Megley Colleen M, Dickson Luisa A, Maddalo Scott L, Chandler Gabriel J, Zimmer Marc
Chemistry Department, Connecticut College, New London, Connecticut 06320, USA.
J Phys Chem B. 2009 Jan 8;113(1):302-8. doi: 10.1021/jp806285s.
Green fluorescent protein (GFP) and GFP-like fluorescent proteins owe their photophysical properties to an autocatalytically formed intrinsic chromophore. According to quantum mechanical calculations, the excited state of chromophore model systems has significant dihedral freedom, which may lead to fluorescence quenching intersystem crossing. Molecular dynamics simulations with freely rotating chromophoric dihedrals were performed on green, yellow, and blue fluorescent proteins in order to model the dihedral freedom available to the chromophore in the excited state. Most current theories suggest that a restriction in the rotational freedom of the fluorescent protein chromophore will lead to an increase in fluorescence brightness and/or quantum yield. According to our calculations, the dihedral freedom of the systems studied (BFP > A5 > YFP > GFP) increases in the inverse order to the quantum yield. In all simulations, the chromophore undergoes a negatively correlated hula twist (also known as a bottom hula twist mechanism).
绿色荧光蛋白（GFP）及类GFP荧光蛋白的光物理性质源于自身催化形成的内在发色团。根据量子力学计算，发色团模型系统的激发态具有显著的二面角自由度，这可能导致荧光猝灭和系间窜越。为模拟发色团在激发态下的二面角自由度，对绿色、黄色和蓝色荧光蛋白进行了发色团二面角自由旋转的分子动力学模拟。目前大多数理论认为，荧光蛋白发色团旋转自由度的限制将导致荧光亮度和/或量子产率增加。根据我们的计算，所研究系统（蓝色荧光蛋白>BFP>A5>黄色荧光蛋白>绿色荧光蛋白）的二面角自由度与量子产率呈相反顺序增加。在所有模拟中，发色团都经历了负相关的呼啦圈扭转（也称为底部呼啦圈扭转机制）。
