[The nature of different influence of Cd2+ ions on the conformation of three-stranded polyU-polyA-polyU and polyI-polyA-polyI in aqueous solution].

The methods of UV (DUV) spectroscopy and thermal denaturation were used to study the effect of Cd2+ ions on the conformational equilibrium of three-stranded (A21, A2U) and single-stranded (poly U, poly A and poly I) polynucleotides in aqueous solutions containing 0.1 M Na+ (pH 7). An analysis of the form and intensities of DUV-spectra of poly A, poly I and A2I revealed the presence of two types of complexes: interaction with N7 of purines, resulting in the formation of macrochelates and binding to N1 of poly A and poly I.

[Interaction of divalent metal ions with four-stranded polyriboinosinic acid].

Interaction of Mg2+, Ca2+, Cu2+ ions with the four-stranded poly(I) was studied using differential UV and visible spectroscopies. It was shown that, up to concentrations of approximately 0.1 M, Mg2+ and Ca2+ ions do not bind to heteroatoms of hypoxanthine of the four-stranded poly(I).

[Interaction of Ag+ ions with DNA and its monomers].

Differential UV spectra of DNA and its monomers that were induced by Ag+ ions were measured, and the effect of ions on the parameters of the helix-coil transition was studied. The data obtained confirm the existence of "strong" and "weak" modes of binding of Ag+ to DNA. The earlier proposed proton transfer from N1G to N3C, which is determined by the interaction of Ag+ with N7G (a "strong" complex), follows immediately from the shape of the differential UV spectra.

[Interaction of Ag+ ions with ribonucleotides of canonical bases].

The interaction of Ag+ ions with ribonucleotides of canonical bases in aqueous solution was studied by differential UV spectroscopy. Atoms coordinating silver ions (N7, O6 of guanosine 5'-monophosphate, N3, O2 of cytidine 5'-monophosphate, N7, N1, N3 of adenosine 5'-monophosphate and N3 of uridine 5'-monophosphate) and the binding constants characterizing the formation of appropriate complexes were determined. The differences in the relative affinity of Ag+ ions for the atoms of nucleotide bases correlate with the potential on them.

[Calorimetric study of the helix-coil transition in DNA during interaction with Cu2+ ions].

Using the method of differential scanning calorimetry, the DNA helix-coil transition was studied in solutions (10(-3) M Na+, 10(-3) M tris HCl, pH 7.0) containing divalent copper ions at relative metal ion concentrations (Mt2+/PDNA) ranging from 0.2 to 20.

[Calorimetric study of Ca2+ and Mn2+ ions' effect on DNA helix-coil transition].

Using the method of differential scanning calorimetry, the DNA helix-coil transition studied in solutions (10(-3) M Na+, 10(-3) M tris HCl, pH 7.0) containing divalent metal ions (Mn2+ and Ca2+) at relative metal ion concentrations (Me/PDNA) ranging from 0.2 to 20.

[Effect of low temperatures on molecular parameters of DNA].

Cryoconservation effects on macromolecular parameters of DNA from reproductive cells of fishes are studied as well as cryodamages of DNA in solutions under various freezing conditions, by the viscometry method. A dependence of the low temperature action on DNA concentration in solution and on the action duration is determined. It is stated as well that the nitrogen temperature action on the biopolymer solution results in the formation of both double- and single-stranded breaks.

[The "condensation" and "ligand" theory in describing DNA helix-coil transition: comparative analysis].

Experimental data on DNA melting in the presence of magnesium and calcium ions are compared with the calculated results by the "ligand" theory and "condensation" theory developed by de Marky and Manning (TMM). The maximum is observed in TMM dependences of DNA melting temperature change (delta Tm) on the ion concentration (D), absent in the experimental dependences and the "ligand" theory. The main cause of the discrepancy of calculated and experimental dependences delta Tm (D) is the fact that TMM neglects Na+ ion effects on Me2+ ion binding ("condensation") to DNA.

[Interaction of DNA with calcium ions by a vibrational spectroscopy].

DNA complexes with Ca2+ ions formed in films at various relative humidities were studied by IR-spectroscopy for molar concentration ratio of calcium ions and DNA phosphate groups [Ca2+]/[P] = 0.4-20. It is shown that the transition of DNA complexed with Ca2+ ions into B-form occurs at higher average numbers (n) of water molecules absorbed per nucleotide: n > 18 at the ratio [Ca2+]/[P] = 10, n > 24 at [Ca2+]/[P] = 20 and n > 12 in the absence of Ca2+ ions.

[Structural and physicochemical characteristics of DNA from animal tissue subjected to chronic irradiation in the Chernobyl area].

The properties of animal DNAs exposed to prolonged irradiation in the Chernobyl zone, have been studied by the methods of viscometry, thermal denaturation, IR-spectroscopy, and electrophoresis. High content of low-molecular fractions have been observed in the preparations of DNA from liver and spleen, their quantities increasing with age and generation of animals. This effect is especially strong in DNA from liver.

[Study of the interaction of DNA with copper ions using IR- and Raman spectroscopy].

DNA with Cu2+ ions in solution and films is studied by IR and Raman spectroscopy at different relative humidities (R.H. = 51 divided by 98%).

[Study of the interaction of DNA with manganese ions by IR-spectroscopy].

DNA complexed with Mn2+ ions in films is studied at different relative humidities and ion contents ([Mn2+]/[P] = 0.4-1) by IR spectroscopy. It is shown that substantially more sorbed water molecules are necessary for the transition of DNA complexed with Mn2+ ions into the double helical conformation (preferentially B-form) that for macromolecules in the absence of ions.

[Interaction of DNA with divalent metal ions].

The interaction between the native DNA macromolecules and Ca2+, Mn2+, Cu2+ ions in solutions of low ionic strength (10(-3) M Na+) is studied using the methods of differential UV spectroscopy and CD spectroscopy. It is shown that the transition metal ions Mn2+ exercise binding to the nitrogen bases of DNA at concentrations approximately 5 x 10(-6) M and form chelates with guanine of N7-Me(2+)-O6 type. Only at high concentrations in solution (5 x 10(-3) M) do Ca2+ ions interact with the nitrogen bases of native DNA.

[The study of complex-formation of DNA with the antimicrobial drug decamethoxine].

The interaction of effective antibacterial drug decametoxyn with natural DNA was studied by UV-spectroscopy. Decametoxyn shows a specificity to nucleotides: it decreases the cooperativity of melting and the thermal stability of DNA parts enriched by AT pairs. The characteristics of the helix-coil transition on the DNA parts enriched by GC-pairs are invariable.

[Thermodynamic and spectral study of DNA-prospidin complex].

By the methods of heat denaturation and luminescence the interaction between an antitumor drug prospidine and DNA in aqueous solutions at two ionic strengths (0.1 and 0.001 M NaCl) and at various prospidine concentrations was studied.

[Interaction of carminomycin with DNA according to data of laser polarized fluorescence].

Anti-tumour antibiotic carminomycin interaction with chicken erythrocyte DNA is studied in aqueous-salt solutions by the laser polarized fluorescence method. Fluorescence quenches almost equally effectively during the antibiotic absorption on native (nDNA) and denatured (dDNA) DNAs, but the polarization degree of residual fluorescence differs about two times. Carminomycin binding to dDNA is characterized by one interaction type with a large density of occupancy sites - one antibiotic molecule per base pair.

[Infrared spectra of associated and hydrated pyrimidine bases of nucleic acids in argon matrix].

The spectral characteristics of interacting pyrimidine bases of nucleic acids--cytosine, 1-methylcytosine, uracil in autoassociates and hydrates--are investigated using the high-resolution infrared spectroscopy in argon matrices. Shifts of vibration frequencies in simple complexes are stated to be from 10 to 30 cm-1 in the 4000-400 cm-1 region observed. The isolated state-solid phase transition is followed by the absorption maximum shift, the latter being some hundreds of cm-1 in the 4000-2000 cm-1 region and some tens of cm-1 in the 1800-400 cm-1 region.

[Effect of copper ions on the photochemical activity of quinacrine and its interaction with DNA].

The influence of cuprum ions on the interaction between the antimalarial drug quinacrine (QA) and DNA is studied by polarized laser luminescence spectroscopy and fluorescence microscopy at molecular and cellular levels. An alteration of quinacrine luminescence intensity in complex with DNA caused by cuprum ions is explained in terms of redistribution of QA molecules from quenching GC- to fluorescent AT-DNA binding sites due to the competition of Cu2+ with the dye. Mechanisms of component interactions in the triplex "DNA-QA-Cu2+" in model and cellular systems are shown to be in qualitative agreement.

[Infrared spectra of uracil and thymine in an argon matrix].

High-resolution IR spectra of uracil, thymine, methyl-derivatives of uracil and 5,6-dihydrouracil are obtained using the matrix isolation method.

[Spectroscopic study of the effect of binding of bivalent manganese ions on the conformation of polyriboadenylic acid].

UV-differential spectra and CD spectra of poly(A) were studied in the presence of manganese ions at 10(-3) and 0.1 M Na+ in solution. It was shown that at at both low and high ionic strengths Mn2+ ions in low concentrations form bindings with phosphates of the polymer, increasing the degree of its helicity.

[Electron-oscillatory spectra of pyrimidine bases of nucleic acids in argon matrices].

The studies on the oscillatory structure of adsorption spectra of pyrimidine bases of nucleic acids isolated in Ar matrix at 11 K are described. To clear up the importance of molecule isolation in the matrix, amorphous films of the materials studied were investigated experimentally at 11 and 77 K. The work was carried out using the low temperature optic attachment developed by the authors.

[Effect of bivalent copper ions on conformation of polyriboadenylic acid].

Ultraviolet differential spectra (UDS) and CD-spectra of poly (A) in the presence of Cu2+ ions are studied at different degrees of phosphate groups screening. The binding of cu2+ ions with bases of phosphates is shown to lead to disordering or to ordering respectively, of the mutual orientation of nucleotides. The UDS components due to conformation variations in poly (A) and association between Cu2+ ions and its bases are calculated.