[Fungicidal properties of the nanosystems of silkworm (Bombyx mor) chitosan with copper ions].

The fungicidal activity of some chitosan samples and of its nanostructured systems with copper was studied. The samples of Bombyx mori chitosan and its nanostructured systems with copper were found to inhibit growth and development of phytopathogenic fungi Fusarium solani 169 and Verticillium dahlie 57. The growth inhibition zone was of considerable size (22 to 60 mm).

[Thermoadsorptive separation of DNA by size using a polymeric sorbent].

The article describes theoretical aspects of isolation and separation of DNA fragments by size using a polymeric sorbent. On this basis we presented a theoretical model of thermal desorption of DNA fragments of different length. Assuming that, under certain pH, interaction of DNA with the polymer sorbent is of an ion-dipole character and moving dipoles interact with the sorbent according to the Boltzmann distribution with the total charge of the DNA fragment in its pore, the expression for the interaction energy as a function of temperature is obtained. Equating the thermal energy to the interaction energy of the ion-dipole character, we have found the critical temperature of DNA separation from the sorbent. Account of the conformation of single-stranded DNA in the coil form leads to the dependence of DNA separation temperature, i.e., desorption, on the length of the DNA chain. The temperature for desorption increases symbatically to the contour length of DNA.

[Quantum theory of the hydrogen key in DNA].

A quantum theory of the redistribution of the hydrogen atom that links nucleotide bases between two DNA strands at the moment of its untwisting has been advanced, which is based on two tunneling mechanisms: the Andreev-Meierovich mechanism of tunneling with spontaneous emission of a phonon and the Kagan-Maksimov mechanism of tunneling during the scattering of the phonon. It was shown that the probability for the hydrogen atom to be in a foreign pit, i.e., in the mutated form, decreases as the rate of untwisting increases. According to the model, the probability of mutation smoothly increases with temperature to a value of 1/2.

Bionanocompositional chitosan-silica sorbent for liquid chromatography.

Preparation of hybrid nanocompositional chitosan/silica sorbent was carried out. It was shown that formation of gel in sol-gel process of hydrolytic polycondensation of tetraethoxysilane (TEOS) with including of chitosan consists of two stages. Suppression of crystallization of chitosan in obtained two-phase system and changes in IR spectra are evidenced of interactions between molecules of chitosan and silanol groups of silica network. The resulting hybrid chitosan/silica sorbent was tested by high-performance liquid chromatography (HPLC).

[Role of calcium ions in the development of the catalytic activity of phospholipase D]. / Rol' ionov kal'tsiia v proiavlenii kataliticheskoi aktivnosti fosfolipazy D.

The peculiarities of the reaction of mycellar lecithine cleavage by phospholipase D and the role of Ca2+ in the catalytic activity of the enzyme were studied. It was shown that Ca2+ participates in the formation of a catalytically active intermediary enzyme-substrate complex with a strict stoichiometric ratio of substrate, phospholipase activator (Na-DS) and Ca2+. The kinetics of inhibition for this reaction by lantane and fluoride ions and EDTA were studied. The inhibition of the reaction in a lecithine-Na-Ca2+-phospholipase D system by La3+ is due to substitution of bivalent Ca2+ by trivalent La3+ within the intermediary complex. The inhibiting effect of F- is due to penetration of the electron-negative ion into the coordination sphere of the intermediary complex and to disturbances in the hydrophobic binding between the ligands. The inhibitory action of EDTA is revealed during protein binding to the substrate and is not due to the chelating capacity of EDTA with respect to Ca2+. It was demonstrated that the role of Ca2+ is not restricted by its binding to phospholipase C. Ca2+ are also necessary for neutralization of the extra charge on the surface of substrate mycelles, production of an appropriate ionic strength and modification of the substrate phase surface at the interface. The catalytic function of Ca2+ consists in a formation of a "recognition" site in the active center of phospholipase D.

[The dependence of the effects of calcium ions on enzymatic hydrolysis of phospholipids on the physical state of the substrate]. / Vliianie ionov kal'tsiia na fermentativnyi gidroliz fosfolipidov v zavisimosti otfizicheskogo sostoianiia substrata.

The role of calcium ions in the phospholipid hydrolysis by phospholipase D was studied. It was shown that the enzyme does not split egg lecithine in the absence of Ca2+. In the presence of Ca2+ the reaction occurs via different routes, depending on the type of initiation of the reaction. The optimal concentrations of Ca2+ necessary for activation of phospholipase D are different in the systems activated by various treatments (organic solvents, detergents and solid adsorbents). Optimal concentrations of Ca2+ for the hydrolysis and methanolysis catalyzed by phospholipase D are also different. It was found that the need for Ca2+ and their optimal concentrations are determined by the state of phospholipids at the substrate phase. The data suggest that the enzymatic hydrolysis may occur in the absence of Ca2+. Thus, Ca2+-induced activation is merely an alternative pathway of catalytically active conformation of lypolytic enzymes.