Bagley K, Dollinger G, Eisenstein L, Singh A K, Zimányi L
Proc Natl Acad Sci U S A. 1982 Aug;79(16):4972-6. doi: 10.1073/pnas.79.16.4972.
Fourier transform infrared difference spectroscopy has been used to obtain the vibrational modes in the chromophore and apoprotein that change in intensity or position between light-adapted bacteriorhodopsin and the K and M intermediates in its photocycle and between dark-adapted and light-adapted bacteriorhodopsin. Our infrared measurements provide independent verification of resonance Raman results that in light-adapted bacteriorhodopsin the protein-chromophore linkage is a protonated Schiff base and in the M state the Schiff base is unprotonated. Although we cannot unambiguously identify the Schiff base stretching frequency in the K state, the most likely interpretation of deuterium shifts of the chromophore hydrogen out-of-plane vibrations is that the Schiff base in K is protonated. The intensity of the hydrogen out-of-plane vibrations in the K state compared with the intensities of those in light-adapted and dark-adapted bacteriorhodopsin shows that the conformation of the chromophore in K is considerably distorted. In addition, we find evidence that the conformation of the protein changes during the photocycle.
傅里叶变换红外差光谱已被用于获取发色团和脱辅基蛋白中的振动模式，这些振动模式在光适应型细菌视紫红质与其光循环中的K和M中间体之间，以及暗适应型和光适应型细菌视紫红质之间，强度或位置会发生变化。我们的红外测量为共振拉曼结果提供了独立验证，即在光适应型细菌视紫红质中，蛋白质 - 发色团连接是质子化的席夫碱，而在M状态下，席夫碱是未质子化的。尽管我们无法明确识别K状态下席夫碱的伸缩频率，但对发色团氢面外振动的氘位移最可能的解释是K中的席夫碱是质子化的。与光适应型和暗适应型细菌视紫红质中氢面外振动的强度相比，K状态下氢面外振动的强度表明K中发色团的构象有相当大的扭曲。此外，我们发现有证据表明蛋白质的构象在光循环过程中会发生变化。
