Potential Energy Landscape of the Photoinduced Multiple Proton-Transfer Process in the Green Fluorescent Protein:  Classical Molecular Dynamics and Multiconfigurational Electronic Structure Calculations

• Published in: Journal of the American Chemical Society 2006-03, Vol.128 (11), p.3564-3574
• Main Authors: Vendrell, Oriol, Gelabert, Ricard, Moreno, Miquel, Lluch, José M
• Format: Article
• Language: English
• Subjects: Green Fluorescent Proteins - chemistry; Models, Molecular; Photochemistry; Protein Conformation; Protons; Quantum Theory; Thermodynamics
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0549998

The green fluorescent protein proton wire operating upon photoexcitation of the internally caged chromophore is investigated by means of classical molecular dynamics and multiconfigurational electronic structure calculations. The structure of the proton wire is studied for the solvated protein, showing that the wire is likely to be found in a configuration ready to operate as soon as the chromophore is photoexcited, and leading to a total of three proton translocations in the vicinity of the chromophore. Multiconfigurational CASSCF and CASPT2 calculations provide a detailed overview of the energy landscape of the proton wire for the ground electronic state S0, the photoactive 1ππ* state, and the charge-transfer 1πσ* state. The results allow discussion of the operation of the wire in terms of the sequence of proton-transfer events and the participation of each electronic state.