Peptide mapping using capillary electrophoresis offline coupled to matrix-assisted laser desorption ionization time of flight mass spectrometry

This article reports the results of a study carried out to evaluate the offline hyphenation of capillary zone electrophoresis with matrix-assisted lased desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) for the analysis of low-abundant complex samples, represented by the tryptic phosphorylated peptides of phosphoproteins, such as α-casein, β-casein, and fetuin. The proposed method employs a latex-coated capillary and consists in the online preconcentration of the tryptic peptides by a pH-mediated stacking method, their separation by capillary zone electrophoresis, and subsequent deposition of the separated analytes onto a MALDI target for their MS analysis. The online preconcentration method allows loading a large sample volume (～150?nL), which is introduced into the capillary after the hydrodynamic injection of a short plug of 1.0?M ammonium hydroxide solution and is sandwiched between two plugs of the acidic background electrolyte solution (BGE) filling the capillary. The sample spotting of the separated analytes onto the MALDI target is performed either during or postseparation using an automatic spotting device connected to the exit of the separation capillary. The proposed method allows the separation and identification of multiphosphorylated peptides from other peptides and enables their identification at femtomole level with improved efficiency compared with LC approaches hyphenated to MS.     

CE coupled to MALDI with novel covalently coated capillaries

CE offers the advantage of flexibility and method development options. It excels in the area of separation of ions, chiral, polar and biological compounds (especially proteins and peptides). Masking the active sites on the inner surface of a bare fused silica capillary wall is often necessary for CE separations of basic compounds, proteins and peptides. The use of capillary surface coating is one of the approaches to prevent the adsorption phenomena and improve the repeatability of migration times and peak areas of these analytes. In this study, new capillary coatings consisting of (i) derivatized polystyrene nanoparticles and (ii) derivatized fullerenes were investigated for the analysis of peptides and protein digest by CE. The coated capillaries showed excellent run‐to‐run and batch‐to‐batch reproducibility (RSD of migration time ≤0.5% for run‐to‐run and ≤9.5% for batch‐to‐batch experiments). Furthermore, the capillaries offer high stability from pH 2.0 to 10.0. The actual potential of the coated capillaries was tested by combining CE with MALDI‐MS for analysing complex samples, such as peptides, whereas the overall performance of the CE‐MALDI‐MS system was investigated by analysing a five‐protein digest mixture. Subsequently, the peak list (peptide mass fingerprint) generated from the mass spectra of each fraction was entered into the Swiss‐Prot database in order to search for matching tryptic fragments using the MASCOT software. The sequence coverage of analysed proteins was between 36 and 68%. The established technology benefits from the synergism of high separation efficiency and the structure selective identification via MS.     

Measurement of the antiproton-nucleus annihilation cross-section at very low energies

The ASACUSA collaboration at the Antiproton Decelerator at CERN is planning to measure the hyperfine splitting of the ground state of antihydrogen using an atomic beam line. This will be a measurement of the antiproton magnetic moment, and also a test of the CPT invariance. The planned experimental method and setup, including the radiofrequency resonance cavity, are described, and results of Monte Carlo simulations are shown. These simulations predict that the antihydrogen ground-state hyperfine splitting can be determined with a relative precision of ～10^???7.     

Very high order PNPM schemes on unstructured meshes for the resistive relativistic MHD equations

In this paper we propose the first better than second order accurate method in space and time for the numerical solution of the resistive relativistic magnetohydrodynamics (RRMHD) equations on unstructured meshes in multiple space dimensions. The nonlinear system under consideration is purely hyperbolic and contains a source term, the one for the evolution of the electric field, that becomes stiff for low values of the resistivity.     

An Algebraic Presentation of Term Graphs, via GS-Monoidal Categories

We present a categorical characterization of term graphs (i.e., finite, directed acyclic graphs labeled over a signature) that parallels the well-known characterization of terms as arrows of the algebraic theory of a given signature (i.e., the free Cartesian category generated by it). In particular, we show that term graphs over a signature are one-to-one with the arrows of the free gs-monoidal category generated by . Such a category satisfies all the axioms for Cartesian categories but for the naturality of two transformations (the discharger ! and the duplicator ), providing in this way an abstract and clear relationship between terms and term graphs. In particular, the absence of the naturality of and ! has a precise interpretation in terms of explicit sharing and of loss of implicit garbage collection, respectively.     

Model compounds of nylons—I. The crystal structure of N,N′-Diethyladipamide

The conformation of the molecule of N,N′-diethyladipamide (NNDEA) has been investigated in the crystalline state by X-ray analysis. NNDEA crystallizes in the monoclinic system, space group $\text{P2}{}_1\text{/c}\text{with}\text{a = 13 · 76(2), b = 4 · 90(1), c = 8 · 99(2)}\text{A}\text{?}\text{and}\text{β = 92 · 0°(1)}$. 661 independent non-zero reflections collected by counter techniques with CuK_a were used in the refinement to the final value of R = 7 · 6 per cent. The conformation of the adipic acid moiety shows a succession of carbon-carbon bonds (from one carbonyl group to the other) of the type skew (+), gauche (?), trans, gauche (+), skew (?).Analogous conformations (instead of the all-trans planar) may be present as point or linear defects in the crystals of nylon 6-6.     

Activation and isomerization of n-butane on sulfated zirconia model systems--an integrated study across the materials and pressure gaps

Butane activation has been studied using three types of sulfated zirconia materials, single crystalline epitaxial films, nanocrystalline films, and powders. A surface phase diagram of zirconia in interaction with SO(3) and water was established by DFT calculations, which was verified by LEED investigations on single-crystalline films and by IR spectroscopy on powders. At high sulfate surface densities a pyrosulfate species is the prevailing structure in the dehydrated state; if such species are absent, the materials are inactive. Theory and experiment show that the pyrosulfate can react with butane to give butene, H(2)O and SO(2), hence butane can be activated via oxidative dehydrogenation. This reaction occurred on all investigated materials; however, isomerization could only be proven for powders. Transient and equilibrium adsorption measurements in a wide pressure and temperature range (isobars measured via UPS on nanocrystalline films, microcalorimetry and temporal analysis of products measurements on powders) show weak and reversible interaction of butane with a majority of sites but reactive interaction with <5 micromol g(-1) sites. Consistently, the catalysts could be poisoned by adding sodium to the surface in a ratio S/Na = 35. Future research will have to clarify what distinguishes these few sites.