Relative importance of basicity in the gas phase and in solution for determining selectivity in electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry is a critically important technique for the determination of small molecules, but its application for this purpose is complicated by its selectivity. For positive ion ESI-MS analysis of basic analytes, several investigators have pointed to the importance of analyte basicity as a source of selectivity. Currently, however, it is not known whether basicity in the gas phase or in solution is ultimately most important in determining responsiveness. The objective of these studies was to investigate the relative importance of basicity in solution and in the gas phase as factors that predict selectivity in positive ion ESI-MS analysis. ESI-MS response was compared for a diverse series of protonatable analytes in two different solvents, neat methanol and methanol with 0.5% acetic acid. A correlation was observed between analyte pK(b) and electrospray response. However, the response for the analytes with very high pK(b) values was significantly higher than would be expected based on concentration of the protonated form or the analyte in solution, and this higher response did not appear to result from gas-phase proton transfer reactions. Although all of the analytes investigated had higher gas-phase basicities than the solvent, their relative responses were not dictated by gas-phase basicity. Higher response was observed for all of the analytes studied in acidified methanol compared with neat methanol, and this higher response was most pronounced for weakly basic analytes. These findings support the use of analyte pK(b) for rational method development in ESI-MS analysis of small molecules.     

On the Massive Antenna Suspension System in the Brazilian Gravitational Wave Detector SCHENBERG

SCHENBERG is a resonant-mass gravitational wave detector built in Brazil. Its spherical antenna, weighting 1.15 t, is connected to the outside world by a suspension system whose main function is to attenuate the external seismic noise. In this work, we report how the system was modeled using finite elements method. The model was validated on experimental data. The simulation showed that the attenuation obtained is of the order of 260 dB, which is sufficient for decreasing the seismic noise below the level of the thermal noise of the detector operating at 50 mK.     

High performance liquid chromatography/electrospray ionization mass spectrometry for simultaneous analysis of alkamides and caffeic acid derivatives from Echinacea purpurea extracts

Extracts of the plant Echinacea purpurea are widely used for medicinal purposes. Effective quality control of these extracts requires rapid methods to determine their chemical composition. A new method for analysis of caffeic acid derivatives and alkamides from Echinacea extracts has been developed. With this method, isomeric isobutylamides and 2-methylbutylamides can be distinguished, a capability that previously published methods have lacked. Quantitative analyses carried out with this method on E. purpurea extracts that have been stored for 18 months indicate that they contain caftaric acid, cichoric acid, and undeca-2Z,4E-diene-8,10-diynoic acid isobutylamide at concentrations of 0.7, 0.71 and 2.0mg/mL, respectively.     

Multiscale Modeling of Colloid and Fluid Dynamics in Porous Media Including an Evolving Microstructure

We consider colloidal dynamics and single-phase fluid flow within a saturated porous medium in two space dimensions. A new approach in modeling pore clogging and porosity changes on the macroscopic scale is presented. Starting from the pore scale, transport of colloids is modeled by the Nernst?CPlanck equations. Here, interaction with the porous matrix due to (non-)DLVO forces is included as an additional transport mechanism. Fluid flow is described by incompressible Stokes equations with interaction energy as forcing term. Attachment and detachment processes are modeled by a surface reaction rate. The evolution of the underlying microstructure is captured by a level set function. The crucial point in completing this model is to set up appropriate boundary conditions on the evolving solid?Cliquid interface. Their derivation is based on mass conservation. As a result of an averaging procedure by periodic homogenization in a level set framework, on the macroscale we obtain Darcy??s law and a modified averaged convection?Cdiffusion equation with effective coefficients due to the evolving microstructure. These equations are supplemented by microscopic cell problems. Time- and space-dependent averaged coefficient functions explicitly contain information of the underlying geometry and also information of the interaction potential. The theoretical results are complemented by numerical computations of the averaged coefficients and simulations of a heterogeneous multiscale scenario. Here, we consider a radially symmetric setting, i.e., in particular we assume a locally periodic geometry consisting of circular grains. We focus on the interplay between attachment and detachment reaction, colloidal interaction forces, and the evolving microstructure. Our model contributes to the understanding of the effects and processes leading to porosity changes and pore clogging from a theoretical point of view.     

Optimal glucose and inoculum concentrations for production of bioactive molecules by Paenibacillus polymyxa RNC-D

The production of antimicrobial metabolites by Paenibacillus polymyxa RNC-D was assessed. Two process variables, glucose and inoculum concentrations, were evaluated at different levels (5?C40 g L^?1, and at ?? _r = 2.5?C5.0 %, respectively), and their effects on biomass formation, minimal inhibitory concentration (MIC) against Escherichia coli, and surface tension reduction (STR) were studied. When the fermentation process was carried out under non-optimised conditions, the biomass, MIC, and STR achieved the following values: 0.6 g L^?1, 1 g L^?1, and 18.4 mN m^?1, respectively. The optimum glucose (16 g L^?1) and inoculum volume ratio (?? _r = 5.0 %) were defined in order to maximise the biomass formation, with a low value of MIC and high STR of extract. The experiments carried out under optimal conditions showed the following values for the dependent variables: biomass concentration 2.05 g L^?1, MIC 31.2 ??g mL^?1, and STR 10.7 mN m^?1, which represented improvement of 241.7 %, 96.9 %, and 41.9 % for the responses of biomass, MIC, and STR, respectively. This is the first recorded study on the optimisation of culture conditions for the production of antimicrobial metabolites of P. polymyxa RNC-D, and constitutes an important step in the development of strategies to modulate the production of antimicrobial molecules by this microorganism at elevated levels.     

Examining the Potential of Plasma-Assisted Pretreated Wheat Straw for Enzyme Production by <Emphasis Type="Italic">Trichoderma reesei</Emphasis>

Plasma-assisted pretreated wheat straw was investigated for cellulase and xylanase production by Trichoderma reesei fermentation. Fermentations were conducted with media containing washed and unwashed plasma-assisted pretreated wheat straw as carbon source which was sterilized by autoclavation. To account for any effects of autoclavation, a comparison was made with unsterilized media containing antibiotics. It was found that unsterilized washed plasma-assisted pretreated wheat straw (which contained antibiotics) was best suited for the production of xylanases (110 IU ml⁻¹) and cellulases (0.5 filter paper units (FPU) ml⁻¹). Addition of Avicel boosted enzyme titers with the highest cellulase titers (1.5 FPU ml⁻¹) found with addition of 50 % w/w Avicel and with the highest xylanase production (350 IU ml⁻¹) reached in the presence of 10 % w/w Avicel. Comparison with enzyme titers from other nonrefined feedstocks suggests that plasma pretreated wheat straw is a promising and suitable substrate for cellulase and hemicellulase production.     

Demonstration of the two-chamber approach for high-voltage measurements using collinear laser spectroscopy

An electronic measurement of high-voltages of several ten kV with accuracy as required for precision experiments is currently only feasible using highly sophisticated voltage dividers. Collinear laser spectroscopy can provide a direct and precise measurement of high-voltages using the Doppler shift of accelerated ions. Although proposed already in 1982, a measurement with relative accuracy better than 10^?4 was not reported so far. To improve this accuracy, a dedicated new setup for high-voltage measurements will be installed at the Technische Universität Darmstadt. A two-chamber approach will be used to remove uncertainties due to the insufficiently known starting potential inside the ion source. Here we present a demonstration of the pump-and-probe technique performed in preparatory studies at the TRIGA-LASER experiment in Mainz.