title: Far-Red Emission of mPlum Fluorescent Protein Results from Excited-State Interconversion between Chromophore Hydrogen-Bonding States.
abstract: Fluorescent proteins with large Stokes shifted emission beyond 600 nm are actively sought for live-cell imaging applications. The mechanism of excited-state relaxation leading to the Stokes shift in the mPlum fluorescent protein, which emits at a peak wavelength of 650 nm, has been previously investigated by both ultrafast spectroscopy and theoretical methods. Here, we report that femtosecond time-resolved area-normalized emission spectra of mPlum show a clear isoemissive point. This feature can only result from a system with two emitting states, rather than a system that undergoes a continuous spectral red shift, for example, as expected from typical solvation. Global analysis of the femtosecond time-resolved fluorescence spectra reveals time constants associated with chromophore relaxation, excited-state population transfer, and an excited-state lifetime of the final state. The observations confirm the findings of recent quantum chemical calculations on mPlum.
authors.affiliation: Department of Chemistry, Pohang University of Science and Technology , Pohang, South Korea 790-784.
authors.forename: Eunjin
authors.initials: E
authors.lastname: Yoon
authors.affiliation: JILA, University of Colorado and NIST , 440 UCB, Boulder, Colorado 80309-0440, United States.
authors.forename: Patrick E
authors.initials: PE
authors.lastname: Konold
authors.affiliation: Department of Chemistry, Pohang University of Science and Technology , Pohang, South Korea 790-784.
authors.forename: Junghwa
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Chemistry, Pohang University of Science and Technology , Pohang, South Korea 790-784.
authors.forename: Taiha
authors.initials: T
authors.lastname: Joo
authors.affiliation: JILA, University of Colorado and NIST , 440 UCB, Boulder, Colorado 80309-0440, United States.|Department of Chemistry & Biochemistry, University of Colorado , 215 UCB, Boulder, Colorado 80309-0215, United States.
authors.forename: Ralph
authors.initials: R
authors.lastname: Jimenez
mesh_terms: D049452:Green Fluorescent Proteins / Q000737:chemistry*; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D049452:Green Fluorescent Proteins