[Conformation of a DNA molecule in water-salt solutions depends on the salt anion type]. / Konformatsiia molekuly DNK v vodno-solevykh rastvorakh zavisit ot tipa aniona soli.

The methods of viscosimetry and flow birefringence were used to study the effect of anions F-, Cl-, Br-, J-, NO3-, ClO4-, SCN-, CH3COO- on the dimensions and thermodynamic rigidity of the DNA molecule in solutions in a wide range of ionic strengths and at different temperatures. It was shown that the persistent lengtH of DNA is independent of the anion type at all values of ionic strength, and the changes in its dimensions, which are determined from the changes in intrinsic viscosity, are due to the influence of anions and their hydration on long-range interactions in the macromolecule. Possible reasons for this phenomena and the role of structural changes in water upon hydration of anions are discussed.

[Effect of monovalent anions of various nature on conformation of DNA molecules in a water-salt solution]. / Vliianie odnozariadnykh anionov razlichnoi prirody na konformatsiiu molekuly DNK v vodno-solevykh rastvorakh.

Methods of intrinsic viscosity [eta] and beam flow birefringence were used to study the effects of some single-charged ions (F-, Cl-, Br-, J-, NO2-, NO3-, ClO4-, SCN-, CH3COO-) on the size and thermodynamic rigidity of DNA molecule in aqueous solutions of sodium salts in a broad interval of ionic strength mu when temperature T is changed. It has been shown that the close interactions in a macromolecule and the resulting persistent length a of DNA are independent of the type of the salt anion over the whole interval of mu. On the contrary, specific volume of DNA molecule in solution, proportional to [eta] value, is quite sensitive to the anionic composition of a solvent which is due to the effect of anions and their hydration on the remote interactions in the macromolecule. The presence of polyatomic and halide anions is manifested differently in the [eta] value of DNA. Possible factors responsible for the observed effect and the role of structural alterations of water upon anion hydration are discussed.

[Study of the effect of halogen series anions on DNA molecular conformation in solution]. / Issledovaniia vliianiia anionov galogenovogo riada na konformatsiiu molekuly DNK v rastvore.

Effect of halogen-series anions (F-, Cl-, Br-, I-) in sodium, potassium and ammonium halogide solutions with ionic strengths of mu = 0.1, 0.01, and 0.005 M on the dimensions and thermodynamic rigidity of the DNA molecule in solution was studied by viscosimetry and flow birefrigence. Flow birefrigence measurements showed that close-range interactions along the macromolecular chain and accordingly the persistent length of DNA did not change with a change of anion. However, the specific volume of the molecule depends on the anion type. In our opinion, the observed effect is connected with the different ability of anions to "neutralize" the cation screening effect on DNA phosphates.

[Effect of temperature on the conformation of native DNA in aqueous solutions of various electrolytes]. / Vliianie temperatury na konformatsiiu molekuly nativnoi DNK v vodnykh rastvorakh razlichnykh élektrolitov.

Effect of the temperature on the conformation of the native DNA molecule in solution of different electrolytes (LiCl, NaCl, KCl, CsCl, Gu-HCl) at ionic strengths mu = 5; 0.1; 0.01; 0.005 and temperatures ranging from 10 to 40 degrees C were studied by the methods of flow birefringence and viscometry. The experiments showed that the value of intrinsic viscosity [eta] of DNA increases at increase of temperatures in solutions of all the chlorides studied, excluding guanidine. The effect of temperature on the value of [eta] doesn't depend on the type of the cation at a fixed value of mu and is elevated when mu decreases. The observed alterations of the value of [eta] for DNA in water-salt solutions at different temperatures can be explained by an increase in the hydration of the alkaline ions at temperature increase. The experiments showed the specificity of the effect of different ions on the dimensions of the DNA molecule in solution. The data on optical anisotropy of the DNA molecule testify, that the thermodynamic rigidity of the latter doesn't depend on the temperature of solutions of different electrolytes in the temperature range studied.

[Optical and hydrodynamic properties of DNA complexes with histones H1 from the calf thymus and sea urchin sperm]. / Issledovanie opticheskikh i gidrodinamicheskikh svo'istv kompleksov DNK s gistonami H1 is timusa telenka i spermiev morskogo ezha.

A comparative study of the complexes between DNA and H1 histones from calf thymus (H1-T) and sea urchin sperm (H1-S) has been performed using methods of flow birefringence, viscometry and circular dichroism (CD). Both nucleohistone complexes undergo a conformational transition with the increase of protein content. A two-fold drop of intrinsic viscosity was observed when the histone content in the complex increased up to 9-12%. The transition is not accompanied by essential changes in the nucleohistone anisotropy, the latter coincides with the anisotropy of DNA in H1-T containing complexes and is close to that in H1-S containing complexes. CD spectra of the two types of complexes are not the same. For the H1-S containing complexes the decrease of the amplitude of the CD positive band and the shift of its maximum to the longwave region are observed while the spectrum of H1-T containing complex coincides with that of DNA. The spectral changes are partly due to slight aggregation of the H1-S containing complexes. It is also possible that changes in the local structure of DNA within the H1-S containing nucleohistone complexes take place.

[Investigation of DNA complexes with histones F3 and F3+F2a2]. / Issledovanie kompleksov DNK s gistonami F3 i F3+F2A2.

Characteristic viscosity, sedimentation constant and optical anisotropy were studied of the complexes formed between DNA and histone fractions F3 and F3+F2a2. The parameters mentioned continuously change with the increase of protein content within the complex. Analysis of experimental data shows that binding of a histone bads to a decrease of size and thermodynamic rigidity of the DNA molecule. On the basis of results obtained a model of F3 histone binding with DNA is suggested, amino acid sequence of this protein being taken into account. Comparison of behaviour of nucleohistones DNA+F3 and DNA+F1 studied previously testifies different way of binding of these histones to DNA.