Quantitative profiling of tryptophan metabolites in serum, urine, and cell culture supernatants by liquid chromatography-tandem mass spectrometry

A sensitive, selective, and comprehensive method for the quantitative determination of tryptophan and 18 of its key metabolites in serum, urine, and cell culture supernatants was developed. The analytes were separated on a C18 silica column by reversed-phase liquid chromatography and detected by electrospray ionization tandem mass spectrometry in positive ion multiple reaction monitoring (MRM) mode, except for indoxyl sulfate which was measured in negative ion MRM mode in a separate run. The limits of detection and lower limits of quantification were in the range of 0.1–50 and 0.5–100 nM, respectively. Fully ¹³C isotope-labeled and deuterated internal standards were used to achieve accurate quantification. The applicability of the method to analyze serum, urine, and cell culture supernatants was demonstrated by recovery experiments and the evaluation of matrix effects. Precision for the analysis of serum, urine, and cell culture supernatants ranged between 1.3% and 16.0%, 1.5% and 13.5%, and 1.0% and 17.4%, respectively. The method was applied to analyze changes in tryptophan metabolism in cell culture supernatants from IFN-γ-treated monocytes and immature or mature dendritic cells.     

Multichromophore light harvesting in hybrid solar cells

A new technologically relevant method for multichromophore sensitizing of hybrid blend solar cells is presented. Two dyes having complementary absorption in the UV-visible regions are individually adsorbed on nanocrystalline TiO(2) powder. These dyed TiO(2) nanoparticles are blended with an organic hole-conductor (HC) Spiro-OMeTAD in desired compositions and applied on a conducting substrate by doctor-blading at room temperature to fabricate multichromophore-sensitized hybrid blend solar cells. The external quantum efficiency (EQE) of the single hybrid layer system fabricated with two dyes, that absorb mainly UV (TPD dye) and visible regions (Ru-TPA-NCS dye), exhibited a clear panchromatic response with the sum of the EQE characteristics of each single dye cell. The first results of a multichromophore-sensitized solid-state solar cell showed J(sc) of 2.1 mA cm(-2), V(oc) of 645 mV, FF of 47% and efficiency of 0.65% at AM 1.5 G, 100 mW cm(-2) illumination intensity. The J(sc) of the multichromophore cell is the sum of the individually dyed solar cells. The process described here is technically very innovative and very simple in procedure. It has potentials to be adopted for panchromatic sensitization using more than two dyes in a single hybrid layer or layer-wise fabrication of a tandem structure at room temperature.     

Tunable Properties of Inclusion Complexes Between Amylose and Polytetrahydrofuran

Amylose and polytetrahydrofuran (PTHF) are mixed in an aqueous solution to form inclusion complexes. DSC shows that immediate mixing results in complexes having lower melting temperatures compared with complexes prepared with longer mixing times. The washed complexes melt at higher temperatures compared with the corresponding unwashed complexes. XRD indicates that amylose–PTHF complexes diffract similar to amylose–fatty acids complexes (V_6I‐amylose helices), with additional diffractions correlating with amylose–alcohol complexes (V_6II‐amylose helices). This suggests that the structure of amylose–PTHF complexes is an intermediate or a mixture between V_6I‐ and V_6II‐amylose. This shows that, besides residing inside the amylose helices, some PTHF chains are located in between the amylose helices.

     

Erste Komplexe von Yttrium und Lutetium mit schwefelfunktionalisierten Cyclopentadienylliganden

Organometallic Compounds of the Lanthanides. 132 First Complexes of Yttrium and Lutetium with Sulfur functionalized Cyclopentadienyl Ligands Yttrium trichloride reacts with 2 equivalents of Na[C₅H₄CH₂CH₂SEt] ( 1 ) to form (η⁵-C₅H₄CH₂CH₂SEt)₂YCl ( 2 ). The stepwise reaction of lutetium trichloride with one equivalent of 1 and one equivalent of Na[C₅Me₅] yields (η⁵-C₅Me₅)(η⁵-C₅H₄CH₂CH₂SEt)LuCl ( 4 ). Alkylation of 2 and 4 with LiMe gives (η⁵-C₅H₄CH₂CH₂SEt)₂YMe ( 3 ) or (η⁵-C₅Me₅)(η⁵-C₅H₄CH₂CH₂SEt)LuMe ( 5 ), respectively. The new compounds have been characterized by elemental analysis, NMR spectroscopy and mass spectrometry. The molecular structures of 2 and 4 were determined by single crystal X-ray diffraction.     

Automatically and electronically controllable hydrogel based valves and microvalves – design and operating performance

This paper describes automatically and electronically controlled valves and microvalves based on smart hydrogels. The operating performance of such devices will be discussed in dependence on various design parameters. Furthermore, it will be shown that hydrogel based valves are showing an outstanding possibility of miniaturization, a leakage free switching behavior up to a pressure drop of 8.4 bar, and a pronounced particle tolerance.     

Chromatographic–mass spectrometric analysis of peptidic analytes (2–10 kDa) in doping control urine samples

Peptides with a molecular mass between 2 and 10 kDa that are prohibited in elite sports usually require dedicated sample preparation and mass spectrometric detection that commonly cannot be combined with other (lower molecular mass) substances. In most instances, the physicochemical differences are too significant to allow for a generic analytical procedure. A simplification of established and comparably complex analytical approaches is therefore desirable and has been accomplished in the context of this study. With urine samples representing still the most frequently collected doping control specimens, efficient extraction of peptidic analytes from this matrix was a major goal of this method, as demonstrated for the included compounds such as insulins (human, lispro, aspart, glulisine, tresiba, glargine metabolite, bovine insulin, porcine insulin), growth hormone-releasing hormones (sermorelin, CJC-1295, tesamorelin) incl. their respective metabolites, insulin-like-growth factors (long-R₃-IGF-I, R₃-IGF-I, des_1–3-IGF-I), synacthen, gonadorelin and mechano growth factors (human MGF, MGF-Goldspink). Sample preparation and detection are controlled by five internal standards, covering all five included peptide drug categories. Nearly all requirements of the recent technical documents from the World Anti-Doping Agency (WADA) considering their minimum required performance levels (MRPL) are fulfilled, and the method was validated for its utilisation as initial testing procedure in doping controls. Finally, the approach was applied to authentic post-administration study urine samples (for insulins and gonadorelin) in order to provide proof of principle.     

Validation of Material Models in Grain Scale Simulation based on EBSD Experimental Data

A crystal plasticity model and a homogenization method are used to analyze the local and global mechanical behavior of a ferritic stainless steel. In the first step the material constants are determined based on tensile tests and used to simulate the local deformation behavior on the grain scale in the second step. For that 2D EBSD data are discretized by finite elements. The computed local grain reorientations of three different BCC slip systems are compared to experimental data at the state of 20% elongation. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)