Increase in scleral collagen stability during glycosylation with threose in vitro

A systematic study of changes in the physicochemical characteristics of scleral collagen in the course of glycosylation by threose, including their dependence on the time changes of transverse cross-linking, was performed. Glycosylation by threose leads to a significant increase in heat, proteolytic, and biomechanical stability of collagen in the scleral tissue and has been shown to be a useful approach for stabilizing scleral collagen. It was found that a fraction of collagen with a reduced denaturation temperature is, apparently, an intermediate in the reaction of glycosylation by threose. The most likely reason for its occurrence is the elongation of the side chains of amino acid residues of the protein in the early stages.     

Hydration of Bromine Ions in Water

A mass spectrographic method electrospraying electrolyte solutions in vacuum was used to determine the enthalpy of hydration of bromine ions by different numbers of water molecules. The mass spectra of negative ions from aqueous solutions of NaBr were measured over the temperature range of 15–50°C and showed that the most intense peaks correspond to the hydrated bromine ions with one and two water molecules. It was found that the Van't Hoff equation holds for bromine hydrates containing up to three water molecules, whereas addition of the fourth water molecule leads to a violation of the Van't Hoff equation. The enthalpy of bromine ion hydration by the first and the second water molecules was found to be –(28.5 ± 1.7) and –(21 ± 4.2) kJ/mol, respectively.     

Igor’ Alekseevich Myasnikov (1918–2005)

Chronicle

Igor’ Alekseevich Myasnikov (1918–2005)     

Ivan Pavlovich Bazarov (1916–2005)

Chronicle

Ivan Pavlovich Bazarov (1916–2005)     

In search for a pentacoordinated monoorgano stannyl cation

Alkylation of Sn(OCH₂CH₂NMe₂)₂ (1) by MeI or MeOTf leads to a mixture of quaternary ammonium salts by alkylation of the NMe₂ moiety. Reaction of Sn(acac)₂ (2) with MeOTf gives unexpected redistribution product Sn(acac)OTf (3), which is a rare example of mono acetylacetonato tin (II) derivatives. Pentacoordinated monoorgano stannyl cation was generated by salt metathesis from PhSn(OCH₂CH₂NMe₂)₂Cl (5) and Ag[Al(OCH(CF₃)₂)₄] or Ag[B(C₆F₅)₄]. This cation was not isolated due to its strong electrophilic nature. It abstracts substituents from aluminate and borate weakly coordinating anions (WCAs) leading to redistribution products [Al[OCH(CF₃)₂]₂OCH₂CH₂NMe₂]₂ (6) and [Ph(C₆F₅)Sn(OCH₂CH₂NMe₂)₂][H₂OB(C₆F₅)₃] (9), respectively. Structures of 3 and 6 were established by single-crystal X-ray diffraction analysis.     

A copper catalyst on nonporous supports based on copper oxalate as a precursor

A method for obtaining copper catalysts on nonporous supports by the thermal decomposition of copper oxalate in the absence of oxygen was suggested. The catalytic properties of the catalyst were studied in the model reaction of the conversion of propanol-2 into acetone and propylene. The influence of the content of copper in the catalyst, reaction temperature, and conditions of oxalate decomposition on the degree of alcohol conversion and ratio between reaction channels was studied. Electron photomicrographs were obtained, specific surface areas were measured, and X-ray powder patterns of the catalyst were recorded.     

The composition of iron-containing microphases in the structure of multiwalled carbon nanotubes

The phase composition of carbon nanotubes (CNTs) with encapsulated iron atoms was studied by ⁵⁷Fe Mössbauer spectroscopy. The synthesis of CNTs was shown to stabilize iron atoms as both thermodynamically stable iron carbide and oxide phases and phases not characteristic under synthesis conditions (γ-Fe and γ-Fe₂O₃). In addition, an analysis of the data obtained led us to suggest the existence of Fe-CNT atomic complexes in interlayer positions. CNTs and iron-containing phases were shown to be stable when subjected to prolonged annealing in air at temperatures up to 670 K.