Metabolic fingerprinting of high-fat plasma samples processed by centrifugation- and filtration-based protein precipitation delineates significant differences in metabolite information coverage

Metabolomics and metabolic fingerprinting are being extensively employed for improved understanding of biological changes induced by endogenous or exogenous factors. Blood serum or plasma samples are often employed for metabolomics studies. Plasma protein precipitation (PPP) is currently performed in most laboratories before LC–MS analysis. However, the impact of fat content in plasma samples on metabolite coverage has not previously been investigated. Here, we have studied whether PPP procedures influence coverage of plasma metabolites from high-fat plasma samples. An optimized UPLC-QTOF/MS metabolic fingerprinting approach and multivariate modeling (PCA and OPLS-DA) were utilized for finding characteristic metabolite changes induced by two PPP procedures; centrifugation and filtration. We used 12-h fasting samples and postprandial samples collected at 2 h after a standardized high-fat protein-rich meal in obese non-diabetic subjects recruited in a dietary intervention. The two PPP procedures as well as external and internal standards (ISs) were used to track errors in response normalization and quantification. Remarkably and sometimes uniquely, the fPPP, but not the cPPP approach, recovered not only high molecular weight (HMW) lipophilic metabolites, but also small molecular weight (SMW) relatively polar metabolites. Characteristic SMW markers of postprandial samples were aromatic and branched-chain amino acids that were elevated (p < 0.001) as a consequence of the protein challenge. In contrast, some HMW lipophilic species, e.g. acylcarnitines, were moderately lower (p < 0.001) in postprandial samples. LysoPCs were largely unaffected. In conclusion, the fPPP procedure is recommended for processing high-fat plasma samples in metabolomics studies. While method improvements presented here were clear, use of several ISs revealed substantial challenges to untargeted metabolomics due to large and variable matrix effects.     

Novel Vinylpyridine Based Cationic MIP Monoliths for Enantiomer Separation in CEC

Cationic vinylpyridine based molecularly imprinted polymer monoliths were, for the first time, applied to enantiomer separation using capillary electrochromatography. In order to map the synthesis conditions under which superporous monoliths are obtained, capillary columns were prepared by an in situ polymerization technique using varying monomer and porogen compositions. Both electrolyte pH and percentage of the organic modifier acetonitrile were found to affect the electrochromatographic behaviour on such columns. An interesting observation is that the electroosmotic flow changed direction from cathodic at high pH to anodic at low pH of the electrolyte, opening up the opportunity to manipulate the flow. This is attributed to the vinylpyridine based MIP becomes protonated and positively charged at low pH, whereas it is uncharged at high pH where instead negatively charged silanol groups drive the electroosmotic flow. Improved enantiomer resolution, as well as increased retention, was observed when the concentration of acetonitrile in the electrolyte decreased, indicating a significant element of hydrophobic effects in the molecular recognition of the imprinted enantiomer. Enantiomer separation of the non-steroidal anti-inflammatory drug ibuprofen was studied and efficiencies as high as 30,000 plates per meter with an asymmetry factor below 4 were obtained for the last eluting imprinted enantiomer. These values are better than that obtained generally using MIP based chromatography.     

An organocatalytic approach to 2-hydroxyalkyl- and 2-aminoalkyl furanes

The first enantioselective methodology for the synthesis of electron-poor 2-hydroxyalkyl- and 2-aminoalkyl furanes is demonstrated in this study. It utilizes a highly stereoselective organocatalytic one-pot reaction cascade: epoxidation or aziridination of α,β-unsaturated aldehydes followed by Feist-Be?nary reaction of various 1,3-dicarbonyl compounds to give the target furanes. This efficient multibond forming reaction cascade benefits from low catalyst loadings and readily available starting materials. Furthermore, the possibility to interrupt the reaction sequence at the stage of the corresponding optically active 2-hydroxyalkyl- and 2-aminoalkyl 2,3-dihydrofuranes with three stereogenic centers is also presented. Finally, models which account for the formation of the optically active 2,3-dihydrofuranes are proposed.     

Solubility and density measurements of palmitic acid in supercritical carbon dioxide + alcohol mixtures

Solubility data of palmitic acid (hexadecanoic acid) in supercritical carbon dioxide were measured in the pressure range from 10 to 25 MPa at temperatures of 313 and 318 K. Densities for this binary mixture in the homogeneous phase and at saturation conditions were measured in the same range of temperature. The influence of 3 and 6 mol% ethanol and 2-propanol as co-solvent on the solubility and density data for the CO₂ + palmitic acid mixture was also determined at 313 K. Measurements were carried out in a static-synthetic sapphire cell coupled to a vibrating-tube densitometer. The self-consistency of the data was tested according to the density-based models proposed by Mendez-Santiago and Teja.     

Der erste Polyiodokomplex – Triethylsulfoniumtriiodomercurat(II)-tris(diiod), (Et3S)[Hg2I6]1/2 · 3 I2

The First Polyiodo Complex – Triethylsulfoniumtriiodomercurate(II)-tris(diiodine), (Et₃S)[Hg₂I₆]_1/2 · 3 I₂ After Raman spectroscopic investigation of the system HgI₂/Et₃SI_x, x = 3, 5, 7, triethylsulfoniumtriiodomercuratetris(diiodine), (Et₃S)[Hg₂I₆]_1/2 · 3 I₂ was synthesized by reacting of HgI₂ and liquid Et₃SI₇. The compound crystallizes at room temperature triclinically in the space group P1 with a = 879.4(7), b = 1 209.1(5), c = 1 291.5(5) pm, α = 96.16(3)°, β = 103.82(6)°, γ = 99.05(5)° and Z = 2. The crystal structure is composed of disordered Et₃S⁺ cations, the centrosymmetric complex anion [HgI_2/2I₂]₂^2? and three connecting iodine molecules I₂.