title: Absorption studies of neutral retinal Schiff base chromophores.
abstract: The neutral retinal Schiff base is connected to opsin in UV sensing pigments and in the blue-shifted meta-II signaling state of the rhodopsin photocycle. We have designed and synthesized two model systems for this neutral chromophore and have measured their gas-phase absorption spectra in the electrostatic storage ring ELISA with a photofragmentation technique. By comparison to the absorption spectrum of the protonated retinal Schiff base in vacuo, we found that the blue shift caused by deprotonation of the Schiff base is more than 200 nm. The absorption properties of the UV absorbing proteins are thus largely determined by the intrinsic properties of the chromophore. The effect of approaching a positive charge to the Schiff base was also studied, as well as the susceptibility of the protonated and unprotonated chromophores to experience spectral shifts in different solvents.
authors.affiliation: Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors.forename: Iben B
authors.initials: IB
authors.lastname: Nielsen
authors.forename: Michael Axman
authors.initials: MA
authors.lastname: Petersen
authors.forename: Lutz
authors.initials: L
authors.lastname: Lammich
authors.forename: Mogens Brøndsted
authors.initials: MB
authors.lastname: Nielsen
authors.forename: Lars H
authors.initials: LH
authors.lastname: Andersen
mesh_terms: D000818:Animals; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008027:Light; D008956:Models, Chemical; D011522:Protons; D012160:Retina / Q000378:metabolism*; D012243:Rhodopsin / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry*; D015398:Signal Transduction; D012997:Solvents / Q000737:chemistry; D013053:Spectrophotometry; D055672:Static Electricity; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D011522:Protons; D012545:Schiff Bases; D012997:Solvents; D012243:Rhodopsin