QUANTUM EFFICIENCY FOR THE PHOTOCONVERSION OF BACTERIORHODOPSIN AT VERY LOW TEMPERATURES |
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| Authors: | Tatsuo Iwasa Fumio Tokunaga Tôru Yoshizawa Thomas G Ebrey |
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| Institution: | Department of Biophysics, Faculty of Science, Kyoto University, Kyoto, Japan;?Department of Physiology and Biophysics, University of Illinois, Urbana, IL 61801, U.S.A. |
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| Abstract: | Abstract— Quantum efficiencies for photoconversion of bacteriorhodopsin (trans-bR) to a bathochromic product (batho-bRt) and its photoreversion in purple membrane at 77 and 9 K were investigated with low temperature spectrophotometry. The kinetics of the photoconversion and its photoreversion cannot be expressed by a single exponential curve. The photoconversions at 77 and 9 K showed the same slope in the early stage. The kinetics of the photoreversions were identical at the two temperatures. These results indicate that the quantum efficiencies for the conversion of trans-bR to batho-bRt or for its photoreversion are identical at the two temperatures.
The fact that the photoreversion cannot be expressed by a single exponential curve suggests the existence of several conformational states of batho-bRt due to the trimer structure of the purple membrane. |
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