Electron impact mass spectrometry of the acetates of zinc,magnesium, cobalt and manganese

The electron impact mass spectra of the acetates of zinc, magnesium, cobalt and manganese have been investigated using a direct inlet probe. Volatile tetrahedral complexes are produced on heating, and ions of the form [M₄(OCOCH₃)₆O]^+˙ (M = Co and Mn) and [N₄(OCOCH₃)₅O]⁺ (N = Zn or Mg) are observed. A mixture of magnesium and cobalt acetates produces ions of the form [Mg_nCo_4–n(OCOCH₃)₆O]^+˙.     

A ten-residue fragment of an antibody (mini-antibody) directed against lysozyme as ligand in immunoaffinity chromatography

The interaction between an antibody molecule and a protein antigen is an example of "natural" protein modelling. Amino acids of the antigen-binding site consisting of three hypervariable segments (L1, L2, L3) of the light (L) and three (H1, H2, H3) of the heavy (H) chain of an antibody molecule interact with amino acids present in an epitope of a protein. A ten-residue peptide was synthesized with an amino acid sequence analogous to the hypervariable L3 segment of a monoclonal antibody directed against lysozyme. The peptide was immobilized on CH-Sepharose 4B and the affinity adsorbent was used to purify lysozyme added to a detergent extract of insect cells infected with a recombinant baculovirus. This methodology may also be applicable to other antigen-antibody combinations, in immunoaffinity chromatography for selective purification of a protein or in an immunosensor for detection of a protein.     

Diphenylcarbazone as an internal indicator in mercurimetric analysis: The determination of cerium by potassium thiocyanate

Summary The quantitative oxidation of thiocyanate by ceric sulphate has been studied and the method utilised for the determination of small quantities of cerium by back titrating the excess (unreacted) KSCN against standard mercuric nitrate with diphenylcarbazone as the internal indicator. Accurate results are obtained under the specified experimental conditions and the procedure is more simple and direct than that adopted during earlier studies of the above redox reaction.Grateful thanks of the author are due to Professor S. S. Joshi for facilities during the work and to the National Institute of Sciences of India for award of a Research Fellowship.     

The phosphorescence of Fe ions in oxide host lattices. Zero-phonon transitions in Fe/LiAl5O8

Phosphorescence and excitation spectra have been measured of Fe³⁺-doped LiAl₅O₈, β-NaAlO₂, Na-silicate glass and crystalline alumino-silicates. All excitation spectra fit quite well the Tanabe-Sugano diagram for a high spin d⁵ configuration. The expected tetrahedral site symmetry of Fe³⁺ in the host lattices and the value of the crystalline field parameter are strong evidence for phosphorescence of Fe³⁺ ions in tetrahedral oxygen coordination.     

The Effects of Beating,Web Forming and Sizing on the Surface Energy of <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> Kraft Fibres Evaluated by Inverse Gas Chromatography

In this work attention has been focused on the effects of papermaking beating, web forming and sizing operations on the physical/chemical surface properties of bleached Eucalyptus globulus kraft fibres. Inverse gas chromatography (IGC) was used to determine the dispersive component of surface tension (γ_s^d) as well as the acidic/basic character (according to the Lewis concept) of the solid surfaces (pulp fibres and pulp handsheets). The results have shown that the main effect of beating is to increase the fibre's Lewis acidic character. Web forming caused a strong decrease in γ_s^d and significant increments in the adhesion works of both acidic and basic probes, lowering the ratio between the two. Nevertheless, the surface of handsheets still exhibited a dominant acidic character. The sizing operation did not change the dispersive component of the surface tension significantly but decreased the difference between the adhesion works of the acidic and basic probes, rendering the handsheet surface less Lewis acidic and more Lewis basic. Thus, although internal sizing is expected to strongly influence liquid spreading at the paper surface and liquid penetration of the fibre's network, it is concluded that beating and web forming lead to important changes in the surface energetic properties of the Eucalyptus globulus kraft fibres.     

Solution structure of a beta-peptide ligand for hDM2

We recently reported a beta-peptide foldamer, beta53-1, that folds into a 14-helix in aqueous solution, binds the oncoprotein hDM2 with submicromolar affinity, and potently inhibits the interaction of hDM2 with a peptide derived from the activation domain of p53 (p53AD). Here, we present the solution structure of beta53-1 in methanol. Details of the structure illustrate fundamental and novel elements of beta-peptide folding and recognition. These elements include the detailed arrangement of a complex, 14-helix-stabilizing salt bridge on one helical face, and a unique "wedge into cleft" packing interaction along a second. The structure also reveals how a subtle distortion in the beta53-1 14-helix geometry alters the presentation of its recognition epitope, rendering it particularly well suited for alpha-helix mimicry. The solution structure of beta53-1 demonstrates that well folded beta-peptide oligomers can effectively present an extended, highly variable surface that could be used as a general platform for targeting critical protein-protein interfaces.     

Effect of plasmatron excitation conditions on the determination of traces

Optimal analysis conditions can be selected and errors caused by variations in the excitation conditions can be decreased or corrected based on the results of studying the temperature distribution along the plasma torch height and correlations between the analytical signal Y and the correcting signal Z that follows the temperature variation in the plasma torch. The obtained correlations can be used to create automated feedback between the spectrum recording system and the mode control system of the plasmatron.     

Chromatographic studies of corrosion sites in metallic materials

Many types of corrosion phenomena are controlled by the ionic composition of a small volume of solution at the surface. Localized corrosion and atmospheric corrosion are two examples in which < 1 μl of solution can cause dramatic damage. Ion chromatographic (IC) techniques have been used to analyze these solutions in order to gain a better understanding of the mechanisms which govern them. Two examples are presented. The presence of minor alloying elements at localized corrosion sites in two aluminum alloys has been demonstrated, indicating non-stoichiometric dissolution of the alloy during localized corrosion. In addition, IC analysis allowed the determination of the species responsible for the atmospheric corrosion failure of electrical connectors, including their likely origin.