Agmon Noam
Department of Physical Chemistry and the Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel.
J Phys Chem B. 2007 Jul 12;111(27):7870-8. doi: 10.1021/jp071403p. Epub 2007 Jun 15.
The emission from the acidic form of the green fluorescence protein (GFP) changes with increasing time and temperature from t-1/2 to t-3/2 asymptotics. It is shown that a model of proton diffusion along a one-dimensional hydrogen-bond network within the protein, with a switch (Thr203) allowing for proton escape, explains the data quantitatively. From a comparison of the model with experiment, we obtain the rate parameters for proton dissociation from the chromophore (showing an inverse temperature effect), the ratio of the proton association constant squared to its diffusion constant (exhibiting no temperature effect), and the time constant for switch opening (with a significant Arrhenius dependence). Thus, proton dissociation has a small negative activation energy (assigned to a complex of the anionic chromophore with H3O+), whereas the switch has a large positive activation energy (assigned to Thr203 side-chain rotation). Proton migration is possibly the outcome of the concerted motion of several protons within GFP.
绿色荧光蛋白（GFP）酸性形式的发射随时间和温度从t - 1/2到t - 3/2渐近线增加而变化。结果表明，蛋白质内沿一维氢键网络的质子扩散模型，以及允许质子逸出的开关（Thr203），能够定量解释这些数据。通过将模型与实验进行比较，我们获得了发色团质子解离的速率参数（显示出反温度效应）、质子缔合常数平方与其扩散常数的比值（无温度效应）以及开关打开的时间常数（具有显著的阿仑尼乌斯依赖性）。因此，质子解离具有较小的负活化能（归因于阴离子发色团与H3O + 的复合物），而开关具有较大的正活化能（归因于Thr203侧链旋转）。质子迁移可能是GFP内几个质子协同运动的结果。
