Donati Greta, Petrone Alessio, Caruso Pasquale, Rega Nadia
Dipartimento di Scienze Chimiche , Università di Napoli 'Federico II' , Complesso Universitario di M.S.Angelo , via Cintia , I-80126 Napoli , Italy . Email:
Italian Institute of Technology , IIT@CRIB Center for Advanced Biomaterials for Healthcare , Largo Barsanti e Matteucci , I-80125 Napoli , Italy.
Chem Sci. 2018 Jan 2;9(5):1126-1135. doi: 10.1039/c7sc02803b. eCollection 2018 Feb 7.
We simulated an excited state proton transfer in green fluorescent protein by excited state dynamics, and examined the reaction mechanism in both the time and the frequency domain through a multi resolution wavelet analysis. This original approach allowed us, for the first time, to directly compare the trends of photoactivated vibrations to femtosecond stimulated Raman spectroscopy results, and to give an unequivocal interpretation of the role played by low frequency modes in promoting the reaction. We could attribute the main driving force of the reaction to an important photoinduced softening of the ring-ring orientational motion of the chromophore, thus permitting the tightening of the hydrogen bond network and the opening of the reaction pathway. We also found that both the chromophore (in terms of its inter-ring dihedral angle and phenolic C-O and imidazolinone C-N bond distances) and its pocket (in terms of the inter-molecular oxygen's dihedral angle of the chromophore pocket) relaxations are modulated by low frequency (about 120 cm) modes involving the oxygen atoms of the network. This is in agreement with the femtosecond Raman spectroscopy findings in the time-frequency domain. Moreover, the rate in proximity to the Franck Condon region involves a picosecond time scale, with a significant influence from fluctuations of nearby hydrogen bonded residues such as His148. This approach opens a new scenario with simulations as routinely used tools to understand photoreactivity and the results of advanced time resolved spectroscopy techniques.
我们通过激发态动力学模拟了绿色荧光蛋白中的激发态质子转移，并通过多分辨率小波分析在时域和频域研究了反应机理。这种原创方法首次使我们能够直接将光活化振动的趋势与飞秒受激拉曼光谱结果进行比较，并明确解释低频模式在促进反应中所起的作用。我们可以将反应的主要驱动力归因于发色团环-环取向运动的重要光致软化，从而使氢键网络收紧并打开反应途径。我们还发现，发色团（就其环间二面角以及酚羟基C-O和咪唑啉酮C-N键距离而言）及其口袋（就发色团口袋的分子间氧的二面角而言）的弛豫都受到涉及网络中氧原子的低频（约120 cm）模式的调制。这与时域-频域中的飞秒拉曼光谱结果一致。此外，在弗兰克-康登区域附近的速率涉及皮秒时间尺度，附近的氢键残基（如His148）的波动会产生重大影响。这种方法开辟了一种新的局面，将模拟作为常规使用的工具来理解光反应性以及先进的时间分辨光谱技术的结果。
