A New Method for the Characterization of Strain-Specific Conformational Stability of Protease-Sensitive and Protease-Resistant PrPSc

Although proteinacious in nature, prions exist as strains with specific self-perpetuating biological properties. Prion strains are thought to be associated with different conformers of PrPSc, a disease-associated isoform of the host-encoded cellular protein (PrPC). Molecular strain typing approaches have been developed which rely on the characterization of protease-resistant PrPSc. However, PrPSc is composed not only of protease-resistant but also of protease-sensitive isoforms. The aim of this work was to develop a protocol for the molecular characterization of both, protease-resistant and protease-sensitive PrPSc aggregates. We first set up experimental conditions which allowed the most advantageous separation of PrPC and PrPSc by means of differential centrifugation. The conformational solubility and stability assay (CSSA) was then developed by measuring PrPSc solubility as a function of increased exposure to GdnHCl. Brain homogenates from voles infected with human and sheep prion isolates were analysed by CSSA and showed strain-specific conformational stabilities, with mean [GdnHCl]1/2 values ranging from 1.6 M for MM2 sCJD to 2.1 for scrapie and to 2.8 M for MM1/MV1 sCJD and E200K gCJD. Interestingly, the rank order of [GdnHCl]1/2 values observed in the human and sheep isolates used as inocula closely matched those found following transmission in voles, being MM1 sCJD the most resistant (3.3 M), followed by sheep scrapie (2.2 M) and by MM2 sCJD (1.6 M). In order to test the ability of CSSA to characterise protease-sensitive PrPSc, we analysed sheep isolates of Nor98 and compared them to classical scrapie isolates. In Nor98, insoluble PrPSc aggregates were mainly protease-sensitive and showed a conformational stability much lower than in classical scrapie. Our results show that CSSA is able to reveal strain-specified PrPSc conformational stabilities of protease-resistant and protease-sensitive PrPSc and that it is a valuable tool for strain typing in natural hosts, such as humans and sheep

On the influence of laminate stacking on buckling of composite cylindrical shells subjected to axial compresssion

The buckling loads of laminated cylinders can strongly depend on the position of the differently oriented layers within the shell. This paper deals with two different laminated orthotropic cylinders with opposite stacking sequence of the laminate layers. Cylinders of this construction had been thoroughly tested within a BRITE EURAM project. Analytical and semi-analytical methods have been used to predict the buckling loads, and the results are reported in this paper as well as test results for comparison. An explanation of the striking influence of stacking sequence is given. With some more examples the findings are verified. It is suggested that the presented results can be used for benchmarking purpose

Buckling loads of CFRP composite cylinders under axial and torsional loading - experiments and computations

During the years 1994 through 1999, a European research project under the title Design and Validation of Imperfection-Tolerant Laminated Shells (DEVILS) was carried out. In this project, 11 European partners were involved. The goal of the project was an analytical and experimental study of the buckling behavior of thin-walled carbon fibre reinforced polymer (CFRP) laminated shells under combined axial and torsion loading. An additional aim was to compose a guideline for the dimensioning of such shells. This paper deals with the experimental and the analytical work conducted by DLR (Institute of Structural Mechanics, Braunschweig), ETH Zürich (former Institute of Lightweight Structures and Ropeways) and EMPA Dübendorf (Department of Polymers/Composites) in that project. The study was aimed at the determination of buckling loads of circular cylindrical shells of different laminate lay-ups. Nine shells were tested at DLR in Braunschweig for axial compression and at EMPA in Dübendorf under axial load and under combined axial compression and superimposed torsion. To determine the geometrical quality, the internal and the external surfaces of the specimens were mapped. ETH used photogrammetry and laser scanning prior to loading, while EMPA applied coordinate measurements for the unloaded shells and Moiré projection to monitor the lateral deflection of the cylindrical wall during loading and after buckling. At DLR, strain measurements were performed to assess regularity of the load distribution throughout the loading. The investigation showed that buckling loads of cylinders which are imperfection-sensitive under axial loading may not be so sensitive to combined loads. Furthermore, it was found that the stiffness eccentricity of the laminate played a significant role on the magnitude of the axial buckling load, while for combined loads this effect was somewhat reduced. This paper contains the results of those tests and also the comparison with results of analytical investigations and FE modeling; the obtained data can be used as benchmark reference

Space engineering - Buckling of structures ECSS-E-HB-32-24A

This Handbook is one document of the series of ECSS Documents intented to be used as supporting material for ECSS Standards in space projects and applications. ECSS is a cooperative effort of the European Space Agency, national space agencies and European industry associations for the purpose of developing and maintaining common standards. This handbook has been prepared by the ECSS-E-HB-32-24A Working Group, reviewed by the ECSS Executive Secretariat and approved by the ECSS Technical Authority