[Stimulation of DNA molecules association with amphiphilic derivatives of 1,3-diazaadamantane containing hydrophobic side chanins].

Earlier, a new class of compounds--amphiphilic derivatives of 1,3-diazaadamantanes, capable of facilitating the strand exchange in the system of short oligonucleotides was revealed. Longer hydrophobic side chains of 1,3-diazaadamantanes promoted stronger acceleration of the reaction. In this study, interaction with DNA of two 1,3-diazaadamantane derivatives containing different side chains was investigated by use of optical methods. Concentration of the investigated 1,3-diazaadamantans micelles formation were determined by the means of monitoring fluorescence intensity enhancement of 1-anilinonaphtalene-8-sulphonate probe; as well as the ranges of concentrations where the compounds/water mixtures existed as true solutions. 1,3-diazaadamantanes affinity to DNA was determined with Fluorescent Intercalator Displacement (FID) approach. Significant increase in hydrodynamic volume of short DNA hairpins in the complexes with 1,3-diazaadamantanes was revealed by estimation of the fluorescence polarization of ethidium bromide probe bound to the hairpins. Intermolecular association of DNA hairpins upon binding with 1,3-diazaadamantans was confirmed by Förster resonance energy transfer in system of an equimolar mixture of fluorescently labeled with Cy-3 and Cy-5 hairpins. In this study, the number of positive charges at 1,3-diazaadamantane derivatives containing side chains of different lengths was demonstrated to affect their affinity to DNA, whereas longer length of the hydrophobic side chains ensured more efficient interaction between the DNA duplexes that may facilitate, in particular, DNA strand exchange.

[Conformational transitions of DNA in concentrated neutral salt solutions]. / Konformatsionnye perekhody DNK v kontsentrirovannykh rastvorakh neitral'nykh solei.

Salt anions can be arranged in lyotropic series of the action of conformational stability of DNA. This effect is universal for proteins and DNA. It is explained by the salt changes of transfer free energy of macromolecular inner groups to the solvent. Effect mechanism is the combination of anion direct interaction with the exposed inner groups and in indirect way through the changes of water structure. Individual features of the salt effect on DNA are the induced transitions in DNA duplex and the changes of differential stability of AT- and GC-base pairs. An important role in these phenomena plays the dehydration of DNA in the reduction of water activity in concentrated salt solutions. Local changes in medium polarity, hydration level of DNA molecule at different stages of their functioning can explain the regulatory role in intracellular processes, as well as selectivity and specificity of the action of individual ions in the cell.

[Solubility of adenosine in concentrated salt solutions]. / Rastvorimost' adenozina v kontsentrirovannykh solevykh rastvorakh.

The solubility of adenosine has been measured in concentrated neutral salt solutions of NaClO4 (salt-destabilizer) and Na2SO4 (salt-stabilizer) as a function of salt concentration and temperature. The thermodynamic functions of adenosine transfer from water to salt solutions have been estimated. The values of delta Ftr, delta Htr, delta Str adenosine transfer in NaClO4 solutions are negative, in Na2SO4--positive. The results are considered in connection with the mechanism of high concentrations of salt action on DNA in the water solutions.