Analysis of EU priority polycyclic aromatic hydrocarbons in food supplements using high performance liquid chromatography coupled to an ultraviolet, diode array or fluorescence detector

High performance liquid chromatography coupled to an ultraviolet, diode array or fluorescence detector (HPLC/UV-FLD) has been used to set up a method to detect the 15(+1) EU priority polycyclic aromatic hydrocarbons (PAHs) in food supplements covering the categories of dried plants and plant extracts excluding oily products. A mini validation was performed and the following parameters have been determined: limit of detection, limit of quantification, precision, recovery and linearity. They were in close agreement with quality criteria described in the Commission Regulation (EC) No 333/2007 concerning the PAH benzo[a]pyrene in foodstuffs, except the not fluorescent cyclopenta[c,d]pyrene for which the UV detection leads to a higher limit of detection. Analysis of twenty commercial food supplements covering mainly the class of dried plants was performed to evaluate their PAHs contamination levels and to test the applicability of the method to various plant matrices. Fifty percent of analyzed samples showed concentration exceeding 2 μg kg⁻¹ for one or more PAHs.     

Bicarbonate as an interference in B. stearothermophilus assays.

The screening analysis of antibiotic residues in meat products is readily accomplished by a suite of bacterial inhibition assays. Inhibition of B. stearothermophilus is a standard assay noted for its sensitivity to penicillins. In New Zealand, a test kidney from slaughtered animals is accompanied by a urine sample. Generally, penicillins and tetracyclines are both richer in the urine sample, which is applied directly to wells cut in bacterially seeded agar plates. An interference in the assay for B. stearothermophilus has been traced to excessive amounts of bicarbonate in the urine. It is the bicarbonate, not the pH nor the ionic strength that causes the problem. Removal of the bicarbonate was by mild acetic acid treatment to pH 5.5 and vortex mixing to de-gas carbon dioxide. This resulted in complete eradication of the interference without affecting the ability to detect penicillin. The pH change was readily monitored by the indicator bromcresol purple and no complex equipment was needed.     

Differential expression of molecular chaperones in brain of patients with Down syndrome

Heat shock proteins (HSPs) in their molecular capacity as chaperones have been reported to regulate the apoptotic pathway and also play a critical role in protein conformational diseases such as Alzheimer's disease (AD). As all Down syndrome (DS) brains display AD-like neuropathology, neuronal loss in DS was shown to be mediated by apoptosis. We decided to investigate the expression patterns of HSPs in seven brain regions of adults with DS using two-dimensional polyacrylamide gel electrophoresis (2-DE). Following 2-DE, approximately 120 protein spots were successfully identified by matrix-assisted laser desorption/ionization--mass spectrometry (MALDI-MS) followed by quantification of the identified proteins. We unambiguously identified and quantified nine different chaperone proteins. Accordingly, all but three chaperone proteins did exhibit a significant change in expression. HSP 70 RY, heat shock cognate (HSC) 71 and glucose-regulated protein (GRP) 75 showed a significant decrease (P < 0.05) in DS temporal cortex whereas HSP 70.1 and GRP 78 were significantly increased (P<0.05) in cerebellum. Whilst T-complex 1 (TCP-1) epsilon subunit showed a significant decrease (P< 0.05) in parietal cortex, a similar extent of increase (P<0.05) as that observed in cerebellum was obtained in parietal levels of GRP 78. Alpha-crystallin B, HSP 60 and GRP 94 did not show any detectable changes in expression patterns. This report presents the first approach to quantify nine different chaperones simultaneously at the protein level in different brain regions and provides evidence for aberrant chaperone expression patterns in DS. The relevance of this aberrant expression patterns are discussed in relation to the biochemical and neuropathological abnormalities in DS brain.     

Dynamics of vitreous and molten zinc chloride

The dynamics of vitreous and molten zinc chloride have been studied with inelastic neutron scattering at the Intense Pulsed Neutron Source. The results are analyzed in terms of the scattering function, S(Q,E) and the effective vibrational density of states, G(E). The vibrational spectra of both glass and liquid are dominated by broad features centered at 15 and 35 meV which are identified with F₂ modes ZnCl₄²⁻ tetrahedra. The other two normal modes are note observed because of inadequate resolution and broadening and overlap resulting from coupling between tetrahedra. The behavior of ZnCl₂ is contrasted with other tetrahedrally coordinated glasses that have been studied with the same technique.     

The inhibition of carbon deposition on stainless steel by prior selective oxidation

The tendency for carbonaceous deposits to accumulate on steel surfaces exposed to hydro-carbon-containing gaseous environments can be influenced strongly by the chemical nature of the elements present on their surfaces. This is known to be the case for (20% Cr, 25% Ni, 1% Nb) steel, which is used to contain the fuel in the core of the British Advanced Gas-Cooled reactor. It is shown here that carbonaceous deposition on to this steel can be monitored dynamically at temperature in an RF plasma discharge system containing CO₂/CH₄ gas and that the steel can be rendered inert to such deposition, at temperatures up to 650°C by subjecting it to prior annealing (at 800°C) in H₂/H₂O, thereby producing a surface which is free from iron or nickel.     

Algebraic cycles and infinite loop spaces

Summary In this paper we use recent results about the topology of Chow varieties to answer an open question in infinite loop space theory. That is, we construct an infinite loop space structure on a certain product of Eilenberg-MacLane spaces so that the total Chern map is an infinite loop map. An analogous result for the total Stiefel-Whitney map is also proved. Further results on the structure of stabilized spaces of alebraic cycles are obtained and computational consequences are also outlined.Oblatum XII-1991 & 4-II-1993All authors were partially supported by the NSF     

Isomérie Conformationnelle autour de la Liaison Carbone–Carbone dans les Sels de Propénylylidène Ammonium

¹H n.m.r. measurements of a series of propenylylideneammonium salts at temperatures varying from ?90 °C to 70 °C reveal the existence of two conformers. Values of chemical shifts and coupling constants are explained by rotation about a carbon–carbon bond; this hypothesis is supported by the ¹³C n.m.r. results. Free energies of activation are given for various substituents.     

Further studies on the structural determination of esters of 4-Oxo-4H-1-heiizopyran-2-carboxylic acids using the paramagnetic shift reagent eu(FOD)3

The effect of Eu(fod)₃ on the signals of benzylic ruethvlene protons in the pmr spectra of 4-oxo-4H-1-benzopyran derivatives is described. Assignments were confirmed by decoupling experiments. The technique provides a method for distinguishing between structural isomers.