ABSTRACT
On the basis of molecular biophysics, a methodology for the analysis of intramolecular structural order of the polynucleotide duplex poly(A).poly(U) has been developed. It was shown that the combination of circular dichroism spectroscopy with differential scanning calorimetry is an optimal approach, which ensures the screening of a wide set of substances and interaction conditions and the choice of compound(s) that can stabilize the structure and increase the biological activity of this duplex. The study is aimed at obtaining a new and highly active antiviral remedy.
Subject(s)
Antiviral Agents/chemistry , Platinum Compounds/chemistry , Poly A-U/chemistry , Circular Dichroism/methodsABSTRACT
The influence of different MgCl2 and MnCl2 concentrations on DNA conformational transitions in water-ethanol solutions was studied. It was shown that the presence of magnesium ions in solution at a concentration of 5 x 10(-4) M did not influence the decrease in the size of DNA without change in its persistent length at an alcohol concentration of about 17 % v/v. In contrast, manganese ions prevent this change in DNA parameters. At sufficiently high ethanol concentrations, the compaction of DNA followed by its precipitation takes place, which is accompanied by an increase of scattering in solution. As the concentration of Mg2+ and Mn2+ in solution increases, this process is observed at lower ethanol concentrations.
Subject(s)
Chlorides/chemistry , DNA/chemistry , Magnesium Chloride/chemistry , Manganese Compounds/chemistry , Cations, Divalent , Circular Dichroism , Nucleic Acid Conformation , Solutions , Spectrophotometry, UltravioletABSTRACT
The formation and physicochemical properties of high-molecular thymus and plasmid DNA complexes with synthetic polymers based on (dimethyl-amino)ethyl methacrylate (DMAEM), (diethyl-amino)ethyl methacrylate (DEAEM), and polyvinyl amine (PVA) were investigated in solutions of different ionic strength by low-gradient viscometry, electrophoresis, circular dichroism, spectrophotometry, and dynamic light scattering. The toxicity of complexes in T98G cells was studied. It was shown that, when the ratio of polycations to DNA charged groups concentration (N+/P) reaches values > 1, DNA condensation occurs. It is accompanied by increasing optical density of solutions. Changes in DNA size after condensation were estimated. Phase diagrams of systems DNA/polycation in the presence of NaCl were obtained. It was shown by MTT-analysis that DNA complexes with polycations in the range of concentrations used have low toxicity.
Subject(s)
DNA/chemistry , Methacrylates/chemistry , Polyamines/chemistry , Polymers/chemistry , Polyvinyls/chemistry , Transfection/methods , Amines/chemistry , Animals , Cattle , Cell Line , DNA/toxicity , Humans , Nylons , Osmolar Concentration , Plasmids , Polyamines/toxicity , Polyelectrolytes , Solutions , Thymus Gland/chemistryABSTRACT
Conformational properties of DNA molecule upon its complexation with binuclear compounds of bivalent platinum in the cis configuration containing pyrazine ligand were studied by circular dichroism, viscometry, and dynamic birefringence. Comparison with active antitumor therapeutic cis-diamminedichloroplatinum (cis-DDP) was made. Experimental data indicates that interaction of these compounds with DNA results in the formation of coordination bond of platinum with nitrogen bases. The structure of the complex depends on the ratio of platinum and DNA concentrations in initial solution. The study of DNA protonation in complex with the binuclear coordination compound showed that the binding of platinum with DNA bases occurs at the N7 atom of guanine. It was observed a competition between the studied compound and cis-DDP for binding site on DNA. The macromolecule binds stronger to the binuclear platinum compound as compared with cis-DDP.
Subject(s)
Antineoplastic Agents/chemistry , Cisplatin/chemistry , DNA/chemistry , Platinum Compounds/chemistry , Antineoplastic Agents/metabolism , Circular Dichroism , Cisplatin/metabolism , DNA/metabolism , Ligands , Platinum Compounds/metabolism , Pyrazines/chemistry , ViscosityABSTRACT
The interaction of DNA with Fe3+, Al3+, Co(NH3)6(3+) in a solution containing MnCl2 was studied. It was shown that there exists a competition for the binding sites between Mn2+ and Al3+, while the binding of Mn2+ to DNA does not depend on the presence of Fe3+ and Co(NH3)6(3+) in solution. We proposed that Fe3+ and Co(NH3)6(3+) ions prefer to bind to phosphates, and Al3+ ions are capable to bind to the nitrogen bases of DNA.
Subject(s)
Aluminum Compounds/chemistry , Cobalt/chemistry , DNA/chemistry , Ferric Compounds/chemistry , Manganese Compounds/chemistry , Cations , Circular Dichroism , Nucleic Acid Conformation , SolutionsABSTRACT
The interaction of DNA with coordination compounds of divalent platinum and trivalent cobalt was studied. Complexes containing simultaneously different coordination compounds were prepared by various procedures. It was shown that the binding of trans-diaminodichloroplatinum (DDP) to DNA prevents its further complexing with cis-DDP, while in the presence of cis-DDP the possibility for trans-DDP to bind to DNA in solution remains. The study of similar DNA complexes with trans-DDP and cobalt hexamine indicated the competition for the binding sites of these compounds to the DNA molecule.
Subject(s)
Antineoplastic Agents/chemistry , Cisplatin/chemistry , Cobalt/chemistry , DNA/chemistry , Circular Dichroism , Solutions , StereoisomerismABSTRACT
The interaction of DNA molecule with some coordination compounds of the divalent platinum: cis-DDP, trans-DDP, [(NH3)4Pt]Cl2 and K2PtCl4 was studied. It was shown that the transition of the cis-DDP, trans-DDP, and [PtCl4]2- to aquo-complexes is necessary for their binding with DNA in solution. It was shown that the labile chloride groups are responsible for the formation of the energetically strong binding. The distance between chloride groups in cis-DDP is optimal for incorporation of two groups of DNA bases into the first coordination sphere of platinum. The complexes are also stabilized with phosphate in the external coordination sphere of platinum. The sterical non-conformity between the DNA structure and positions of chloride groups and the orientation of the amino groups in trans-DDP are the main obstructions for the formation of bidentate DNA-trans-DDP complexes. The existence of more than two vacant positions for binding with DNA in [PtCl4]2- does not stabilise the complex. The compound [(NH3)4Pt]Cl2 cannot produce coordination bonds with DNA, because its first coordination sphere is completed with amino groups; it interacts with DNA, forming principally different complexes.
Subject(s)
Cisplatin/chemistry , DNA/chemistry , Circular Dichroism , Ligands , Nucleic Acid Conformation , SolutionsABSTRACT
DNA interaction with cis-diaminodichloroplatinum (cis-DDP in solutions of different ionic strength was studied by flow birefringence, viscometry, circular dichroism. Though cis-DDP is not an electrolyte, electrostatic interactions are important for binding of cis-DDP with DNA probably for transporting cis-DDP to a macromolecule. The charges aqua-complex is formed by cis-DDP. The complexation being dependent on the platinum/DNA ratio in solution. Along with the increase of platinum concentration, it forms first the complexes with phosphate groups, then with bases without destruction of the DNA secondary structure. The next type of complex formation is accompanied by the local destruction of the hydrogen bonds and stacking interactions. And when the Pt/DNA ratio grows high enough, DNA is denatured. It is suggested that the stability of the complex is provided by nitrogen groups of the bases incorporated in the platinum first coordination sphere. The phosphate DNA groups play the role of counterions in the external coordination sphere.
Subject(s)
Cisplatin/chemistry , DNA Adducts/chemistry , DNA/chemistry , Circular Dichroism , Nucleic Acid Conformation , Nucleic Acid Denaturation , SolutionsABSTRACT
The hydrodynamic and optical properties (intrinsic viscosity and optical anisotropy of DNA) have been studied at the high ionic strength mu greater than or equal to 1 M. It has been shown that the effective volume of DNA molecule doesn't depend of mu when mu greater than or equal to 1 M. In these conditions the electrostatical interactions in DNA disappear. But thermodynamic excluded volume effects do not depend on mu and play also an important role in this range of mu (mu greater than or equal to 1 M). It has been concluded that the condensation of DNA in solutions of high salt concentration is the result of local denaturation of DNA. It has been shown that the optical anisotropy of DNA increases drastically at mu congruent to 2 M but the persistence length of DNA does not change under these conditions.
Subject(s)
DNA/analysis , Mathematics , Models, Theoretical , Optics and Photonics , Osmolar Concentration , ViscosityABSTRACT
The interaction of DNA with divalent metal ions: Ba2+, Mg2+, Mn2+, Ni2+, Cu2+ in solutions at different ionic strengths mu was investigated. The combination of following methods: flow birefringence, viscometry, UV-spectroscopy and circular dichroism made possible to follow the state of the secondary and tertiary structure of the DNA molecule during its interaction with ions. The presence of divalent ions in solution affects the hydrodynamic properties of DNA only at low mu. At high mu the difference in the action of mono- and divalent ions disappears. The persistence length of DNA does not change during the experiment. It is shown that the Mg2+ and Ba2+ ions interact only with phosphate groups of DNA but Mn2+, Ni2+, Cu2+ ions interact also with the nitrogen bases of the macromolecule.
Subject(s)
Cations, Divalent/metabolism , DNA/metabolism , Metals/metabolism , Circular Dichroism , Nucleic Acid Conformation , Osmolar Concentration , Spectrophotometry, UltravioletABSTRACT
The hydrodynamical and optical properties of DNA were investigated in the wide-range of pH by the methods of streaming birefringence, viscometry and spectrophotometry for the different ionic strengths of environment. The measurements of the intrinsic viscosity as a function of pH allow us to determine the compactization of protonated DNA without the destruction of double-helical conformation. This transition is accompanied by a decrease in the optical anisotropy of DNA and the coefficient of molar extinction E260 (P). The increase of volume and persistence length of DNA was observed in the alkaline range of pH. Analyses of experimental data lead to an assumption that the predominant cause of these effects is the change of flexibility of DNA as a result of ionization of its bases. The data obtained were compared with those for polycationic molecules.
