Zadok Uri, Khatchatouriants Artium, Lewis Aaron, Ottolenghi Michael, Sheves Mordechai
Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel.
J Am Chem Soc. 2002 Oct 9;124(40):11844-5. doi: 10.1021/ja0274251.
Bacteriorhodopsin's photocycle is initiated by the retinal chromophore light absorption. It has usually been assumed that light primarily isomerizes a retinal double bond which in turn induces protein conformational alterations and biological activity. We have studied several artificial pigments derived from retinal analogues tailored to substantially reduce the light-induced chromophore polarization. The lack of chromophore polarization was reflected in an undetectable second harmonic generation (SHG) signal. It was revealed that these artificial pigments did not exhibit any detectable light-induced photocycle nor light acceleration of the hydroxylamine-bleaching reaction. We suggest that light-induced retinal polarization triggers protein polarization which controls the course of the isomerization reaction by determining the relative efficiency of forward versus back-branching processes.
细菌视紫红质的光循环由视黄醛发色团吸收光引发。通常认为，光主要使视黄醛双键异构化，进而诱导蛋白质构象改变和生物活性。我们研究了几种源自视黄醛类似物的人工色素，这些类似物经过设计可大幅降低光诱导的发色团极化。发色团极化的缺失反映在无法检测到的二次谐波产生（SHG）信号上。结果表明，这些人工色素未表现出任何可检测到的光诱导光循环，也未出现光加速羟胺漂白反应的情况。我们认为，光诱导的视黄醛极化引发蛋白质极化，而蛋白质极化通过确定正向与反向分支过程的相对效率来控制异构化反应的进程。
