title: Effect of microhydration on the electronic structure of the chromophores of the photoactive yellow and green fluorescent proteins.
abstract: Electronic structure calculations of microhydrated model chromophores (in their deprotonated anionic forms) of the photoactive yellow and green fluorescent proteins (PYP and GFP) are reported. Electron-detachment and excitation energies as well as binding energies of mono- and dihydrated isomers are computed and analyzed. Microhydration has different effects on the excited and ionized states. In lower-energy planar isomers, the interaction with one water molecule blueshifts the excitation energies by 0.1-0.2 eV, whereas the detachment energies increase by 0.4-0.8 eV. The important consequence is that microhydration by just one water molecule converts the resonance (autoionizing) excited states of the bare chromophores into bound states. In the lower-energy microhydrated clusters, interactions with water have negligible effect on the chromophore geometry; however, we also identified higher-energy dihydrated clusters of PYP in which two water molecules form hydrogen-bonding network connecting the carboxylate and phenolate moieties and the chromophore is strongly distorted resulting in a significant shift of excitation energies (up to 0.6 eV).
authors: Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA.
authors: Dmitry
authors: D
authors: Zuev
authors: Ksenia B
authors: KB
authors: Bravaya
authors: Maria V
authors: MV
authors: Makarova
authors: Anna I
authors: AI
authors: Krylov
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D004583:Electrons; D049452:Green Fluorescent Proteins / Q000737:chemistry*; D020607:Halorhodospira halophila / Q000737:chemistry; D008164:Luminescent Proteins / Q000737:chemistry*; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*; D055668:Photochemical Processes; D014867:Water / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D002264:Carboxylic Acids; D008164:Luminescent Proteins; D010636:Phenols; C054562:yellow fluorescent protein, Bacteria; D014867:Water; D049452:Green Fluorescent Proteins