Molecular basis and species specificity of high affinity binding of vasoactive intestinal polypeptide by the rat secretin receptor

The affinity and specificity of the binding interaction between ligands and their receptors are key for appropriate hormonal regulation of target tissues. However, it is now apparent that vasoactive intestinal polypeptide (VIP) binds to the rat secretin receptor with similar affinity to that for its natural ligand, secretin (Holtmann et al., 1995). In this report, we establish that this is not a characteristic of the human secretin receptor, and use rat-human secretin receptor chimeras, site mutants and truncated receptor constructs to establish the molecular basis for this unusual binding interaction. Of note, isolated N-terminal domains of the rat secretin and the VIP receptors are capable of high affinity binding of VIP. In the recently recognized secretin family of receptors, this domain has six conserved cysteine residues and disulfide bonds that are likely important to achieve the complex conformation critical for this binding. A single acidic residue (Asp98) present in the rat secretin receptor appears to be critical, because a site-mutant changing this to the polar, but uncharged residue present in that position in the human receptor (Asn) eliminates the high affinity binding of VIP. Of interest, a previously identified critical basic residue in VIP (Lys15) provides a candidate for charge-pairing with this residue, potentially aligning the peptide ligand in a nonproductive orientation within this receptor.     

Verminderung des Gehaltes von Blei und anderen Elementen in Wein mit Hilfe von Pectins?ure

Zusammenfassung Der Bleigehalt von Wein kann durch Zusatz von Pectinsäure (PS) vermindert werden. Die Wirksamkeit der Bleiverminderung durch PS hängt von der Qualitätsstufe des Weines ab. In Auslesewein (Wein A) senkten 6250 mg PS/1 den Bleigehalt in 24 h von 0,88 mg/l auf 0,28 mg/l und in Spätlese (Wein B) von 0,83 mg/l auf 0,06 mg/1. Unter den gleichen Bedingungen nahm in Wein A der Gehalt an Fe, Zn und Cu von 8,85 mg/l auf 7,05 mg/1, von 4,75 mg/l auf 1,25 mg/l and von 0,67 mg/l auf 0.57 mg/l ab; bei Wein B reduzierte sich der Gehalt von Fe, Zn und Cu von 6,70 mg/l auf 5,41 mg/1, von 1,17 mg/l auf 0,28 mg/l und von 0,46 mg/l auf 0,28 mg/1. Durch Filtration des Weines wurde PS nahezu quantitativ entfernt. Eine geschmackliche Beeinträchtigung des Weines durch PS ist bei 750 mg and 1500 mg PS/1 nicht feststellbar, jedoch bei 6 250 mg PS/1 nicht auszuschließen. Aufgrund ihrer hohen Bindungsaffinität zu Blei scheint PS geeignet, Blei auch aus anderen flüssi-gen Lebensmitteln zu entfernen.

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Reduction of lead content and of other metals in wine by means of pectic acid

Summary A procedure for reducing the Pb content in wines containing high levels of Pb is described. The reduction of Pb by means of pectic acid (PA) depends on the quality grade of the wine. In Auslese (wine A) 6250 mg PA/l diminished Pb content in 24 h from 0.88 mg/l to 0.28 mg/1; in Spatlese (wine B) from 0.83 mg/l to 0.06 mg/1. Under the same conditions the content of Fe, Zn, Cu decreased in wine A from 8.85 mg/l to 7.05 mg/1, from 4.75 mg/l to 1.25 mg/1, from 0.67 mg/l to 0.57 mg/l and in wine B from 6.70 mg/l to 5.41 mg/1, from 1.17 mg/l to 0.28 mg, 0.46 mg/l to 0.28 mg/l, respectively. PA is removed almost quantitatively by filtration. Sensory properties of treated wines were unchanged with concentrations of PA of 750 mg and 1500 mg/l. A slight effect on taste at 6250 mg PA/l wine cannot be excluded. On account of its high affinity to Pb, PA will probably remove Pb from other liquid foods as well.

     

Polycyclic Aromatic Hydrocarbons Activate the Aryl Hydrocarbon Receptor and the Constitutive Androstane Receptor to Regulate Xenobiotic Metabolism in Human Liver Cells

Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants produced by incomplete combustion of organic matter. They induce their own metabolism by upregulating xenobiotic-metabolizing enzymes such as cytochrome P450 monooxygenase 1A1 (CYP1A1) by activating the aryl hydrocarbon receptor (AHR). However, previous studies showed that individual PAHs may also interact with the constitutive androstane receptor (CAR). Here, we studied ten PAHs, different in carcinogenicity classification, for their potential to activate AHR- and CAR-dependent luciferase reporter genes in human liver cells. The majority of investigated PAHs activated AHR, while non-carcinogenic PAHs tended to activate CAR. We further characterized gene expression, protein abundancies and activities of the AHR targets CYP1A1 and 1A2, and the CAR target CYP2B6 in human HepaRG hepatoma cells. Enzyme induction patterns strongly resembled the profiles obtained at the receptor level, with AHR-activating PAHs inducing CYP1A1/1A2 and CAR-activating PAHs inducing CYP2B6. In summary, this study provides evidence that beside well-known activation of AHR, some PAHs also activate CAR, followed by subsequent expression of respective target genes. Furthermore, we found that an increased PAH ring number is associated with AHR activation as well as the induction of DNA double-strand breaks, whereas smaller PAHs activated CAR but showed no DNA-damaging potential.     

Effect of Grain Size on Mechanical Properties of Submicrometer 3Y-TZP: Fracture Strength and Hydrothermal Degradation

This paper considers fracture strength, fracture origins, and hydrothermal degradation of 3Y-TZP with grain sizes in the range of 110–480 nm. Biaxial fracture strength testing was used to show that the fracture strength increases with grain size and is governed by the concurrent change in fracture toughness. Hydrothermal degradation was studied by means of fractography, Raman microscopy and its effect on fracture strength. Up to 200 nm grain size, hydrothermal degradation of strength is limited. Larger grain sizes exhibit either premature failure or an increase in strength. A surface transformation zone was found to be responsible for both phenomena.     

The Estimation of the Molecular Weight of Polytetrafluoroethylene Based on the Heat of Crystallisation. A Comment on Suwa's Equation

Summary: The influence of number‐average molecular weight ranging from 1.4 · 10⁴ to 1.2 · 10⁶ g/mol on the thermal behaviour of polytetrafluoroethylene (PTFE) has been studied. Samples have been prepared by radiation‐induced degradation of commercial PTFE. The molecular weight has been calculated using end‐group concentration determined by infrared (IR) spectroscopy and ¹⁹F solid‐state nuclear magnetic resonance (NMR) spectroscopy. Melting and crystallisation heats were investigated by differential scanning calorimetry (DSC). The results have been discussed with respect to quantitative relationships between number‐average molecular weight and heat of crystallisation of PTFE described in the literature. The molecular weight calculated from Suwa's equation, which is often used in the literature, has been found to be too low.

Concentration of end‐groups and the molecular weight of PTFE versus the irradiation dose.     

Reinigung lösungsmittelhaltiger Abluft – alternative Möglichkeiten

Purification of solvents containing air – Alternative methods. Different processes are used for the purification of solvents containing air: condensation, absorption, adsorption, combustion, membrane permeation, and biofilters or bioscrubbers. The processes will be explained by examples. The specifications required by “TA Luft” often cannot be reached only by condensation and membrane permeation. The success of absorption depends on the scrubbing liquid. Glycol ethers are useful scrubbing liquids – especially for chlorinated hydrocarbons. The choice of the process depends on the volume flow rate, the solvent concentration, and the kind of solvent. Recycling of the solvents reduces the costs of the process.     

Nitrate Radicals in Tropospheric Chemistry

Nitrate radicals are being recognized as key intermediates in a growing list of important chemical processes in the atmosphere. Here, the role of nitrate radicals (NO₃) in tropospheric chemistry is discussed, with special emphasis on results from field measurements, most of which have been made by differential optical absorption spectroscopy (DOAS), with matrix-isolation electron spin resonance being an alternative technique. Nitrate radicals were observed in the atmosphere at peak mixing ratios of 350 ppt. Long-term observation of NO₃ shows that 24-h averages in rural air masses are closer to a few ppt. Nevertheless, the NO₃ radical plays an important role in the non-photochemical conversion of NO_x to HNO₃. Also, NO₃ is a strong oxidizing agent and initiates the night-time removal of atmospheric trace species such as olefins, aromatic hydrocarbons, and organic sulfur compounds. Finally, night-time peroxy radical production and release of reactive halogen species from sea salt aerosol might be initiated by NO₃ reactions.     

Detailed Molecular Structure Modeling – A Path Forward to Designing Application Properties of ldPE

Summary: This paper describes a step on the ambitious aim to “design” application properties of ldPE by first simulating the detailed molecular structure of a high‐pressure tubular reactor product. The reactor of a certain configuration produces under well‐defined operating conditions. The next step is to correlate the structure with the application properties. Finally, the sequence will be reversed in order to deduce the operating conditions, which lead to the desired product quality. Two‐dimensional distributions, in molecular weight and branching frequency, as well a two compartment models with a core and a shell stream were simulated and compared with experimental results. Therefore, CFD simulations were carried out to discretize the reaction medium. Samples were taken from both pilot and commercial plants. The TREF‐SEC analytical method was successfully applied in order to measure the microscopic structure of the material. The tremendous numerical problems were solved with the help of the software PREDICI .

Detailed MWD for a pilot scale reactor product.