Photoelectric response of bacteriorhodopsin and its mutants

• Main Authors: Chu-Chun, Hsieh, 謝竺君
• Other Authors: Hsiu-Mei Chen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/aed2a8

碩士 === 國立臺灣科技大學 === 化學工程系 === 94 === Bacteriorhodopsin (bR), the only protein in the purple membrane (PM) of Halobacterium salinarium, is a light-driven proton pump. To verify the release and uptake of protons in the light-on and light-off photocycle, respectively, of an illuminated PM solution, a cuvette photoelectric system was set up to trace the photocurrent arising from proton pumping. First, the role of the copper-plate medium in the photoelectric system and the reactions taking place on its both sides while the PM solution was continuously illuminated for 30 min were revealed by monitoring the pHs of the solutions facing either side (the working and counter parts). We analyzed by XPS (X-ray photoelectron spectroscopy, SEM (Scanning electron microscopy) and XRD (X-ray diffraction), and suggested that the continuous illumination induced the oxidation of the counter-copper plate. Then we used the counter-copper plate as the working-copper plate to contact with PM solutions. This resulted in the enhancement of the photoelectric signals in the following experiments. Secondly, the photoelectric signals, light-on and light-off, of the illuminated solutions of native, wild-type, G241C, and D96N PMs were each detected and compared. The results showed that the photoelectric peak signals arisen from continuously illuminated PM solutions were higher and accompanied by more after-peaks than those from the fresh solutions. Finally, we compared the native, wild-type, G241C and D96N PM by change the frequency of excited light and the surrounding pH. We found that D96N PM could still yield photoelectric response at higher frequency. About the pH, D96N PM changed from BR to BRblue and BRa easier than native and wild-type PM and the following was G241C PM. The color of native and wild-type PM maintained as purple at wider pH range.