Reversed-phase chromatography of proteins and peptides on compressed continuous beds

Summary The polymer beds described are synthesized in aqueous solution directly in the column or batchwise in the form of large clusters of small particles. The conventional, expensive step involving prepreparation of beads in an organic solvent is thus omitted. Beds were synthesized from piperazine diacrylamide, methacrylamide and allyl glycidyl ether. The epoxy-activated beds thus obtained were used for covalent attachment of either nonpolar ligands (e.g. octadecanol) or polar OH-rich substances (e.g. dextran). The non-polar beds were used for reversed-phase chromatography, as were polar ones following coupling with 1,2-epoxyoctadecane. Coating with OH-rich substances serves two purposes: (I) the matrix becomes hydrophilic, decreasing nonspecific interactions (modifiers can be excluded) and hence increases resolution and (II) many—OH groups are available (e.g. for coupling to epoxides), a prerequisite for high ligand density. Resolution of proteins was high even at high flow rates. Depending on the method used for the synthesis of the bed, resolution of proteins either increased with an increase in flow rate or decreased slinghtly. Choice of the correct temperature was very important for high resolution of CNRr-digested peptides.     

A coated wire-type lead(II) ion-selective electrode based on a phosphorylated calix[4]arene derivative.

The preparation of a lead-selective electrode based on 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(diphenylphosphinoylmethoxy)calix[4]arene (1) as an ionophore is reported. The plasticized PVC membrane containing 30% PVC, 57% ortho-nitrophenyloctylether (NPOE), 4% sodium tetraphenylborate (NaTPB) and 9% ionophore 1 was directly coated on a graphite electrode. It exhibits a nearly Nernstian slope of 28.0 +/- 0.2 mV decade(-1) over a concentration range of 1 x 10(-5) - 1 x 10(-2) mol dm(-3) with a detection limit of 1.4 x 10(-6) mol dm(-3). The response time of the electrode was found to be ca. 17 s. The potential of the sensor was independent of the pH variation in the range 3.5 - 5.0. The selectivity of the electrode performance towards lead ions over Th4+, La3+, Sm3+, Dy3+, Y3+, Ca2+, Sr2+, Cd2+, Mn2+, Zn2+, Ni2+, Co2+, NH4+ Ag+, Li+, Na+ and K+ ions was investigated. The prepared electrode was used successfully as an indicator electrode for a potentiometric titration of a lead solution using a standard solution of EDTA. The applicability of the sensor for Pb2+ measurements in various synthetic water samples spiked with lead nitrate was also checked.     

Sol-gel preparation and properties of interpenetrating, encapsulating and blend silica-based urea-formaldehyde hybrid composite materials

Four different silica-based urea-formaldehyde (UF/SiO₂) composite materials were prepared by various sol-gel synthetic procedures to yield an interpenetrating (IPN-UF/SiO₂), a micro-size UF resin encapsulated inside silica shell (Encap-UF/SiO₂), a micro-size silica encapsulated inside UF shell (Encap-SiO₂/UF), and a blend mixture (Blend-UF/SiO₂) hybrid systems. The thermal properties of the obtained organic-inorganic hybrid composite materials were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The structure and morphology of the obtained systems were investigated by infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Their surface porosity and acidity were evaluated from the nitrogen adsorption isotherm and the pH of the corresponding 10% aqueous suspension, respectively. All the results provided evidence for the formation of different hybrid systems with different surface, structural and morphological characteristics.     

Ferric Nitrate/Molibdatophosphoric Acid as a New and Efficient System in the Oxidative Deprotection of Trimethylsilyl Ethers to Corresponding Carbonyl Compounds under Solvent‐Free Conditions

Oxidative deprotection of a variety of trimethylsilyl ethers were performed by Fe(NO₃)₃.9H₂O in the presence of H₃PMo₁₂O₄₀.xH₂O as catalyst at room temperature in good to high yields under solvent‐free conditions.     

Solvent-free and room temperature synthesis of thiochromans in the presence of a catalytic amount of tungstophosphoric acid

Tungstophosphoric acid catalyzed rapid and good yielding reactions of α,β-unsaturated aldehydes with arenethiols to give the corresponding 4-thioaryl-1,2,3,4-tetrahydro-1-benzothiopyrans (thiochromans) under solvent-free and room temperature conditions.     

Reactions between isocyanides and dialkyl acetylenedicarboxylates in the presence of 1,2-diacylhydrazines. One-pot synthesis of highly functionalized pyrazoles

The reactive 1:1 intermediate produced in the reaction between isocyanides and dialkyl acetylenedicarboxylates was trapped with 1,2-diacylhydrazines to yield highly functionalized pyrazoles in good yields.     

Calculation of Density for Mixtures of Carbon Dioxide with Nitrogen and Methane from the ISM Equation of State

In this paper the analytical equation of state (EoS) proposed by Ihm‐Song‐Mason was applied to calculate molar volume of mixtures of carbon dioxide with nitrogen and methane. The pair interaction potential has been used to evaluate the second virial coefficients and the ISM EoS parameters (i.e. α and b). The calculated values of the aforesaid quantities were applied to predict the molar volumes for mixtures of carbon dioxide with nitrogen and methane. Agreement with experiment was excellent for both mixtures.     

Weak Density of Smooth Maps in W 1, 1(M,N) for Non-Abelian π1(N)

We prove that smooth maps are dense in the sense of biting convergence in W ^{1, 1}(M, N) when M and Nare compact Riemannian manifolds and N is closed.