Direct analysis of silica gel extracts from immunostained glycosphingolipids by nanoelectrospray ionization quadrupole time-of-flight mass spectrometry

A combined strategy of preparative high-performance thin-layer chromatography overlay assay and mass spectrometry was established for the structural characterization of immunostained glycosphingolipids (GSLs) in silica gel extracts. Crude chloroform/methanol/water (30/60/8, v/v/v) extracts of immunostained TLC bands were analyzed by nanoelectrospray low-energy CID mass spectrometry without further purification. The GSL species investigated were isomeric monosialogangliosides of the neolacto series from a ganglioside preparation of human granulocytes, the disialoganglioside GD3 from a human melanoma lipid extract, and ganglio series Gg3Cer of a neutral GSL preparation from murine lymphoreticular MDAY-D2 cells. For the specific detection of lipid-bound oligosaccharides, polyclonal chicken IgY, murine monoclonal IgG3, and IgM antibodies were used. The resulting mass spectra show that only analytical quantities of approximately 1 microg of a single GSL within a complex mixture are required for the structure determination of immunostained GSLs by MS and MS/MS. All species investigated were detected as singly charged deprotonated molecular ions, and neither buffer-derived salt adducts nor coextracted contaminants from the immunostaining procedure or the silica gel layer were observed. This effective HPTLC-MS-joined procedure offers a wide range of applications for any carbohydrate binding agents such as bacterial toxins, plant lectins, and others.     

A kinetic model of aqueous-phase alkali hydrolysis of 2,4,6-trinitrotoluene

Alkali hydrolysis of 2,4,6-trinitrotoluene (TNT) was studied using batch experiments with starting pH values 11 and 12 in glass conical flasks covered with aluminum foil. Isothermal (25 and 40 degrees C) as well as non-isothermal experiments were conducted. Experiments starting at pH 12 resulted in >95% reduction in the concentration of TNT; those starting at pH 11 had a maximum reduction of 20-25% in TNT concentration. In all the experiments, one major stable intermediate was produced but it could not be identified. The experimental data were used to determine the overall stoichiometry of TNT and hydroxyl ions. Approximately 100 M (standard deviation 11.4) of hydroxyl ions were consistently consumed per mole of TNT. However, control experiments showed that all but 13 M (standard deviation 2) of hydroxyl ions were consumed in reactions not related to TNT. A simple kinetic model involving formation of the intermediate was proposed to account for changes in concentrations of TNT and hydroxyl ions. The rate constants and activation energies of the reactions were identified using isothermal data and the kinetic model was then used to predict the experimental data in the non-isothermal experiments reasonably well.     

Enhancement of nonlinear effects using photonic crystals

The quest for all-optical signal processing is generally deemed to be impractical because optical nonlinearities are usually weak. The emerging field of nonlinear photonic crystals seems destined to change this view dramatically. Theoretical considerations show that all-optical devices using photonic crystal designs promise to be smaller than the wavelength of light, and to operate with bandwidths that are very difficult to achieve electronically. When created in commonly used materials, these devices could operate at powers of only a few milliwatts. Moreover, if these designs are combined with materials and systems that support electromagnetically induced transparency, operation at single-photon power levels could be feasible.     

A Windows computer application for long term data acquisition, storage and presentation of biological signals

We developed a windows application dedicated to recording, displaying and storing large amounts of biological signals on a standard PC. The application works in Matlab and uses an A/D-converter interface that enables a user to run the same software for signal acquisition, display and processing with different A/D-converter boards. The software program consists of three integrated modules, for setting the protocol for signal acquisition; for commands that can be accessed during data acquisition and for software routines that enable off-line viewing, pre-processing and processing of recorded data. It adapts to different computer hardware configurations by enabling the user to define file size, data resolution and file storage on local and network hard disks during signal acquisition.     

Basicity of the amino groups of the aminoglycoside amikacin using capillary electrophoresis and coupled CE-MS-MS techniques

This paper describes the use of capillary electrophoresis (CE), and coupled CE and mass spectrometric techniques, to measure the values of the pKa of the amino groups of the aminoglycoside antibiotic amikacin and of its acetylated derivatives. These values of pKa (8.4, 6.7, 9.7, 8.4) were determined by measuring the electrophoretic mobilities of the molecules as a function of pH; they are within 0.7 unit of certain values reported in the literature (by 13C and 15N NMR spectroscopies) but resolved ambiguities left by these earlier studies. The range of values of pKa of amino groups also indicates the complex dependence of the acidity of a functional group (and thus the extent of ionization at a specified value of pH) on the molecular environment of that group.     

Quantitative analysis of bacterial and mammalian proteomes using a combination of cysteine affinity tags and 15N-metabolic labeling

We describe the combined use of 15N-metabolic labeling and a cysteine-reactive biotin affinity tag to isolate and quantitate cysteine-containing polypeptides (Cys-polypeptides) from Deinococcus radiodurans as well as from mouse B16 melanoma cells. D. radiodurans were cultured in both natural isotopic abundance and 15N-enriched media. Equal numbers of cells from both cultures were combined and the soluble proteins extracted. This mixture of isotopically distinct proteins was derivatized using a commercially available cysteine-reactive reagent that contains a biotin group. Following trypsin digestion, the resulting modified peptides were isolated using immobilized avidin. The mixture was analyzed by capillary reversed-phase liquid chromatography (LC) online with ion trap mass spectrometry (MS) as well as Fourier transform ion cyclotron resonance (FTICR) MS. The resulting spectra contain numerous pairs of Cyspolypeptides whose mass difference corresponds to the number of nitrogen atoms present in each of the peptides. Designation of Cys-polypeptide pairs is also facilitated by the distinctive isotopic distribution of the 15N-labeled peptides versus their 14N-labeled counterparts. Studies with mouse B16 cells maintained in culture allowed the observation of hundreds of isotopically distinct pairs of peptides by LC-FTICR analysis. The ratios of the areas of the pairs of isotopically distinct peptides showed the expected 1:1 labeling of the 14N and 15N versions of each peptide. An additional benefit from the present strategy is that the 15N-labeled peptides do not display significant isotope-dependent chromatographic shifts from their 14N-labeled counterparts, therefore improving the precision for quantitating peptide abundances. The methodology presented offers an alternate, cost-effective strategy for conducting global, quantitative proteomic measurements.     

Explanation of Performance Degradation in Turn Model

The Turn model routing algorithms for mesh interconnection network achieve partial adaptivity without any virtual channels. However, the routing performance measured by simulations is worse than with the simple deterministic routing algorithm. Authors have explained these results simply by uneven dynamic load through the network. However, this phenomenon has not been studied further. This paper investigates performance degradation with Turn model and drawbacks of partially adaptive routing in comparison with the deterministic routing, and it introduces some new concepts. Our simulations deal with individual channels and results are presented by 3D graphs, rather than by commonly used averages. An additional parameter—channel occupation, which is consistent with queuing theory commonly used in many proposed analytical models, is introduced. We also propose a new structure, the Channel Directions Dependency Graph (CDDG). It provides a new approach in analysis, helps in understanding of dynamic routing behaviour, and it can be generalized in other routing algorithms.     

Electrodeposition of Ni–Mo alloy coatings and their characterization as cathodes for hydrogen evolution in sodium hydroxide solution

The hydrogen evolution reaction on the electrodeposited Ni–Mo alloy coatings, as well as their electrochemical properties in the NaOH solutions, have been investigated by the polarization measurements, cyclic voltammetry and EIS technique. It was shown that the Ni–Mo alloy coatings electrodeposited from the pyrophosphate-sodium bicarbonate bath possess high catalytic activity for hydrogen evolution in the NaOH solutions. Their stability in the 1 M NaOH at 25 °C under the condition of the reverse polarization was shown to be very good, while in the 33% NaOH at 85 °C (conditions of the industrial electrolysis) the electrodeposited Ni–Mo alloy coatings exhibited also high catalytic activity, but low stability, as a consequence of a deterioration of the alloy coatings.     

Controller order reduction for robust control of parallel operating dc/dc converters

 A useful straightforward controller order reduction procedure for multivariable robust control is presented. Reduced controllers regarding robust stability criterion and robust performance criterion are developed. Weighted Balanced Truncation is used as the concept for the real reduction work. The procedure is applied to Loop Shaping Design Procedure, Internal Model Control and Decentralized robust controllers of parallel operating dc/dc converters. Uncertainty robustness and performance of the closed-loop systems with reduced controllers are investigated. The reduction procedure efficiently decreases high controller orders, from which robust theory suffers, preserving at the same time closed-loop robust stability and robust performance at a desired level.