Anharmonic Vibrational Calculations Modeling the Raman Spectra of Intermediates in the Photoactive Yellow Protein (PYP) Photocycle
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- 作者：Adeyemi A. Adesokan ; Duohai Pan ; Erick Fredj ; Richard A. Mathies ; R. Benny Gerber
- 刊名：Journal of the American Chemical Society
- 出版年：2007
- 出版时间：April 18, 2007
- 年：2007
- 卷：129
- 期：15
- 页码：4584 - 4594
- 全文大小：250K
- 年卷期：v.129,no.15(April 18, 2007)
- ISSN：1520-5126
文摘
The role of anharmonic effects in the vibrational spectroscopy of the dark state and two majorchromophore intermediates of the photoactive yellow protein (PYP) photocycle is examined via ab initiovibrational self-consistent field (VSCF) calculations and time-resolved resonance Raman spectroscopy.For the first time, anharmonicity is considered explicitly in calculating the vibrational spectra of an ensembleconsisting of the PYP chromophore surrounded by model compounds used as mimics of the importantactive-site residues. Predictions of vibrational frequencies on an ab initio corrected semiempirical potentialenergy surface show remarkable agreement with experimental frequencies for all three states, thus sheddinglight on the potential along the reaction path. For example, calculated frequencies for vibrational modes ofthe red-shifted intermediate, PYPL, exhibit an overall average error of 0.82% from experiment. Upon analysisof anharmonicity patterns in the PYP modes we observe a decrease in anharmonicity in the C8-C9 stretchingmode 
29 (trans-cis isomerization marker mode) with the onset of the cis configuration in PYPL. This canbe attributed to the loss of the hydrogen-bonding character of the adjacent C9-O2 to the methylamine(Cys69 backbone). For several of the modes, the anharmonicity is mostly due to mode-mode coupling,while for others it is mostly intrinsic. This study shows the importance of the inclusion of anharmonicity intheoretical spectroscopic calculations, and the sensitivity of experiments to anharmonicity. The characterization of protein active-site residues by small molecular mimics provides an acceptable chemical structuralrepresentation for biomolecular spectroscopy calculations.
29 (trans-cis isomerization marker mode) with the onset of the cis configuration in PYPL. This canbe attributed to the loss of the hydrogen-bonding character of the adjacent C9-O2 to the methylamine(Cys69 backbone). For several of the modes, the anharmonicity is mostly due to mode-mode coupling,while for others it is mostly intrinsic. This study shows the importance of the inclusion of anharmonicity intheoretical spectroscopic calculations, and the sensitivity of experiments to anharmonicity. The characterization of protein active-site residues by small molecular mimics provides an acceptable chemical structuralrepresentation for biomolecular spectroscopy calculations.