Molecular characterization of two monoclonal antibodies specific for the LDL receptor-binding site of human apolipoprotein E

Apolipoprotein E (apoE), a 299 amino acid protein, is a ligand for the low density lipoprotein receptor (LDLr). It has been established that basic amino acids situated between apoE residues 136 and 150 participate in the interaction of apoE with the LDLr. Evidence suggests that apoE is heterogeneous on lipoproteins in its conformation and in its ability to react with cell surface receptors. Our goal was to produce mAbs that could serve as conformational probes of the LDLr binding site of apoE. We used a series of apoE variants that have amino acid substitutions at residues 136, 140, 143, 144, 145, 150, 152, and 158 to identify the epitopes of two anti-human apoE monoclonal antibodies (mAbs), 1D7 and 2E8, that inhibit apoE-mediated binding to the LDLr. We show that most of the variants that have reduced reactivity with the LDL receptor also have reduced reactivity with the mAbs. The epitopes for both mAbs appear to include residues 143 through 150 and thus coincide with the LDLr-binding site of apoE. It is notable that mAb 2E8, but not 1D7, resembles the LDLr in showing a reduced reactivity with apoE (Arg158 --> Cys). While most of the receptor-defective variants involve replacement of apoE residues directly implicated in binding, substitution of Arg158 by Cys is thought to indirectly affect binding of apoE to the LDLr by altering the conformation of the receptor-binding site. To determine whether the similarity in specificities of the mAbs and the LDLr reflect structural similarities, we cloned and characterized the cDNAs encoding the light and heavy chains of both mAbs. Primary sequence analysis revealed that, although these two antibodies react with overlapping epitopes, their respective complementarity determining regions (CDRs) share little homology, especially those of their heavy chains. The two mAbs, therefore, likely recognize different epitopes or topologies within a limited surface of the apoE molecule. Four negatively charged amino acids were present in the second CDR of the 2E8 heavy chain that could be approximately aligned with acidic amino acids within the consensus sequence of the LDLr ligand-binding domain. This could indicate that mAb 2E8 and the LDLr use a common mode of interaction with apoE.     

The critical current density of deformed and annealed superconducting Nb-26% Zr and Nb-32% Zr and its dependence on the amount of deformation

A study of the low-field critical current densities (computed from magnetization data) which can be achieved by heat-treating for 1 h Nb-Zr alloys deformed various amounts, has shown that a peak critical current density is always reached after annealing at around 750°C. The magnitude of this peak depends upon the amount of deformation, but is not increased by deforming beyond 80%. Superconducting transition temperatures are also reported.The microstructure was unusual in that deformation was very unevenly distributed and there was little tendency for the dislocations to cross-slip or to form a cellular structure. Precipitation of _Zr occurred in regions of high deformation only, so that equilibrium was not achieved below 80% deformation. The measured superconducting properties are explained in terms of this microstructure, with _Zr as the dominant flux pinning agent.     

A practical approach to data modelling in spatial applications

The storage and manipulation of spatial data requires a different style of support from that normally found in commercial database systems. This paper explores the use of the functional data model and the high level language Daplex to provide an integrated tool for the conceptual modelling of spatial data and the manipulation of data values. Importance is attached to allowing dynamic schema definition and to the provision of abstract data types to support spatial objects. The implementation comprises three separate modules and uses an underlying relational DBMS to store all metadata and data values. This modular design has enabled the user interface, Daplex language and storage aspects of the software to be developed independently, creating a system which has already proved to be easily portable. Consideration has also been given to ways of improving system performance.     

Gurney Analysis of Porous Shells

There are many application areas, where the ability to accurately predict the speed of expansion of fragments from explosively disseminated porous shells is important. For inert materials this speed in part determines the size of the resulting cloud. For reactive materials this speed in part determines the ability to ignite the material and determines the trade‐off between reactive and inertial fragment effects. Gurney analysis has been used extensively for many years to approximate the speed of fragmenting solid material shells. This work investigates the behavior of HE driven porous shells in spherical and cylindrical geometry and identifies factors to use to multiply solid shell Gurney velocity by to predict the speed of a porous shell.     

家用洗涤剂中的氧漂白体系(英)

洗涤过程中氧漂白对去除污斑起着重要的作用，介绍了活性氧漂白体系的生产、活化和应用过程。还了工业上可接受氧漂白产品的市场需求。