title: Excited states of GFP chromophore and active site studied by the SAC-CI method: effect of protein-environment and mutations.
abstract: Excited states of fluorescent proteins were studied using symmetry-adapted cluster-configuration interaction (SAC-CI) method. Protein-environmental effect on the excitation and fluorescence energies was investigated. In green fluorescent protein (GFP), the overall protein-environmental effect on the first excitation energy is not significant. However, glutamine (Glu) 94 and arginine (Arg96) have the red-shift contribution as reported in a previous study (Laino et al., Chem Phys 2004, 298, 17). The excited states of GFP active site (GFP-W22-Ser205-Glu222-Ser65) were also calculated. Such large-scale SAC-CI calculations were performed with an improved code containing a new algorithm for the perturbation selection. The SAC-CI results indicate that a charge-transfer state locates at 4.19 eV, which could be related to the channel of the photochemistry as indicated in a previous experimental study. We also studied the excitation and fluorescence energies of blue fluorescent protein, cyan fluorescent protein, and Y66F. The SAC-CI results are very close to the experimental ones. The protonation state of blue fluorescent protein was determined. Conformation of cyan fluorescent protein indicated by the present calculation agrees to the experimentally observed structure.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto-Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
authors.forename: Jun-Ya
authors.initials: JY
authors.lastname: Hasegawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Fujimoto
authors.forename: Ben
authors.initials: B
authors.lastname: Swerts
authors.forename: Tomoo
authors.initials: T
authors.lastname: Miyahara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakatsuji
mesh_terms: D000465:Algorithms; D001665:Binding Sites; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D049452:Green Fluorescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation / Q000235:genetics*
chemical_list: D050505:Mutant Proteins; D049452:Green Fluorescent Proteins