Pycnometric, viscometric and calorimetric studies of the process to release the double-stranded DNA from the Un bacteriophage.

Knowledge of both the packaging of the linear, double-stranded (ds)DNA in bacteriophages and its subsequent release into the bacterial host is vital to our understanding of phage infection. There is now strong evidence that packaging requires a powerful rotary motor fuelled by ATP. From thermodynamic studies, however, it has been proposed that, at least for those viruses with a contractile tail, the dsDNA ejection from the phage head is a relatively simple physical process that does not require cellular energy and is facilitated by the difference in the conditions of the medium in the environments inside and outside the head. In this case, there should be no enthalpic effects associated with the dehiscence of the capsid and no destruction of it or the other structural elements of the phage. For the present study of temperature-induced phage dehiscence, we used a newly discovered phage with a contractile tail, named the Un (unknown) bacteriophage. Evidence is given of its characteristics in terms of ultrastructural morphology, serological parameters, host range and interaction with host cell. These show that, although it has similarities with the T-even phages and, in particular, the DDVI phage, it appears to be a new type. Earlier viscometric studies with it had shown that the temperature-induced release of the capsid dsDNA was completed at 70 degrees C. In the present investigation, a concentrated suspension of purified phage was subjected to pycnometric analysis through the temperature range of 30 to 70 degrees C. This showed that a significant and abrupt increase in the phage partial volume takes place, which remarkably is in the order of threefold. Viscometric measurements over time at 72 degrees C gave a kinetic curve from which evidence it was suggested that the temperature-induced DNA release is similar to a second order phase transition. At the same time, data from differential scanning calorimetry over the same temperature range showed no enthalpic effect. Our results indicate that the ejection of DNA from the capsid tail is driven by an entropy change.

[Microcalorimetric and electron spin resonance study of the influence of UV radiation on collagen].

It has been shown by microcalorimetry that UV-irradiation cardinally alters the temperature dependence of heat capacity of a collagen solution and decreases the enthalpy of collagen heat denaturation. By using the method of electron spin resonance (ESR), it was found that the primary products of UV-irradiated acid-soluble collagen are the atomic hydrogen and the anion radical of acetic acid. The latter, under the influence of long-wavelength UV light, is transformed into the methyl radical, which interacts with acetic acid to produce acetic acid radical. The above free radicals interact with the collagen molecule, as a result of which seven superfine components with the split of deltaH = 1.13 mT are obtained in the ESR spectrum. It is assumed that this spectrum is related to the free radical that occurred in the proline residue of the collagen molecule. In this particular case, this is a major structural defect in the triple helix of collagen, which results in instability of the macromolecule.

[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.

Liposome-DNA interaction: microcalorimetric study.

The authors applied differential scanning calorimetry (DSC) for studying the thermodynamic characteristics of DNA-liposome interactions. At the first stage, the melting curves of the 'order-disorder' thermal transition for lipid component and of the 'helix-coil' transition for DNA were obtained. At the second stage, the phase behavior of the DNA-lipid mixture as a function of both components (lipid/DNA ratio) was obtained. The liposome-DNA interaction was investigated comparing the melting curves of the pure components and the mixture.

[Cu(II) complexes with biomacromolecules. The use of Cu(II) ions as a structural spin label]. / Kompleksy Cu(II) s biomakromolekulami. Ispol'zovanie ionov Cu(II) v kachestve strukturnogo "spin-zonda".

Complexes of Cu(II) ions with globular proteins (human serum albumin, bovine serum albumin, egg albumin, lisozim and DNA) have been studied using the ESR method. It was shown that Cu(II) ions may be use as structural "spin-label" to study conformational dynamics of macromolecules, including structural transition in biopolymers.

[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.

[Aperiodic structures, fractals, and low temperature heat capacity of biological macromolecules]. / A periodicheskie struktury, fraktaly i nizkotemperaturnaia temploemkost' biologicheskikh makromolekul.

Low-molecular heat capacity of biological macromolecules has been analyzed in terms of modern conceptions of the physics of disordered systems and noncrystalline solids. It is shown that the fundamental thermodynamic features of these systems (amorphous and aperiodic structures, fractals polymers, etc.) are also inherent in biopolymers--proteins and nucleic acids, which gives a better insight into their structural-conformational and dynamic properties.

[Heat capacity of native DNA fibers at 2-25 K]. / Teploemkost' nativnykh volokon DNK pri temperaturakh 2-25 K.

The data on low-temperature heat capacity (2-25 K) of native DNA strands at different humidities are presented, which take into account the specificity of hydration of DNA due to its chemical composition (GC-content). The temperature dependence of DNA heat capacity (Cp = f(T)) at 2-4 K was analyzed. Analysis of Cp = f(T) involves both the ordinary Debay density and excessive low-energy density of oscillatory states (DOS) peculiar to noncrystalline solids. It is concluded that heat capacity of DNA at very energies (less than 1 K) is well described in terms of the generally accepted model of two-level systems. The nature of excessive DOS at energies 3-10 K is related to oscillatory excitations on structural inhomogeneities, which can represent clusters of hydrate water molecules (approximately 1-2 nm) "grown" in DNA matrix.

[Hydration and stability of the B-form of LiDNA]. / Gidratatsiia i stabil'nost' B-formy LiDNK.

Hydration and structure of Li DNA in films and solutions have been investigated by methods of IR spectroscopy, piezogravimentry, UHF dielectrometry, and microcalorimetry. The hydration energy and the water sorption range in which the DNA undergoes the transition from the unordered state to the B-form have been determined, making it possible to evaluate the contribution of water molecules of the DNA hydration shell to the total stabilization energy of the DNA helical structure.

[Appearance of fractal properties of globular proteins at low temperatures]. / Proiavlenie fraktal'nykh svoistv globuliarnykh belkov pri nizkikh temperaturakh.

The dependence on temperature of the heat capacity of cytochrome c has been measured in the range 4-40 K at various water content. The fractal (Hausdorff) dimension of the protein (D) has been determined and shown to depend on the rate of protein hydration (1.1 < D < 1.9). The intrinsic energy of the globule is a uniform function of the dimension of the order (D + 1).

[Difference in DNA enthalpies in the helical and coiled states near 0 K]. / Raznost' éntal'pii DNK v spiral'nom i klubkoobraznom sostoianiiakh vblizi 0 K.

On the basis of experimental data of DNA heat capacity in a wide range of temperatures the fundamental characteristics of DNA-H(0)0-the enthalpy of helix coil transition at 0(0)K were estimated. H(0)0 = 8.41 +/- 1.6 kJ/MBP. It was shown that a deviation from Nernst theorem (resulting from metastability of the system) was not obtained within the range of experimental error.

[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.

[A theoretical model of DNA packaging in the phage head]. / Teoreticheskaia model' upakovki DNK v golovke faga.

Statistical model of dsDNA packaging to icosahedral bacteriophage capsid is presented. The model describes intraphage DNA as a globule, i.e. intramolecular liquid crystal. We analyse the free energy of DNA, which has a globulized part inside the phage capsid and coil-like tail outside it. Conditions when processes of DNA movement into capsid or back are thermodynamically favorable are investigated. These processes are not accompanied with any thermal effects. It is not "all or none" type process, i.e. intermediate stable states are possible. The role of DNA interaction with the capsid inner wall is considered. The essential model abilities for qualitative explanation of experimental data are exhibited.

[Calorimetric study of aqueous solutions of histone H1 and poly-L-proline II at low temperatures]. / Kalorimetricheskoe issledovanie vodnykh rastvorov gistona H1 i poli-L-prolina II pri nizkikh temperaturakh.

Low temperature differential scanning microcalorimetric investigation of water-histone H1 and water-poly-L-proline investigation was carried out. The concentrational dependence of the thermodynamic parameters (delta H(C), Tmax(C), delta S(T, C] for "bulk" water layers were studied. It was shown that the influence of these macromolecules on the structure and properties of surrounding water layers at the same degree of hydration is different.

[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.

[Low-temperature heat capacity of DNA in various conformation states]. / Nizkotemperaturnaia teploemkost' DNK, nakhodiashcheisia v razlichnykh konformatsionnykh sostoianiiakh.

Experimental results are presented on temperature--dependent DNA heat capacity in three different states: a) intact--native DNA in the conformation of double helix, b) disordered conformation of polynucleotide chains in the state of statistical coils, c) completely "degenerated" polynucleotide chains--mechanical mixture of nucleotides. Data on heat capacity (4-400 K) at different water content in the specimens allow a definition of relative changes in the pattern of the entropy temperature dependence for these conformational states with the account for the structural effect of water.

[Study of dynamic properties of water in poly(A) and poly(U) solutions by proton magnetic resonance]. / Issledovanie dinamicheskikh svoistv vody v rastvorakh poli(A) i poli(U) metodom protonnogo magnitnogo rezonansa.

Proton magnetic relaxation in aqueous solutions of polyadenylic and polyuridylic acids in the temperature range (10-80 degrees C) and acidities (pH 3-9.7) has been investigated. Activation energies of water molecule diffusion and proton exchange, as well as the velocities of these processes have been determined. It is established that from the point of view of magnetic relaxation, the state of single helices resulted from the thermal conformation transition, are not equal to the state obtained by the change of the pH of solution; it refers both to the secondary structure of the chains and the dynamical behaviour of the biopolymer hydrate layers.

[Heat-capacity of DNA at low temperatures and varying humidities]. / Teploemkost' DNK pri nizkikh temperaturakh i razlichnykh vlazhnostiakh.

Adiabatic low temperature microcalorimeter working in a wide temperature range, including that of liquid helium, is described. Heat capacity of DNA at various water concentrations was measured at 4-400 degrees K. It is shown that the pattern of its change is determined by the hydration parameter n (number of water molecules per mole of base pairs). According to the experimental findings the DNA molecule can be modelled by a sufficiently rigid "thin rod" and the dynamic characteristics of the subject under study can be explained in terms of monomeric continuum model. When studying low temperature heat capacity of DNA, account should be taken of the double helic hydration depending on GC-content. Measurement of heat capacity of DNA in native and denaturated states in a wide temperature range (4-400 degrees K) taking into account specific hydration of double helix allows a correct description of its thermodynamic properties.