Synthesis of blood group Forssman pentasaccharide GalNAcα1-3GalNAcβ1-3Galα1-4Galβ1-4Glcβ–R

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Do complex matrices modify the sorptive properties of polydimethylsiloxane (PDMS) for non-polar organic chemicals?

The partitioning of non-polar analytes into the silicone polydimethylsiloxane (PDMS) is the basis for many analytical approaches such as solid phase microextraction (SPME), stir bar sorptive extraction (SBSE) and environmental passive sampling. Recently, the methods have been applied to increasingly complex sample matrices. The present work investigated the possible effect of complex matrices on the sorptive properties of PDMS. First, SPME fibers with a 30 μm PDMS coating were immersed in 15 different matrices, including sediment, suspensions of soil and humic substances, mayonnaise, meat, fish, olive oil and fish oil. Second, the surface of the fibers was wiped clean, and together with matrix-free control fibers, they were exposed via headspace to 7 non-polar halogenated organic chemicals in spiked olive oil. The fibers were then solvent-extracted, analyzed, and the ratios of the mean concentrations in the matrix-immersed fibers to the control fibers were determined for all matrices. These ratios ranged from 92% to 112% for the four analytes with the highest analytical precision (i.e. polychlorinated biphenyls (PCBs) 3, 28, 52 and brominated diphenyl ether (BDE) 3), and they ranged from 74% to 133% for the other three compounds (i.e. PCBs 101, 105 and γ-hexachlorocyclohexane (HCH)). We conclude that, for non-polar, hydrophobic chemicals, the sorptive properties of the PDMS were not modified by the diverse investigated media and consequently that PDMS is suited for sampling of these analytes even in highly complex matrices.     

Proteome analysis of conditioned medium from cultured adult hippocampal progenitors

It is known that proliferation and survival of neural stem/progenitor cells in vitro not only depend on exogenous factors, but also on autocrine factors secreted into the conditioned medium. It is also well known that the identification of bioactive proteins secreted into the conditioned medium poses a substantial challenge. Recently, neural stem/progenitor cells were shown to secrete a survival factor, cystatin C, into the conditioned medium. Here, we demonstrate an approach to identify other low molecular weight proteins in conditioned medium from cultured adult rat hippocampal progenitor cells. A combination of preparative two-dimensional gel electrophoresis (2-DE) and mass spectrometry was utilized in the analysis. We were able to identify a number of proteins, which include Rho-guanine nucleotide dissociation inhibitor 1, phosphatidylethanolamine binding protein (PEBP), also termed Raf-1 kinase interacting protein, polyubiquitin, immunophilin FK506 binding protein 12 (FKBP12) and cystatin C. The presence of PEBP and FKBP12 in conditioned medium was confirmed immunologically. All nestin-positive progenitor cells showed immunoreactivity for antibodies against PEBP and FKBP12. To our knowledge we are the first to use this preparative proteomic approach to search for stem cell factors in conditioned medium. The method could be used to identify novel bioactive proteins secreted by stem/progenitor cells in vitro. Identification of bioactive proteins in vitro is of potential importance for the understanding of the regulatory mechanisms of the cells in vivo.     

Synthesis of R-(-)-imperanene from the natural lignan hydroxymatairesinol

A convenient and high yielding method for the synthesis of R-(-)-imperanene, starting from the readily available natural lignan hydroxymatairesinol from Norway spruce, was developed. Hydroxymatairesinol was degraded in strongly basic aqueous conditions to (E)-4-(4-hydroxy-3-methoxyphenyl)-2-(4-hydroxy-3-methoxyphenylmethyl)but-3-enoic acid, which was esterified and then reduced by LiAlH(4) to afford R-(-)-imperanene. The configuration at the crucial stereocenter was preserved in the synthesis, and the obtained product was identified by optical rotation measurements and chiral HPLC analyses as the R-(-)-enantiomer (ee 86-92%).     

Peracid dependent stereoselectivity and functional group contribution to the stereocontrol of epoxidation of (E)-alkene dipeptide isosteres

Twelve Boc-protected phenylalanyl-phenylalanine and phenylalanyl-glycine trans-vinyl isosteres were epoxidised with magnesium monoperoxyphtalate hexahydrate (MMPP) and trifluoroperacetic acid, and the results have been compared with those from earlier studies on epoxidations with m-CPBA. The alkenes were synthesised in high yields with high E/Z-selectivities using either the Julia or Schlosser reactions. The formation of threo isomers was favoured in all epoxidation reactions except with CF₃CO₃H on substrates containing two allylic/homoallylic functional groups directing the peracid to opposite faces of the alkene. The switch to erythro selectivity observed with CF₃CO₃H is suggested to emanate from coordination to the allylic ester functionalities via hydrogen bond donation from the peracid. The other peracid reagents seem to be preferentially coordinated to the allylic carbamate function. The contribution of individual functional groups to the stereopreference was also investigated.     

Changes in Optical Properties of Human Whole Blood in vitro Due to Slow Heating

Optical properties of human whole blood were investigated in vitro at 633 nm using a double integrating sphere set-up. The blood flow was maintained at a constant rate through a flow cell while continuously heating the blood at 0.2–1.lC/min from approximately 25 to 55°C in a heat exchanger. A small, but rather abrupt decrease in the scattering asymmetry factor (g-factor) of 1.7 ± 0.6% and a similar increase in the scattering coefficient of 2.9 ± 0.6% were observed at approximately 45–46°C yielding an increase in the reduced scattering coefficient of 40 ± 10%. Furthermore, a continuous, manifest increase in the absorption coefficient was seen with increasing temperature, on average 80 ± 70% from 25 to 50°C. The effect of the heating on the blood cells was also studied under a white-light transmission microscope. A sudden change in the shape of the red blood cells, from discshaped to spherical, was observed at approximately the same temperature at which the distinct changes in g-factor and scattering coefficient were observed, i.e. at 45–46°C. The results indicate that this shape transformation could explain the sudden change in scattering properties.