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Unraveling CD spectra of Gquadruplexes 1 2 1,2 Zalevsky, A.O , Dyuba A.V. , Golovin A.V.
1 Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia 2 A. N. Belozersky Institute of PhysicoChemical Biology, Lomonosov Moscow State University, Moscow, Russia azlvk@b.s.u oaesyfbmur

Studying structures of Gquadruplexes (fourstranded nucleic acids comprised of guanine stacks) is a challenging issue. Such structures are usually very versatile so that classic methods like Xray or NMR sometimes fail to determine even strands direction[1]. Circular dichroism (CD) spectroscopy is rapid and simple method which is commonly used to describe topological features of quadruplexes[2]. Nevertheless the origin of quadruplex CD spectra still remains unclear. Some efforts have recently been done to address this issue but there are many things yet to be clarified[3]. In this work we use recent stateoftheart quantum chemistry techniques to provide detailed description of Gquadruplex CD. Our calculations reproduce the most prominent features of experimental spectra at 260 and 290 nm. The strong connection between quartet stacking mode, geometry and a shape of corresponding CD curve is shown. Results of quantum chemical calculations are compared with the classical dipoledipole interpretation of CD spectra. This work was supported by Russian Foundation for Basic Research grant no. 140431688. 1. S.Haider, G.N.Parkinson, S.Neidle (2002) Crystal structure of the potassium form of an Oxytricha nova Gquadruplex, Journal of molecular biology, 2:189­200. 2. J.Kypr, I.KejnovskА, D.Renciuk, M.VorlМckovА (2009) Circular dichroism and conformational polymorphism of DNA, Nucleic Acids Research, 6:1713­1725. 3. J.C.Lech, A.T.Phan, M.E. MichelBeyerle, A.A. Voityuk (2015) Influence of Base Stacking Geometry on the Nature of Excited States in GQuadruplexes: A TimeDependent DFT Study, The Journal of Physical Chemistry B 9:36973705.