Phase equilibria up to the solidus line in the system Fe2O3−Fe8V10W16O85

Phase equilibria up to the solidus line in the system Fe₂O₃?Fe₈V₁₀W₁₆O₈₅ were determined by means of X-ray phase powder diffraction and differential thermal analysis. This system is one of the intersections of the three-component system Fe₂O₃?V₂O₅?WO₃. The studies revealed that this is not a real binary system, even in the solid state.     

Phase equilibria up to the solidus line in the system Fe2WO6−Fe8V10W16O85

Phase equlibria in the solid state in the system Fe₂WO₆?Fe₈V₁₀W₁₆O₈₅ were studied by means of X-ray phase powder diffraction and differential thermal analysis, This system is one of the intersections of the three-component system Fe₂O₃?V₂O₅?WO₃. The investigation demonstrated that the system is not a real two-component system even below the solidus line.     

New renin inhibitors containing pseudodipeptidic units in P3-P2 and P1-P1' positions

A series of four non-peptidic renin inhibitors have been designed and synthesized. All of them contain in their molecule (3S,4S)-4-amino-5-cyclohexyl-3-hydroxypentanoic acid (ACHPA), a hydrophobic portion at the C-terminus and a second dipeptide-like transition state analog or unnatural dipeptidic fragment at the N-terminus. Inhibitory activity of the compounds was measured in vitro by high performance liquid chromatography (HPLC). Their IC50 (M/l) values were: <10(-3) (12), 1.0 x 10(-6) (19), 4.0 x 10(-4) (23) and 1.0 x 10(-6) (29), respectively. All the compounds are stable against chymotrypsin.     

Characterization of a cross-linked DNA-Endonuclease VIII repair complex by electrospray ionization mass spectrometry

Electrospray mass spectrometry techniques were used to characterize components of the active site in Endonuclease VIII by identifying the amino acid sequence and the binding site for a tryptic peptide derived from Endo VIII in a cross-linked DNA-peptide complex. Endo VIII, a DNA repair enzyme with both glycosylase and lyase activities, was covalently bound to a thymidine glycol-containing oligodeoxynucleotide duplex by converting a transient Schiff base formed during the course of the glycosylase activity to a stable covalent bond by chemical reduction with sodium borohydride. After tryptic digestion of the initial product, the identification of the cross-linked peptide was deduced initially from the molecular mass of the tryptic product obtained by negative ion electrospray mass analysis. Nanospray tandem mass spectrometry (MS/MS) analysis of the tryptic product corroborated the molecular mass of the peptide fragment and verified the point of attachment to the oligomer, but failed to produce sufficient fragmentation to sequence the peptide completely. Direct evidence for the amino acid sequence of the peptide was obtained after enzymatic digestion of the DNA portion of the cross-linked DNA-peptide product and analysis by negative ion nanospray MS/MS. Examination of the ions from collision induced fragmentation disclosed that this substance was the N-terminal tryptic fragment of Endo VIII cross-linked to a portion of the oligomer, and that the N-terminal proline from Endo VIII was covalently bound to the residual deoxyribose moiety at the original location of the thymine glycol in the oligomer.     

Competitive binding of Na<Superscript>+</Superscript> and Ca<Superscript>2+</Superscript> ions to teichoic acid analogues

The competitive binding of monovalent and divalent counterions to poly(alkylene phosphate) related to bacterial teichoic acids and poly(styrenesulfonate) was studied experimentally by potentiometry with ion-selective electrodes. The binding of calcium ions and the release of sodium ions accompanying calcium ions binding in aqueous solutions of the polyelectrolytes was analysed and the mean exchange ratio Na⁺/Ca²⁺ was estimated. It was found that in the process of addition of calcium ions to sodium poly(alkylene phosphate) and sodium poly(styrenesulfonate) solutions all the Ca²⁺ ions added are bound to polyions and the initially condensed Na⁺ ions are released proportionally to the concentration of the added Ca²⁺ ions up to the critical concentration of the Ca²⁺ ions added. For a molar concentration ratio of calcium counterions to charged groups on the polyion up to 0.20 the exchange ratio was approximately equal to 1 or 2 for the sodium poly(alkylene phosphate)/CaCl₂ and sodium poly(styrenesulfonate)/CaCl₂ systems, respectively.     

Reduction of nitrobenzene to aniline with carbon monoxide and water

Modified catalytic system composed of selenium and cocatalysts such as pyridine and aniline, applied in the reduction of nitrobenzene to aniline in the presence of carbon monoxide and water is described. The reaction proceeds at 150–200°C and 3–4 MPa gauge pressure. After 1–2 h the reaction is complete, reaching nitrobenzene conversions of up to 98% with selectivity to aniline near 100%.     

Spatially resolved solvent interaction with glassy HPMC polymers studied by magnetic resonance microscopy

Magnetic resonance microscopy was used to study the interaction of an alkaline water solvent (pH=12) with hydroxypropylmethyl cellulose (HPMC) matrices with different molecular masses Mw=12,000, 86,000, and 120,000. The polymers in the form of cylinders were hydrated at 37 degrees C and monitored at equal time intervals with a 300MHz Bruker AVANCE. The spatially resolved spin-spin relaxations times T2 and diffusion coefficients D of the solvent molecules within the gel layer of HPMC samples, along with changes in the dimension of the glass core of the polymers were determined as a function of hydration times. The experimental data allows us to characterize the diffusion mechanism as being Fickian and to determine the mean diffusivity values D of the solvent molecules for each voxel within the gel of the studied polymers. The influence of the molecular mass of the HPMC polymers on swelling properties has been shown.     

7α-methoxy-2-[(substituted)methylene]cephem sulfones as inhibitors of human leukocyte elastase and thrombin

A series of 7-methoxy-2-[(substituted)methylene]cephem sulfones was synthesized. The compounds with an acetoxy group at the C-3 position as a leaving group were found to be potent inhibitors of HLE. Selected compounds are also found to be antithrombin agents.SynPhar Laboratories Inc. #2 Taiho Alberta Centre, 4290-91A Street, Edmonton, Canada T6E 5V2. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1510–1516, November, 1998.     

Mesogenic derivatives of 2S,3S-2-halogeno-3-methylpentanoic acid with helix twist inversion in the smectic C* phase

Two homologous series of chloro and bromo derivatives of S,S-3-methylpentanoic acid were synthesized and studied. For some of these compounds an inversion of helix twist sense in the smectic C* phase was observed. Dielectric dispersion measurements showed a pronounced anomaly of the Goldstone mode relaxation frequency and strength close to the helix inversion point. Moreover, a qualitative difference in behaviour of the mode in samples with planar and with homeotropic alignment was detected; this is due to surface interactions.     

Chiraloptical properties of adducts derived from cyclic nitrones and 2(5H)-furanones. Combined experimental and theoretical studies

The validity of the Bucourt–Legrand empirical rule, which relates the configuration at the α-carbon atom in the lactone unit with the sign of the lactone n→π^* transition observed in the electronic circular dichroism (ECD) spectrum of 5-5-5 and 5-5-6 fused heterocyclic systems, was investigated. For this purpose, a combination of ECD spectroscopy, time-dependent density functional theory (TD-DFT) and molecular modelling calculations supported additionally by X-ray diffraction analysis, was applied. Model compounds were obtained via the 1,3-dipolar cycloaddition of 2(5H)-furanones and five- and six-membered cyclic nitrones. In addition, cycloadducts either with or without an additional interfering chromophore were selected. A comparison of the recorded ECD spectra with those simulated by the TD-DFT calculations gave a reasonable interpretation of the excitations observed in the 210–230 nm spectroscopic range. Generally, calculations confirmed the validity of the Bucourt–Legrand rule and demonstrated that ECD may be used as a highly sensitive probe for the three-dimensional molecular structure of the systems studied herein. Notable behaviour, however, was observed in the case of some 5-5-6 fused systems substituted with BnO group. In these cases, the conformational liability and coupling of molecular lactone excitation with other chromophores cause a change of orientation of the transition dipole moments resulting in a breakdown of the rule.