Theoretical studies of nonlinear optical properties of fluorescent proteins by novel low-cost quantum chemistry methods
Final Report Abstract
In this project that aimed at investigating nonlinear optical properties of novel fluorescent proteins (FPs) by low-cost quantum chemistry methods. The initial questions were leading to three different work packages addressed in this project: 1) improvement of the sTD-DFT method, 2) improvement of the ground state tight-binding scheme, and 3) applications to large biomolecules. The simplified time-dependent density functional theory (sTD-DFT) was improved by replacing semi-empirical two-electron intregrals by exact ones. The eXact integral sTD-DFT (XsTD-DFT) method provides globally improved excitation energies and oscillator strengths in comparison with sTD-DFT with respect to TD-DFT. First hyperpolarizabilities are also drastically improved, especially for their frequency dispersions. In comparison to TD-DFT, XsTD-DFT is at least 20 orders of magnitudes faster, while providing comparable results. Furthermore, sTD-DFT and XsTD-DFT scheme were extended to the evaluation of two-photon absorption (2PA) crosssections, giving rather good to excellent agreements with respect to experimental 2PA spectra. Besides that, a dual-threshold termed method was introduced for expanding the truncation of the CI space without enhancing the computational cost. A new ground-state tight-binding method, termed PTB was developed. As it seems to be robust for a wide variety of molecules including unusual bonding situations, it may be used in the future as input for excited state and response calculations. A thorough benchmark will soon be conducted. Finally, we proposed a new all-atom quantum mechanics methodology to compute the SHG and 2PA of FPs. Striking agreement with respect to experiment are observed for the secondharmonic generation of the bacteriorhodopsin (~4000 atoms) and the 2PA of iLOV. This allatom quantum mechanics methodology was then applied to novel fluorescent proteins such as UnaG and mutants. We were able to rationalize differences in the SHG response of UnaG and variants. We are waiting for the experimental confirmation of our findings. This new methodology opens the door to a plethora of new applications e.g., providing new design guidelines to improve FP biotags for nonlinear optical imaging techniques.
Publications
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All-Atom Quantum Mechanical Calculation of the Second-Harmonic Generation of Fluorescent Proteins. The Journal of Physical Chemistry Letters, 12(39), 9684-9690.
Beaujean, Pierre; Champagne, Benoît; Grimme, Stefan & de, Wergifosse Marc
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Perspective on Simplified Quantum Chemistry Methods for Excited States and Response Properties. The Journal of Physical Chemistry A, 125(18), 3841-3851.
de Wergifosse, Marc & Grimme, Stefan
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Ultrafast Evaluation of Two-Photon Absorption with Simplified Time-Dependent Density Functional Theory. The Journal of Physical Chemistry A, 126(41), 7534-7547.
de Wergifosse, Marc; Beaujean, Pierre & Grimme, Stefan
