Preparation and certification of zearalenone mass concentration of two low-level maize reference materials

The contamination of maize by fungi, especially by Fusarium species, is a worldwide problem. One of the most prevalent Fusarium mycotoxins frequently found on European maize is zearalenone (ZON), which has been implicated in a range of human and animal diseases. It shows remarkable estrogenic properties and can cause severe infertility problems in farm animals. Currently, 9 countries have set maximum tolerable levels for ZON in food, ranging from 0 to 1000 microg/kg. This paper describes the preparation of 2 maize reference materials (BCR-716 very low level ZON and BCR-717 low level ZON) and the certification of their individual ZON contents (mass concentration and mass fraction). Uncertainties were calculated in compliance with the Guide to the Expression of Uncertainty in Measurement and include uncertainties that are due to possible inhomogeneity and instability. Finally, BCR-716 was certified at a level of <5 microg/kg and BCR-717 at a level of 83 microg/kg with an expanded uncertainty (k = 2) of 9 microg/kg.     

Synthesis of branched poly(methyl methacrylate)s via controlled/living polymerisations exploiting ethylene glycol dimethacrylate as branching agent

With appropriate choice of reaction composition and conditions, copolymerisation of methyl methacrylate and ethylene glycol dimethacrylate using Cu-based ATRP or GTP methodologies yields soluble branched polymers in facile one-pot reactions.     

Methoxysilane purification

Distillable nonionic chloride impurities at 50 to 2000 ppm Cl are conveniently removed from alkoxysilanes by treatment with sodium metal. When free of these contaminants, thought to be 2° and 3° alkyl chlorides, MeSi(OMe)₃ hydrolyzes substantially more slowly than before treatment.     

Energy of activation and temperature for the hydrolysis of sucrose

We have reinvestigated temperature effects on the rates of hydrolysis of 0.0585M sucrose in 0.57M HCl solutions over the range of 10–40°C using polarimetry as a physical method to follow the reaction while simultaneously analyzing the solutions by HPLC for the disappearance of sucrose and by GLC for the appearance of glucose. When the polarimetric data are corrected for the mutarotation lag, the energy of activation values are the same by all three analytical methods and are temperature-independent.     

PHOTOCHEMICAL LABELING OF YEAST ALCOHOL DEHYDROGENASE WITH AN AZIDE ANALOG OF NAD +

Abstract— 3-Azidopyridine adenine dinucleotide, an azide analog of NAD⁺, has been synthesized as a potentially general photochemical labeling reagent for the active sites of NAD-dependent dehydrogenases. The analog is a competitive inhibitor of NAD reduction by yeast alcohol dehydrogenase (YADH). Upon photolysis of the ³H-analog in the presence of YADH, 7% of the label becomes covalently bound. The results are discussed in terms of desired properties of a photochemical labeling reagent.     

Immunostimulatory effects of three classes of CpG oligodeoxynucleotides on PBMC from HCV chronic carriers

Background  

Chronic hepatitis C virus (HCV) infection results from weak or absent T cell responses. Pegylated-interferon-alpha (IFN-α) and ribavirin, the standard of care for chronic HCV, have numerous immune effects but are not potent T cell activators. A potent immune activator such as TLR9 agonist CpG oligodeoxynucleotide (CpG) may complement current treatment approaches.     

On the numerical integration of an odd periodic function over a half-period

A method is described for the numerical evaluation of integrals of the form ∫ ₀ ^p f(t)dt, wheref is an odd periodic function with period 2p. The method is based on term-by-term integration of the Fourier sine series forf(t).