title: Time-resolved spectroscopy of ultrafast photoisomerization of octopus rhodopsin under photoexcitation.
abstract: A primary process in vision is the cis-trans photoisomerization of a chromophore of rhodopsin, called retinal. In the present work, we have performed ultrafast time-resolved spectroscopy of octopus rhodopsin using a sub-5-fs pulse laser. In comparison with our previous study on bacteriorhodopsin, we found that octopus rhodopsin follows similar dynamics after photoexcitation but with different time constants. Spectrogram analysis showed that a C═N stretching mode appeared directly after photoexcitation. After reaching the conical intersection region at 80 fs, the overlapping hydrogen out-of-plane and in-plane C═C-H modes emerged as distinct peaks at ~200 fs, finishing a rapid relaxation along the coordinate related with these modes. The intensities of these peaks and a C═C stretching mode were found to be modulated at a period of ∼500 fs, reflecting torsional motion around the C═C double bond before thermalization with the distribution of structural variations in the all-trans structure in configuration space.
authors.affiliation: Department of Electrophysics, National Chiao-Tung University, Hsinchu 300, Taiwan. yabushita@mail.nctu.edu.tw
authors.forename: Atsushi
authors.initials: A
authors.lastname: Yabushita
authors.forename: Takayoshi
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Tsuda
mesh_terms: D000465:Algorithms; D007536:Isomerism; D007834:Lasers; D012172:Retinaldehyde / Q000737:chemistry; D012243:Rhodopsin / Q000737:chemistry*; D013053:Spectrophotometry; D013997:Time Factors
chemical_list: D012243:Rhodopsin; D012172:Retinaldehyde