[Effect of temperature on the acid-base equilibrium in a DNA molecule].

The influence of temperature on structural transitions in a protonated DNA molecule has been studied by means of circular dichroism (CD). The measurements were carried at continuos heating over a temperature range from 288 to 343 K at an average rate of (15-30) x 10(-4) K/sec. The objects were diluted DNA solutions (30.

[Polyelectrolyte invariance of the acid-base equilibrium in native DNA with varying GC-pair levels].

The influence of the ionic strength of solution on the protonation of the Micrococcus lysodeicticus DNA molecule was studied by means of circular dichroism, spectrophotometric and potentiometric titration in a wide range of the supporting electrolyte concentration ([NaCl] = 0.5-0.005 M).

[The effect of spermine on acid-base equilibrium in DNA molecule].

The influence of spermine (Sp) on the acid-induced predenaturational and denaturational transitions in the DNA molecule structure has been studied by means of circular dichroism, spectrophotometric and viscometric titration at supporting electrolyte concentration 10 mM NaCl. The data available indicate that at [N]/[P] less than or equal to 0.60 (here [N] and [P] are molar concentrations of Sp nitrogen and DNA phosphours, respectively) the cooperative structural B----B(+)----S transitions are accompanied by the DNA double-helice winding.

[Differential scattering of circularly polarized light in protonated DNA in the presence of spermine].

The protonation of the spermine containing calf thymus DNA (molecular mass 15 and 5 MDa) solutions has been studied by means of circular dichroism method. It has been shown that the acid-induced transition from the low-protonated B(+)-form to the double-stranded structure with presumably Hoogsteen complementation of syn-G.C-base-pairs (S-form) in case of high-molecular partially condensed DNA is accompanied by differential scattering of circularly polarized light (DSCPL).

[Binding of polyamines by the double-helical DNA molecule in unfolded and compact forms].

The influence of the natural polyamines [spermine (Sp) and spermidine (Spd)] on the conformation of thymus DNA molecule (M = 4 and 15 MDa) was studied by means of the viscometric method over the range of low supporting electrolyte concentrations (CNaCl = 0.6 divided by 8.4 mM).

[Effect of ionic strength of a solution on the protonation of DNA molecule].

The influence of the ionic strength of solution on the DNA molecule protonation was studied by means of circular dichroism (CD), spectrophotometric and potentiometric titration methods over a wide range of the supporting electrolyte concentrations [( NaCl] = 0.0005 divided by 4 M). Consideration of the obtained CD spectra shown that the acidation of the solution induces two cooperative structural transitions in the double stranded DNA molecule in the pre-denaturation pH region.

[Effect of solvent structure on amide reaction with native DNA molecules. II. Aqueous acetamide mixtures].

The influence of acetamide (AA) on the native DNA molecule conformation has been studied by methods of flow birefringence and viscometry. On one hand, it was shown that hydrodynamical and optical behaviour of the macromolecule at extremely low additions of AA is qualitatively the same as in the presence of nonelectrolytes which stabilize the water structure. On the other hand, the influence of intermediate and large AA concentrations on the native DNA molecule conformation is qualitatively the same as of corresponding urea concentrations, which is known to be a structure-breaker.

[Effect of solvent structure on amide reaction with native DNA molecules. I. Aqueous mixtures of N,N-dimethylformamide and urea].

The influence of N,N-dimethylformamid (DMF) and urea (U) on the conformation of the native DNA molecule has been studied by methods of flow birefringence and viscometry. The investigations have been performed over a wide range of amides and supporting electrolyte concentrations. An essentially different influence of small additions of DMF and U on the macromolecule's dimensions was observed.

[Influence of ionic strength on the thermodynamic rigidity of the native DNA molecule in aqueous and aqueous-organic solvents].

The analysis of experimental and theoretical data for the dependence of the thermodynamic rigidity of the native DNA molecule on the ionic strength of solution has been fulfilled. It has been shown that in aqueous-salt solutions of DNA the statistical segment length (A) of the DNA molecule remains constant over the range of intermediate ionic strengths (mu > 0.002) and considerably increases over the range of small mu < 0.

[Calculation of the intrinsic viscosity of synthetic and biological polyelectrolytes of various rigidity].

On the basis of the excluded-volume effect theory for nonionic polymer molecules developed by Alexandrowicz semi-empirical formulas for calculation of the intrinsic viscosity [eta] of polyelectrolytes of various rigidity are proposed. The expression for the second virial coefficient of gas consisting of cylindrical particles is used for the determination of explicit form of the effective excluded volume of the segment upsilon0. In addition the alteration of Flory's parameter phi (epsilon) by the expansion of a macromolecule, and the alteration of thermodynamic rigidity A of the polyelectrolyte molecule in the range of low ionic strengths mu have been taken into account.