Livnah N, Sheves M
Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel.
Biochemistry. 1993 Jul 20;32(28):7223-8. doi: 10.1021/bi00079a019.
The Schiff base linkage bond configuration of bacteriorhodopsin was studied using model compounds consisting of all-trans- and 13-cis-retinal-protonated Schiff bases bearing C = N anti and syn bond configurations. The C = N configuration was analyzed using a combination of Fourier transform infrared spectroscopy and isotopically labeled chromophores. It was found that, in the model compounds, the coupling between the C14--C15 stretching frequency and the N--H rock is weak in the all-trans-retinal-protonated Schiff base in both the anti and syn C = N configurations. However, this coupling is relatively strong in the 13-cis-retinal-protonated Schiff base in both the anti and syn C = N configurations. Thus, it is concluded that, in model compounds, the C14--C15 mode can serve as a marker for the C13 = C14 bond configuration but not for the C = N. A different situation may prevail in bacteriorhodopsin due to different conformations of the retinal chromophore in the protein binding site and in solution. This difference suggests that the C14--C15/NH coupling in retinal-protonated Schiff bases is affected by the retinal conformation.
利用由带有C=N反式和顺式键构型的全反式和13-顺式视黄醛质子化席夫碱组成的模型化合物，研究了细菌视紫红质的席夫碱连接键构型。使用傅里叶变换红外光谱和同位素标记发色团相结合的方法分析C=N构型。研究发现，在模型化合物中，在反式和顺式C=N构型的全反式视黄醛质子化席夫碱中，C14--C15伸缩频率与N--H摇摆之间的耦合较弱。然而，在反式和顺式C=N构型的13-顺式视黄醛质子化席夫碱中，这种耦合相对较强。因此，可以得出结论，在模型化合物中，C14--C15模式可作为C13 = C14键构型的标记，但不能作为C=N的标记。由于蛋白质结合位点和溶液中视黄醛发色团的构象不同，细菌视紫红质中可能存在不同的情况。这种差异表明，视黄醛质子化席夫碱中的C14--C15/NH耦合受视黄醛构象的影响。
