水在菌紫质光循环和质子泵中的作用

THE ROLES OF WATER IN THE PHOTOCYCLE AND PROTON PUMP OF BACTERIORHODOPSIN

用圆二色仪和闪光动力学先谱仪分别测量了空气干燥紫膜薄层的圆二色谱及紫膜LB膜的M_(412)的衰减过程.在于燥紫膜的圆二色谱上出现412nm的正峰,它是光循环中间体M_(412)的特征峰.在无水介质中,紫膜LB膜中的BR仍能进行先化学循环而检测到中间体M_(412),但M_(412)的衰减速度减慢,产生M_(412)的堆积,质子化过程受阻.在有水的介质中,只要有足够的H^+存在,紫膜LB膜中的BR的中间体M_(412)的衰减速度明显加快.说明水介质的H^+是完成正常光化学循和质子化过程必不可少的.

The CD spectra of air-dried purple membrane thin films (PMTF) and M412 decay of PMLBF were measured by circular dichroism and flash kinetics spectroscopy, respectively. The positive CD peak of 412nm. the characteristic peak of M412 of photocvcle intermediates of BR occurred in the PMTF. In PMLBF immersed in anhydrous medium. M412 was also detected. the photocvcle of BR was retained, but M412 decay slowed down, so that M412 accumulated and protonation process retarded. The M412 decay became apparently faster if PMLBF immersed in aqueous medium with sufficient H-. This suggested that. H- in aqueous medium is necessary for normal photocvcle and protontion process.