FEMTOSECOND SPECTROSCOPY OF HALORHODOPSIN AND RHODOPSIN IN A BROAD SPECTRAL RANGE OF 400-1000 NM

Femtosecond pump-probe spectroscopy of halorhodopsin from Halobacteriu m halobium and rhodopsin from octopus (paroctopus defleini) has been s tudied in a wide spectral range extending from 400 to 1000 nm. There a re live common features to halorhodopsin and rhodopsin in the transien t absorption and gain spectra. A comparative description of the primar y photochemistries in the retinal proteins including bacteriorhodopsin is presented to explain the present experimental results systematical ly together with the previous studies. In the model there is a branchi ng from the Franck-Condon state into coherent and incoherent channels. The former is the rapid process of direct formation of the first inte rmediate (bathorhodopsin for rhodopsin and hR(K) intermediate for halo rhodopsin), and the latter is the thermalization of the excited state in the retinoid proteins, from which slow formation of the first inter mediate takes place.