Method development for mono- and disaccharides monitoring in cell culture medium by capillary and microchip electrophoresis

The rapidly growing, competitive biopharmaceutical market requires tight bioprocess monitoring. An integrated, automated platform for the routine online/at-line monitoring of key factors in the cell culture medium could greatly improve process monitoring. Mono- and disaccharides, as the main energy and carbon source, are one of these key factors. A CE-LIF method was developed for the analysis of several mono- and disaccharides, considering requirements and restrictions for analysis in an integrated, automated monitoring platform, such as the possibility for miniaturization to microchip electrophoresis. Analysis was performed after fluorescent derivatization with 8-aminopyrene-1,3,6-trisulfonic acid. The derivatisation reaction and the separation BGE were optimized using design of experiments. The developed method is applicable to the complex matrix of cell culture medium and proved transferable to microchip electrophoresis.     

X-ray study on the effect of moisture on the crystalline state of cellulose

A method is presented for measuring the change of the intensity of x-ray diffraction peaks of cellulose specimens as a consequence of humidity changes of the specimens. Measurements performed showed a decrease of this intensity after drying pulp specimens initially kept in humid air. Thus the order in cellulose decreased during drying.     

R?ntgenstrahl-Untersuchung der thermischen Ausdehnung von Baumwollecellulose

Ohne Zusammenfassung     

Comparison of 1D, 2D and 3D quench onset simulations

Measured and simulated minimum quench energies (MQE) for short samples are doubtful when estimating disturbance tolerance of an impregnated superconducting magnet. If measurements are performed at liquid cryogen, the cooling provided by the cryogen causes MQE to be high. At a conduction-cooled system, the transverse heat conduction is neglected causing low MQE. Even though these conditions can be artificially brought closer to the ones in an impregnated magnet, it is difficult to estimate by short-sample measurement the MQE of a superconducting coil. These similar difficulties are present at simulations. On the other hand, 1D and 2D measurements and simulations can be used, e.g., to compare wires or consider effect of insulation layer thickness, but according to the results only in a rough quantitative way. In this paper, we compare MQE and normal zone propagation velocity simulations of an MgB₂ wire with 1D, 2D and 3D finite element method models to focus on the different results given by the models employing different dimensions.     

Carboxylate Catalyzed Isomerization of β,γ-Unsaturated N-Acetylcysteamine Thioesters**

We demonstrate herein the capacity of simple carboxylate salts – tetrametylammonium and tetramethylguanidinium pivalate – to act as catalysts in the isomerization of β,γ-unsaturated thioesters to α,β-unsaturated thioesters. The carboxylate catalysts gave reaction rates comparable to those obtained with DBU, but with fewer side reactions. The reaction exhibits a normal secondary kinetic isotope effect (k_1H/k_1D=1.065±0.026) with a β,γ-deuterated substrate. Computational analysis of the mechanism provides a similar value (k_1H/k_1D=1.05) with a mechanism where γ-reprotonation of the enolate intermediate is rate determining.     

Stability considerations of a high-temperature superconductor tape at different operating temperatures

Stability of a Bi-2223/Ag multifilamentary composite conductor against fast transport current ramps was studied by using a numerical model. The model was based on the two-dimensional magnetic diffusion and heat conduction equations. Calculations were carried out both in an adiabatic mode and pool boiling modes in liquid helium, hydrogen and nitrogen. When estimating the heat load (AC losses), real temperature dependent current density–electric field characteristics were used. The results computed by the finite element method are presented and discussed with special emphasis on differences of the stability considerations between high-temperature and low-temperature superconductors.     

Analysis of amino acids in cell culture supernatant using capillary electrophoresis with contactless conductivity detection

CE-C⁴D methods for the analysis of amino acids (AAs) are presented. Combining the results from two methods with acetic acid and cyclodextrin-based BGEs, 20 proteinogenic AAs could be analyzed using CE. CE-C⁴D was also, for the first time, applied to analyze free AAs in samples of mammalian cell culture supernatant. After dilution as only sample preparation, combining the results of the two CE methods allowed monitoring the concentration changes of 17 AAs in samples taken during the cultivation of CHO cells.