Evaluation of multidimensional (ion-exchange/reversed-phase) protein separations using linear and step gradients in the first dimension

The performance characteristics of multidimensional liquid chromatographic protein separations were evaluated using on-line electrospray mass detection, and a novel workflow for automated LC/MS data processing. Two-dimensional ion exchange/reversed-phase LC separations of Escherichia coli cytosol were conducted using either a continuous linear or discontinuous step gradient in the first dimension. Chromatographic profiles of the top 100 most abundant components were characterized to assess overall separation reproducibility within each mode, and to characterize differences in component distribution between the two modes of operation. Analysis of the resulting data indicates that multidimensional separations of complex protein mixtures can be done reproducibly. Furthermore, under the conditions employed within this study, a linear first dimension gradient was more effective at fractionating the protein mixture, distributing fewer major components to multiple second dimension cycles than an equivalent step gradient. The application of on line mass spectrometry, and automated processing of the resulting data, proved valuable for producing component level analysis of multidimensional protein separations.     

SSZ-53 and SSZ-59: two novel extra-large pore zeolites

The syntheses, structure solutions, and physicochemical and catalytic characterizations of the novel zeolites SSZ-53 and SSZ-59 are described. SSZ-53 and SSZ-59 were synthesized under hydrothermal conditions with the [1-(4-fluorophenyl)cyclopentylmethyl]trimethyl ammonium cation and 1-[1-(4-chlorophenyl)cyclopentylmethyl]-1-methyl azocanium cation, respectively, as structure-directing agents. The framework topology of SSZ-53 was solved with the FOCUS method, and the structure of SSZ-59 was determined by model building. Rietveld refinement of synchrotron X-ray powder diffraction data confirms each proposed model. SSZ-53 and SSZ-59 each possess a one-dimensional channel system delimited by 14-membered rings. Results from transmission electron microscopy, electron diffraction, catalytic experiments (spaciousness index and constraint index tests), and argon and hydrocarbon adsorption experiments are consistent with the proposed structures.     

A synthesis of some novel 4,5-dihydroazepines by the reaction of oxazolium 5-oxides with 1,2-dicyanocyclobutene

Heating primary or secondary α-amino acids in acetic anhydride in the presence of 1,2-dicyanocyclobutene leads to 4,5-dihydroazepines via the intermediacy of mesoionic oxazolium 5-oxides.     

Studies on growth and characterization of l-alanine strontium chloride trihydrate single crystals for optical applications

The optically transparent nonlinear optical single crystals of l-alanine strontium chloride trihydrate (LASCT) were grown by slow evaporation solution growth method using water as solvent. The purity of the crystals was increased by the method of recrystallization. The grown crystals were analyzed by the single crystal X-ray diffraction pattern which proved that LASCT belongs to monoclinic crystal system. The presence of various functional groups and modes of vibrations were identified by FTIR spectroscopy. The optical absorption study confirms the suitability of the crystal for device applications. The thermal strength and the decomposition of the grown crystals were studied using TG/DTA analyses. The dielectric constant and dielectric loss measurements of the grown crystals at different frequencies of the applied field were measured and reported. The mechanical strength of the crystal is estimated by Vicker's hardness test. The nonlinear optical properties of the grown crystals were confirmed by second harmonic generation test which shows the suitability of NLO applications.     

Semi-automated data processing of hydrogen exchange mass spectra using HX-Express

A Microsoft Excel utility, HX-Express, that significantly accelerates the analysis of hydrogen exchange mass spectrometry data is described. HX-Express generates deuterium uptake and peak width plots from peaks in mass spectral data. Data analysis is intentionally semi-automated, requiring that the user find the peaks to be analyzed. The peaks are entered in the form of x, y lists of m/z versus intensity or can be directly imported from Waters MassLynx software. Analysis of data with HX-Express provides the same results as manual data processing but is substantially faster. In addition to speed, HX-Express provides and preserves visual and numeric displays of the analysis process for quality control.     

Synthesis of butane-like SiGe hydrides: enabling precursors for CVD of Ge-rich semiconductors

The synthesis of butane-like (GeH(3))(2)(SiH(2))(2) (1), (GeH(3))(2)SiH(SiH(3)) (2), and (GeH(3))(2)(SiH(2)GeH(2)) (3) Si-Ge hydrides with applications in low-temperature synthesis of Ge-rich Si(1-x)Ge(x) optoelectronic alloys has been demonstrated. The compositional, vibrational, structural, and thermochemical properties of these compounds were studied by FTIR, multinuclear NMR, mass spectrometry, Rutherford backscattering, and density functional theory (DFT) simulations. The analyses indicate that the linear (GeH(3))(2)(SiH(2))(2) (1) and (GeH(3))(2)(SiH(2)GeH(2)) (3) compounds exist as a mixture of the classic normal (n) and gauche (g) conformational isomers which do not seem to interconvert at 22 degrees C. The conformational proportions in the samples were determined using a new fitting procedure, which combines calculated molecular spectra to reproduce those observed by varying the global intensity, frequency scale, and admixture coefficients of the individual conformers. The (GeH(3))(2)(SiH(2))(2) (1) species was then utilized to fabricate Si(0.50)Ge(0.50) semiconductor alloys reflecting exactly the Si/Ge content of the precursor. Device quality layers were grown via gas source MBE directly on Si(100) at unprecedented low temperatures 350-450 degrees C and display homogeneous compositional and strain profiles, low threading dislocation densities, and atomically planar surfaces. Low energy electron microscopy (LEEM) analysis has demonstrated that the precursor is highly reactive on Si(100) surfaces, with H(2) desorption kinetics comparable to those of Ge(2)H(6), despite the presence of strong Si-H bonds in the molecular structure.     

Non perturbative effective potentials of quantum oscillators

Non perturbative analogues of the Gaussian effective potential (GEP) are defined for quantum oscillators obeyingq—or (q,p)—deformed commutation relations. These are called the non perturbativeq-effective potential (NP _q EP) and the non perturbativeqp effective potential (NP _qp EP), in the respective cases. A system-specific effective potential (SSEP) is also introduced by means of an additional minimization with respect to theq orq andp parameters. The method is applied toq and (q,p) oscillators of the quartic and sextic types. The SSEP in the case of ground states of theq-oscillators corresponds toq=1, which is the ordinary bosonic limit. A potential shape transition that involves the conversion of a double well to a single well or vice versa, is seen to exist in the case of quantum oscillators sitting in a double well potential.     

Analysis of residual trifluoroacetic acid in a phosphate-buffered saline matrix by ion chromatography with suppressed conductivity detection

As part of the formulation of a cell-based pharmaceutical product, cells were harvested from mice and incubated in a cocktail containing cell culture media and high levels of trifluoroacetic acid (TFA). The cells were washed with a phosphate-buffered saline solution to remove residual cell culture media and other reagents before the cells were infused back into the mice from which they originated. Because of the potentially toxic nature of the TFA, the cells were washed multiple times and the final wash was monitored for residual TFA in order to demonstrate the efficient removal of the reagent before the cell product could be reintroduced into the test animal. This report describes the method that was developed incorporating anion-exchange chromatography with suppressed conductivity detection for the analysis of residual TFA (down to 50 ng/ml) in the presence of high concentrations of phosphate and chloride interferences. The ultimate sensitivity of the method was improved by selectively removing halide anions using a silver cartridge before sample analysis. The method proved to be rugged and reproducible enough to be validated and used to monitor residual TFA levels in cell washes in support of an acute toxicological study. Results demonstrating the method’s sensitivity, selectivity, precision and linearity were reported.