[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.

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.

[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.