Effect of Solvation on Electron Detachment and Excitation Energies of a Green Fluorescent Protein Chromophore Variant.
Hybrid quantum mechanics/molecular mechanics (QM/MM) is applied to the fluorinated green fluorescent protein (GFP) chromophore (DFHBDI) in its deprotonated form to understand the solvatochromic shifts in its vertical detachment energy (VDE) and vertical excitation energy (VEE). This variant of the GFP chromophore becomes fluorescent in an RNA environment and has a wide range of applications in biomedical and biochemical fields. From microsolvation studies, we benchmark (with respect to full QM) the accuracy of our QM/MM calculations with effective fragment potential (EFP) as the MM method of choice. We show that while the solvatochromic shift in the VEE is minimal (0.1 eV blue shift) and its polarization component is only 0.03 eV, the effect of the solvent on the VDE is quite large (3.85 eV). We also show by accurate calculations on the solvatochromic shift of the VDE that polarization accounts for ∼0.23 eV and therefore cannot be neglected. The effect of the counterions on the VDE of the deprotonated chromophore in solvation is studied in detail, and a charge-smearing scheme is suggested for charged chromophores.
Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory , Pune 411008, India.
Samik
S
Bose
Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory , Pune 411008, India.
Suman
S
Chakrabarty
Physical and Materials Chemistry Division, CSIR-National Chemical Laboratory , Pune 411008, India.
Debashree
D
Ghosh
D004583:Electrons; D049452:Green Fluorescent Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D011522:Protons; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry*; D055672:Static Electricity; D013816:Thermodynamics
D011522:Protons; D012997:Solvents; D049452:Green Fluorescent Proteins