Photo-induced dynamics of proteins

利用光学Kerrgate技术的飞秒发光光谱研究了黄蛋白在水溶液中的光诱导动力学的早期阶段。直接观测到了显著的振荡成分，时间分辨率为180fs，光谱分辨率为5 nm。对各波长振荡的时间位相作图表明，每一次振荡都被限制在各自的窄谱范围内，其周期和幅度分别为500-800飞秒和100-200厘米。由于每个组分的平均光谱位置似乎与分子振动能有关，因此振荡组分可能是发色团的分子内振动和周围蛋白质运动的组合。为了更定量地研究蛋白质在光循环过程中的运动动力学，我们建立了一个时域THz光谱系统。来自钛蓝宝石振荡器(迈泰，光谱物理)的飞秒激光脉冲被用来发射和探测太赫兹辐射。发射端采用了砷化镓晶片上的蝴蝶结形状的金漆天线，而探测器则使用了砷化镓晶片上的偶极子形状的金漆天线。发射极施加2 kHz，±20V的交流偏置电压。前置放大的太赫兹信号由锁定放大器检测。为了评价太赫兹光谱系统，测量了水-甲醇混合物和水-乙醇混合物在较大浓度比范围内的反射光谱。我们成功地获得了混合溶液的介电振幅和介电相位的浓度依赖关系。在可见激光脉冲触发的光周期过程中，光活性蛋白质的时间域太赫兹光谱学现在正在取得进展。

The early stage in the photoinduced dynamics of photoactive yellow protein in aqueous solution has been investigated at room temperature by the femtosecond luminescence spectroscopy using an optical Kerrgate technique. Remarkable oscillatory components have been directly observed with the time resolution of 180 fs and the spectral resolution of 5 nm. Mapping the phase of oscillations in time at each wavelength reveals that each oscillation is restricted in the respective narrow spectral region, the period and amplitude of which are 500-800 fs and 100-200 cm^<-1>, respectively. Since the mean spectral position of each component seems to be related to the molecular vibrational energy, the oscillatory components are possibly attributed to the combination of the intramolecular vibrations of the chromophore and the surrounding protein motionsIn order to investigate the dynamics of protein motions in the course of the photo cycle more quantitatively, a time-domain THz spectroscopic system has been constructed. Femtosecond laser pulses from a Ti;Sapphire oscillator (MaiTai, Spectra Physics) are used to emit and detect THz radiation. A bowtie-shaped gold-paint antenna on a GaAs wafer is used for the emitter, while a dipole-shaped gold-paint antenna on a GaAs wafer is used for the detector. A 2 KHz, ±20V ac bias voltage is applied to the emitter. A pre-amplified THz signal is detected by a lock-in-amplifier. In order to evaluate the THz spectroscopic system, reflection spectra of water-methanol mixture and waterethanol mixture in a wide range of the concentration ratio have been measured. We have successfully obtained the concentration dependence of dielectric amplitude and phase for the mixture solutions. Time-domain THz spectroscopy for photoactive proteins in the course of the photo cycle triggered by a visible laser pulse is now progressing.