Excited States of the Green Fluorescent Protein Chromophore: Performance of Ab Initio and Semi-Empirical Methods

Physica Status Solidi B 249, 392 - 400 (2012)

Excited States of the Green Fluorescent Protein Chromophore: Performance of Ab Initio and Semi-Empirical Methods

Marius Wanko, Pablo García-Risueño, Angel Rubio

The complex photophysical properties of fluorescent proteins give rise to a wide field of applications as markers in molecular biology. Understanding these properties is essential for rational genetic engineering of new fluorescent proteins. Here, theoret- ical models are required to support the interpretation of structural and spectroscopic experimental data. This requires the accurate and reliable prediction of excited-state features of the chromophore and its interactions with the protein matrix. Here, we compare calculations of absorption and emission energies of semi-empirical (OM2/MRCI, ZINDO/S, and TD- DFTB) and ab initio (SORCI, CC2, and TDDFT) approaches for the HBDI chromophore in vacuo and wild-type green fluorescent protein (GFP) using QM/MM models. We discuss the influence of electrostatic fields, the chromophore geometry, the size of the QM region, and methodological aspects, in particular charge-transfer states in TDDFT and the applicability of real-space TDDFT codes. We revisit previous opposing theoretical studies and benchmark gas-phase measurements.

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http://dx.doi.org/10.1002/pssb.201100536

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