1995 Fiscal Year Final Research Report Summary
Time-resolved fluorescence excitation spectroscopy of retinal proteins
| Project/Area Number |
06680645
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Biophysics
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
OHTANI Hiroyuki Tokyo Institute of Technology, Department of Biomolecular Engineering, Associate Professor, 生命理工学部, 助教授 (80203826)
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| Project Period (FY) |
1994 – 1995
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| Keywords | Time-resolved fluorescence excitation spectroscopy / Sequentially-gated photoncounter / Laser photolysis / Bacteriorhodopsin / Purple membrane / Halobacterium halobium / Photocycle intermediate |
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| Research Abstract |
The fluorescence excitation spectroscopy with millisecond time-resolution was developped. It enabled us to measure the absorption (fluorescence excitation) spectra of transient species, the fluorescence quantum yields of which are 0.001. In this work we measured the weakly fluorescent photointermediates of retinal proteins and obtained the following results.
1) Samples should be fluorescent in the measurement of fluorescence excitation spectrum. However, our present system enables us to measure the absorption (fluorescence excitation) spectra of "nonfluorescent" species with the fluorescence quantum yields of 0.001.
2) Furthermore, the near-IR fluorescence of the samples (700-850 nm) was measured without cooling the photoelectric detectors used.
3) The excitation spectra was measured at the most efficient delay time because the formation and the decay kinetics of the intermediates were always monitored with a sequentially-gated photoncounter.
4) The fluorescence spectrum of the 0640 intermediate, which is formed in the last step of the photocycle of bacteriorhodopsin, was measured. It was clarified that its absorption maximum is located at 620 nm, i.e.it is shorter than that previously measured by absorption spectroscopy (640 nm).
5) The fluorescence spectrum of the Q intermediate, which is formed under alkaline conditions, was also measured. Its absorption maximum at 590 nm shows that Q is a chromoprotein different from bacteriorhodopsin and the 0 intermadiate.
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