Associate Professor, Department of Biomolecular Engineering
PhD 1981, The University of Tokyo
Office: Room1020, B2 building, Suzukakedai campus
Areas of Research: Biophysical Chemistry, Photochemistry, Time-Resolved Spectroscopy, Ultraweak Emission Measurement.
Keywords: Retinal, Bacteriorhodopsin, Femtosecond, Fluorescence Quantum Yield,
Photoncounting, Photoisomerization, Transient Intermediate
Photochemical reactions of retinal proteins have been studied by time-resolved spectroscopy in the time region from femtosecond to kilosecond. Ultraweak photoemission processes (fluorescence yield <1/10000) of retinal proteins have also been studied.
The primary photoprocess of bacteriorhodopsin (bR, archaea-type rhodopsin) is the trans-cis isomerization of the chromophore in the excited singlet state. This process occurs within 1 picosecond. Our most interested phenomenon is the highly selective reaction. The allowed isomerization occurs at C13=C14 bond with a yield of 0.64, and the other decay pass (yield 0.36) in the excited singlet state is the recovery to the ground state molecule without any byproduct. The characteristics of bR in the excited state, ultrashort lifetime and ultraweak fluorescence, may be derived from the excited state potential surface of bR which is designed to accomplish the highly selective reaction rather than the 100% reaction yield. We will clarify whether only bR in the lowest excited singlet state or the protein with a retinal chromophore has the excellent property.
- Real-time spectroscopy of transition states in bacteriorhodopsin during retinal isomerization
T. Kobayashi, T. Saito, and H. Ohtani (2001) Nature 414, 531-534.