title: Deactivation pathways of an isolated green fluorescent protein model chromophore studied by electronic action spectroscopy.
abstract: The mechanism of fluorescence and fluorescence quenching of the green fluorescent protein (GFP) is not well-understood. To gain insight into the effect of the surrounding protein on the chromophore buried at its center, the intrinsic electronic absorption and deactivation pathways of a gaseous model chromophore, p-hydroxybenzylidene-2,3-dimethylimidazolone (HBDI) were investigated. No fluorescence from photoactivated gaseous HBDI(-) was detected in the range 480-1100 nm, in line with the ultrafast rate of internal conversion of HBDI(-) in solution. Two different gas-phase deactivation pathways were found: photofragmentation and electron photodetachment. Electronic action spectra for each deactivation pathway were constructed by monitoring the disappearance of HBDI(-) and appearance of product ions as a function of excitation wavelength. The action spectra measured for each pathway are distinct, with electron photodetachment being strongly favored at higher photon energies. The combined (total) gas-phase action spectrum has a band origin at 482.5 nm (23340 cm(-1)) and covers a broad spectral range, 390-510 nm. This extended gas-phase action spectrum exhibits vibronic activity that matches well with the results of previous cold condensed-phase experiments and high-level in vacuo computations, with features evident at +550, +1500, and +2800 cm(-1) with respect to the band origin.
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6.
authors.forename: Matthew W
authors.initials: MW
authors.lastname: Forbes
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Jockusch
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D049452:Green Fluorescent Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D008956:Models, Chemical; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D049452:Green Fluorescent Proteins