Influence of heavy metals on the early hydration of calcium sulfoaluminate

The hydration of calcium sulfoaluminate $ ( {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} ) $ in the presence of heavy metal is essential not only for applying the cement in solidification/stabilization (s/s) process, but also for preparing modern green cements from wastes containing heavy metals. In this study, the influence of gypsum, types, and concentrations of heavy metal nitrates (Pb(NO₃)₂, Cr(NO₃)₃·9H₂O, Cu(NO₃)₂·3H₂O, Zn(NO₃)₂·6H₂O) on the hydration of $ {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} $ during the first 24 h were investigated by isothermal conduction calorimetry, X-ray diffraction, and thermogravimetric analysis. The addition of 20 % of gypsum to $ {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} $ leads to a rapid formation of ettringite against monosulfate and acceleration of hydration. The effects of heavy metals on the hydration of $ {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} $ depend on the types of heavy metals and the addition of gypsum. Without any gypsum addition, heavy metal nitrates such as Cr, Cu, and Zn promote the hydration of $ {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} $ , whereas Pb presents a strong retardation effect at the early age of $ {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} $ hydration. When 20 % of gypsum is added to $ {\text{C}}_{4} {\text{A}}_{3} \overline{\text{S}} $ , heavy metals tend to accelerate the hydration of the blended pastes except Zn. However, heavy metal containing phases were not detected in this work, which needs to be supplemented by further investigations.     

Chemical Synthesis of a Glycopeptide Derived from Skp1 for Probing Protein Specific Glycosylation

Skp1 is a cytoplasmic and nuclear protein, best known as an adaptor of the SCF family of E3‐ubiquitin ligases that label proteins for their degradation. Skp1 in Dictyostelium is posttranslationally modified on a specific hydroxyproline (Hyp) residue by a pentasaccharide, which consists of a Fucα1,2‐Galβ‐1,3‐GlcNAcα core, decorated with two α‐linked Gal residues. A glycopeptide derived form Skp1 was prepared to characterize the α‐galactosyltransferase (AgtA) that mediates the addition of the α‐Gal moieties, and to develop antibodies suitable for tracking the trisaccharide isoform of Skp1 in cells. A strategy was developed for the synthesis of the core trisaccharide‐Hyp based on the use of 2‐naphthylmethyl (Nap) ethers as permanent protecting groups to allow late stage installation of the Hyp moiety. Tuning of glycosyl donor and acceptor reactivities was critical for achieving high yields and anomeric selectivities of glycosylations. The trisaccharide‐Hyp moiety was employed for the preparation of the glycopeptide using microwave‐assisted solid phase peptide synthesis. Enzyme kinetic studies revealed that trisaccharide‐Hyp and trisaccharide‐peptide are poorly recognized by AgtA, indicating the importance of context provided by the native Skp1 protein for engagement with the active site. The trisaccharide‐peptide was a potent immunogen capable of generating a rabbit antiserum that was highly selective toward the trisaccharide isoform of full‐length Skp1.     

Free-flow zone electrophoresis and isoelectric focusing using a microfabricated glass device with ion permeable membranes

This paper describes a microfabricated free-flow electrophoresis device with integrated ion permeable membranes. In order to obtain continuous lanes of separated components an electrical field is applied perpendicular to the sample flow direction. This sample stream is sandwiched between two sheath flow streams, by hydrodynamic focusing. The separation chamber has two open side beds with inserted electrodes to allow ventilation of gas generated during electrolysis. To hydrodynamically isolate the separation compartment from the side electrodes, a photo-polymerizable monomer solution is exposed to UV light through a slit mask for in situ membrane formation. These so-called salt-bridges resist the pressure driven fluid, but allow ion transport to enable electrical connection. In earlier devices the same was achieved by using open side channel arrays. However, only a small fraction of the applied voltage was effectively utilized across the separation chamber during free-flow electrophoresis and free-flow isoelectric focusing. Furthermore, the spreading of the carrier ampholytes into the side channels resulted in a very restricted pH gradient inside the separation chamber. The chip presented here allows at least 10 times more efficient use of the applied potential and a nearly linear pH gradient from pH 3 to 10 during free-flow isoelectric focusing could be established. Furthermore, the application of hydrodynamic focusing in combination with free-flow electrophoresis can be used for guiding the separated components to specific chip outlets. As a demonstration, several standard fluorescent markers were separated and focused by free-flow zone electrophoresis and by free-flow isoelectric focusing employing a transversal voltage of up to 150 V across the separation chamber.     

(Tetracycline)europium(III) Complex as Luminescent Probe for Hydrogen Peroxide Detection

Luminescence spectra of aqueous solutions containing a fixed concentration of tetracycline (TC) and increasing concentrations of Eu³⁺ were recorded both in the absence and presence of hydrogen peroxide (H₂O₂). In H₂O₂‐free solutions in which the Eu/TC molar ratio was varied from 1 : 1 to 8 : 1, the ⁵D₀→⁷F₀ transition consisted of only one peak at 580 nm. In the presence of H₂O₂, an extra peak appeared in the spectrum at 578 nm when the Eu/TC molar ratios were above 2.5. A detailed analysis of this spectral region revealed that at lower Eu/TC molar ratios (up to 2 : 1), the ⁵D₀→⁷F₀ transition experienced a slight blue shift. This indicates that at low Eu/TC molar ratios, the presence of H₂O₂ leads to two different environments of the trivalent europium ions, which most likely form bridged peroxide complexes with hydrogen peroxide (μ‐H₂O₂ ligand). Luminescence spectra measured in the presence of molybdate ions, which catalytically decompose H₂O₂, led to the disappearance of the extra europium(III) site that was formed in the presence of H₂O₂. The intensity of the hypersensitive ⁵D₀→⁷F₂ transition did not linearly depend on the H₂O₂/TC molar ratio. For H₂O₂/TC ratios up to 10, a sharp linear increase of the peak intensity was observed, but with further increase of the H₂O₂ concentration, the intensity remained nearly constant. For H₂O₂/TC ratios above 100, the intensity of this transition even started to decrease, which limits the use of the (tetracycline)europium(III) system to quantify hydrogen peroxide in solution.