Analysis of complex protein mixtures with SDS-polyacrylamide gel elektroforesis

De routinematige analyse van complexe eiwitmengsels in polyacrylamide gels in aanwezigheid van natriumdodecylsulfaat wordt beschreven in een aantal varianten. Door het percentage acrylamide te varieren kunnen verschillende moleculair gewicht trajecten onderzocht worden. Dit wordt geillustreerd aan de hand van standaardmengsels en praktijkmengsels. Ook zijn verschillende kleuringen onderzocht. Hieruit bleek dat er grote verschillen optraden bij de verschillende kleuringen zowel in de gevoeligheid van de kleuring als in het kwantitatieve eiwitpatroon. De zilverkleuring, uitgevoerd na de Coomassie blauw kleuring, bleek de gevoeligste kleuring. Tevens worden voorlopige resultaten getoond met het scannen van de gels. Hierbij lijkt het beeld analyse systeem een veelbelovende techniek.RIV

New insights into the nature of the active phase of VPO catalysts : a quantitative static LEIS study

The atomic composition of the outermost atomic layer of equilibrated VPO catalysts was studied with low-energy ion scattering. Using external reference samples, absolute numbers for the atomic densities of both P and V could be determined. VPO catalysts prepared in either aqueous or organic media showed large amounts of carbonaceous surface species. From catalysts prepared in an aqueous medium the carbonaceous species could be removed using a mild oxidation treatment without significantly changing the average valence of the vanadium atoms in the catalyst as evidenced from XPS. After this cleaning treatment the surface concentration of vanadium (atoms/cm2) agrees well with that expected for a vanadyl pyrophosphate structure. However, the surface phosphorus concentration is twice as high as that in vanadyl pyrophosphate, leading to a surface P/V ratio of 2.0±0.2. This shows that VPO catalysts may be terminated by a distorted vanadyl pyrophosphate structure, where the excess amount of phosphorus is positioned between the vanadyl units and the phosphate groups. The catalyst surface is also compared to VOPO4 phases. A significant contribution of a phase such as a -VOPO4 could explain the observed surface P/V ratio of 2.0

Insight in the outside: New applications of low-energy ion scattering

Low energy ion scattering is used to selectively probe the outermost atomic layer of the surface. The development of double toroidal analyzers has improved the detection sensitivity of low energy ion scattering by orders of magnitude. The features of these analyzers are discussed. It is shown that the absence of matrix effects makes it possible to quantify the surface density of fluorine in polymers with a LiF(1 0 0) surface. The extreme surface sensitivity of LEIS also enables one to study intramolecular segregation processes. As an example the aging of a polypropylene surface that has been activated with atomic oxygen is described. As an example of the LEIS analysis of highly dispersed isolating surfaces, the formation of coke on a commercial three-way catalyst is discussed