Immunofiltration as sample cleanup for the immunochemical detection of beta-agonists in urine

Despite the ban of the European Union on use of drugs to improve animal growth, occasionally beta-agonist drugs are still found in samples from cattle. Over time, the specified limits for the detection of these illegal drugs have been lowered. To improve the immunochemical screening of urine samples to detect lower levels of several beta-agonists, immunofiltration (IF) was applied for sample cleanup in combination with a beta-agonist-ELISA. In the applied IF format, free (non-immobilised) anti-salbutamol polyclonal antibodies were mixed with the urine sample in an ultra-filtration device (cut off 30 kDa) and the sample was removed by centrifugation. The antibody bound beta-agonists were freed from the antibodies by the addition of a mixture of methanol and 0.1 M acetic acid (1:1; v/v) and centrifugation. The filtrate, containing the free beta-agonists, was evaporated to dryness and the residue dissolved in buffer, an aliquot of which was analysed with the beta-agonist ELISA. Compared with the direct beta-agonist ELISA, this IF cleanup procedure resulted in a 30-times lower limit of detection (LOD) of 0.14 ng ml(-1) (salbutamol equivalents). The anti-salbutamol antibodies recognised several beta-agonists and the combination of IF with the beta-agonist ELISA was found suitable for the detection of at least ten beta-agonists in urine with comparable LODs.     

Characterization of modification sites during peptide synthesis using liquid secondary ion/collision-induced dissociation mass spectrometry and a computer program

Side-reactions often occur during peptide synthesis resulting in modified amino acid moieties. To identify these residues, liquid secondary ion/collision-induced dissociation mass spectra were recorded. The main fragments are generated by cleavage of the peptide bond. To facilitate interpretation of the spectra and assignment of the structure, a simple, but flexible and efficient, computer program is presented. The program allows the verification of the correct structure of the synthesized peptides and the deduction of the type of side-products formed, such as alkylation of tryptophan residues.     

Tunability of the photoluminescence in porous silicon due to different polymer dielectric environments

In this report we demonstrate control over porous silicon (PSi) emission properties by changing the dielectric environment surrounding the silicon crystallites, as well as provide information on the effects of pore infiltration of PSi. This is achieved by making PSi–polymer nanocomposites by diffusing or polymerizing a range of varying dielectric constant polymers into the pores. The degree of modification in photoluminescence (PL) depends on the dielectric constant of the polymers. By increasing the dielectric constant of the environment surrounding the crystallites, a blue shift in PL as high as 222 meV has been observed. The blue shift is attributed to the high dielectric constant of the polymers relative to PSi, which causes a partial screening of the excitons allowing the excitonic levels to shift closer to the bandgap. The shift in excitonic levels increases when the dielectric constant of the polymer increases. PSi–polymer nanocomposites also exhibit an increase in PL intensity, which suggest that the inert infiltrated polymers are able to passivate existing nonradiative channels.     

Convection from a stretching surface with suction and power-law variation in species concentration

The problem of laminar natural convection flow from a permeable semi-infinite accelerating vertical surface that is coated with a reacting chemical species is studied. The plate velocity and the species concentration vary as power laws. The fundamental parameters of the problem are the Schmidt number, the surface permeability and the reaction rate. The governing equations were transformed to a non-similar form and then solved analytically and numerically using the Keller box method. A parametric study illustrating the effects of the flow parameters on the velocity and the concentration fields was conducted and the physical aspects of the problem discussed. The study found, inter alia, that the fluid motion is decelerated by increases in the permeability of the accelerating surface and that the rate of mass transfer increases with Schmidt numbers but reduces with increasing reaction rates and the porosity of the accelerating surface.     

Anisotropy of domain wall resistance

The resistive effect of domain walls in FePd films with perpendicular anisotropy was studied experimentally as a function of field and temperature. The films were grown directly on MgO substrates, which induces an unusual virgin magnetic configuration composed of 60 nm wide parallel stripe domains. This allowed us to carry out the first measurements of the anisotropy of domain wall resistivity in the two configurations of current perpendicular and parallel to the walls. At 18 K, we find 8.2% and 1.3% for the domain wall magnetoresistance normalized to the wall width (8 nm) in these two respective configurations. These values are consistent with the predictions of Levy and Zhang.     

Partially autoionizing states of atomic oxygen

The Rydberg states 3d′ ³P_2,^o₁, ₀ and ³s″ ³P_2,^o₁, ₀ and the inter-shell transition 2sp⁵³P_2,⁰₁, ₀, which are forbidden to autoionize on the basis of LS coupling, have been observed in emission spectroscopy and in autoionization spectra produced in the photoelectron spectrum of atomic oxygen.     

Polymérisation anionique de i'isoprene et du butadiene en presence d'agents complexants

With the aid of DCHE and [222], solutions of sodium, potassium, rubidium, and cesium have been prepared in tetrahydrofuran (THF) and in benzene. All these new species initiate the polymerization of butadiene and isoprene avoiding the inconvenience of heterogeneous reactions. The presence of free ions and/or complexed ion pairs allows the increase of vinyl structures even in benzene.     

Structure in excimer line shape

Recently monomer-like structured emission has been observed in the spectra of excimers both in solids and in solution. In a two-dimensional model potential an intramolecular mode is considered in addition to the relative degree of freedom. It is shown that under certain conditions structured line shapes are obtained.     

Oxidative addition with methyl group transfer in Diplatinum complexes: Crystal structure of a bridged platinum(IV)-platinum(II) complex

Reactions of [Me₂Pt(μ-dmpm)₂PtMe₂], (dmpm = Me₂PCH₂PMe₂) with halogens, (X₂) or methyl iodide give the platinum(IV)-platinum(II) complexes [Me₃Pt(μ-X)(μ-dmpm)₂PtMe]X or [Me₃IPt(μ-dmpm)₂PtMe₂] respectively, and the former reactions involve methyl group transfer between the platinum atoms of the binuclear complex; one of the derivatives ([Me₃Pt(μ-I)(μ-dmpm)₂PtL]I₃, L = 1/2I + 1/2 Me) is characterized by an X-ray crystal structure determination.