Divergent pathways in photobleaching of 7,9-dicis-rhodopsin and 9,11-dicis-12-fluororhodopsin: one-photon-two-bond and one-photon-one-bond isomerization

Abstract

Through low-temperature photochemistry, UV/vis spectroscopy, and chromophore extraction experiments, we have established that 7,9-dicis-rhodopsin undergoes one-photon-two-bond photoisomerization to a batho intermediate (its absorption maximum is slightly blue shifted from that of bathorhodopsin) containing the all-trans geometry, while 9,11-dicis-12-fluororhodopsin undergoes one-photon-one-bond isomerization to the corresponding 9-cis isomer and then the all-trans batho intermediate. The difference in the photochemical properties of the two dicis pigment analogs was rationalized by possible local protein perturbation, lability of the 11-cis geometry, and photochemical properties of the chromophores.