Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA.
J Chem Phys. 2011 Nov 21;135(19):194304. doi: 10.1063/1.3660350.
Electronic structure calculations of microhydrated model chromophores (in their deprotonated anionic forms) of the photoactive yellow and green fluorescent proteins (PYP and GFP) are reported. Electron-detachment and excitation energies as well as binding energies of mono- and dihydrated isomers are computed and analyzed. Microhydration has different effects on the excited and ionized states. In lower-energy planar isomers, the interaction with one water molecule blueshifts the excitation energies by 0.1-0.2 eV, whereas the detachment energies increase by 0.4-0.8 eV. The important consequence is that microhydration by just one water molecule converts the resonance (autoionizing) excited states of the bare chromophores into bound states. In the lower-energy microhydrated clusters, interactions with water have negligible effect on the chromophore geometry; however, we also identified higher-energy dihydrated clusters of PYP in which two water molecules form hydrogen-bonding network connecting the carboxylate and phenolate moieties and the chromophore is strongly distorted resulting in a significant shift of excitation energies (up to 0.6 eV).
报告了光致变色黄色和绿色荧光蛋白（PYP 和 GFP）的微水合模型生色团（其去质子化的阴离子形式）的电子结构计算。计算和分析了单水合和双水合异构体的电子离解和激发能以及结合能。微水合对激发态和离子态有不同的影响。在能量较低的平面异构体中，与一个水分子的相互作用将激发能蓝移 0.1-0.2 eV，而离解能增加 0.4-0.8 eV。重要的结果是，仅仅一个水分子的微水合将生色团的共振（自电离）激发态转化为束缚态。在较低能量的微水合团簇中，水分子与生色团的相互作用对生色团的几何形状几乎没有影响；然而，我们还确定了 PYP 的高能双水合团簇，其中两个水分子形成氢键网络，连接羧酸盐和酚盐部分，并且生色团强烈扭曲，导致激发能显著移动（高达 0.6 eV）。
