G. P. Yampol'skaya

Trends in the synthesis of metal oxide nanoparticles through reverse microemulsions in hydrocarbon media.

In recent years, more and more attention is given to production and use of nanoparticles dispersed in hydrocarbon medium and synthesized in reverse microemulsions. In this article the data and research results on synthesis of inorganic nanoparticles in reverse microemulsions are summarized. The major attention is paid to thermochemical approach for nanoparticle synthesis in reverse microemulsions with precursors of Мо, Al, Ni, Co and Fe oxides being active components of the catalysts for petroleum chemistry and refinery. A high efficiency of native crude oil surfactants for the production of catalyst nanoparticles in reverse microemulsions has been found.

Development of the Rehbinder’s concept on structure-mechanical barrier in stability of dispersions stabilized with proteins

Abstract The structure-mechanical barrier as the factor of dispersions stability was introduced by academician Rehbinder. Peculiarities of the display of structure mechanical barrier in stability of foams and emulsions and, respectively, thin liquid films, when protein interfacial layers with specific rheological behaviour (especially, elasticity) are formed at surfaces, are considered to deeper insight the Rehbinder’s concept. Proteins are surface active substances with surface activity determined by details of their molecular structure. Adsorption of proteins at interfaces leads to the formation of quasi-two-dimensional solid-like structures, correlating, in these conditions, with infinite rise in dispersion stability. The quantitative judgement on structure mechanical barrier was obtained as the evaluation of the energies (forces) balance of molecular attraction and repulsion of elastic origin. Lifetime of dispersions is determined as the rupture probability of thin liquid films and stabilizing interfacial layers. The contribution of failure of protein adsorption layers in coalescence processes is analyzed. Kinetic parameters of drops coalescence in emulsions and individual drops at the flat interface of a macroscopic liquid phase allow to distinguish the systems stable due to Rehbinder’s structure mechanical barrier from unstable dispersions. Experimental results for fluid interfaces together with published data on repulsion between solid surfaces coated with protein on distances of twice the thickness of the protein adsorption layer, corroborate the universal character of structure mechanical barrier.

Rheological parameters of protein interfacial layers as a criterion of the transition from stable emulsions to microemulsions

Proteins are considered as surface active substances. On the basis of experimentally measured rheological parameters of interfacial layers, protein accumulation at an interface between two immiscible liquids, isotherms of interfacial tension, accounting theoretical ideas elaborated for multicomponent systems, the formation of interfacial layers was referred to phase transition. The property of proteins to stabilise emulsions supposedly is connected with the formation of middle phases of lamellar structure. The correlation between elastic properties of interfacial layers and a phase transition of the middle phase upon addition of salts or lipids has been shown. Lipids being added as cosurfactants lead to the transition from lamellar to other structures, which does not provide emulsion stabilisation.

Properties of Interfacial Layers in Multicomponent Systems Containing Gelatin

The review is devoted to the analysis of the effect of the addition of various surfactants on the composition, structure, and the properties of the interfacial adsorption layers (IALs) formed at equilibrium in the aqueous gelatin solution–hydrocarbon system. Associates of variable compositions that are determined by the component ratio and the concentration of added surfactant are formed due to the interaction between gelatin and surfactant. The formation of associates is equivalent to the modification of gelatin. The properties of the IALs of modified gelatins are discussed on the basis of our own results and published data on the interfacial tension, the mass accumulation of surface-active components at the interfaces during the IAL formation, the IAL rheological properties and the stability of emulsion films varied with the conditions of IAL formation (the nature of low-molecular-weight surfactant, component concentrations, pH of aqueous phase, and temperature). It was concluded that modified gelatins can be considered as new surfactants governing the dynamics of the formation and fracture mechanism of the IALs and the stability of emulsion films. The properties of the IALs of modified gelatins are compared with those of IALs formed by gelatin and low-molecular-weight surfactants under the conditions when associates are formed directly at the interface due to the use of oil-soluble surfactants.

Properties of Spreaded Collagen I Monolayers on the Surface of Aqueous tert-Butanol and n-Hexanol Solutions

Properties of the monolayers of collagen isolated from the sclera of pigs eye are studied at the air–water interface with increasing tert-butanol or n-hexanol concentrations in a subphase. In the case of aqueous n-hexanol solutions, its adsorption on the subphase surface results in the formation of mixed monolayer whose properties depend on n-hexanol concentration in the subphase and the ratio between the number of alcohol and collagen molecules in the monolayer. At higher n-hexanol surface concentration, the phase separation of the monolayer into the domains of the condensed phase of alcohol and fibrous collagen occurs. A decrease in water activity in the presence of tert-butanol leads to a drastic reduction of collagen surface activity. This effect can be explained by both the constrained collagen spreading on the surface of tert-BuOH solutions and adsorption of alcohol molecules on collagen resulting in macromolecule hydrophilization. Alcohol critical concentrations are disclosed above which collagen monolayers are not formed.

Collagen Denaturation in Spread Monolayers at the Air-Water Interface: Experiments and a Possible Model of the Process

Spread monolayers of the fibril protein collagen were studied at the air-water interface in the presence of denaturants, urea and thiourea. The most prominent feature of spread collagen monolayers at the air-water interface is the ability to form supramolecular structures (fibrils), which themselves can form monolayers with collapse points of their own. The surface pressure isotherms of collagen monolayers have two “quasi-linear” centers, which are separated by a plateau and correspond to liquid-expanded and liquid-condensed states; this unique capability makes collagen different from other proteins. When in monolayer, collagen acquires the same level of structural organization as in the bulk. In the presence of denaturants, subphase characteristics of collagen monolayers change rapidly and irreversibly. Thiourea exerts more pronounced denaturing action on collagen monolayers than urea; this effect increases with exposure time and denaturant concentration. A hypothetical mechanism of thiourea-induced denaturation of fibril proteins is proposed according to which interactions between hydrophobic C=S groups of thiourea and nonpolar surface groups of the protein lead to reorientation of carbonyl groups to formation of intrinsic hydrogen bonds with NH2-groups of thiourea eventually resulting in the rupture of intrinsic hydrogen bonds and denaturation of the protein.

Monolayer Parameters of Gelatin Chemically Modified with N-Hydroxysuccinimide Ester of Caprylic Acid

The behavior of gelatin chemically modified with N-hydroxysuccinimide ester of caprylic acid at the aqueous (NH4)2SO4 solution–air interface is studied. The compression isotherms of gelatin monolayers whose pattern is dependent on the degree of gelatin modification are obtained. It is established that the area corresponding to the beginning of isotherm rise, two-dimensional pressure of completely compressed monolayer, and the modulus of monolayer surface elasticity increase with the degree of gelatin hydrophobization. The surface (“adsorption”) activity of gelatin with the modification degree of 85% is approximately threefold higher than for the initial gelatin.

Colloid-chemical aspects of protein crystallization

Problems and prospects of the crystallization of water-soluble and membrane proteins are discussed. The main focus is on colloid-chemical aspects of crystallization processes and the use of surfactants and various structured dispersions (surfactant-based gels and lyotropic phases). Advantages of the protein crystallization on solid supports of different nature, including biopolymer supports, are considered. Apparently, we are witnesses to the rise of a new field, nanocrystallography, dealing with the determination of protein structures from the investigation of nanocrystals.

Physico-Chemical Background of the Foaming Protein Separation for Waste Minimization

In the modern society a great amount of food, water, fuel etc. flows into human dwellings from outer environmental and in the form of waste is discarded to the outer environmental again. Among these substances water is consumed in largest amount in cities. The modern period based upon the rapid volume transportation with a large scale simple production way is about to be ended by environmental restrictions. It can be concluded, that all water systems are now in crisis.

Influence of the Molecular‐Mass Distribution of Gelatins Modified with a LIKI‐1 Tanning Agent on the Rheological Parameters of Interphase Adsorption Layers at the Interfase of an Aqueous Solution of Gelatin–Metaxylene

The influence of the interaction of gelatin with a protected formaldehyde tanning agent on the rheological parameters of interphase adsorption layers formed at the interface of a 0.1% aqueous solution of gelatin–metaxylene has been investigated as a function of the mass‐molecular distribution of initial gelatins. It has been shown that the chemical modification of gelatin with tanning agents weakens the process of gel formation in the interphase layer directly with the depth of the tanning process. This dependence is the most pronounced for gelatin with a high content of fractions with a molecular mass of more than 285 kDa.