Total Synthesis of a Partial Structure from Arabinogalactan and Its Application for Allergy Prevention

Arabinogalactan, a microheterogeneous polysaccharide occurring in plants, is known for its allergy-protective activity, which could potentially be used for preventive allergy treatment. New treatment options are highly desirable, especially in a preventive manner, due to the constant rise of atopic diseases worldwide. The structural origin of the allergy-protective activity of arabinogalactan is, however, still unclear and isolation of the polysaccharide is not feasible for pharmaceutical applications due to a variation of the activity of the natural product and contaminations with endotoxins. Therefore, a pentasaccharide partial structure was selected for total synthesis and subsequently coupled to a carrier protein to form a neoglycoconjugate. The allergy-protective activity of arabinogalactan could be reproduced with the partial structure in subsequent in vivo experiments. This is the first example of a successful simplification of arabinogalactan with a single partial structure while retaining its allergy-preventive potential.     

Broadband 10 Gb/s operation of graphene electro‐absorption modulator on silicon

High performance integrated optical modulators are highly desired for future optical interconnects. The ultra‐high bandwidth and broadband operation potentially offered by graphene based electro‐absorption modulators has attracted a lot of attention in the photonics community recently. In this work, we theoretically evaluate the true potential of such modulators and illustrate this with experimental results for a silicon integrated graphene optical electro‐absorption modulator capable of broadband 10 Gb/s modulation speed. The measured results agree very well with theoretical predictions. A low insertion loss of 3.8 dB at 1580 nm and a low drive voltage of 2.5 V combined with broadband and athermal operation were obtained for a 50 μm‐length hybrid graphene‐Si device. The peak modulation efficiency of the device is 1.5 dB/V. This robust device is challenging best‐in‐class Si (Ge) modulators for future chip‐level optical interconnects.     

Combined liquid and gas chromatographic characterisation of polyglycerol fatty acid esters

In the present study a combined liquid and gas chromatographic technique is described for the analysis of polyglycerol fatty acid esters. Liquid chromatographic fractionation of samples resulted in pure standards of monoesters of di- and triglycerols and diesters of di- and triglycerols. Confirmation of their identity was achieved by LC-MS analysis. Moreover, a chromatographic identification of the mono- and diesters of cyclic diglycerol was proposed. From the isolation of pure esters and their gas chromatographic analysis, it was revealed that co-elution of several compounds occurred. Thus it was shown that prefractionation of the sample using a simplified liquid chromatographic separation, was necessary in order to characterise the esters correctly. In combination with some other chemical analyses, a complete profile of the chemical composition of polyglycerol fatty acid esters can be obtained.     

Multiple-stage mass spectrometry in structural characterization of organophosphorus compounds

Multiple-stage mass spectrometry involving consecutive collision-activated dissociation reactions was used to examine the structures of fragment ions commonly formed on electron ionization of organophosphorus esters. The compounds studied include several aryl thiophosphates, some of which are analogs of common pesticides. Energy-resolved collisionactivated dissociation experiments allow the dissociation of the molecular ions of these compounds in such a manner that only a few fragment ions dominate the spectrum. An abundant fragment ion of m/z 109, formed from all of the compounds studied, can have at least four different stable structures: (CH₃O)₂PO⁺, CH₃CH₂OP(O)OH⁺, CH₂ =CHOP(H)(OH)₂ ⁺, and (CH₂O)₂P(H)OH⁺. The structure of the fragment ion of m/z 109 was found to reflect the phosphorus-containing part of the compounds studied. Another abundant fragment ion obtained for all the aryl esters studied is structurally characteristic of the aromatic moiety of the molecule. This fragment ion is the result of a complex rearrangement involving transfer of an alkylene group to the aromatic ring from the phosphoruscontaining part of the molecular ion. The utility of these fragment ions in the structural characterization of unknown organophosphorus esters is discussed.     

Applied radiation research around a 15 MeV high-average-power linac

The Department of Subatomic and Radiation Physics of the University Gent is equipped with a 15 MeV 20 kW linear electron accelerator (linac) facility. In its present configuration the accelerator is used as a multipurpose apparatus for research in the fields of polymer chemistry, biomedical materials, medicine, food technology, dosimetry, solid state physics, agriculture and nuclear and radiation physics. We present an overview of both the various research projects around our linac facility involving radiation chemistry and physics and the specialised technologies facilitating this research.     

Development of chromatographic method for the determination of degree of polymerisation of polyglycerols and polyglycerol fatty acid esters

Summary From polyglycerol samples, pure standards of tri and tetraglycerol were obtained using a column chromatographic technique. Polyglycerols were derivatised to trimethyl silyl derivatives to obtain gas chromatographic identification of all linear, branched and cyclic diglycerol isomers and all linear and branched triglycerols. Moreover, quantitative gas chromatographic analysis of the di-, tri- and tetraglycerol content of a polyglycerol sample was developed. Finally a method to characterise, on a quantitative basis, the polyglycerol content of polyglycerol fatty acid esters was developed. It consisted of saponifying the esters, without affecting the degree of polymerisation of the polyglycerols, followed by gas chromatographic analysis of the isolated polyglycerol fraction.     

Enhanced levels of dioxins in eggs from free range hens; a fast evaluation approach

As a consequence of an initiative of the local authorities of the city of Antwerp (Belgium), dioxin levels were determined in eggs from free range hens owned by private owners in the Northern districts of Antwerp. The reasons for this survey stem from some fears that free range eggs could be contaminated by local environmental sources (e.g. soil, grass, earthworms) as a result of the presence in this area of intensive industrial and domestic activities. The analyses revealed high levels of PCDD/F in the home-produced eggs (average = 9.9 pg WHO-TEQ per g of fat; n = 15). An evaluation of the available results has been carried out by the Scientific Committee of the Belgian Federal Agency for the Safety of the Food Chain. From this evaluation, it appeared that the analysis of congener profiles was of limited use because all profiles were dominated by the OCDD congener, independently of the level of contamination. There were not enough indications allowing a causal link to be established between high dioxin levels in eggs and soil contamination and, on the other hand, it was assumed that other factors such as feeding habits, physiological state and egg laying rhythm of the hens could not be ruled out as potential causes of aggravation. A quick risk assessment led to the conclusion that the impact of this contamination is highly relevant for the consumer’s health due to the important contribution of such home-produced eggs in the estimations of total body burden.