title: Concerted asynchronous hula-twist photoisomerization in the S65T/H148D mutant of green fluorescent protein.
abstract: Fluorescence emission of wild-type green fluorescent protein (GFP) is lost in the S65T mutant, but partly recovered in the S65T/H148D double mutant. These experimental findings are rationalized by a combined quantum mechanics/molecular mechanics (QM/MM) study at the QM(CASPT2//CASSCF)/AMBER level. A barrierless excited-state proton transfer, which is exclusively driven by the Asp148 residue introduced in the double mutant, is responsible for the ultrafast formation of the anionic fluorescent state, which can be deactivated through a concerted asynchronous hula-twist photoisomerization. This causes the lower fluorescence quantum yield in S65T/H148D compared to wild-type GFP. Hydrogen out-of-plane motion plays an important role in the deactivation of the S65T/H148D fluorescent state.
authors.affiliation: Key Laboratory of Theoretical and Computational Photochemistry of the Chinese Ministry of Education, Chemistry College, Beijing Normal University, Beijing 100875 (China).
authors.forename: Qiangqiang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Xuebo
authors.initials: X
authors.lastname: Chen
authors.forename: Ganglong
authors.initials: G
authors.lastname: Cui
authors.forename: Wei-Hai
authors.initials: WH
authors.lastname: Fang
authors.forename: Walter
authors.initials: W
authors.lastname: Thiel
mesh_terms: D019943:Amino Acid Substitution; D049452:Green Fluorescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D007536:Isomerism; D008027:Light; D056004:Molecular Dynamics Simulation; D017434:Protein Structure, Tertiary; D011789:Quantum Theory
chemical_list: D049452:Green Fluorescent Proteins
keywords: QM/MM; green fluorescent protein; hula-twist; photoisomerization; proton transfer