title: Local vibrational coherences drive the primary photochemistry of vision.
abstract: The role of vibrational coherence-concerted vibrational motion on the excited-state potential energy surface-in the isomerization of retinal in the protein rhodopsin remains elusive, despite considerable experimental and theoretical efforts. We revisited this problem with resonant ultrafast heterodyne-detected transient-grating spectroscopy. The enhanced sensitivity that this technique provides allows us to probe directly the primary photochemical reaction of vision with sufficient temporal and spectral resolution to resolve all the relevant nuclear dynamics of the retinal chromophore during isomerization. We observed coherent photoproduct formation on a sub-50 fs timescale, and recovered a host of vibrational modes of the retinal chromophore that modulate the transient-grating signal during the isomerization reaction. Through Fourier filtering and subsequent time-domain analysis of the transient vibrational dynamics, the excited-state nuclear motions that drive the isomerization reaction were identified, and comprise stretching, torsional and out-of-plane wagging motions about the local C11=C12 isomerization coordinate.
authors.affiliation: Institute for Optical Sciences and Departments of Chemistry and Physics, University of Toronto, 80 St George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Philip J M
authors.identifier: http://orcid.org/0000-0002-7251-4815
authors.initials: PJ
authors.lastname: Johnson
authors.affiliation: Institute for Optical Sciences and Departments of Chemistry and Physics, University of Toronto, 80 St George Street, Toronto, Ontario M5S 3H6, Canada.
authors.forename: Alexei
authors.initials: A
authors.lastname: Halpin
authors.affiliation: Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Takefumi
authors.initials: T
authors.lastname: Morizumi
authors.affiliation: Max Planck Institute for the Structure and Dynamics of Matter, Atomically Resolved Dynamics Division, Building 99 (CFEL), Luruper Chaussee 149, Hamburg 22761, Germany.
authors.forename: Valentyn I
authors.initials: VI
authors.lastname: Prokhorenko
authors.affiliation: Department of Biochemistry, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.|Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario M5S 1A8, Canada.
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Ernst
authors.affiliation: Institute for Optical Sciences and Departments of Chemistry and Physics, University of Toronto, 80 St George Street, Toronto, Ontario M5S 3H6, Canada.|Max Planck Institute for the Structure and Dynamics of Matter, Atomically Resolved Dynamics Division, Building 99 (CFEL), Luruper Chaussee 149, Hamburg 22761, Germany.
authors.forename: R J Dwayne
authors.initials: RJ
authors.lastname: Miller
mesh_terms: D000818:Animals; D002417:Cattle; D007536:Isomerism; D010777:Photochemistry; D012243:Rhodopsin / Q000737:chemistry*; D013057:Spectrum Analysis; D014732:Vibration
chemical_list: D012243:Rhodopsin