Untersuchung von Butter, Margarine, Tran und anderen Fetten

Ohne Zusammenfassung     

An Enantiopure Cyclometallated Iridium Complex Displaying Long‐Lived Phosphorescence both in Solution and in the Solid State

A new enantiopure cyclometallated iridium complex bearing a [4]helicenic ‐coordinating and two ‐coordinating dfppy (2‐(2,4‐difluorophenyl)‐pyridyl) ligands was prepared. This complex displayed long‐lived phosphorescence both in solution and in the solid state. Its chiroptical properties, namely electronic circular dichroism and circularly polarized luminescence, were also examined. Comparison with former chiral complexes enabled assignment of the Δ_Ir‐(?) and Λ_Ir‐(+) absolute configurations.     

Inherently Chiral Spider‐Like Oligothiophenes

The racemate of an inherently chiral “spider‐like” octathiophene monomer T8₃ , in which chirality is generated by torsion in its backbone, was synthesized. The racemate was resolved into configurationally stable antipodes by HPLC on a chiral stationary phase. Electrooxidation of the enantiomers resulted in materials displaying high enantiorecognition ability towards the antipodes of some chiral probes. Moreover, the T8₃ racemate demonstrated great aptitude to stimulate formation of 3D rigid architectures if used as a cross‐linking monomer for molecular imprinting. This feature was exploited to devise a molecularly imprinted polymer‐based chemosensor selective for a thymine–adenine oligonucleotide.     

Photochemistry and Reactivity of the Phenyl Radical–Water System: A Matrix Isolation and Computational Study

The reaction of the phenyl radical 1 with water has been investigated by using matrix isolation spectroscopy and quantum chemical calculations. The primary thermal product of the reaction between 1 and water is a weakly bound complex stabilized by an OH???π interaction. This complex is photolabile, and visible‐light irradiation (λ>420 nm) results in hydrogen atom transfer from water to radical 1 and the formation of a highly labile complex between benzene and the OH radical. This complex is stable under the conditions of matrix isolation, however, continuous irradiation with λ>420 nm light results in the complete destruction of the aromatic system and formation of an acylic unsaturated ketene. The mechanisms of all reaction steps are discussed in the light of ab initio and DFT calculations.     

An ATR-FTIR study of different phosphonic acids adsorbed onto boehmite

An ATR-FTIR study of the vibrational spectra of N,N-bis(2-hydroxyethyl) aminomethylphosphonic acid (BHAMP), 1-hydroxyethane-1,1′-diphosphonic acid (HEDP) and nitrilotris(methylenephosphonic acid) (NTMP) adsorbed onto boehmite is presented. The study was performed in the pH range from 5 to 9, and bands assignments are given in the 1200–900 cm^?1 wavenumber range, where the bands associated with various P–O(H) vibrations can be found. The three phosphonic acids adsorb onto boehmite by forming inner-sphere surface complexes. ATR-FTIR data indicates the presence of both protonated and deprotonated mononuclear surface species. In all cases, the surface-bound ions undergo protonation reactions as pH is decreased. The results are in good agreement with previously proposed surface complexation models.     

Protein expression dynamics during replicative senescence of endothelial cells studied by 2-D difference in-gel electrophoresis

Endothelial senescence contributes to endothelium dysfunctionality and is thereby linked to vascular aging. A dynamic proteomic study on human umbilical vein endothelial cells, isolated from three umbilical cords, was performed. The cells were cultured towards replicative senescence and whole cell lysates were subjected to 2-D difference gel electrophoresis (DIGE). Despite the biological variability of the three independent isolations, a set of proteins was found that showed senescence-dependent expression patterns in all isolations. We focused on those proteins that showed significant changes, with a paired analysis of variance (RM-ANOVA) p-value of < or =0.05. Thirty-five proteins were identified with LC-Fourier transform MS, and functional annotation revealed that endothelial replicative senescence is accompanied by increased cellular stress, protein biosynthesis and reduction in DNA repair and maintenance. Nuclear integrity becomes affected and cytoskeletal structure is also changed. Such important changes in the cell infrastructure might accelerate endothelium dysfunctionality. This study provides biological information that will initiate studies to further unravel endothelial senescence and gain more knowledge about the consequences of this process in the in vivo situation.     

Two-dimensional capillary liquid chromatography: pH gradient ion exchange and reversed phase chromatography for rapid separation of proteins

In the present work, an orthogonal two-dimensional (2D) capillary liquid chromatography (LC) method for fractionation and separation of proteins using wide range pH gradient ion exchange chromatography (IEC) in the first dimension and reversed phase (RP) in the second dimension, is demonstrated. In the first dimension a strong anion exchange (SAX) column subjected to a wide range (10.5-3.5) descending pH gradient was employed, while in the second dimension, a large pore (4,000 A) polystyrene-divinylbenzene (PS-DVB) RP analytical column was used for separation of the protein pH-fractions from the first dimension. The separation power of the off-line 2D method was demonstrated by fractionation and separation of human plasma proteins. Seventeen pH-fractions were manually collected and immediately separated in the second dimension using a column switching capillary RP-LC system. Totally, more than 200 protein peaks were observed in the RP chromatograms of the pH-fractions. On-line 2D analysis was performed for fractionation and separation of ten standard proteins. Two pH-fractions (basic and acidic) from the first dimension were trapped on PS-DVB RP trap columns prior to back-flushed elution onto the analytical RP column for fast separation of the proteins with UV/MS detection.     

Short communication controlling LC-SPE-NMR systems

There are several stages of the LC-SPE-NMR process that should be monitored closely to ensure an efficient isolation and concentration of the target analyte, for instance analyte break-through and compound transfer from the LC-SPE to the NMR probe. In this study, analyte break-through monitoring was performed with a UV detector and a mass spectrometer placed after the SPE unit. Easy break-through was a problem when attempting multiple trapping of various compounds using C18 SPE cartridges with the original commercial system. However, on lowering the flow rate over the SPE system and using SPE cartridges packed with porous carbon, the number of trappings possible increased five-fold. To increase control over the on-line SPE-NMR transfer, a gradient pump-UV system was used to elute compounds trapped on an SPE to an NMR probe. The analyte band was placed in the active volume of the probe by a stop-flow mechanism. The modified LC-SPE system was also coupled with off-line NMR analysis for determination of a degradation product of the insecticide monuron, present in the low ppm range.     

Mechanism of the temperature-dependent degradation of polyamide 66 films exposed to water

Experiments were performed to elucidate the degradation mechanism of hot-pressed polyamide 66 upon exposure to water. For films exposed to water over the temperature range 25 °C-90 °C, degradation was monitored using FTIR and solid-state ¹³C NMR spectroscopies. The data are consistent with a mechanism in which (1) a radical is formed on the methylene carbon adjacent to the amide nitrogen, (2) this radical reacts with oxygen to form a hydroperoxide, and (3) the hydroperoxide decomposes to form an imide or a hydroxylated amide, both of which may cleave leading to chain scission. Water appears to facilitate degradation by increasing the flexibility of the polymer matrix through swelling rather than acting as a reactive species, at least at the early stages of the process. An apparent activation energy of 15 ± 2 kJ/mol is observed for the early stages of degradation, suggesting that segmental motions in the polymer associated with water and oxygen sorption or inter-chain radical reactions are indeed key components of the degradation process.