title: Probing microhydration effect on the electronic structure of the GFP chromophore anion: Photoelectron spectroscopy and theoretical investigations.
abstract: The photophysics of the Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI(-)), an analog of the GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab initio methods, we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.
authors.affiliation: Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: Kiran
authors.initials: K
authors.lastname: Bhaskaran-Nair
authors.affiliation: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA.
authors.forename: Marat
authors.initials: M
authors.lastname: Valiev
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, K8-88, P.O. Box 999, Richland, Washington 99352, USA.
authors.forename: S H M
authors.initials: SH
authors.lastname: Deng
authors.affiliation: Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
authors.forename: William A
authors.initials: WA
authors.lastname: Shelton
authors.affiliation: William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352, USA.
authors.forename: Karol
authors.initials: K
authors.lastname: Kowalski
authors.affiliation: Physical Sciences Division, Pacific Northwest National Laboratory, K8-88, P.O. Box 999, Richland, Washington 99352, USA.
authors.forename: Xue-Bin
authors.initials: XB
authors.lastname: Wang
mesh_terms: D000838:Anions / Q000737:chemistry; D001597:Benzylidene Compounds / Q000737:chemistry*; D004583:Electrons; D049452:Green Fluorescent Proteins / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D056951:Photoelectron Spectroscopy; D011789:Quantum Theory; D014867:Water / Q000737:chemistry*
chemical_list: D000838:Anions; D001597:Benzylidene Compounds; D007093:Imidazoles; C000611006:p-hydroxybenzylidene-2,3-dimethylimidazolinone; D014867:Water; D049452:Green Fluorescent Proteins