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

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

Numerical simulation of convective flow of the melt in the classical Czochralski method and in CACRT. 2 : simulation of combined free and forced convection

In part 2 of this report, we describe the extension of our procedure presented in part 1 for the numerical solution of the time-dependent Navier-Stokes equations with Boussinesq approximation and the convective he at conduction equation in the Czochralski crystal-growth arrangement. By means of several digital simulations with a low kinematic viscosity, typical for liquid metals, and characteristic rotational angular velocities of crystal and crucible, the influence of free buoyancy driven convection on the familiar forced convective flow patterns of part 1 is studied with special emphasis on the occurrence of flow and temperature oscillations. Additionally, we show the combined free and forced convective flow patterns in the isorotational and the counterrotational Czochralski Accelerated Crucible (and Crystal) Rotation Technique arrangement (CACRT) for a fluid of the viscosity of liquid silicon

A model for macroscopic Czochralski growth : |btheoretical and experimental investigations

A very important process to grow single crystals is the method developed by Czochralski /1/. It is used in industry to grow single crystals of silicon, germanium, gallium phosphide, and arsenide and several other substances. It is also used in research to produce more or less perfect metal single crystals for neutron and electron scattering, superconductivity, NMR, residual resistance, optical, and Fermi surface experiments. In some cases, e.g. if the crucible attacts the melt or if the melting temperature is so high that there exists no suitable crucible material, the floating zone method is used (e.g. for growth of tungsten, niobium, and oxygen free silicon single crystals) /2/. To get an impression of the importance of crystal growth, the industrial production of single crystals in 1977 is given in table 1 /3/. However, the Czochralski and the floating zone process are very complicated, because the shape of the crystal and also, but in an even more complicated way, the perfection, are determined by the g r o w t h p a r a m e t e r s. For example a sudden change in the melt temperature of 1 °C means for a copper crystal with a diameter of 1 cm a decrease or an increase of the crystal diameter of about 5 % /4/. It is therefore necessary to control the temperature very weIl, but in order to grow a crystal with a constant diameter, the melt temperature additionally [Tabelle 1 ...] has to be increased or decreased continuously during the growth process in dependence on the crystal diameter (see paragraph 4.1). So for a particular crystal shape, a certain melt temperature program is necessary. To reproduce this shape this m e l t t e m p e r a t u r e p r o g r a m has to be controlled automatically. For that reason, and additionally for direct control of the crystal diameter (in order to apply the optimizing theory), the knowledge of the influence of the different growth parameters on the macroscopic shape is very important. The purpose of this investigation has been the study of this influence on the macroscopic shape for the Czochralski method applied on non-faceting metals. In consequence of these considerations, a growth model was developed to calculate the temperature distribution in the solid and the melt temperature program. This model is described in the second chapter. In thethird chapter the different methods for c o n t a c t l e s s t e m p e r a t u r e a n d g r o w t h p a r a m e t e r m e a s u r e m e n t s are described. In the fourth chapter the experimental da ta are compared with the theoretical results

Numerical simulation of convective flow of the melt in the classical Czochralski method, in ACRT and CACRT 1 : Simulation of forced convection

In part 1 of this report, a procedure is described for the numerical solution of the time-dependent Navier-Stokes equations governing the forced convective flow in a crystal-growth crucible. By means of five digital simulations of the classical Czochralski crystal-pulling process, we show the excellent agreement of our calculations with the experimental data of Carruthers and Nassau [3], not only qualitatively but quantitatively, too. Moreover, for the Accelerated Crucible-Rotation Technique (ACRT) and its application to the Czochralski method (CACRT), the first numerical simulations are presented assuming the fluid model to be the same 1:1 glycerine-water mixture of moderate kinematic viscosities as in [3]. But our programme can also deal with low viscosities typical for semiconductors and liquid metals: This is demonstrated by our simulations of the classical Czochralski,the ACRT and the CACRT arrangements with the viscosity of liquid copper