[Structure and stability of liposomes in complex with PEG-chitosan branched copolymer].

Liposomes are of great interest in biotechnology, as a drug delivery systems, due to their biocompatibility and low immunogenicity. However, low stability and tendency to aggregate still limits their application in medicine. Therefore, the actual problem is to obtain the effective stabilizing additives for the liposomes on the base of polymeric materials. In this paper we suggested to use the branched copolymers on the base of chitosan modified by polyethylene glycol (PEG-chitosan) as stabilizing additives for the liposomes. The method of copolymer synthesis of chitosan modified with PEG molecules by using mPEG-suc-NHS was developed and the PEG-chitosan copolymers of different modification degrees were obtained to investigate the influence of the complex formation of PEG-chitosan on the structure and stability of mixed anionic liposomes of dipalmitoylphosphatidylcholine (DPPC) and cardiolipin (CL) (80/20% w/w). It has been found by using FTIR spectroscopy and DLS methods that the PEG-chitosan co-polymers form a Complex of electrostatic nature by interaction with the anionic groups in liposomes. It was found that the main binding sites of the copolymer with liposomes are phosphate and carbonyl groups. Analysis of the IR spectra yields that the complex formation of liposomes with PEG-chitosan resulted to significant stabilization of liposomes against aggregation upon storage. This result is particularly important, taking into account the fact that the aggregation is one of the key factors limiting the use of liposomes in medicine. These results offer the prospect of the copolymer PEG-chitosan as an effective additive for stabilizing liposomes and hold promise for creating new drug delivery systems.

[Stabilization of alkaline proteinase and cellulases via complex formation with chitosan for use as detergent components].

An effective approach to the stabilization of hydrolytic enzymes (alkaline proteinase and cellulases) via the complex formation with chitosan for their further use as detergent components has been developed. Interaction with chitosan results in a 35-50% increase in the level of catalytic activity of the enzymes after incubation for 60 min under the conditions of detergent use (alkaline pH, increased temperature, the presence of anionic surfactants) as compared to the system in the absence of chitosan both due to the enzyme stabilization and the increase of the starting level of catalytic activity. A twofold decrease of the enzyme inactivation constant is observed under the aforementioned conditions in the case of alkaline proteinase. In the case of cellulase preparation, the method for the control of the concentration of the active enzyme in the system modeling synthetic detergents has been suggested. The method is based on the enzymatic destruction of the stabilizing agent, chitosan, by enzymes of the cellulase complex. The destruction of chitosan removed the stabilizing effect, thus resulting in the inactivation of cellulases. The developed approaches allow for the widening of the field of the possible application of enzymes as detergent components.

[The contents of ascorbic acid and its oxidized forms at the aging of red blood cells produced in conditions of the normal and intense of erythropoesis].

Levels of ascoroic acid, its oxidized forms, dehydroascorbic acid (DHA) and diketogulonic aci (DKGA), and the sum of all forms of ascorbic acid (SAA) were investigated in aging red blood cells produced under physiological and stress conditions (massive hemorrhage) Aging of red blood cells o intact animals is accompanied by accumulation of DKGA and decrease of AA, DHA and SAA concentrations. Comparison of these parameters between young and old red blood cells produced befor and after hemorrhage revealed decrease of AA concentration (52%) and accumulation of DKGA (27%) on the 7th day. On the 7th, 20th, 30th days after hemorrhage red blood cells are characterize by increased concentrations of DHA, DKGA, SAA with simultaneously decreased contents of the AA as compared with red blood cells of intact animals. Similar changes were the most pronounced o the 7th day; on the 20th day they decreased and on the 30th day they returned to control levels.

[The effect of hydrophobic surface properties of protein on its resistance to denaturation by organic solvents (using modified alpha-chymotrypsin as an example]. / Vliianie gidrofobnykh svoistv poverkhnosti belka na ego ustoichivost' k denaturatsii organicheskimi rastvoriteliami (na primere modifitsirovannogo alpha-khimotripsina).

Catalytic activity of covalently modified alpha-chymotrypsin in water/cosolvent solutions was investigated. The stability of chymotrypsin increases upon modification with hydrophilic reagents, such as glyceraldehyde, pyrometallic and succinic anhydrides, and glucosamine. Correlation was observed between the protein's stability in organic solvents and the degree of hydrophilization of the protein's surface. The protein is the more stable, the higher are the modification degree and the hydrophilicity of the modifying residue. At a certain critical hydrophilization degree of chymotrypsin a limit of stability is achieved. The stabilization effect can be accounted for by the fact that the interaction between water molecules on the surface and protein's functional groups become stronger in the hydrophilized protein.