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Biomedical use of two-photon absorption: computer-assisted design of non-linear optical materials for photodynamic therapy and fluorescent labels.

Two-photon (TP) fluorescent microscopy employs nonlinear optical process when molecule simultaneously absorbs two photons and emits one. It has a number of advantages over the standard (linear) microscopy, including high three-dimensional resolution (due to quadratic dependence on intensity), and increased penetration depth in tissue with reduced photodamage (by operating with incident light in the visible red-NIR region). These allow for real-time imaging of the living tissue, if effective TP absorbing chromophores are introduced into it. In this project we apply virtual screening and combinatorial chemistry methods to design better TP chromophores. Recently we developed a novel approach to prediction of non-linear optical properties, based on Time-Dependent Density Functional Theory. It gives accurate TP cross-sections for large conjugated molecules. We are improving the accuracy of this method further by taking into account vibrational line broadening, and selecting significant molecular descriptors for nonlinear optical properties. Based on these descriptors, new molecules will be designed from molecular fragments collected in a virtual library and suggested as candidates for an experimental study.

Among the findings of my past research projects are: first topological analysis of experimental electron density in crystal, local models of superconductivity in cuprates, understanding the role of secondary bonds in structures of inorganic dihalides and molecular crystals, ab initio prediction of polymorph relative stability, first comprehensive molecular dynamics study of potential of mean force between ionizable aminoacid sidechains in aqueous solution, development of intermediate (between micro- and macroscopic) solvation model, extension of Density Functional Theory to strongly correlated systems, and discovery of counterion-induced charge transfer excited states of organic chromophores in aqueous solution.

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Advanced Materials Processing and Analysis Center