New methods of analysing for antigens and glycoproteins in complex mixtures

The analysis of complex mixtures of proteins and particularly those which make up macromolecular assemblies including membranes, received a major fillip in the late 1960s with the introduction of sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The resolving power of electrophoresis in polyacrylamide gels is considerably superior to that achieved with any other support medium including agar, the immunochemist's standby. The essential physical property which makes polyacrylamide the medium of choice is the limiting pore size of the gel: its sieving effect on the movement of macromolecules and the reduction of diffusion together result in increased sharpness of bands. On the other hand, in all the standard immunochemical techniques such as immunodiffusion, immunoelectrophoresis, and rockets, free diffusion of protein molecules in the support medium is essential and agar or agarose satisfy this requirement. There has therefore been a search for ways in which polycrylamide gel electrophoresis, particularly SDS-gel electrophoresis of aggregates of proteins (as in membranes, viruses, the cellular cytoskeleton), can be adapted to immunochemical analysis of their constituent antigens. Here Brian Anderton and Robin Thorpe discuss several of the methods now in use.