The membranes surrounding cells and organelles constitute their interface with the local environment. The functions of membrane proteins include cell/cell and cell/extracellular matrix recognition, the reception and transduction of extracellular signals, and the tra- port of proteins, solutes and water molecules. Abnormal membrane protein expression has profound biological effects and may, for example, underlie phenotypic and functional differences between normal and tumour cells. Moreover the accessibility, particularly of plasma proteins traversing the plasma membrane of cells, makes them...