title: Toward understanding the redox properties of model chromophores from the green fluorescent protein family: an interplay between conjugation, resonance stabilization, and solvent effects.
abstract: The redox properties of model chromophores from the green fluorescent protein family are characterized computationally using density functional theory with a long-range corrected functional, the equation-of-motion coupled-cluster method, and implicit solvation models. The analysis of electron-donating abilities of the chromophores reveals an intricate interplay between the size of the chromophore, conjugation, resonance stabilization, presence of heteroatoms, and solvent effects. Our best estimates of the gas-phase vertical/adiabatic detachment energies of the deprotonated (i.e., anionic) model red, green, and blue chromophores are 3.27/3.15, 2.79/2.67, and 2.75/2.35 eV, respectively. Vertical/adiabatic ionization energies of the respective protonated (i.e., neutral) species are 7.64/7.35, 7.38/7.15, and 7.70/7.32 eV, respectively. The standard reduction potentials (E(red)(0)) of the anionic (Chr•/Chr–) and neutral (Chr+•/Chr) model chromophores in acetonitrile are 0.34/1.40 V (red), 0.22/1.24 V (green), and −0.12/1.02 V (blue), suggesting, counterintuitively, that the red chromophore is more difficult to oxidize than the green and blue ones (in both neutral and deprotonated forms). The respective redox potentials in water follow a similar trend but are more positive than the acetonitrile values.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States.
authors.forename: Debashree
authors.initials: D
authors.lastname: Ghosh
authors.forename: Atanu
authors.initials: A
authors.lastname: Acharya
authors.forename: Subodh C
authors.initials: SC
authors.lastname: Tiwari
authors.forename: Anna I
authors.initials: AI
authors.lastname: Krylov
mesh_terms: D049452:Green Fluorescent Proteins / Q000737:chemistry*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D011789:Quantum Theory; D012995:Solubility; D012997:Solvents / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D012997:Solvents; D049452:Green Fluorescent Proteins