CHANGES IN STRUCTURE OF THE CHROMOPHORE IN THE PHOTOCHEMICAL PROCESS OF BOVINE RHODOPSIN AS REVEALED BY FTIR SPECTROSCOPY FOR HYDROGEN OUT-OF-PLANE VIBRATIONS

The hydrogen out-of-plane bending (HOOP) vibrations were studied in th e difference Fourier transform infrared spectra of lumirhodopsin and m etarhodopsin I by use of a series of specifically deuterated retinal d erivatives of bovine rod outer segments. The 947 cm(-1) band of lumirh odopsin and the 950 cm(-1) band of metarhodopsin I were assigned to th e mode composed of both 11-HOOP and 12-HOOP vibrations. This result su ggests that the perturbation near C-12-H of the retinal in the earlier intermediate, bathorhodopsin (Palings, van den Berg, Lugtenburg and M athies, Biochemistry, 28 (1989) 1498-1507), is extinguished in lumirho dopsin and metarhodopsin I. Unphotolyzed rhodopsin and metarhodopsin I exhibited the 14-HOOP bands in the 12-D derivatives at 901 and 886 cm (-1), respectively. Lumirhodopsin, however, did not show the 14-HOOP i n the 12-D derivatives. The result suggests a change in geometrical al ignment of the C-14-H bond in lumirhodopsin with respect to the N-H bo nd of the Schiff base.