5314027793

POSTER SESSION. H60

EXCITED STATE STRUCTURE OF THE BACTERIORHODOPSINS CHROMOPHORE STUDIED BY FOURIER TRANSFORM IN-FRARED SPECTROSCOPY

EYGENI TERPUGOY AND OLGA DEGTYAREVA, Institute of

Celi Biophysics Russian Academy of Sciences, 142292 Puschino Moscow

Region , Russia.

The light induced primary steps of the bacteriorhodopsin ( BR) photocycle is extremely fast with a time constant of about 3 ps to reach The high resolution structure of initial photophysical intermediate which would help immensely to elucidate the primary events mechanism unfortunately does not exist. This is partly due to the fact that the needed infrared data are not available. In the previous work based on Fourier transform infrared technique we first obtained the emission spectra of the infrared electronic transitions of the photoexcited chromophore of BR at room temperaturę, which demonstrated several nrw vibrational features as compared to the esonance Raman data. In the present study we have developed this approach including new methodology for obtaning both the ground and the excitcd state structuresof BR chromophore BR and its K photointermediate. We were able to register infrared emission spectra of both the parent BR568 and K forms as well as infrared absorption spectrum of photoexcit.ed BR molecule and the excited-state -ground state absorption difference spectra for aąueous solution and for BR films. We confirmed that the vibrational coupling between the photoexcited retinal and the amino acid environment ( Asp 96 and asp 115 ) takes place and contribute to the emission and absorption spectra. This result indicat.es that in the excited-state dynamie of BR both the chromophore and the microenvironment of protein are involved. Besides, these spectra give de taił inforination about the nonradiative relaxation channels in BR.