Simultaneous measurement of proline and related compounds in oak leaves by high-performance ligand-exchange chromatography and electrospray ionization mass spectrometry for environmental stress studies

A mass spectrometer was coupled to high-performance ligand-exchange liquid chromatography (HPLEC) for simultaneous analysis of stress associated solutes such as proline, hydroxyproline, methylproline, glycine betaine and trigonelline extracted from leaves of drought stressed oaks and an internal standard namely N-acetylproline. Methanol/chloroform/water extracts were analyzed using an Aminex HPX-87C column and specifically quantified by the positive ion mode of an electrospray ionisation-mass spectrometry (ESI-MS) in single ion monitoring (SIM) mode. The recovery of N-acetyl proline added to oak leaf extracts ranged from 85.2 to 122.1% for an intra-day study. Standard calibration curves showed good linearity in the measured range from 0.3125 to 10 μmol L⁻¹ with the lowest correlation coefficient of 0.99961 for trigonelline. The advantages of this alternative procedure, compared to previously published methods using fluorescence or amperometric detections, are the simultaneous and direct detection of osmoprotectants in a single chromatographic run, a minimal sample preparation, a good specificity and reduced limits of quantification, ranging from 0.1 to 0.6 μmol L⁻¹. Fifty-six days of water deficit exposure resulted in increased foliar free proline levels (2.4-fold, P < 0.001, 155 μmol g⁻¹ FW) and glycine betaine contents (2.5-fold, P < 0.05, 175 μmol g⁻¹ FW) of drought stressed oak compared to control.     

Photopatterned polymer brushes promoting cell adhesion gradients

The ability to spatially control cellular adhesion in a continuous manner on a biocompatible substrate is an important factor in designing new biomaterials for use in wound healing and tissue engineering applications. In this work, a novel method of engineering cell-adhesive RGD-ligand density gradients to control specific cell adhesion across a substrate is presented. Polymer brushes exhibiting spatially defined gradients in chain density are created and subsequently functionalized with RGD to create ligand density gradients capable of inducing cell adhesion on an otherwise weakly adhesive substrate. Cell studies indicate that these ligand-functionalized surfaces are noncytotoxic, with cellular adhesion increasing with RGD-ligand density across the gradient brush surface.     

Variants of Dynamic Mode Decomposition: Boundary Condition, Koopman, and Fourier Analyses

Dynamic mode decomposition (DMD) is an Arnoldi-like method based on the Koopman operator. It analyzes empirical data, typically generated by nonlinear dynamics, and computes eigenvalues and eigenmodes of an approximate linear model. Without explicit knowledge of the dynamical operator, it extracts frequencies, growth rates, and spatial structures for each mode. We show that expansion in DMD modes is unique under certain conditions. When constructing mode-based reduced-order models of partial differential equations, subtracting a mean from the data set is typically necessary to satisfy boundary conditions. Subtracting the mean of the data exactly reduces DMD to the temporal discrete Fourier transform (DFT); this is restrictive and generally undesirable. On the other hand, subtracting an equilibrium point generally preserves the DMD spectrum and modes. Next, we introduce an ??optimized?? DMD that computes an arbitrary number of dynamical modes from a data set. Compared to DMD, optimized DMD is superior at calculating physically relevant frequencies, and is less numerically sensitive. We test these decomposition methods on data from a two-dimensional cylinder fluid flow at a Reynolds number of?60. Time-varying modes computed from the DMD variants yield low projection errors.     

Method development for mono- and disaccharides monitoring in cell culture medium by capillary and microchip electrophoresis

The rapidly growing, competitive biopharmaceutical market requires tight bioprocess monitoring. An integrated, automated platform for the routine online/at-line monitoring of key factors in the cell culture medium could greatly improve process monitoring. Mono- and disaccharides, as the main energy and carbon source, are one of these key factors. A CE-LIF method was developed for the analysis of several mono- and disaccharides, considering requirements and restrictions for analysis in an integrated, automated monitoring platform, such as the possibility for miniaturization to microchip electrophoresis. Analysis was performed after fluorescent derivatization with 8-aminopyrene-1,3,6-trisulfonic acid. The derivatisation reaction and the separation BGE were optimized using design of experiments. The developed method is applicable to the complex matrix of cell culture medium and proved transferable to microchip electrophoresis.     

Entwicklung eines Enzymimmunoassays zur Bestimmung von Prolactin (Enzymun-Test? Prolactin)

Ohne Zusammenfassung

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Enzyme-immunoassay of prolactin, hybridoma characterization

     

Absorption of toluene in poly(aryl-ether-ether-ketone)

The absorption and swelling of poly(aryl-ether-ether-ketone) (PEEK) in toluene as a function of resin morphology and temperature in the range 35–95°C was investigated. In all cases the weight gain curves exhibit three characteristics: (1) an induction period, which is a strong function of both temperature and initial crystallinity, (2) a main absorption region, which is linear with square-root time, and (3) a final equilibrium value, namely, solubility. The solubility of amorphous PEEK decreases with temperature and the heat of solution is ?0.93 kcal/mol. The induction period varies with the fourth power of the crystallinity and decreases with temperature with an apparent activation energy of 50 kcal/mol. The strength of the interaction between the crystalline regions is markedly reduced at temperatures greater than 80°C. Swelling accompanying the absorption of the toluene is highly anisotropic with most of the dimensional changes occurring in the thickness direction. The deswelling process, however, is essentially isotropic. The concentration of toluene in solution has a strong effect on the transport process; the equilibrium solubility of toluene in amorphous PEEK immersed in a toluene/iso-octane mixture is a linear function of toluene concentration; but the pseudo-diffusion coefficient for the absorption of toluene varies approximately with the fourth power of its concentration.     

Site‐ and Enantioselective C−H Oxygenation Catalyzed by a Chiral Manganese Porphyrin Complex with a Remote Binding Site

A chiral manganese porphyrin complex with a two‐point hydrogen‐bonding site was prepared and probed in catalytic C?H oxygenation reactions of 3,4‐dihydroquinolones. The desired oxygenation occurred with perfect site selectivity at the C4 methylene group and with high enantioselectivity in favor of the respective 4S‐configured secondary alcohols (12 examples, 29–97 % conversion, 19–68 % yield, 87–99 % ee). Mechanistic studies support the hypothesis that the reaction proceeds through a rate‐ and selectivity‐determining attack of the reactive manganese oxo complex at the hydrogen‐bound substrate and an oxygen transfer by a rebound mechanism.     

Mechanical performance of metal-ceramic interfaces produced by laser processing

This paper concentrates on the mechanical performance of various ceramic coatings of Cr₂O₃ on steel (SAF2205), as produced by CO₂ laser processing. The thickness of the coating that can be applied by laser coating is limited to about 200 m setting a limit to the maximum strain energy release rate that can be measured in a 4 point flexure test before severe yielding occurs. In addition, a network of cracks with spacings of the order of 200 m was always present in the laser applied coating preventing steady state crack growth along the interface.It is concluded that a firmly bonded coating of Cr₂O₃ on steel could be produced by high power laser processing. The actual interface strength of a (Fe, Cr)-spinel applied to stainless steel by laser coating depends strongly on the composition of the substrate and coating materials. The energy release rate was extremely high and delamination occurred by fracture through the coating and partially along the interface, indicating that the interface strength is similar to or higher than the fracture strength of (Fe, Cr)-spinel.     

Potential cerebral perfusion agents. Synthesis and evaluation of new radioiodinated barbituric acid analogs

Two new ¹²⁵I-labeled barbituric acid analogs, 5-ethyl-5-(E-1-iodo-1-penten-5-yl)2-thiobarbituric acid ( 4 ) and 5-ethyl-5-( m -iodophenyl)barbituric acid ( 7 ), have been prepared and evaluated in rats as potential cerebral perfusion agents. Annulation of 2-ethyl-2-(E-1-iodo-1-penten-5-yl)malonate ( 3 ) with thiourea in the presence of sodium ethoxide gave the 5-ethyl-5-(E-1-iodo-1-penten-5-y1)-thiobarbituric acid ( 4 ). Diethyl 2-ethyl-2-phenyl-malonate was treated with thallium(III) trifluoroacetate followed by addition of aqueous potassium iodide to provide diethyl 2-ethyl-2-(m-iodophenyl)malonate ( 10 ). The malonic ester derivative 10 was condensed with urea in the presence of sodium hydride to give the desired 5-ethyl-5-(m-iodophenyl)barbituric acid ( 7 ), and a decarbethoxylation product, 2-(m-iodophenyl)butyric acid ( 11 ). Iodine-125-labeled 4 and 7 were synthesized in the same manner and the tissue distribution of these new agents evaluated in rats. Both [¹²⁵I] 4 and [¹²⁵I] 7 showed high brain uptake. Significant in vivo deiodination was detected with [¹²⁵I] 4 whereas [¹²⁵I] 7 was found to be stable to deiodination.     

High speed separation of the light rare earths on centri-fugally accelerated ion-exchange paper

The separation of the rare earths, La, Cc, Pr, Nd, Sm and Y on centrifugally accelerated Amberlitc SA-2 cation-exchange paper was studied. All combinations of the elements can be completely separated except the Pr-Nd pair by using as cluant glycolic acid of a 'properly-chosen concentration (0.30 or 0.40 M) and pH (3.0 to 4.5). The Pr-Nd pair can be partially separated. The average number of ligand glycolato ions per rare earth ion in the resin phase was determined for each rare earth over the pa range 0.7 to 1.0.