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The comparative study of the interaction of ethidium bromide, acridine orange, and isoquinoline alkaloids such as sanguinarine and berberine with DNA in aqueous solutions using the optical spectroscopy methods is presented. The dependences of the spectral characteristics of ligands on the concentration ratio P/D between the DNA base pairs and ligands molecules in solutions are considered. The character of binding is found to depend on P/D. The parameters of the binding with DNA are determined for the external binding and the intercalation, by using the modified Scatchard and McGhee-von Hippel equations. The influence of a ligand form on binding ways is shown.

Natural alkaloid berberine has long been used in medicine for treating a number of diseases. Moreover, recently berberine was found to possess antitumor properties. Such activity of alkaloid is attributed to its ability to build into the DNA macromolecule by blocking the processes of replication and transcription [1]. To clarify the mechanism of therapeutic effect of berberine it is necessary to know the mechanisms of its complexation with DNA. Earlier [2] by the Raman spectroscopy method we revealed the fact of the resonance interaction of the berberine and DNA vibrations in the range of their Raman spectra overlapping (1000-1700 cm -1 ). To explain this interaction the detail information about the vibration spectra of berberine and DNA is needed.The Raman spectra of berberine is obtained by using an optical setup made on the basis of a double-grating DFS-24 monochromator, with He-Ne laser emission (λ=6328Ǻ) excitation. Spectra were recorded in the range of 40-4000 cm -1 . The IRabsorption spectra were recorded in the range of 400-4000 cm -1 by using the Fourier spectrometer Nicolet NEXUS-470 by the ATR technique.The optimized geometry of the berberine cation was calculated by DFT at the B3LYP/6-311++ G(d,p) level using the "Gaussian03" program package [3]. At this level Raman and IR-absorption spectra were calculated. For the first time in optimized structure was found intermolecular hydrogen bond CH…O between OCH 3 groups of berberine.The calculated spectrum consists of 123 nondegenerated vibrations, 62 of it in the actual region of 800-1700 cm -1 . Frequencies up to 720 cm -1 correspond to out-ofplane vibrations of rings and associated groups, in-plane vibrations of rings appear beginning with 720 cm -1 , particularly a unique out the range of 1200-1700 cm -1 intensive Raman mode 727 cm -1 . In-plane vibrations are characteristic to all range from 720 to 1700 cm -1 . The high-frequency region of 3000-3300 сm -1 consists of the modes corresponding to vibrations of С-Н-bonds.Because of the DFT method usually overvalues frequencies the experimentally determined scaling factor of 0.985 was used for comparison calculated and experimental data. The good correlation between experimental and calculated Raman spectra is observed in the range of 1000-1700 cm -1 -both between frequencies and intensities of vibrations (Fig1). In the range up to 1000 cm -1 , besides a 727 cm -1

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