Biopolym. Cell. 1995; 11(3-4):42-54.
Investigation of the interaction of ethidium bromide with self complementary deoxytetranucleotide 5'-d (ApCpGpT) in aqueous solution by the method of 1H NMR spectroscopy
1Veselkov A. N., 1Djimant L. N., 1Bolotin P. A., 1Baranovsky S. F., 1Veselkov D. A., 2Shipp D., 2Davies D. B.
  1. Sevastopol National Technical University
    33, Universytetska Str., Sevastopol, Ukraine, 99053
  2. Birkbeck, University of London
    Malet Str., Bloomsbury, London WC1E 7HX, UK


Complex formation between dye ethidium bromide (3,8-diamino-6-phenyl-5-etliyl-phenan-thridinium) and self-complementary deoxytetraribonucleoside triphosphate 5'd-(ApCpGpT) in aqueous salt solution has been studied by method of one-dimensional (500 MHz) and two-dimensional 1H NMR spectroscopy (600 MHz). Two-dimensional homonuctear 1H NMR spectroscopy was used for qualitative analysis of the nature of interactions of ethidium bromide with tetranucleotide. Concentration dependences of proton chemical shifts of the molecules have been measured at fixed temperature (T=298K). Different schemes of complex formation between dye molecules and tetranucleotide have been examined taking into account various molecular associations in solution. Analysis of the relative content of different types of complexes has been made and special features of dynamic equilibrium have been revealed as a function of both the dye and tetranuclee-tide concentrations. The present analysis leads to the conclusion that ethidium bromide binds preferentially to pyrimidine-purine sequence (CG-site) of the tetranucleotide duplex similar to the observed proflavine-(ApCpGpT) binding studied earlier. Ethidium bromide intercalates from the minor groove of the double helix in contrast to proflavine which binds from the major groove. The most favourable structure of the 1:2 complex of dye with the tetranucleotide has been constructed using calculated values of induced chemical shifts of ethidium bromide protons in conjunction with intermolecular NOEa,


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