Purification and characterization of two high-density-lipoprotein-binding proteins from rat and human liver.

The liver plays a major role in the metabolism of plasma high-density lipoprotein (HDL). Several groups have postulated, but others refuted, the existence of a classical membrane receptor which recognizes HDL. In the present study, we identified and purified two liver HDL-binding proteins of 120 kDa (HB1) and 100 kDa (HB2), with apparent specificity for HDL3 devoid of E apolipoprotein. The plasma membrane was the richest source of the HDL-binding protein. Both proteins bound A-I and A-II apolipoproteins and retained HDL-binding activity after final purification. HB1 activity, but not that of HB2, was lost after treatment with beta-mercaptoethanol, but reduction did not change the apparent molecular mass of either protein. Antibodies against HB1 or HB2 did not cross-react, and preliminary structural investigations provide evidence to suggest that HB1 and HB2 are not structurally related. We thus provide evidence for at least two liver plasma-membrane proteins which bind HDL apolipoproteins, suggesting that protein-protein interaction participates to some degree in the mechanism of HDL recognition by cells

Animation of data refinements

Refinement is the process of deriving verifiably-correct software from its specification. In practice, however refinement steps are complex and difficult to prove correct. We show how animation can be used to provide insights into the correctness, or otherwise, of refinement steps for the most general form of data refinement in which the whole system design can be changed in a single step

Visualisation of refinements

Animation tools have proven to be effective as a means of visualising formal specifications. Specifications that might otherwise be impenetrable can be communicated to a wide range of people involved in the software development process. Here we argue that animation can also aid understanding of formal program development, or refinement. We examine two case studies that demonstrate the effectiveness of visualisations generated from a specification animation tool for improving the understanding of refinements

A partial-correctness semantics for modelling assembler programs

Previous work on formally modelling and analysing program compilation has shown the need for a simple and expressive semantics for assembler level programs. Assembler programs contain unstructured jumps and previous formalisms have modelled these by using continuations, or by embedding the program in an explicit emulator. We propose a simpler approach, which uses techniques from compiler theory in a formal setting. This approach is based on an interpretation of programs as collections of program paths, each of which has a weakest liberal precondition semantics. We then demonstrate, by example, how we can use this formalism to justify the compilation of block-structured high-level language programs into assembler