Heat capacities of aqueous solutions of amino acid and dipeptide derivatives of fullerene

The concentration dependences of heat capacities of aqueous solutions of several amino acid and peptide derivatives of fullerene were measured by scanning differential calorimetry at 298 K. The heat capacities for the arginine, alanylalanine, and glycylvaline derivatives dissolved in water depend slightly on concentration. The concentration dependences of the heat capacities of aqueous solutions of the serine and alanine derivatives display extrema. The calculated contributions of hydration to the heat capacities of the dissolved fullerene derivatives have both positive and negative signs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2202–2204, November, 1998.     

Adsorption at the air-water interface and emulsification properties of grain legume protein derivatives from pea and broad bean

Functional properties of native and modified (through induced autolysis) pea (Pisum sativum L.) and broad bean (Vicia faba L.) protein derivatives are studied. In specific, protein solubility and behavior at the air–water interface through surface pressure measurements are investigated. Furthermore the ability of the protein products to act as emulsifying agents and to stabilize emulsions is studied through oil droplet size distribution measurements and by the protein adsorbed at the oil–water interface. The data reveal that the ability of the proteins to act as surfactants and build up a rigid film around the oil droplets, mainly depends on their suitable molecular configuration and structure. Hydrolysis did not promote the functionality of the legume proteins. Broad bean exhibited better functionality than pea, before and after hydrolysis. Some comparisons were also made with lupin (Lupinus albus L.) protein isolate.     

Conformational transition and aggregation of ϰ-carrageenan macromolecules in solution

Summary Consideration has been given to the processes of conformational transition and aggregation in the aqueous solutions of -carrageenan depending on its concentration, the temperature of the system as a whole and the content of the potassium ions by the methods of polarimetry and spectroturbidimetry. It has been established that one and the same degree of mutarotation can be attained on variation of the concentration of both -carrageenan and potassium ions. The aggregation of the -carrageenan macromolecules occurs under the action of the potasssium ions and is independent of temperature.With 8 figures and 1 table     

PROTEINS AND ANIONIC POLYSACCHARIDES AS STABILIZERS OP 0/W EMULSIONS

The possibilities of stabilizing emulsions by means of proteins and polysaccharides have been discussed. It is shown that the use of anionic polysaccharides makes it possible to increase considerably the stability of protein-containing emulsions. The developed methods of stabilizing emulsions by means of anionic polysaccharides are protein-universal and useful for the preparation of emulsions based on phases of different polarity. The use of these methods allows to avoid the use of low-molecular surfactants for the preparation of protein-containing C/W emulsions.     

Boundary conditions for ionotropic gelation of polyuronides

The determination of reagent concentrations sufficient for gelation in the course of a crosslinking reaction in solution enables characterization of macromolecular coil dimensions as a function of solvent quality and calculation of the apparent equilibrium constant and the reaction order with respect to polymer. Interactions of polyuronides with polycoordinative metal ions are discussed.     

Interaction of sodium and potassium ions withκ-carrageenan

Summary NMR and potentiometric methods revealed at least two types of interactions of Na⁺ and K⁺ ions with -carrageenan, viz., Coulombic interaction with polysaccharide sulfate groups, and a coordination one, leading, in the case of the Na⁺ ions, to formation of nonstoichiometric complexes. The absence of any correlation between the coordination binding density of the cations and their promoting effect on gelation process was demonstrated.     

Studies on the mechanisms of gelation of kappa-carrageenan and agarose

It has been established that hydrogen bonds control both gelation and helix formation completely in the case of agarose and partially in the case of kappa-carrageenan, the major role belonging in the latter case to the interactions of a polysaccharide with metal ions. Na⁺ and K⁺ ions form contact ion pairs with sulphate groups of kappa-carrageenan. It is supposed that an increase in the number of contact ion pairs together with association of macromolecules having unordered conformation, a decrease in the second virial coefficient, and a decrease in the refraction index increment (i.e., an increase in the solvation degree of dissolved particles) is a necessary condition for forming the kappa-carrageenan gel netwórk. A sufficient condition of kappa-carrageenan gelation is the intermolecular coordination binding of ions such as K⁺ ions, promoting gelation. The coil-to-helix transition of the polysaccharide is controlled by shielding the charge of kappa-carrageenan-sulphate groups. Hydrophobic interactions proved to be unessential for gelation of either agarose or kappa-carrageenan.     

Formation and structure of anisotropic gels III.: Electron-microscopic investigation of the formation process of calcium alginate laminated gels

Summary Formation of calcium alginate laminated gels proceeds at least in two stages: at first a reticular structure is formed that then transforms into a compact structure, the transition rate decreasing with the increase of alginate concentration. The fibrillar nature of the reticular structure is confirmed by freeze-drying studies.With 4 figures     

Creep study of high-esterified pectin gels.

Summary A creep study has been made of pectin gels concentrated to 0.5–2.5% in the temperature interval 25 to 50°C. In the region of linear viscoelasticity the pectin gels are capable of being strained both reversibly and irreversibly. The shape of the reversible strain relaxation curves corresponds to the transition region between the glassy and highly elastic states. The temperature dependence of the largest Newtonian viscosity is described by de Guzmán-Arrhenius equation. The break-down enthalpy of the gel cross-links is between 51 and 74 kJ/mole, showing an increase with concentration.With 10 figures and 1 table