Fermi Resonance as a Tool for Probing Peridinin Environment
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- 作者：Elizabeth Kish ; Maria Manuela Mendes Pinto ; Daniele Bovi ; Marie Basire ; Leonardo Guidoni ; Rodolphe Vuilleumier ; Bruno Robert ; Riccardo Spezia ; Alberto Mezzetti
- 刊名：Journal of Physical Chemistry B
- 出版年：2014
- 出版时间：June 5, 2014
- 年：2014
- 卷：118
- 期：22
- 页码：5873-5881
- 全文大小：408K
- 年卷期：v.118,no.22(June 5, 2014)
- ISSN：1520-5207
文摘
In the present paper, we provide an extended study of the vibrational signature of a butenolide carotenoid, peridinin, in various solvents by combining resonance Raman spectroscopy (RRS) with theoretical calculations. The presence of a Fermi resonance due to coupling between the lactonic C鈺怬 stretching and the overtone of the wagging of the C鈥揌 in the lactonic ring provides a spectroscopic way of differentiating between peridinins lying in different environments. This is a significant achievement, given that simultaneous presence of several peridinins (each with a peculiar photophysical role) in different environments occurs in the most important peridinin containing proteins, the peridinin-chlorophyll proteins (PCPs) and the Chl a-c2-peridinin binding proteins. In RRS, small modifications of solvent polarity can give rise to large differences in the intensity and splitting between the two bands, resulting from the Fermi resonance. By changing the polarity, we can tune the frequency of stretching of the C鈺怬 and, while the C鈥揌 wagging frequency is almost always constant in different solvents, move the system from a perfect resonance condition to off-resonance ones. We have corroborated our spectroscopic findings with a quasi-classical dynamical model of two coupled oscillators, and DFT calculations on peridinin in different solvents; we have also used calculations to complete the peridinin vibrational mode assignments in the 800鈥?600 cm鈥? region of RRS spectra, corresponding to polyene chain motion. Finally, the presence of Fermi resonance has been used to reinterpret previous vibrational spectroscopic experiments in PCPs.