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First-principle DFT calculations of the electronic and optical properties of various DNA-based assemblies, including G4-wires

The electronic structure of periodic G4-wires indicates that a pure band-like conduction mechanism is unlikely. However, the p-p overlap between consecutive planes originates channels for helectron/hole motion [Arrigo Calzolari, Rosa Di Felice, Elisa Molinari, Anna Garbesi, "G-Quartet Biomolecular Nanowires", Appl. Phys. Lett. 80, 3331 (2002); A. Calzolari, R. Di Felice, E. Molinari, A. Garbesi, J. Phys. Chem. B 108, 2509 (2004); J. Phys. Chem. B 108, 13058 (2004)]. The electronic structure parameters (band gaps and widths) are very sensitive to various geometrical factors, such as twisting and axial strain [R. Di Felice, A. Calzolari, A. Garbesi, S.S. Alexandre, J.M. Soler, "Strain-dependence of the electronic properties in periodic quadruple helical G4-wires", J Phys. Chem. B 109, 22301 (2005)]. The optical properties of nucleobases and their assemblies were computed from first principles in the framework of Time-Dependent DFT for the first time, and compared to available experimental data with success [D. Varsano, R. Di Felice, M.A.L. Marques, A. Rubio, "A TDDFT study of the excited states of DNA bases and their assemblies", J. Phys. Chem. B 110, 7129 (2006)]. The optical investigations are currently continuing with the implementation and test of circular dichroism (CD) spectra at the same level of theory: reliable CD spectra computed in this way can be employed for the interpretation of in-situ post-synthesis data, since CD is often used for routine characterization

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