title: Deactivation mechanism of the green fluorescent chromophore.
abstract: We report time-resolved fluorescence data for the anion of p-hydroxybenzylidene dimethylimidazolinone (p-HBDI), a model chromophore of the green fluorescence protein, in viscous glycerol-water mixtures over a range of temperatures, T. The markedly nonexponential decay of the excited electronic state is interpreted with the aid of an inhomogeneous model possessing a Gaussian coordinate-dependent sink term. A nonlinear least-squares fitting routine enables us to achieve quantitative fits by adjusting a single activation parameter, which is found to depend linearly on 1/T. We derive an analytic expression for the absolute quantum yield, which is compared with the integrated steady-state fluorescence spectra. The microscopic origins of the model are discussed in terms of two-dimensional dynamics, coupling the phenyl-ring rotation to a swinging mode that brings this flexible molecule to the proximity of a conical intersection on its multidimensional potential energy surface.
authors.affiliation: Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Rinat
authors.initials: R
authors.lastname: Gepshtein
authors.forename: Dan
authors.initials: D
authors.lastname: Huppert
authors.forename: Noam
authors.initials: N
authors.lastname: Agmon
mesh_terms: D005453:Fluorescence; D005990:Glycerol / Q000737:chemistry; D048288:Imidazolines / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D008956:Models, Chemical; D015394:Molecular Structure; D013696:Temperature; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: C502519:4-hydroxybenzylidene-1,2-dimethylimidazolinone; D048288:Imidazolines; D014867:Water; D005990:Glycerol