[A viscosimetric study of thermally induced release of ds-DNA from Un phage]. / Viskozimetricheskoe issledovanie ternoindutsirovannogo vysvobozhdeniia ds-DNA iz Un phage.

The thermally induced ejection of DNA from the head of the Un phage was studied by viscosimetry, pH was used as a variable external factor. The results obtained suggest that the infection of the bacterium by the phage occurs in the pH range 6-10 rather than in the acidic medium (pH 4-5) because the infection can take place only if the DNA is completely ejected from the phage head. It was shown that the ejection of DNA upon dilution of the initial concentration of the phage depends on the time required for the equilibrium of the phage suspension in the corresponding buffer solution to be established after which the measurements can be performed. In our experiments, this time interval was 24 h.

[Denaturation increment of heat capacity in diluted aqueous solutions of collagen]. / Denaturatsionnyi inkrement teploemkosti v razbavlennykh vodnykh rastvorakh kollagena.

The experimental values of the denaturation increment of collagen heat capacity in diluted aqueous solutions, obtained at different scanning rates, are presented. It is shown that the dependences of the "equilibrium" enthalpy and entropy of collagen denaturation on denaturation-induced variation in heat capacity do not obey the empiric law of the linear correlation of the thermodynamic parameters of denaturation at 25 degrees C for globular proteins, indicating that the stabilization of the triple collagen helix proceeds by a special mechanism with the participation of water molecules.

[Heat capacity of DNA in native and denatured states]. / Teploemkost' DNK v nativnom i denaturirovannom sostoianiiakh.

Heat capacity of DNA in native and denatured states was estimated by the method of microcalorimetry. This value was shown to depend on the transition temperature and is determined by an increase of the number of oscillative freedom degrees of the polynucleotide chains in the state of statistical coils, and by hydrophobic effects and by "the melting of water ridge" located in native DNA in the B-form.

[Energy of cooperative transitions in bacteriophage SD]. / Energetika kooperativnykh perekhodov v bakteriofage SD.

Heat denaturation of native phages SD suspensions, phage "shadows", and isolated phage DNA solutions were studied by scanning microcalorimetry and viscosimetry. Energetic parameters of cooperative transitions of protein fraction and DNA were measured. DNA melting was shown to be preceded by the destruction of capsid and protein denaturation. The melting curve of isolated DNA and DNA in the presence of protein component is characterized by a fine structure which is completely restored at repeated denaturation only in the presence of the protein component. "Creeping" of DNA out of the capsid in heated suspensions at 50-52 degrees C was shown to proceed with "zero" enthalpy without significant endo- and exo-thermal effects. No change of specific heat capacity of the suspension was also observed. It is emphasized that the mechanism of DNA going out of the capsid can be understood by studying DNA hydration inside the phage and its change in the course of liberation of the phage genome from the protein capsid.

[Study of the hydrodynamic properties of solutions of T2 phage DNA using a rotation viscosimeter]. / Issledovanie gidrodinamicheskikh svoistv rastvorov DNK faga T2 s pomoshch'iu rotatsionnogo viskozimetra.

Viscosity of DNA solutions of phage T2 at different rate gradients was investigated in relation to ionic strength and solution temperature. Measurements were performed by means of rotation viscosimeter with a magnetic support of the rotor. The slope of gradient relationship was shown to increase with a decrease of ionic strength of DNA solution. A significant temperature relationship of solution viscosity at T less than Tm was observed. A slope of the curves eta sp = f (T) depends on DNA concentration in solution. It was shown that in the presence of Cu+2 or Mg+2 ions at a cyclic change of temperature a small irreversible change of DNA solution viscosity was observed.