Deuterium Substitution Effect on the Excited-State Dynamics of Rhodopsin

Abstract

We investigated the excited-state dynamics of the cis−trans photoisomerization of rhodopsin by analyzing deuterium substitution effects for hydrogen atoms bonded to C11 and C12 of the retinal chromophore by the method of Fourier transform of optical absorption spectra (FTOA). Plotting the absolute value of the time correlation function of modified vibrational wave packet, we found that the deuterium substitution effects do not appear in the excited-state dynamics until about 20 fs after photon absorption, weakly appear in the time range 20−60 fs, significantly appear in the time range 70−110 fs, and complicatedly appear in the time range 110−170 fs. By analyzing those deuterium substitution effects, we obtained a result that the concerted motions of hydrogen out-of-plane (HOOP) waggings at C11 and C12, which are found to exist in native rhodopsin in the time range 20−60 fs, do not contribute to the excited-state dynamics in its time range appreciably and that the coupled motions of hydrogen atoms at C11 a...