Equilibrium behaviour of self-complimentary deoxytetranucleotides d(ApGpCpT) in D2O solution has been studied by the method of proton magnetic resonance spectroscopy (500 MHz). Complete assignments of the d(ApGpCpT) protons were obtained from both two-dimensional homonuclear COSY- and NOESY-experiments. Concentration and temperature dependences of tetranucleotide proton chemical shifts have been investigated. The equilibrium association constants and thermodynamical parameters of self-association of the molecules have been calculated using theoretical models and regression equations based on experimental results.

Complex formation between acridine dye proflavine and self-complementary deoxytetraribonucleoside triphosphate 5'-d(ApGpCpT) in water-salt solution was studied by the method of one- and two-dimensional 1H-NMR spectroscopy (500 MHz). Two-dimensional homonuclear 1H-NMR spectroscopy (2D-COSY and 2D-NOESY) was used for complete assignments of proton signals of molecules in solution and for qualitative analysis of the nature of interactions between proflavine and tetranucleotide. Concentration dependences of proton chemical shifts of the molecules were measured at 293 K. Equilibrium reaction constants and limiting chemical shifts of dye protons in the complexes were determined using suggested schemes of complex formation. Based on the obtained data possible types of complexes were considered. Analysis of relative content of different types of complexes was made and special features of dynamic equilibrium were revealed as a function of correlation of dye and tetranucleotide concentrations. The most favourable structure of 1:2 complex of dye with tetranucleotide was constructed using the calculated values of induced chemical shifts of proflavine protons and 2D-NOESY spectra.

Temperature relationships of chemical shifts of protons of proflavin mixed with deoxytetraribonucleoside triphosphate 5'-d(ApGpCpT) in water solution were investigated on impulse NMR spectrometer (500 MHz). Procedure is suggested for calculating values of mole fractions of various associates in solution as a function against temperature. Free energies of Gibbs, entalpy and entropy were determined in the reactions of complex formation 1:1, 1:2, 2:1 of proflavin with tetranucleotide. The results point to a significant role of hydrophobic interactions during the formation of dye--tetramere duplex complexes.

Temperature dependences of proton chemical shifts of the molecules in aqueous solutions of proflavine with deoxytetraribonucleoside triphosphates of different base sequence--5'-d(CGCG), 5'-d(GCGC), 5'-d(ACGT) and 5'-d(AGCT) have been studied by 500 MHz NMR spectroscopy. Methods of calculation of thermodynamical parameters of complex formation, giving an opportunity to differentiate the contributions of the reactions leading to the formation of different types of complexes in conditions of the composite equilibrium in solution, have been suggested. Enthalpies and entropies of the reactions of 1:1, 2:1, 1:2, 2:2 complexes formation between proflavine and tetranucleotides have been determined. Comparative analysis of the calculated thermodynamical parameters has been made and assumptions about the nature of intermolecular interactions responsible for the formation of dye complexes with different tetranucleotides have been proposed.