No mutations found by RET mutation scanning in sporadic and hereditary neuroblastoma

Neuroblastoma occasionally occurs in diseases associated with abnormal neurocrest differentiation, e.g. Hirschsprung disease. Expression studies in developing mice suggest that the proto-oncogene RET plays a role in neurocrest differentiation. In humans expression of RET is limited to certain tumor types, including neuroblastoma, that derive from migrating neural crest cells. Mutations of RET are found associated with Hirschsprung disease. These data prompted us to investigate expression of RET and to search for gene mutations in neuroblastoma. Out of 16 neuroblastoma cell lines analyzed, 9 show clear expression of RET in a Northern blot analysis. In a single strandt conformation polymorphism (SSCP) analysis of all exons, no mutations were detected other than neutral polymorphisms. In a patient with neuroblastoma, from a family in which different neurocrestopathies, including neuroblastoma and Hirschsprung disease, had occurred, we also failed to detect RET mutations. Possibly, expression of RET in neuroblastoma merely reflects the differentiation status of the tumor cells. The absence of mutations suggests that RET does not play a crucial role in the tumorigenesis of neuroblastoma.     

Multiphase monolith reactors: Chemical reaction engineering of segmented flow in microchannels

The use of segmented flow in capillaries, also known as Taylor flow, for reaction engineering purposes has soared in recent years. On the one hand, Taylor flow has been used in honeycomb monolith catalyst supports. On the other hand, Taylor flow is the common flow pattern in multiphase microchannel reactors. This contribution reviews the fluid mechanical aspects of this flow pattern in quite general terms, with an emphasis on the underlying principles. From very simple analysis, design estimates for mass transfer, pressure drop and residence time distribution may be obtained with relative ease and—for multiphase reactors—surprising accuracy.     

Accelerated synthesis of all-silica DD3R and its performance in the separation of propylene/propane mixtures

Synthesis of the all-silica Deca-Dodecasil 3 Rhombohedral (DD3R) zeolite was accelerated 10 times by seeding with small amount of crystals (0.02 wt%) with yields approaching 100%. The effects of other synthesis variables, like silica source, the presence of methanol or the synthesis pH on the final product distribution have been studied. The adsorption and separation of propylene and propane mixtures on this material are presented. The improved synthesis may form the basis to scale-up production of DD3R for selective separation processes. The single component adsorption isotherms could be well described with a dual-site Langmuir model. The binary mixture adsorption was determined from breakthrough/desorption experiments at 323, 358 and 383 K. By modelling the adsorptive column, diffusion coefficients at infinite dilution for single component and the effect of propane over propylene adsorption were determined. Cylindrical geometry describes the pore topology of DDR type materials well. Propane decreases the uptake rate of propylene by adsorption in the surface of the crystals. Propylene diffusion is best described by the “strong confinement” model inside the zeolite cages. Separation is due to only propylene adsorption with diffusion as rate determining step.Results revealed DD3R as a very effective molecular sieve for the separation or purification of propane–propylene mixtures.     

Formalizing Arrow’s theorem

A small project in which I encoded a proof of Arrow’s theorem—probably the most famous results in the economics field of social choice theory—in the computer using the Mizar system is presented here. The details of this specific project, as well as the process of formalization (encoding proofs in the computer) in general are discussed.     

Pd and Pt catalysts supported on carbon-coated monoliths for low-temperature combustion of xylenes

Carbon-coated monoliths were prepared from polyfurfuryl alcohol coated cordierite structures obtained by dip-coating. In this way, thin, homogeneous, consistent and good adhered carbon layers were obtained. The different steps followed in the preparation of these catalyst supports were studied by scanning electron microscopy. Pd and Pt catalysts were prepared by equilibrium impregnation of the monolithic supports with an aqueous solution of the corresponding tetraammine metal (II) nitrates. The catalysts were pretreated in H₂ at 300 °C before their characterization by chemisorption or before testing their catalytic activity. This pretreatment was monitored by temperature programme reduction. Catalytic activities in xylene combustion were evaluated as a function of the reaction temperature as well as against time on stream. The monolithic catalysts were thermally stable during the reaction. The Pt catalysts were more active than the Pd ones. The Pd catalysts with smaller Pd-particle sizes were more active. In the case of Pt catalysts however, the opposite was observed, which might be due to a structure sensitivity effect. Complete xylene combustion was reached in the range between 150 and 180 °C with a total selectivity to CO₂ and H₂O. Combustion of m-xylene was easier than p-xylene over Pt.     

Application of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry as a monitoring tool for in‐house brewer's yeast contamination: a proof of concept

Contamination of brewer's pitching yeast cultures with wild‐type yeasts or bacteria is unwanted as it can corrupt the fermentation outcome and causes huge economic losses for the brewing industry. The applicability of matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) as a fast tool to monitor the purity of brewer's yeast cultures was investigated. This proof of concept was examined for a brewer's yeast strain contaminated with wild‐type yeast and for bottled beer produced by fermentation with that particular contaminated brewer's yeast strain. The data demonstrated that MALDI‐TOF MS is very suitable to discriminate between brewing and non‐brewing yeast strains. Copyright © 2014 The Institute of Brewing & Distilling     

Capillary electrophoresis coupled on-line with ultraviolet resonance Raman spectroscopy

Capillary electrophoresis (CE) and resonance Raman spectroscopy (RRS) with excitation in the deep ultraviolet (UV) region (lambda(ex): 244 or 257 nm) were coupled on-line. The potential of this hyphenated technique, denoted as CE-UV-RRS, for analyte confirmation/identification purposes was explored with aromatic sulfonic acids and nucleotides as test compounds. Good-quality UV-RRS spectra could be recorded on-the-fly. Identification limits for the nucleotides were in the 10-125 microg/mL range. The RRS spectra showed sufficient characteristic features to enable analyte confirmation. In addition, the identification power of UV-RRS was studied with substituted pyrenes as model compounds. The compounds were distinguishable on the basis of their RRS spectra at 244 nm.     

A flow injection kinase assay system based on time-resolved fluorescence resonance energy-transfer detection in the millisecond range

A flow injection analysis (FIA) system for biochemical assays using time-resolved fluorescence resonance energy transfer (TR-FRET) in the millisecond time scale was developed. As a model system, we studied a kinase assay, measuring the phosphorylation of poly(GT)-biotin (substrate) by a receptor tyrosine kinase (epidermal growth factor receptor). A streptavidin labeled with XL665 (SA-XL665)-the acceptor-was coupled to the biotin moiety, and an antiphosphotyrosine antibody labeled with europium cryptate (Ab-EuK)-the donor-was coupled to the phosphorylated tyrosine group(s). Long-lived FRET can only occur if the substrate is successfully phosphorylated. For the time-resolved detection of such long-lived luminescence phenomena in a flow system, the repetition rate of the excitation source plays a crucial role. Good results were obtained for a small-sized commercially available quadrupled Nd:YAG laser emitting at 266 nm with a repetition rate of 7.8 kHz and a pulse width of 0.3 ns. The long-lived emissions of the donor at 625 nm and that of the acceptor at 665 nm were monitored simultaneously with two photomultipliers, using a delay time of 50 micros and a gate time of 75 micros to exclude background fluorescence interferences. In the FIA experiments, the Ab-EuK concentration was 6 nM and the substrate concentration and SA-XL665 concentrations were 7 nM. By monitoring the intensity changes at 625 and 665 nm, the inhibition of tyrosine kinase by tyrphostin AG1478 was studied and an IC(50) value of 5.1 +/- 0.4 nM obtained.