[72] Resonance Raman Spectroscopy of Rhodopsin and Bacteriorhodopsin: An Overview

This chapter presents an overview of resonance Raman spectroscopy of rhodopsin and bacteriorhodopsin. With Raman spectroscopy technique, a sample is illuminated with a laser within the absorption of the retinylidene chromophore and the resulting scattered light is focused into a monochromator. The monochromator or spectrograph disperses the light so that the elastically scattered radiation can be separated from that of inelastically scattered photons, which represent the vibrational frequencies of the absorbing retinylidene chromophore responsible for the scattering. A detector is then used to monitor the photon flux at predetermined wavelength intervals away from the laser frequency. To present the current status of our resonance Raman knowledge on rhodopsin/ bacteriorhodopsin, specific vibrational modes or on regions of the vibrational spectra of the retinylidene chromophore are discussed in the chapter. It has been reported that the future prospects for applying resonance Raman spectroscopy to rhodopsin and bacteriorhodopsin are extremely bright. It is almost certain that significant attempts will be made to obtain the resonance Raman spectrum of the chromophore in the rhodopsin and bacteriorhodopsin excited states.