[Surface active properties of isobornylphenols in systems with different degrees of complexity].

Interrelations between the structure of the semi-synthetic phenolic antioxidants -- isobornylphenols and their surface active properties were studied in the chemical (the lecithin aggregation in hexane) and biological (the incubation with the blood erythrocytes) model systems. It has been shown that all studied compounds are able to affect the lecithin aggregation in hexane: the share of the main fraction of the L micelles decreases with increasing the share of particles of greater size. The effect substantially depends on hindered OH group and the presence of the intramolecular hydrogen bond in molecule. The cytotoxic properties of isobornylphenols (the concentration is 100 M) are predominantly due to the molecule structure. The interrelation between the aggregate size of the main fraction of L in the presence of the studied compounds and the discocyte share during mice blood erythrocyte incubation in their presence for 4 h is revealed. Thus, this provides the possibility to assume that the ability of the different biological active substances to affect the lecithin aggregation in non-polar solvent could be used as a model system for the initial assessment of their surface active properties.

Porous materials from titanium-cobalt alloys for hybrid implants.

We proposed a new method to increase the biocompatibility of porous materials that were synthesized from titanium and cobalt allows by the method of self-propagating high-temperature synthesis. This method suggested the introduction of calcium hydroxyapatite into the reaction mixture. Administration of calcium hydroxyapatite into the reaction mixture had a modifying effect on the structure and surface of the pore space and biocompatibility of composite materials. Administration of calcium hydroxyapatite crystals was followed by a significant decrease in the size of pores and appearance of water-soluble fractions, which inhibited the activity of cells. However, treatment with amorphous nanodispersed calcium hydroxyapatite increased the biocompatibility and adhesiveness of materials for mesenchymal stem cells. The pore space and mechanical characteristics of materials obtained with amorphous nanodispersed calcium hydroxyapatite were similar to the properties of natural bone. Moreover, these materials surpassed titanium-cobalt allows in biocompatibility. Our results indicate that the introduction of amorphous nanodispersed calcium hydroxyapatite into the reaction mixture during self-propagating high-temperature synthesis has a modifying effect on the pore space of composite materials and increases their biocompatibility and adhesiveness for cells. We conclude that these materials may be used as a carrier of stem cells and progenitor cells in hybrid implants.

Plant protein interactions with polysaccharides and their influence on legume protein functionality. A review.

Associative interactions between proteins and polysaccharides, both coulombic and non-coulombic, lead to the formation of interpolymer complexes. Complex formation with charged polysaccharides, either anionic or cationic, imparts solubility to seed globulins in the vicinity of their isoelectric points. This has been shown for the complexes "sunflower 11 S globulin (helianthinin)--sodium alginate" and "faba bean legumin (or the product of its limited proteolysis with trypsin--legumin-T)--chitosan". Hysteresis effects allow to control the solubility of seed globulins in weakly acid or weakly basic media. Formation of soluble complexes of faba bean legumin or legumin-T with chitosan substantially increases the emulsion stability of the both proteins.

[Thermodynamic approach to the selection of polyuronide sequestrants for protection of the human body from toxic metal ions. Interactions of polyuronides with lead ions]. / Termodinamicheskii podkhod k vyboru poliuronidnykh kompleksoobrazovatelei dlia zashchity organizma cheloveka ot toksichnykh ionov metallov. Vzaimodeistvie poliuronidov s ionami svintsa.

Binding isotherms of Pb2+ ions with potassium pectate and potassium alginate with relatively low content of blocks of L-guluronic residues (20%) have been determined. Interactions of Pb2+ ions with polyuronides studied is cooperative. Maximum values of binding constants are an order of magnitude higher than previously determined ones for Ca2+ and Sr2+ ions. Along with ion-coordination ("stoichiometric") interactions, alginate is typified by so-called extra-stoichiometric binding of Pb2+ ions, which presumably proceeds by a coprecipitation mechanism. Limitations of the thermodynamic approach to the selection of sequestrants for human body protection from toxic metal ions are discussed.

[Thermodynamic approach to the selection of polyuronide sequestrants for the protection of the human body from toxic metal ions. Interactions of polyuronides with strontium and calcium ions]. / Termodinamicheskii podkhod k vyboru poliuronidnykh kompleksoobrazovatelei dlia zashchity organizma cheloveka ot toksichnykh ionov metallov. Vzaimodeistvie poliuronidov s ionami strontsiia i kal'tsiia.

Selectivity of polyuronide sequestrants (pectate, alginates of various uronide composition) in respect to Sr2+ and Ca2+ ions has been evaluated in terms of thermodynamic affinity. It is suggested that there is no point in the use of pectate as a Sr(2+)-binding agent because at initial stages of reaction it reveals higher affinity to Ca2+ ions in comparison to Sr2+ ions. Contrary to pectate, alginates under similar conditions have higher affinity to Sr2+ ions. It is shown that these ions are bound only by blocks of L-guluronic acid residues in alginate macromolecules. The results obtained lend support to the advisability of the use of alginate preparations with the high content of L-guluronic acid residues for the excretion of Sr2+ ions from human body.

Interactions of flavor compounds with pectic substances.

Investigation has been conducted using equilibrium dialysis on the sorption of flavor compounds (FC) in solutions of low- and high-esterified pectinates (LEP and HEP, respectively). The compounds include 2-acetyl pyridine, 2,3-diethyl pyrazine, 2-acetyl thiophene and some normal 2-ketones. A method of direct gas chromatographic analysis has been developed for the determination of the FC in aqueous solutions at concentrations as low as 10(-3)% v/v. Additional information was obtained by the analysis of circular dichroism (CD) and apparent molar heat capacity. The results indicate: (1) In LEP solutions, sorption of normal aliphatic 2-ketones with chain length greater than C6 presumably proceeds via van der Waals interactions between alkyl groups of the 2-ketone and hydrophobic regions of the pectinate. The sorption increases with increased alkyl chain length. The Gibbs energy of the methylene group transferring from the solvent to the LEP solution is found to be 1.8 kJ/mol for 2-ketones at C7-C9. (2) In acidic media, binding of heterocyclic FC with pectinates mostly proceeds via hydrogen bonding involving the hydrogen atoms in undissociated carboxyl groups in the pectinate macromolecules. It can also be affected by the self-association of the pectinate macromolecules, depending on pH and pectinate concentration. (3) Under neutral conditions, the presence of Mg2+, Ca2 and Zn2+ ions or the formation of the calcium-pectinate gel network has little effect on the sorption of 2-ketones with the LEP. However, in acidic media, metal ions inhibit the sorption of FC through hydrogen bonding. The sorption of 2-octanone in acidic media depends extremely on Ca++ concentration by the correlationship with changes in the structure of LEP solutions in terms of apparent molar heat capacity.

Thermodynamic approach to the selection of polyuronide sequestrants for preventive and medicinal nutrition.

An approach to the analysis of isotherms of cooperative binding is developed that allows to calculate approximately affinity profiles, i.e. dependencies of binding constants on binding densities. The comparison of the affinity profiles of the interactions of Ca2+ and Sr2+ ions with sodium pectate as well as sodium alginates with the different content of the blocks of alpha-L-guluronic acid residues (GG-blocks) and blocks of mixed composition showed that (1) pectate has higher affinity to both ions as compared with alginates; (2) the affinity of pectate to Ca2+ ions is comparable to its affinity to Sr2+ ions but in the case of Ca2+ ions the maximum of the affinity profile falls on the substantially lesser value of the binding density in comparison to Sr2+ ions that seems to be unfavorable from the standpoint of the use of this polyuronide in preventive or medicinal nutrition; (3) the affinity of both alginates to Sr2+ ions at relatively low binding densities exceeds their affinity to Ca2+ ions; (4) the affinity of alginates to Sr2+ ions increases with the increase in the content of GG-blocks, whereas the affinity to Ca2+ ions practically does not depend on the composition of the alginate; (5) the maximum binding density of Sr2+ ions to the alginates approximately corresponds to the content of GG-blocks. These results corroborate the practice of the use of alginates rich in residues of alpha-L-guluronic acid for the removal of radioactive strontium from the digestive tract. The binding constants of Pb2+ ions to pectate over a wide range of binding densities are more than an order of magnitude greater than those of alkali-earth metal ions.

[Electron microscopic study of pectin solutions]. / Elektronno-mikroskopicheskoe issledovanie rastvorov pektina.

Electron microscopic study was carried out of the structure of pectin 0.01% aqueous solutions according to esterification degree at different pH medium. Preparations were prepared by freezing-drying method of solution drop on the formvar film and by the negative contrasting method. Microfibrils of 60-180 A diameter were found. Their aggregation increased with a decrease of the charge of pectin macromolecule (increase of esterification, decrease of pH).