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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Combined Theoretical Modeling of Photoexcitation Spectrum of an Isolated ProtonatedTyrosine
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Combined Theoretical Modeling of Photoexcitation Spectrum of an Isolated ProtonatedTyrosine

机译：分离的质子化酪氨酸光激发光谱的联合理论模型

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摘要

A photodepletion spectrum of gaseous protonated tyrosine molecules was obtained at 150 K by a UV laserspectroscopic technique in conjunction with mass spectrometry and interpreted by theoretical methods. Thespectrum exhibits three distinct bands separated each other by about 800 cm~(-1). Stable conformers of themolecular ion were determined by quantum mechanical density functional theory, and their electronic transitionenergies were obtained by a semiempirical quantum chemistry calculation. The whole pattern of the spectrumwas reasonably reproduced by a combination of theoretical methods, the second-order cumulant expansion,a semiempirical quantum chemistry method, molecular dynamics simulation, and a semiclassical time-correlation function approach. The three spectral bands turned out to arise from the vibronic transition of twovibrational modes constituted by the "benzene breathing" mode and a torsional mode of the amino acidbackbone. It is suggested that the major factor in spectral broadening is not conformational disorder or lifetimebroadening but thermal fluctuation of the stable conformers. The good agreement between experimental andtheoretical spectra exemplifies the validity of the theoretical methods applied for the present molecular system.
机译：气态质子化酪氨酸分子的光耗光谱通过紫外激光光谱技术结合质谱在150 K下获得，并通过理论方法解释。光谱显示出三个不同的带，彼此隔开约800 cm〜（-1）。通过量子力学密度泛函理论确定了分子离子的稳定构象，并通过半经验量子化学计算获得了其电子跃迁能。通过结合理论方法，二阶累积量展开，半经验量子化学方法，分子动力学模拟和半经典时间相关函数方法，合理地再现了光谱的整个模式。证明这三个光谱带是由氨基酸骨架的“苯呼吸”模式和扭转模式构成的两个振动模式的振动跃迁产生的。提示光谱展宽的主要因素不是构象无序或寿命延长，而是稳定构象异构体的热波动。实验光谱和理论光谱之间的良好一致性说明了用于当前分子系统的理论方法的有效性。

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