Sugar profile and physicochemical properties of Ethiopian monofloral honey

Three hundred twenty honey samples were collected from Ethiopia, and categorized into nine monofloral honeys using melissopalynology. Theses monofloral honeys were investigated for their sugar profile, physicochemical properties, and quality of honeys. Sugars (fructose, glucose, sucrose, maltose, turanose, and isomaltose) were identified using high-performance liquid chromatography and physicochemical properties (moisture, water activity, pH, acidity, ash, minerals, conductivity, colour) using the Harmonized Method of the International Honey Commission. Moisture and water activity showed a strong regression coefficient (r² = 0.92). Moisture content alone did not sufficiently describe the quality of honey during storage and processing.     

Viscosity and Surface Tension of Oxynitride Glass Melts

The viscosities and surface tensions of three MgO-Al₂O₃-Y₂O₃-SiO₂-based oxynitride glass melts were measured. Glass transition temperature, Littleton temperature, and sink-in temperature were obtained, and by using the Vogel-Fulcher-Tammann equation the viscosities were calculated from T _g (820° to 940°C) to 1600°C. The surface tensions were measured by the drop weight and the drop geometry methods and displayed values between about 500 and 600 N.mm⁻¹. These values are about a factor of two higher than the surface tensions of oxide glass melts.     

The effects of e‐beam crosslinking of LDPE on the permeation of hydrocarbons

Polyethylene is a useful material in numerous applications, such as packaging, fuel tanks as well as oil and gas pipes. However, it must be considered that polyethylene is permeable to gases and liquids. Small molecules, such as hydrocarbons, may permeate through the material and cause environmental problems. Consequently, a particular aspect of polymer materials is the requirement of a high permeation resistance against low‐molecular‐weight hydrocarbons. Modifications of the commonly used polyethylene material are necessary to achieve adjusted permeation properties. In this contribution, the effect of electron‐beam crosslinking of polyethylene on the resulting permeation characteristics was investigated. Polyethylene sheets were processed and crosslinked by irradiation with high energy electrons. The formation of a network structure was characterized by gel content determination and by rheological measurements. The permeation properties of the polymer sheets were assessed by a gravimetric method. It is demonstrated that—as a result of the crosslinking process—the permeation of low molecular weight hydrocarbon through polyethylene is reduced with respect to the chain length of the aliphatic substances. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44968.     

Ultrafast X-ray absorption studies of the structural dynamics of molecular and biological systems in solution

We review our recent studies of excited state structures and dynamics of chemical and biological systems with pico- and femtosecond X-ray absorption spectroscopy in the liquid phase.     

Assaying sialyltransferase activity with surface plasmon resonance

Here, we describe an activity assay for sialyltransferases based on surface plasmon resonance (SPR). Different natural and synthetic oligosaccharides serving as acceptor substrates for the sialyltransferase ST3Gal-III (EC 2.4.99.6) were immobilized or synthesized on SPR chips. The chip was then exposed to different concentrations of a reaction mixture of ST3Gal-III and CMP-Neu5Ac either by injection or by external application of the reaction mixture to the chip surface. The binding of two lectins, one that specifically recognizes the unmodified acceptor, the other the sialylated oligosaccharide, was utilized to determine the extent of enzymatic turnover. In order to obtain enzymatic activities, the SPR data were correlated to data obtained from a classical radio assay. After regeneration, that is, cleavage of the sialic acid residues by using a sialidase, the chip is available for new experiments. The technique allows the rapid determination of sialyltransferase activity with only nanomolar quantities of acceptor substrates and should be of particular value in cases in which a large variety of samples, including cell lysates, have to be screened for their enzymatic activities.