School of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China.
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.
J Chem Phys. 2018 Aug 21;149(7):074304. doi: 10.1063/1.5043246.
Reversible photoswitching fluorescent protein can reversibly switch between on-state (fluorescent) and off-state (dark). Anionic and neutral chromophores are the on- and off-states in green fluorescent proteins (GFPs), respectively. We investigated the ultrafast - photoisomerization mechanisms of the neutral GFP chromophore upon excitation to the S state by means of surface-hopping dynamics simulations based on the Zhu-Nakamura theory. Two isomers, located in the S state, were taken into consideration in dynamics simulation. After these two isomers are excited to the S state, the molecule moves to a excited-state minimum by increasing the imidazolinone-bridge bond length and decreasing the phenol-bridge bond length. The twist of imidazolinone-bridge bond drives the molecule toward a conical intersection, and internal conversion occurs. Then, a or conformer will be obtained in the S state. The torsion around the imidazolinone-bridge bond plays a key role in the ultrafast photoisomerization of a neutral chromophore. The torsional motion around the phenol-bridge bond is restricted in the S state, while it may occur in the S state. The isomerization reaction of this molecule is predicted to be not sensitive to solvent viscosity, and time-dependent density functional theory (TDDFT) calculations indicate that the fast excited-state decay from the Franck-Condon region of the isomer to the excited-state minimum was almost independent of solvent polarity.
可还原光致变色荧光蛋白可以在开启态（荧光）和关闭态（黑暗）之间可逆切换。阴离子和中性生色团分别是绿色荧光蛋白（GFP）中的开启态和关闭态。我们通过基于 Zhu-Nakamura 理论的表面跳跃动力学模拟研究了中性 GFP 生色团在激发到 S 态时超快光致异构化机制。动力学模拟中考虑了两个位于 S 态的异构体。这两个异构体被激发到 S 态后，通过增加咪唑啉酮桥键长和减小苯酚桥键长，分子移动到激发态最小势能点。咪唑啉酮桥键的扭曲驱动分子向锥形交叉点移动，发生内转换。然后，在 S 态中会得到一个 或 构象。咪唑啉酮桥键的扭转在中性生色团的超快光致异构化中起着关键作用。在 S 态中，苯酚桥键的扭转运动受到限制，但它可能在 S 态中发生。该分子的异构化反应预计对溶剂粘度不敏感，并且含时密度泛函理论（TDDFT）计算表明，从 异构体的 Franck-Condon 区域到激发态最小势能点的快速激发态衰减几乎与溶剂极性无关。
