Time-Resolved Vibrational Spectroscopic Study of Higher Order Structural Changes of Protein Induced by Nanosecond Temperature Jump.

构建了纳秒温度跳跃(T-JUMP)装置，并与时间分辨拉曼测量相结合，首次研究了蛋白质的热去折叠。在D_2气体中，通过种子和放大两步受激拉曼散射，获得了宽度为9 ns、频率为10 Hz的1.56μm热脉冲。为了实现均匀的温升，采用了反向传播几何结构。温升由MoO^&lt；2-gt；_4水溶液的317和897 cm^&lt；-1&gt；带的反斯托克斯强度比决定。在10 ns内实现了高达9℃的T跳跃。用532 nm激发的时间分辨拉曼光谱监测了牛胰腺核糖核酸酶A的去折叠过程。在T跳跃后的最初200 ns内，甲硫氨酸残基的C-S伸展显示出与稳态光谱预期的10%的变化，并在5ms内又变化了10%。在10 0μ的S延迟下，S0和lt；2-&gt；4离子在980 cm-lt；-1&gt；附近的拉曼强度增加，并向低于高温稳态频率的频率移动，这可能是由于活性中心的部分释放所致。在5ms内，S-S伸展运动和酪氨酸二联体变化不大。因此，在展开的初始步骤中的构象变化并不总是一致的。

A nanosecond temperature jump (T-jump) apparatus was constructed and combined with time-resolved Raman measurements to investigate thermal unfolding of a protein for the first time. The 1.56 μm-heat pulse with 9 ns width, 10 Hz was obtained through the two-step stimulated Raman scattering in D_2 gas involving seeding and amplification. To achieve uniform temperature rise, the counter-propagation geometry was adopted. The temperature rise was determined by anti-Stokes to Stokes intensity ratios of the 317 and 897 cm^<-1> bands of MoO^<2->_4 aqueous solution. The T-jump as large as 9℃ in 10 ns was attained. The unfolding of bovine pancreatic ribonuclease A was monitored with time-resolved Raman spectra excited at 532 nm. In the initial 200 ns after T-jump, the C-S stretch of Met residues exhibited 10% change of that expected from the steady state spectra and another 10% in 5 ms. The Raman intensity of S0^<2->_4 ions around 980 cm^<-1> increased at 100 μs delay and was shifted to a lower frequency than the steady state frequency of the elevated temperature, presumably due to partial release from the active site. The S-S stretches and tyrosine doublets displayed little change within 5 ms. Thus, the conformation change in the initial step of unfolding is not always concerted.