Fluorescence Quantum Yields in Complex Environments from QM-MM TDDFT Simulations: The Case of Indole in Different Solvents

Abstract

Fluorescence is commonly exploited to probe microscopic properties. An important example is tryptophan in protein environments, where variations in fluorescence quantum yield, and in absorption and emission maxima, are used as indicators of changes in the environment. Modeling the fluorescence quantum yield requires the determination of both radiative and nonradiative decay constants, both on the potential energy surface of the excited fluorophore. Furthermore, the inclusion of complex environments implies their accurate representation as well as extensive configurational sampling. In this work, we present and test various methodologies based on time-dependent density functional theory (TDDFT) and quantum mechanics/molecular mechanics (QM/MM) dynamics that take all of these requirements into account to provide a quantitative prediction of the effect of the environment on the fluorescence quantum yield of indole, a tryptophan fluorophore. This investigation paves the way for applications to the realistic spectroscopic characterization of the local protein environment of tryptophan from computer simulations.

Short hydrogen bonds enhance nonaromatic protein-related fluorescence

“…For further detail on this implementation, please refer to ref. 38 . The nonadiabatic coupling elements between S0 and S1 ( Eq.…”

Efficient enumeration of bosonic configurations with applications to the calculation of non-radiative rates

“…As an important final test, we apply the new algorithms to the determination of internal conversion rates for three molecular systems: anthracene, tetracene, and indole. We have selected these because they are molecules that are known to have a viable internal conversion pathway, [38][39][40][41] and that have a feasible number of vibrational modes for the calculations.…”

Modeling the Temperature Dependence of the Fluorescence Properties of Indole in Aqueous Solution

“…Over the years, Indole has been the subject of numerous studiesboth experimental [1][2][3][4][5][6] and theoretical [7][8][9][10][11][12][13][14] -as the model system for the absorption and emission properties of the amino acid tryptophan (Trp). This interest arises from the unique spectroscopic properties of Trp, which are largely dependent on the polarity of its surrounding environment and have been successfully exploited to gain structural and dynamic information on proteins [15][16][17][18][19].…”