Solubility in the water-Catamine AB-(alkali metal or ammonium chloride) systems

Solubility in ternary aqueous stratifying systems containing Catamine AB (alkylbenzyldimethylammonium chloride [C _n H_{2n + 1}N⁺(CH₃)₂CH₂C₆H₅] · Cl, a cationic surfactant, where n = 10–18) and LiCl, NaCl, KCl, and NH₄Cl inorganic salts was studied for the first time at 25°C. The boundaries of two-phase liquid equilibrium fields were determined. The studied stratifying systems were proposed for use in the liquid extraction of metal ions.     

Regulation of Catalytic Activity of Recombinant L-Asparaginase from <Emphasis Type="Italic">Rhodospirillum rubrum</Emphasis> by Conjugation with a PEG-Chitosan Copolymer

A new approach for the regulation of catalytic properties of the medically significant enzyme L-asparaginase is suggested based on the formation of conjugates with PEG-chitosan (chitoPEGylation). The efficiency of this approach is demonstrated using recombinant L-asparaginase from Rhodospirillum rubrum (RrA). This preparation is immunologically different from the one used in medical practice preparations of L-asparaginase from E. coli, which offers a promising alternative for applications in the case of hypersentsitivity development. The low level of activity of RrA towards L-glutamine, which decreases significantly the chance of side effects developing, is an advantage of RrA. The technique for the synthesis of the RrA conjugates with PEG-chitosan (chitoPEGylation) of a varying modification degree is developed. It is established that conjugation of RrA with PEG-chitosan increased the specific activity of the enzyme in comparison with the native one. The activity changes from 56 IU/mg (for the native enzyme) to 61–72 IU/mg (for the conjugates) depending on the degree of chitosan PEGylation. The secondary structure of the Rhodospirillum rubrum asparaginase conjugates with PEG-chitosan is examined using CD- and IR-spectroscopy. It is found that the enzyme structure changed only slightly as a result of conjugation with PEG-chitosan: the content of α-helices changed from 36% (for the native enzyme) to 30–33% (for the conjugates). The content of β-structures changed from 15% (for the native enzyme) to 18% (for the conjugate). The obtained data open new opportunities for the synthesis of L-asparaginase preparations with improved biocatalytic properties.     

Solubility of the Copper(II) Salt–Sodium Formate–Water Systems at 25°C

Solubilities in the CuSO₄ (CuCl₂, Cu(NO₃)₂)–NaHCOO–H₂O systems are studied at 25°C using the isothermal sections method. Crystallization regions of copper(II) formate mono- and dihydrate are elucidated. It is proved that copper(II) formate can be synthesized in CuAn₂ + 2NaHCOO ? Cu(HCOO)₂ + 2NaAn–H₂O quaternary reciprocal systems using the conversion method.     

Solubility in the neopentylglycol-sodium formate-methanol-water system

The solubility in the neopentylglycol-sodium formate-methanol-water (reaction mixture) four-component systems (at 30°C) was studied for the first time. The optimal values of the temperature-concentration parameters for the manufacture of neopentylglycol and sodium formate with the use of crystallization of the products from the reaction mixture were determined.     

Potential of magnesium salt–monoalkylpolyethylene glycol–water systems for use in micellar extraction

Solubilities in MgCl₂ (MgSO₄, Mg(NO₃)₂)–syntanol DS-10 (syntanol ALM-10)–water systems have been studied by the visual-polythermal method and the isothermal section method. The liquid–liquid phase separation region was shown to change its topology depending on temperature and the salting-out agent. The salting-out agent anion was shown to influence the cloud point of syntanol solutions. The effect of structure on the ability of syntanol to be salted out by magnesium salts was studied. Optimal temperature and concentration parameters of boron extraction in the studied systems were determined.     

Nonstationary flow of a conducting gas in crossed electric and magnetic fields

The plasma is inviscid, cool, and not thermally conducting; it flows in a channel of constant cross section. The solution is derived by the small parameter method, for which purpose the magnetic interaction N is used. There have been previous studies of the transient-state flow of an inviscid and thermally nonconducting plasma in crossed electric and magnetic fields [1–3]. A plasma of infinite conductivity has been considered [1], as well as flow involving entropy change in an MHD system with strong electromagnetic fields [2, 3].     

Specific features of the salting-out of oxyethylated nonylphenols using inorganic salts at 25°С

The solubility of oxyethylated nonylphenols (neonol AF 9-12 and neonol AF 9-25) in aqueous solutions of inorganic salts is studied at 25°С. Cation and anion abilities to salt out neonols from aqueous solutions are examined. It is found that anions are able to salt out neonols while cations are able to salt in neonols. The concentration parameters of extraction in water–neonol AF 9-12 (neonol AF 9-25)–(NH4)2SO4 systems are optimized.     

A study of the physicochemical properties and structure of moxifloxacin complex with methyl-β-cyclodextrin

The physicochemical properties and structure of moxifloxacin?methyl-β-cyclodextrin complex have been studied by UV spectroscopy, FTIR spectroscopy, and computer simulation. The optimal conditions for the formation of the complex have been determined, and the dissociation constant of the complex in acidic media (K _dis = (5.0 ± 0.3) × 10^–5 М) has been obtained. It has been found that complexation significantly slows down the release of the drug in acidic media. Experimental results are in good agreement with computer simulation data. The following mechanism of complex formation has been proposed: the incorporation of the aromatic fragment of moxifloxacin into the cavity of methyl-β-cyclodextrin is followed by additional stabilization of the complex via multiple hydrophobic interactions and hydrogen bonding.     

Physical and mathematical model of the coagulation of micron and submicron aerosols with regard for evaporation and sedimentation at ultrasonic effect

A physical and mathematical model is proposed, which is based on the Smolukhovsky’s equation describing the dynamics of the variation of the distribution function of aerosol particles over their sizes with regard for ultrasonic action, evaporation (for liquid-drop aerosols), and sedimentation. The expressions are obtained for the coagulation kinetics depending on the main parameters of action, the properties of aerosol and medium: the concentration and dispersion composition of the original aerosol, viscosity and temperature of the medium, physical-chemical parameters of particles material. Computational results obtained by using the proposed model correspond to experimental data.     

Millimeter spectroscopic study of intermolecular interactions in solutions

The absorption of 5 cm^–1 electromagnetic radiation by aqueous solutions of methyl, ethyl, n-, and isopropyl, sec-, iso-, and tert-butyl, and tert-amyl alcohols and ethylene glycol was measured within their solubility limits in water at 20°C. It was found that the observed nonadditivity of absorption (absorption deficit) is a qualitative measure of hydration of alcohols of two types: hydrophilic and hydrophobic. The possibility of distinguishing these effects by millimeter spectroscopy was demonstrated. Hydrophobic hydration makes the basic contribution to the hydration number of aliphatic alcohols. On the example of solutions of ethanol and tert-butanol, it was shown that hydrophobic hydration decreases with an increase in the temperature of the solution due to intensification of hydrophobic interactions between the hydrocarbon radicals.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1755–1761, August, 1989.