title: Spectroscopic mimicry for the protonated retinal Schiff base in vivo with modified amphiphilic clay interlayers as a possible model of opsin environment.
abstract: We have found that clay acts as a novel model matrix for the amphiphilic protein-opsin to mimic the visible absorption spectrum of a protonated retinal Schiff base (RSB) in vivo. Without strong acids at ambient temperature, a visible broad absorption spectrum with a lambda max at 530 nm covering the range from 400 to 680 nm was achieved for the protonated RSB with cationic surfactant-modified montmorillonite clay. The interlayers of the dimethyloctadecylamine (DOA) modified clay were found to provide amphiphilic space allowing the amphiphilic RSB to be intercalated easily and sequentially and protonated by the DOA. It is proposed that the visible absorption spectrum at lambda max 530 nm was attributable to electrostatic effects, permitting the appropriate distance between the nitrogen of the protonated RSB and the negatively charged clay interlayers and also to the anisotropic orientation of the RSB molecules in the interlayers.
authors.affiliation: Research Institute of Science and Technology, Tokai University, Kanagawa, Japan. ssm@keyaki.cc.u-tokai.ac.jp
authors.forename: M
authors.initials: M
authors.lastname: Sasaki
authors.forename: T
authors.initials: T
authors.lastname: Fukuhara
mesh_terms: D006801:Humans; D008956:Models, Chemical; D018462:Photobiology; D011522:Protons; D012172:Retinaldehyde / Q000737:chemistry* / Q000528:radiation effects*; D017299:Rod Opsins / Q000737:chemistry* / Q000528:radiation effects*; D012545:Schiff Bases; D013053:Spectrophotometry
chemical_list: D011522:Protons; D017299:Rod Opsins; D012545:Schiff Bases; D012172:Retinaldehyde