Determination of prostaglandins and thromboxane in whole blood by high-performance liquid chromatography with fluorimetric detection

A highly sensitive and specific assay for the quantitation of prostaglandins (PGs) such as PGE1, PGE2, PGF1 alpha, PGF2 alpha, 6-keto-PGF1 alpha, and including thromboxane B2, is described. The method involves the addition of PGF1 alpha and PGE1 as the internal standards, extraction from whole blood and purification by silica gel column chromatography. Following conversion into the methoximes, purification by reversed-phase chromatography and esterification with panacyl bromide, samples are analysed by high-performance liquid chromatography with fluorimetric detection. The lower limit of detection of the eicosanoids 6-keto-PGF1 alpha, thromboxane B2 and PGF2 alpha in blood is ca. 50 pg/ml and that of PGE2 is 100 pg/ml. Assay linearity is demonstrated over a range from 60 pg to 60 ng of eicosanoid injected. The method allows simultaneous assessment of prostaglandins and thromboxane extracted from complex biological fluids at picogram levels.     

Extraction of plasmid DNA from Escherichia coli cell lysate in a thermoseparating aqueous two-phase system

The primary purification of a 6.1 kilo base pair (kbp) plasmid from a desalted alkaline lysate has been accomplished by a thermoseparating aqueous two-phase system [(50% ethylene oxide-50% propylene oxide)-Dextran T 500]. The partitioning of the different nucleic acids (plasmid DNA, RNA, genomic DNA) in the thermoseparating aqueous two-phase system was followed both qualitatively by agarose gel electrophoresis and quantitatively by analytical chromatography (size exclusion- and anion-exchange mode) and PicoGreen fluorescence analysis. The experimental results showed a complete recovery of the plasmid DNA to the top phase, while 80% of total RNA and 58% of total protein was discarded to the bottom phase. Moreover, a 3.8-fold volume reduction of the plasmid DNA solution was achieved. By using a final thermoseparating step, the EO50PO50 polymer could be efficiently recycled, resulting in plasmid solution containing less than 1% polymer. The developed thermoseparating aqueous two-phase system shows great potential for the large-scale processing of plasmid DNA.     

Theory of plasmon excitations in (SN)x

The anomalous anisotropy and dispersion of plasmons in polymeric sulfur nitride (SN)_x are explained within a model of an electron gas with an anisotropic effective mass ratio. Calculations in the random phase approximation yield very good agreement with the electron loss data. Exchange corrections for the model are shown to be small for systems of the (SN)_x type which exhibit reduced dimensionality.     

Sound attenuation study on the bose-Einstein condensation of magnons in TlCuCl3

We investigate experimentally and theoretically sound attenuation in the quantum spin system TlCuCl3 in magnetic fields at low temperatures. Near the point of Bose-Einstein condensation of magnons a sharp peak in the sound attenuation is observed. The peak demonstrates a hysteresis as a function of the magnetic field pointing to a first-order contribution to the transition. The sound damping has a Drude-like form arising as a result of hard-core magnon-magnon collisions. The strength of the coupling between lattice and magnons is estimated from the experimental data. The puzzling relationship between the transition temperature and the concentration of magnons is explained by their "relativistic" dispersion.     

Stripe conductivity in La1.775Sr0.225NiO4

We report Raman light-scattering and optical conductivity measurements on a single crystal of La1.775Sr0.225NiO4 which exhibits incommensurate charge-stripe order. The extra phonon peaks induced by stripe order can be understood in terms of the energies of phonons that occur at the charge-order wave vector Q(c). A strong Fano antiresonance for a Ni-O bond-stretching mode provides clear evidence for finite dynamical conductivity within the charge stripes.     

Stability and convergence in discrete convex monotone dynamical systems

We study the stable behaviour of discrete dynamical systems where the map is convex and monotone with respect to the standard positive cone. The notion of tangential stability for fixed points and periodic points is introduced, which is weaker than Lyapunov stability. Among others we show that the set of tangentially stable fixed points is isomorphic to a convex inf-semilattice, and a criterion is given for the existence of a unique tangentially stable fixed point. We also show that periods of tangentially stable periodic points are orders of permutations on n letters, where n is the dimension of the underlying space, and a sufficient condition for global convergence to periodic orbits is presented.     

A reference-gene-based quantitative PCR method as a tool to determine <Emphasis Type="Italic">Fusarium</Emphasis> resistance in wheat

In recent years, plant breeders made great progress in breeding Fusarium-tolerant wheat lines. However, total resistance to this genus of plant pathogenic fungi has not yet been achieved as the resistance genes are located on several distinct genetic regions. Visual scoring of disease symptoms in combination with the analysis of mycotoxins is commonly applied to assess the tolerance of new lines. Both approaches are indirect methods and do not mandatorily determine the accumulated fungal biomass. Quantitative PCR is a useful tool to assess fungal biomass based on the abundance of organism-specific DNA. The aim of this study was the development of a quantitative PCR assay for trichothecene-producing Fusarium species and to adapt this method for resistance assessment of wheat lines artificially infected with Fusarium graminearum and Fusarium culmorum. Several DNA-extraction methods for wheat samples were evaluated and optimized for downstream real-time PCR analysis and furthermore, a new reference-gene-based approach for more accurate quantification of Fusarium biomass in cereals is presented. The co-determination of a plant gene was used to compensate for unequal DNA-extraction efficiencies.     

The spin dynamics in distorted kagome lattices: a comparative Raman study

Despite the conceptional importance of realizing spin liquids in solid states only few compounds are known. On the other hand the effect of lattice distortions and anisotropies on the magnetic exchange topology and the fluctuation spectrum is an interesting problem. We compare the excitation spectra of the two s = 1/2 kagome lattice compounds, volborthite and vesignieite, using Raman scattering. We demonstrate that even small modifications of the crystal structure may have a huge effect on the phonon spectrum and low-temperature properties.     

Pretreatment of body fluids by preparative isotachophoresis prior to chromatographic analysis

Summary This study focusses attention on the possibilities of preparative isotachophoresis (ITP) as a sample pretreatment technique prior to liquid chromatographic (HPLC) analysis. The increased demand for accurate and less time consuming analysis necessitates that sample pretreatment procedures, should be develop in parallel with other improvements (e. g. in detection and separation) which can be observed. The preparation isotachophoresis was performed on gel slabs and the zones of interest were subsequently cut out, desorbed and the desorbates analyzed by HPLC. In this study satisfactory recoveries of between 85–90% with a standard deviation of 1–5% were observed for blank experiments. For spiked serum and urine samples the recoveries in general decreased with decreasing spiked drug concentrations. These observations are discussed in this paper.