[Study of DNA complexes with a synthetic fragment of histone H4 and polypeptide (Gly-Orn-Gly)n]. / Issledovanie kompleksov DNK s sinteticheskim fragmentom gistona H4 i polipeptidom (gly-Orn-Gly)n.

Complexes of DNA with synthetic N-terminal peptide of histone H4 (A-13) and with poly(Gly-Orn-Gly) in 0.015 M NaCl solution have been studied by means of viscometry, light scattering and circular dichroism. The process of intramolecular compactization begins to occur at a low content of poly(Gly-Orn-Gly) in complexes, while in the case of A-13 compactization takes place only when the content of A-13 in complexes attains 13--14%. Intermolecular aggregation of both complexes takes place with the increase of peptide content in the complexes. Intramolecular compactization and aggregation do not influence the local conformation of DNA as revealed by CD spectra. The possible mechanism of these peptide-DNA interactions suggested.

[Conformation of the denatured DNA molecule in solutions of different ionic strengths]. / Konformatsiia molekuly denaturirovannoi DNK v rastvorakh s raznoi ionnoi siloi.

The conformation of the denatured DNA molecule of different molecular weights in the solutions of various ionic composition was studied by the methods of viscometry, light scattering and flow birefringence. Formaldehyde purified from metallic ions with the help of ionites was used for fixation of the denatured state of the DNA molecule. It has been shown that theories developed for flexible macromolecules are in a sufficient accordance with hydrodynamical and optical data. The unperturbed dimensions, equilibrium rigidity of the macromolecule in solutions of different ionic strengths, mu, were determined. In the range of mu greater than or equal to 0.005 the length of Kuhn's segment (A) is equal to approximately 40 A and its value increases with an increase of mu. At mu 0.001 A approximately 60 A and mu 0.0005 A approximately 85 divided by 100 A. A relation between intrinsic viscosity and molecular weight of the denatured DNA molecule was established. Data on the flow birefringence in the solutions of the denatured DNA have shown that the sigh of optical anisotrophy of the macromolecule depends on the ionic strength. The observed dependency may be explained only by assuming that ionic strength influences the equilibrium orientation of nitrogen base planes with respect to the main chain of the macromolecule.