagellates. This carotenoid plays its photoprotective role by quenching the potentially dangerous 3Chl-a triplet state through the formation of the non-reactive 3Per triplet state through Dexter energy transfer mechanism. We have investigated by means of Quantum Mechanics/Molecular Mechanics dynamics simulations at room temperature the structural and dynamical properties of a Peridinin model system (PMS) in triplet state in three different solvents: cyclohexane, apolar/aprotic; acetonitrile, polar/aprotic; and methanol (MeOH), polar/protic. Our results of 3PMS in MeOH show that the lactonic carbonyl has a stronger tendency to accept hydrogen bonds compared to the corresponding singlet ground state (1PMS). This effect may play some so far overlooked role in Per-containing proteins (notably the water soluble Peridinin-Chlorophyll-Proteins – PCPs).The vibrational properties of the 3PMS dynamics in the three solvents have been analyzed by means of decomposition of the vibrational density of states in effective normal modes. The results show that the solute-solvent interactions can influence some vibrational bands of 3PMS; in particular, they are able to modulate the position of the lactonic C O stretching band. The situation is particularly evident in the case of MeOH, where the dynamics of the MeOH?OC hydrogen bond interactions can strongly influence the band position and shape. As vibrational spectroscopy (notably step-scan FTIR difference spectroscopy) has been largely used to investigate 3Per in PCPs, especially using the lactonic carbonyl stretching as a marker band to investigate the different photophysical role of each Per in the protein complex, this study represents an important step to understand the experimental spectra and to identify the Per(s) molecule(s) bearing the triplet in PCPs. |
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| Keywords: | Peridinin Carotenoids QM/MM calculations Triplet state Hydrogen bonds Solvent effects on vibrational bands |
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