Synthesen und chemisches Reaktionsverhalten neuer überbrückter Chinonderivate. Kupplungsreaktionen von Diazoniumsalzen mit 2-Methoxy-1,6-methano [10]annulen

Syntheses and Chemical Properties of New Bridged Quinone Derivatives. Coupling Reactions of Aryldiazonium Salts with 2-Methoxy-1,6-methano[10]annulene Coupling of 2-methoxy-1,6-methano[10]annulene (3) with the aryldiazonium salts 4a-4i yields the quinone hydrazones 5a-5i. The spectroscopic properties of these products are described. The reaction of 3 with 4-nitrophenyldiazonium tetrafluoroborate buffered with sodium acetate in dry methanol yielded after chromatographic separation the azo derivative 7 on the one hand and a mixture of the valence tautomers 8a and 8b on the other.     

A Growing Drop Technique for Measuring Dynamic Interfacial Tension

A novel, growing drop technique is described for measuring dynamic interfacial tension due to sorption of surface-active solutes. The proposed method relates the instantaneous pressure and size of expanding liquid drops to the interfacial tension and is useful for measuring both liquid/gas and liquid/liquid tensions over a wide range of time scales, currently from 10 ms to several hours. Growing drop measurements on surfactant-free water/ air and water/octanol interfaces yield constant tensions equal to their known literature values. For surfactant-laden, liquid drops, the growing drop technique captures the actual transient tension evolution of a single interface, rather than interval times as with the classic maximum-drop-pressure and drop-volume tension measurements. Dynamic tensions measured for 0.25 mM aqueous 1-decanol solution/air and 0.02 kg/m³ aqueous Triton X-100 solution/dodecane interfaces show nonmonotonic behavior, indicating slow surfactant transport relative to the imposed rates of interfacial dilatation. The dynamic tension of a purified and fresh 6 mM aqueous sodium dodecyl sulfate (SDS) solution/air interface shows only a monotonic decrease, indicating rapid surfactant transport relative to the imposed rates of dilatation. Conversely, an aged SDS solution, naturally containing trace dodecanol impurities, exhibits dynamic tensions which reflect a superposition of the rapidly equilibrating SDS and the slowly adsorbing dodecanol.     

Reference gene stability in peripheral blood mononuclear cells determined by qPCR and NanoString

Quantitative real-time PCR (qPCR) is commonly used for gene expression analyses with defined documentation guidelines to compare published results. To minimize the impact of variances from qPCR performance, sample handling and processing reference genes are used. Their selection process cannot be completely aligned due to variations in experimental conditions. Furthermore, the named sources of error are also present when determining the stability of the reference genes themselves. Even software applications that are used to identify the best reference genes rarely coincide on their rankings and can be misleading under certain conditions. In previous experiments, peripheral blood mononuclear cells (PBMC) were analyzed to identify the most stable reference gene(s). Twelve of the 13 investigated genes showed sample type specific differences in the expression. Direct mRNA measurement was performed in the form of a NanoString analysis, a multiplexed absolute quantification method. The external validation showed a high concordance of the reference gene expression levels. However, it identified the same sample type specific expression pattern for only some of the tested reference genes. By comparing various combinations of reference genes with both methods we are able to suggest a set of well-performing reference genes. Figure

We here compare the expression of reference genes for qPCR and NanoString data and determine the value of the latter method as a bias-free mRNA quantification method     

On-target derivatization of keratan sulfate oligosaccharides with pyrenebutyric acid hydrazide for MALDI-TOF/TOF-MS

In the present work, a rapid and novel method of on-target plate derivatization of keratan sulfate (KS) oligosaccharides for subsequent analysis by matrix-assisted laser desorption and ionization (MALDI) mass spectrometry is described. MALDI-(time-of-flight)-TOF spectra of labeled KS oligosaccharides revealed that significantly improved ionization can be accomplished through derivatization with pyrenebutyric acid hydrazide (PBH), and the most abundant peak in each spectrum corresponds to the singly charged molecular ion [M - H]- or [M + (n - 1)Na - nH]-, where n = the number of sulfates (n = 1, 2, 3...). The high-energy collision-induced dissociation (heCID) spectra of labeled KS oligosaccharides displayed fragments of compounds similar to those observed with laser-induced dissociation (LID) analysis, suggesting that both heCID and LID fragmentations can be used to analyze KS oligosaccharides. Moreover, fragmentation analysis of all labeled KS oligosaccharides was performed by MALDI-TOF/TOF-MS. With LID mode, sodium adducts showed fragmentation of glycosidic linkages with mainly Y/B/C ions, as well as various cross-ring cleavages providing exact information for the positions of sulfate groups along the KS oligosaccharide chains. This one-step on-target derivatization method makes MALDI-TOF/TOF-MS identification of KS fast, simple and highly throughput for trace amounts of biological samples.     

Kinetics of adsorption and proteolytic cleavage of a multilayer ovalbumin film by subtilisin Carlsberg

Adsorption and proteolytic activity of the enzyme subtilisin Carlsberg have been studied on an immobilized, multilayer ovalbumin film. The cross-linked multilayer substrate permits protease adsorption to be examined unencumbered by the surface inhomogeneity typically observed in monolayer studies of protease surface kinetics. Decline of the protein film was measured over time using ellipsometry. Resulting kinetic data as a function of aqueous enzyme concentration and temperature were well fit by a Langmuir-Michaelis-Menten model for surface proteolysis. We observed that both the protein degradation kinetics and the in situ adsorption data were well described by the proposed model. The temperature dependence of the kinetic rate parameter yielded an activation energy of 12 kcal/mol. Further, the apparent Langmuir adsorption equilibrium constant of the enzyme at the protein/aqueous interface was 0.11 L/mg at 22 degrees C, 0.034 L/mg at 36 degrees C, and 0.011 L/mg at 50 degrees C. Although enzyme adsorption at a given aqueous enzyme concentration decreased at higher temperature, the enzyme cleaved the substrate more rapidly, leading to a net increase in the ovalbumin film degradation rate. We observed that the maximum enzyme coverage on the immobilized protein surface was approximately 40% of a close-packed monolayer at ambient temperature (22 degrees C).     

Estimating the Polydispersity of GPC Slices Due to Coeluting Comb‐Polymers Synthesized by Grafting Monodisperse Side Chains Onto a Backbone Having Broad Molecular Weight Distribution

The molecular weight distribution, polydispersity and the distribution of side chains within a GPC‐slice have been calculated for coeluting comb‐shaped polymers. It is assumed that the polymers were synthesized by grafting monodisperse side chains onto a backbone having a broad molecular weight distribution. Despite the broad polydispersity of the backbone the polydispersity within a GPC‐slice is rather narrow, as is the distribution of side chains. Consequently the effect of polydispersity on properties, which can be obtained by GPC coupled with molar mass sensitive detectors is negligible. However, this result is true only for the specific branching mechanism investigated.