title: Ultrafast photoisomerization of photoactive yellow protein chromophore analogues in solution: influence of the protonation state.
abstract: We investigate solvent viscosity and polarity effects on the photoisomerization of the protonated and deprotonated forms of two analogues of the photoactive yellow protein (PYP) chromophore. These are trans-p-hydroxybenzylidene acetone and trans-p-hydroxyphenyl cinnamate, studied in solutions of different polarity and viscosity at room temperature, by means of femtosecond fluorescence up-conversion. The fluorescence lifetimes of the protonated forms are found to be barely sensitive to solvent viscosity, and to increase with increasing solvent polarity. In contrast, the fluorescence decays of the deprotonated forms are significantly slowed down in viscous media and accelerated in polar solvents. These results elucidate the dramatic influence of the protonation state of the PYP chromophore analogues on their photoinduced dynamics. The viscosity and polarity effects are, respectively, interpreted in terms of different isomerization coordinates and charge redistribution in S(1). A trans-to-cis isomerization mechanism involving mainly the ethylenic double-bond torsion and/or solvation is proposed for the anionic forms, whereas "concerted" intramolecular motions are proposed for the neutral forms.
authors.affiliation: UMR CNRS-ENS 8640 Pasteur, Département de Chimie, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris Cedex 05, France.
authors.forename: Agathe
authors.initials: A
authors.lastname: Espagne
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Paik
authors.forename: Pascale
authors.initials: P
authors.lastname: Changenet-Barret
authors.forename: Monique M
authors.initials: MM
authors.lastname: Martin
authors.forename: Ahmed H
authors.initials: AH
authors.lastname: Zewail
mesh_terms: D000096:Acetone / Q000737:chemistry; D001426:Bacterial Proteins / Q000737:chemistry*; D002627:Chemistry, Physical / Q000379:methods; D002934:Cinnamates / Q000737:chemistry; D000431:Ethanol / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D005990:Glycerol / Q000737:chemistry; D008027:Light; D008164:Luminescent Proteins / Q000737:chemistry*; D010777:Photochemistry / Q000379:methods*; D011506:Proteins / Q000737:chemistry; D011522:Protons; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013997:Time Factors; D014867:Water / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D002934:Cinnamates; D005456:Fluorescent Dyes; D008164:Luminescent Proteins; D011506:Proteins; D011522:Protons; D012997:Solvents; C054562:yellow fluorescent protein, Bacteria; D014867:Water; D000096:Acetone; D000431:Ethanol; D005990:Glycerol