Monolithic sorbents for microscale separations

Over the last decade, the miniaturization of analytical systems has become an increasingly important and interesting research area. Miniaturized systems offer many advantages, including reduced reagent and sample consumption, shorter analysis times, portability and disposability. This dissertation describes novel approaches in this direction, focusing on two areas: the miniaturization of existing column chromatographic systems and the development of microfluidic systems in which the separation is performed in a channel on a microchip. A new type of methacrylate-based monolithic capillary columns for liquid chromatography and capillary electrochromatography were prepared within the confines of fused-silica tubing using Starburst dendrimers to affect porosity. The polyamidoamine (PAMAM) dendrimers were incorporated into a solution of functionalized monomer, cross-linker, solvents, and polymerization initiator. Thermal polymerization, followed by the removal of solvent and dendrimers, produced a continuous rod of polymer with uniform porosity. Different column porosities were obtained by varying the amount of the dendrimer template. The chromatographic performance of these monolithic columns was evaluated using a peptides mixture obtained by tryptic digestion of chicken egg lysozyme. A distinct advantage of polymer monolithic stationary phases over conventional packed chromatographic beds is the ability to prepare them easily and rapidly via free radical polymerization within the channels of a microfluidic device. In this work, continuous polymeric beds were prepared within a channel of three different microchip substrates: glass, poly(dimethylsiloxane) and polycarbonate. The methacrylate-based monolith was cast in-situ via UV-initiated polymerization. The functionalization of the inner wall of the channel with methacryloyl groups enabled the covalent binding of the monolith to the wall. The morphology of the wall-anchored monolith was studied by SEM of chip sections, and by SEM of an extruded segment of non-anchored monolith from a separate chip

Reconstructing an Indo-European Family Tree from Non-native English texts

Mother tongue interference is the phenomenon where linguistic systems of a mother tongue are transferred to another language. Although there has been plenty of work on mother tongue interference, very little is known about how strongly it is transferred to another language and about what relation there is across mother tongues. To address these questions, this paper explores and visualizes mother tongue interference preserved in English texts written by Indo-European language speakers. This paper further explores linguistic features that explain why certain relations are preserved in English writing, and which contribute to related tasks such as native language identification.

Lipidomic biosignature of <i>fat-1</i> mice.

<p>A, Correlation analysis was used to visualize the overall relationships between different features and (B) to identify which features are correlated with EPA. C, Clustering result shown as heatmap (distance measure using Pearson, and clustering algorithm using ward), providing an intuitive visualization of the characteristic lipidomic biosignature found in <i>fat-1</i> mice versus WT mice. Each colored cell on the map corresponds to a concentration value, with samples in rows and features/compounds in columns. Displayed are the top 25 lipids ranked by t-tests.</p

Pathway analysis.

<p>The activities of COX, LOX and CYP450 enzymes catalyze the formation of hundreds of oxylipins species with different biological activities starting from the omega-6 PUFAs precursors (<i>panel A</i>) and the omega-3 PUFAs (<i>panel B</i>). The <i>fat-1</i> mice had marked alterations in the CYP450 pathway and minor alterations in the LOX/COX pathways resulting in the increase of omega-3 oxylipins (green) and decrease of omega-6 oxylipins (red).</p

Overview of the omega-6 and omega-3 PUFAs metabolism.

<p>Diet-derived omega-6 linoleic acid (LA) and omega-3 alpha-linolenic acid (ALA) are transformed into longer chains PUFAs by the sequential action of desaturases and elongases. PUFAs can be found in blood as unesterified fatty acids, esterified to more complex lipids such as cholesteryl esters and phospholipids, or converted into the oxygenated metabolites oxylipins. The figure shows chemical structures of fatty acids and derivatives highlighted in our study.</p

Study design and workflow for the lipidomic analyses.

<p>Heterozygous female <i>fat-1</i> and WT mice were fed a 6-month-long diet containing 10% corn oil, which is particularly enriched in omega-6 PUFAs. Blood was collected and plasma samples were prepared and divided into two aliquots. Before extraction, a mixture of internal standards was added to the plasma to normalize for variations in sample preparation or MS detection. Complementary untargeted and targeted lipidomic analyses were conducted, and the results were integrated for the generation of a unique lipidomic biosignature characteristic of the balanced omega-6/omega-3 ratio found in <i>fat-1</i> mice.</p

Levels of unesterified fatty acids (nmol/ml) in WT and <i>fat-1</i> mice (n = 5).

<p>P- values derived from Student's t test. FDR, false discovery rate.</p

Untargeted lipidomic analysis.

<p>A, PLS-DA analysis showed a marked separation of plasma samples belonging to WT and <i>fat-1</i> mice, highlighting the features that contributed most to the variance between the two groups. B, Important features identified by PLS-DA. The colored boxes on the right indicate the relative concentrations of the corresponding metabolite in each group under study. Variable Importance in Projection (VIP) is a weighted sum of squares of the PLS loadings taking into account the amount of explained Y-variation in each dimension. C, Important features selected by fold-change analysis (relative to WT) with threshold 2. The red circles represent features above the threshold. Note the values are on log scale, so that both up-regulated and downregulated features can be plotted in a symmetrical way. D, Levels of EPA and percent composition of CE-EPA in WT and <i>fat-1</i> mice (n = 5, Student's t test; ***, p<0.001). The data present the mean ± SEM.</p

Composition (% of the total) of cholesteryl esters in WT and <i>fat-1</i> mice (n = 5).

<p>P-values derived from Student's <i>t</i> test.</p