Preparation and properties of antitubercular 1‐piperidino‐3‐arylthioureas

1‐Piperidino‐3‐arylthioureas, of interest in the investigation of novel heterocyclic structures for their anti‐tubercular activity, may be conveniently prepared in good yield and purity by the reaction of 1‐arninopiperi‐dine with aryl isothiocyanates in ethanol. The reaction takes place readily without the complication of thiourethane contaminants, and the products may be suitably identified by significant characteristics in the infrared spectra and the hydrogen and carbon magnetic resonance spectra.     

Use of phage display methods to identify heptapeptide sequences for use as affinity purification 'tags' with novel chelating ligands in immobilized metal ion affinity chromatography

This study describes the screening of a peptide phage display library for amino acid sequences that bind with different affinities to a novel class of chelating ligands complexed with Ni2+ ions. These chelating ligands are based on the 1,4,7-triazacyclononane (TACN) structure and have been chosen to allow enhanced efficiency in protein capture and decreased propensity for metal ion leakage in the immobilized metal ion affinity chromatographic (IMAC) purification of recombinant proteins. Utilising high stringency screening conditions, various peptide sequences containing multiple histidine, tryptophan, and/or tyrosine residues were identified amongst the different phage peptide sequences isolated. The structures, and particularly the conserved locations of these key amino acid residues within the selected heptapeptides, form a basis to design specific peptide tags for use with these novel TACN ligands as a new mode of IMAC purification of recombinant proteins.     

Mixed crystal formation and structural studies in the mullite-type system Bi2Fe4O9–Bi2Mn4O10

The limits of metal cation substitution and distribution in the sequence Bi₂Fe₄O₉–Bi₂Mn₄O₁₀ have been investigated by solid state synthesis, X-ray powder diffraction, and Mössbauer spectroscopy. Rietveld refinements conducted for the entire range along the join indicate the structures are orthorhombic with space group Pbam, with partial transition-metal site disorder confirmed and detailed by Mössbauer spectroscopy. Single-phase regions are found near each end-member and a two-phase region is observed at intermediate compositions, extending from about x=1 to 3, according to the general formula of the mixed crystals Bi₂Fe_4?xMn_xO_10?δ. An incorporation of Mn at octahedral sites replacing Fe is taken into account for the Bi₂Fe₄O₉-related side of the system. Charge compensation is believed to be effected by addition of O, which gives rise to the formation of FeO₅ pyramids. At the Bi₂Mn₄O₁₀-related side of the system, substitution of pyramidal Mn³⁺ by Fe³⁺ is envisaged.     

Peptide mapping with mobile phases of intermediate pH value using capillary reversed-phase high-performance liquid chromatography/electrospray ionisation tandem mass spectrometry

This investigation describes the separation of tryptic peptides by capillary reversed-phase high-performance liquid chromatography (RP-HPLC) with eluents in the intermediate pH range, followed by in-line electrospray ionisation tandem mass spectrometry (ESI-MS/MS) analysis. For these purposes, gradient elution procedures with an aqueous eluent containing 20 mM ammonium formate, and an increasing content of acetonitrile or methanol, were employed. Compared to the analysis of the same tryptic peptides under low-pH conditions with an ion-pairing reagent, the increase in the pH with the 20 mM ammonium formate mobile phase led to significant changes in both peptide retention to the reversed-phase column and the collision-induced dissociation at the MS/MS stage as a consequence of the changes in the physico-chemical properties of these peptides, such as their overall charge, polarity and relative hydrophobicity. Thus, improved selectivity for the peptide separation and favourable tandem mass spectrometry analysis could be obtained with eluents in this intermediate pH range. The number of tryptic peptides identified by the new approach for the proteins investigated were significantly higher than that obtained by the conventional low-pH methods. Moreover, analysis of protein digests at very low concentrations was also performed under both acidic and intermediate pH conditions and similar improvements in selectivity and MS/MS detection limits were observed, i.e. identification of more distinct peptides and higher sequence coverage of the protein was obtained when eluents of intermediate pH were employed. This study therefore highlights the potential of conducting peptide mapping in the intermediate pH range to achieve more reliable and sensitive protein identifications with capillary RP-HPLC–ESI-MS/MS.     

The anomalous thermal expansion of VO2 crystal with the rutile structure

The large coefficient of thermal expansion parallel to the c-axis in the rutile phase of VO₂ is explained using the phonon-softening model of the metal-insulator transition.     

The cleaning of polymer colloids

The current state of knowledge of the cleaning of polymer colloids is reviewed with regard to a wide range of cleaning and characterisation techniques. The type, level and quantity of impurities involved with different polymer latex formulations varies widely. Even for similar formulations, differences in the nature and number of functional groups reported are often a consequence of sometimes subtle differences in the cleaning procedures employed. Not only may surface functionality be affected but also monomer and oligomer extraction procedures may lead to morphological changes in the particles. No single technique alone is likely to be able to remove all impurities. Care is needed to avoid the introduction of new impurities from the equipment, materials and water used as well as possible contamination from atmospheric carbon dioxide, bacteria and fungi. These factors also need to be considered in the storage of latex particle standards.     

Problems associated with the surface characterization of polystyrene latices

It has been shown that polystyrene latices prepared by the surfactant free emulsion polymerization process often contain sufficient residual monomer and possibly low-molecular-weight material and reaction by-products, such as benzaldehyde, which are not efficiently removed by dialysis, to affect their bulk and surface characteristics. These materials have been identified by gel permeation chromatography (GPC) and infrared (IR) spectroscopy studies and their effective removal by steam stripping has been investigated. Steam stripping has proved to be efficient in this process but it led to rapid hydrolysis of the surface sulfate groups and a consequent change in the surface characteristics. The problem of hydrolysis of sulfate groups under various environments has been studied. The problems associated with the identification of weak acid end groups are discussed and several alternative explanations for their occurrence are advanced.     

Reactions of N-aminophthalimide with electrophiles. II. Preparation and properties of araldehyde hydrazones

N-Aminophthalimide (I) reacted with a variety of aromatic aldehydes to give the related arylideneaminophthalimides (III-X), although typical ketones such as acetone and benzophenone did not under the specific conditions employed. Catalytic reduction of benzylideneaminophthalimide (III) led to N-benzylaminophthalimide (XI), a stable acid-free precursor of benzylhydrazine.