Surface tension induced convection in encapsulated liquid metals in microgravity: Apollo-Soyuz test project experiment no. MA-041

This experiment was designed to determine the extent of surface tension induced convection caused by a steplike compositional variation in a liquid metal. Preliminary results are presented

Polarisierter Transport des Prion-Proteins

Several proteins linked to neurodegenerative diseases, such as the -amyloid precursor protein, amyloid -peptide, -secretase, and tau, undergo selective polarized sorting. We investigated polarized sorting of the mammalian prion protein (PrPC) and its homologue doppel (Dpl). In contrast to Dpl, which accumulates on the apical surface, PrPC is targeted selectively to the basolateral side in Madin-Darby canine kidney cells. An extensive deletion and domain swapping analysis revealed that the internal hydrophobic domain (HD) of PrP (amino acids 113–133) confers basolateral sorting in a dominant manner. PrP mutants lacking the HD are sorted apically, while Dpl chimeras containing the HD of PrP are directed to the basolateral membrane. Furthermore, a pathogenic PrP missense mutation within the HD leads to aberrant apical sorting of PrP as well

Doppel and PrPC co-immunoprecipitate in detergent-resistant membrane domains of epithelial FRT cells

Dpl (doppel) is a paralogue of the PrPC (cellular prion protein), whose misfolded conformer (the scrapie prion protein, PrPSc) is responsible for the onset of TSEs (transmissible spongiform encephalopathies) or prion diseases. It has been shown that the ectopic expression of Dpl in the brains of some lines of PrP-knockout mice provokes cerebellar ataxia, which can be rescued by the reintroduction of the PrP gene, suggesting a functional interaction between the two proteins. It is, however, still unclear where, and under which conditions, this event may occur. In the present study we addressed this issue by analysing the intracellular localization and the interaction between Dpl and PrPC in FRT (Fischer rat thyroid) cells stably expressing the two proteins separately or together. We show that both proteins localize prevalently on the basolateral surface of FRT cells, in both singly and doubly transfected clones. Interestingly we found that they associate with DRMs (detergent-resistant membranes) or lipid rafts, from where they can be co-immunoprecipitated in a cholesterol-dependent fashion. Although the interaction between Dpl and PrPC has been suggested before, our results provide the first clear evidence that this interaction occurs in rafts and is dependent on the integrity of these membrane microdomains. Furthermore, both Dpl and PrPC could be immunoprecipitated with flotillin-2, a raft protein involved in endocytosis and cell signalling events, suggesting that they share the same lipid environment

N-Glycans and Glycosylphosphatidylinositol-Anchor Act on Polarized Sorting of Mouse PrPC in Madin-Darby Canine Kidney Cells

The cellular prion protein (PrPC) plays a fundamental role in prion disease. PrPC is a glycosylphosphatidylinositol (GPI)-anchored protein with two variably occupied N-glycosylation sites. In general, GPI-anchor and N-glycosylation direct proteins to apical membranes in polarized cells whereas the majority of mouse PrPC is found in basolateral membranes in polarized Madin-Darby canine kidney (MDCK) cells. In this study we have mutated the first, the second, and both N-glycosylation sites of PrPC and also replaced the GPI-anchor of PrPC by the Thy-1 GPI-anchor in order to investigate the role of these signals in sorting of PrPC in MDCK cells. Cell surface biotinylation experiments and confocal microscopy showed that lack of one N-linked oligosaccharide leads to loss of polarized sorting of PrPC. Exchange of the PrPC GPI-anchor for the one of Thy-1 redirects PrPC to the apical membrane. In conclusion, both N-glycosylation and GPI-anchor act on polarized sorting of PrPC, with the GPI-anchor being dominant over N-glycans

Calculations of shape and stability of menisci in Czochralski growth with tables to determine meniscus heights, maximum heights and capillary constants

The shape and stability of menisci occurring during Czochralski growth have been studied by means of numerical methods for the case of the free surface. The existence of minimal joining angles is shown, beyond which the growing crystal will separate from the melt. The dependence of the interface height on the joiningangle for different crystal diameters was calculated. The maximum stable heights and the corresponding joining angles were determined as a function of crystal diameter. A method for measuring the capillary constant of the melt during Czochralski growth is proposed. Our results are compared with known analyticalapproximations. Limitations of the applications caused by a finite crucible radius or low g values are pointed out. For practical use the following functions have been tabulated: a) meniscus height in dependence on joining angle and crystal radius, b) the radius-height-ratio in dependence on radius and angle for the calculation of the capillary constant, c) the maximum stable height and the corresponding growth angle as a function of crystal radius

Herstellung und Charakterisierung von Einkristallen der kubischen Laves-Phasen Se-Al2_{2}

Im Kristall-Labor des Instituts für Festkörperforschung wurden folgende Legierungseinkristalle für die verschiedensten Experimente gewünscht.La Al$_{2}$ (La Ce) Al$_{2}$ (La Er) Al$_{2}$ Y Al$_{2}$ (Y Ce) Al$_{2}$ Ce Al$_{2}$ Auftraggeber waren: 1. Das Institut für Festkörperforschung Jülich 2. Der Sonderforschungsbereich Köln - Aachen - Jülich / Im folgenden Bericht sollen die Herstellungs- und Charakterisierungsverfahren erläutert werden. 1. Probenpräparation 2. Art und Wahl der Kristallzüchtung 3. Probencharakterisierung 4. Messungen und Ergebnisse der Experimente Aus der Literatur war bis dahin nur ein Hersteller solcher Einkristalle bekannt. Aus den Veröffentlichungen konnten nur wenige Daten und Einzelheiten entnommen werden /1/2/3/4. Es war deshalb notwendig, vorher einige grundlegende Dinge zu erlernen, z. B. Probenpräparation, Wahl des Tiegelmaterials, Impflingherstellung. Die Problemstellung war, Einkristalle in verschiedenen Größen und Orientierungen herzustellen, von 2 $\varnothing$ mm 50 mm lang, bis 10 $\varnothing$ mm 80 mm lang, deren Stabachsen oder sein sollten