title: Steric constraint in the primary photoproduct of an archaeal rhodopsin from regiospecific perturbation of C-D stretching vibration of the retinyl chromophore.
abstract: In visual and archaeal rhodopsins, light energy is stored in the chromophore-protein interaction after retinal photoisomerization. This paper reports a novel method to monitor the steric constraint after retinal isomerization by use of enhanced C-D stretching vibrations. In the difference FTIR spectra between an archaeal light-sensor pharaonis phoborhodopsin (ppR) and the primary K intermediate at 77 K, no peaks were observed in the 2160-2330 cm-1 region for deuterated retinals at position 7, 8, 10, 11, 12, and 15, whereas a strong peak appeared at 2244 cm-1 for the K intermediate of ppR possessing a C14-D-labeled retinal. The 2244-cm-1 band is assigned as the C14-D stretching vibration, and enhanced absorption in the K state probably originates from the local steric constraint at the C14-D position (also possible electrostatic field effects) after the C13=C14 double bond rotation.
authors.affiliation: Department of Materials Science and Engineering, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Sudo
authors.forename: Yuji
authors.initials: Y
authors.lastname: Furutani
authors.forename: Akimori
authors.initials: A
authors.lastname: Wada
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Ito
authors.forename: Naoki
authors.initials: N
authors.lastname: Kamo
authors.forename: Hideki
authors.initials: H
authors.lastname: Kandori
mesh_terms: D015394:Molecular Structure; D010777:Photochemistry; D012172:Retinaldehyde / Q000737:chemistry* / Q000378:metabolism*; D025604:Rhodopsins, Microbial / Q000737:chemistry* / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D013237:Stereoisomerism; D014732:Vibration
chemical_list: D025604:Rhodopsins, Microbial; D012172:Retinaldehyde