Physicochemical Properties of Binary Solvents Based on Morpholine

The density and viscosity of the binary solvents monoethanolamine-morpholine and monoethylene glycol-morpholine were determined in the entire concentration range at 20, 30, 40, 50, and 60°C. The concentration dependences of the Gibbs energy, enthalpy, and entropy of activation of viscous flow were calculated for these systems.     

The Influence of the Natures of the Carrier Gas and the Stationary Phase on the Separating Properties of Monolithic Capillary Columns in Gas Adsorption Chromatography

A model mixture of light hydrocarbons was used to study the separation capacity of monolithic capillary columns based on divinylbenzene with five different carrier gases, including helium, hydrogen, nitrogen, carbon dioxide, and nitrous oxide. The results were correlated with the previously obtained data on monolithic columns based on silica gel. It was shown that the influence of the nature of the carrier gas was weaker than for silica gel columns; the polymeric columns studied behaved similarly to hollow capillary columns with polymeric stationary phases and exhibited an efficiency gain of 20–30% along the series He < H₂ < N₂ ～ N₂O < CO₂. Based on the minimum HETP (～15 μm) obtained for the investigated monolithic columns under optimum conditions with N₂O or CO₂ as a carrier gas, the conclusion was drawn that the creation of divinylbenzene-based monolithic capillary columns with a high specific efficiency was possible.     

The N-domain of angiotensin-converting enzyme specifically hydrolyzes the Arg-5-His-6 bond of Alzheimer's Abeta-(1-16) peptide and its isoAsp-7 analogue with different efficiency as evidenced by quantitative matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Chronic imbalance between production and degradation of the human amyloid-beta peptide (Abeta) is assumed to play an important role in pathogenesis of Alzheimer's disease (AD). Post-translational modifications of Abeta could influence its interactions with specifically cleaving proteases and, therefore, perturb the Abeta homeostasis. The angiotensin-converting enzyme (ACE) was previously shown to degrade non-modified Abeta in vitro and in cells. In the presented work, we investigated the effect of isomerization of Asp-7, a common non-enzymatic age-related modification found in AD-associated Abeta species, on hydrolysis of Abeta by ACE. Two synthetic peptides corresponding to the Abeta region 1-16 with either Asp or isoAsp residues in position 7 were examined as monomeric soluble substrates for the N- as well as for the C-domain of ACE. The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) coupled with the (18)O-labeled internal standard approach has allowed us to show that (i) the N-domain of ACE (N-ACE), but not the C-domain, selectively cleaves the Arg-5-His-6 bond in both peptides, and that (ii) N-ACE hydrolyzes the isoAsp-7 analogue more efficiently than the non-modified one. Our results demonstrate a new endopeptidase activity of N-ACE as well as high preference of the domain to recognize and hydrolyze the isomerized Abeta species that were earlier suggested to promote AD pathogenesis. The results suggest the need for further analysis of biological effects of isomerized Abeta and its interaction with ACE in AD pathogenesis.     

A dynamic way of studying heterogeneous equilibria

A way of studying heterogeneous equilibria in oxide systems under low oxygen pressure, based on dynamic means combined with gravimetric and X-ray techniques, is described.     

Synthesis, crystal structure and thermal behavior of a novel oxoborate SrBi2B4O10

A new compound, SrBi₂B₄O₁₀, has been grown by cooling a melt with the stoichiometric composition. It is triclinic, P−1, a=6.819(1), b=6.856(1), c=9.812(2) Å, α=96.09(1), β=109.11(1), γ=101.94(1)°, V=416.5(1) Å³, Z=2. The crystal structure of the compound has been solved by direct methods and refined to R₁=0.050 (wR₂=0.128). The structure contains Bi-O pseudolayers build up from Bi-O chains involving oxocentred OBi₃ triangles. Sr atoms and [B₄O₉]⁶⁻ isolated anions (4B:3Δ□:<2Δ□>Δ) are located between the Bi-O packages.The thermal treatment as well as DSC experiment showed that the compound melts above 800 °C presumably according to the peritectic reaction: SrBi₂B₄O₁₀ ↔ SrB₂O₄+SrB₄O₇+ Liquid. According to high-temperature X-ray powder diffraction study thermal expansion of SrBi₂B₄O₁₀ structure is anisotropic (α₁₁=13, α₂₂=9, α₃₃=2, α_V=24×10⁻⁶ °C⁻¹).     

On calculation of the rate of mass transfer by periodic waves propagating over the surface of a viscous liquid

A generalization of the Stokes classical drift model describing mass transfer by periodic waves propagating over the surface of an infinitely deep incompressible liquid to the case of a viscous liquid is constructed. An analytic expression is proposed for the velocity of an additional flow into which the liquid is involved by horizontal viscous shear stresses emerging between adjacent horizontal layers of the liquid participating in the drift.     

Increasing the efficiency of the resonance method for breaking an ice cover with simultaneous movement of two air cushion vehicles

This paper describes a study on the possibility of increasing the efficiency of the resonance method for breaking an ice cover due to the flexural-gravitational wave interference arising during simultaneous movement of several air cushion vehicles.     

Reduction of Deuterium Level Supports Resistance of Neurons to Glucose Deprivation and Hypoxia: Study in Cultures of Neurons and on Animals

The effect of a reduced deuterium (D) content in the incubation medium on the survival of cultured neurons in vitro and under glucose deprivation was studied. In addition, we studied the effect of a decrease in the deuterium content in the rat brain on oxidative processes in the nervous tissue, its antioxidant protection, and training of rats in the T-shaped maze test under hypoxic conditions. For experiments with cultures of neurons, 7–8-day cultures of cerebellar neurons were used. Determination of the rate of neuronal death in cultures was carried out using propidium iodide. Acute hypoxia with hypercapnia was simulated in rats by placing them in sealed vessels with a capacity of 1 L. The effect on oxidative processes in brain tissues was assessed by changes in the level of free radical oxidation and malondialdehyde. The effect on the antioxidant system of the brain was assessed by the activity of catalase. The study in the T-maze was carried out in accordance with the generally accepted methodology, the skill of alternating right-sided and left-sided loops on positive reinforcement was developed. This work has shown that a decrease in the deuterium content in the incubation medium to a level of −357‰ has a neuroprotective effect, increasing the survival rate of cultured neurons under glucose deprivation. When exposed to hypoxia, a preliminary decrease in the deuterium content in the rat brain to −261‰ prevents the development of oxidative stress in their nervous tissue and preserves the learning ability of animals in the T-shaped maze test at the level of the control group. A similar protective effect during the modification of the ²H/¹H internal environment of the body by the consumption of DDW can potentially be used for the prevention of pathological conditions associated with the development of oxidative stress with damage to the central nervous system.     

Kinetics of the Dissolution of Silver in Thiocarbamide Solutions

The dependence of the rate of solution of silver on the pH of the solution, the ratio of the iron(III) and thiocarbamide concentrations, and the temperature has been determined. The rate constants for the solution of silver (k _i = 2.3·10^–4 to 9.6·10^–4s^–1) at temperatures from 283-298 K have been calculated and from the temperature dependence of the rate constant the activation energies have been calculated: 68.84 kJ/mol for kinetic control of the rate of solution and 26.06 kJ/mol in the adsorption inhibition region.