Wang J, El-Sayed M A
Laser Dynamics Laboratory, School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Biophys J. 2001 Feb;80(2):961-71. doi: 10.1016/S0006-3495(01)76075-4.
Nanosecond-to-microsecond time-resolved Fourier transform infrared (FTIR) spectroscopy in the 3000-1000-cm(-1) region has been used to examine the polarizable proton continua observed in bacteriorhodopsin (bR) during its photocycle. The difference in the transient FTIR spectra in the time domain between 20 ns and 1 ms shows a broad absorption continuum band in the 2100-1800-cm(-1) region, a bleach continuum band in the 2500-2150-cm(-1) region, and a bleach continuum band above 2700 cm(-1). According to Zundel (G., J. Mol. Struct. 322:33-42), these continua appear in systems capable of forming polarizable hydrogen bonds. The formation of a bleach continuum suggests the presence of a polarizable proton in the ground state that changes during the photocycle. The appearance of a transient absorption continuum suggests a change in the polarizable proton or the appearance of new ones. It is found that each continuum has a rise time of less than 80 ns and a decay time component of approximately 300 micros. In addition, it is found that the absorption continuum in the 2100-1800-cm(-1) region has a slow rise component of 190 ns and a fast decay component of approximately 60 micros. Using these results and those of the recent x-ray structural studies of bR(570) and M(412) (H. Luecke, B. Schobert, H.T. Richter, J.-P. Cartailler, and J. K., Science 286:255-260), together with the already known spectroscopic properties of the different intermediates in the photocycle, the possible origins of the polarizable protons giving rise to these continua during the bR photocycle are proposed. Models of the proton pump are discussed in terms of the changes in these polarizable protons and the hydrogen-bonded chains and in terms of previously known results such as the simultaneous deprotonation of the protonated Schiff base (PSB) and Tyr185 and the disappearance of water molecules in the proton release channel during the proton pump process.
利用3000 - 1000厘米⁻¹区域的纳秒至微秒时间分辨傅里叶变换红外（FTIR）光谱，研究了细菌视紫红质（bR）在其光循环过程中观察到的可极化质子连续体。20纳秒至1毫秒时域内的瞬态FTIR光谱差异显示，在2100 - 1800厘米⁻¹区域有一个宽吸收连续带，在2500 - 2150厘米⁻¹区域有一个漂白连续带，以及在2700厘米⁻¹以上有一个漂白连续带。根据祖德尔（G.，《分子结构杂志》322:33 - 42）的研究，这些连续体出现在能够形成可极化氢键的体系中。漂白连续体的形成表明在基态存在一个在光循环过程中发生变化的可极化质子。瞬态吸收连续体的出现表明可极化质子发生了变化或出现了新的可极化质子。研究发现，每个连续体的上升时间小于80纳秒，衰减时间分量约为300微秒。此外，还发现2100 - 1800厘米⁻¹区域的吸收连续体有一个190纳秒的缓慢上升分量和一个约60微秒的快速衰减分量。利用这些结果以及最近对bR(570)和M(412)的x射线结构研究结果（H. 吕克、B. 朔伯特、H.T. 里希特、J.-P. 卡尔泰勒和J. K.，《科学》286:255 - 260），结合光循环中不同中间体已为人知的光谱性质，提出了在bR光循环过程中产生这些连续体的可极化质子的可能来源。根据这些可极化质子和氢键链的变化，以及诸如质子化席夫碱（PSB）和Tyr185的同时去质子化以及质子泵过程中质子释放通道中水分子的消失等先前已知的结果，讨论了质子泵的模型。
