LASER PHOTOLYSIS OF THE PURPLE MEMBRANE OF Halobacterium halobium IN THE PHOTOSTATIONARY STATE: THE PHOTOBRANCHING PROCESS FROM THE O640 INTERMEDIATE |
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Authors: | Hiroyuki Ohtani Satoru Naramoto Noritaka Yamamoto |
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Institution: | Department of Biomolecular Engineering, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259, Nagatsuta, Midori-ku, Yokohama 227, Japan |
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Abstract: | Abstract The photobranching process from the O640 intermediate (O) in the photocycle of bacteriorhodopsin was studied. The O form accumulated with continuous wave visible light (390–800 nm) irradiation of the acidic (pH 3.9–6.0) purple membrane of Halobacterium halobium at 22°C. The photocycle of O via an L-like (or N-like) intermediate was driven by 630 nm pulsed light. The newly found intermediate has an absorption band in the 450–560 nm region. The "green-light"-absorbing pigment, tentatively called G520, was converted to O with a time constant of (1.2 ± 0.2) ms. No M-like species was found in the cycle. The quantum yield of the cycle was estimated to be 0.30 ± 0.15. |
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