Solid-phase assays provide a simple, rapid and robust method for the analysis of protein–protein interactions; i.e., does protein A interacts with protein B? In this assay, protein A (here termed as ‘receptor’) is adsorbed to the wells of an enzyme-linked immunosorbent assay (ELISA) plate (solid phase). The plate is then blocked using bovine serum albumin (BSA), and biotin-labelled protein B (here termed as ‘ligand’) is added. After washing the wells to remove unbound ligand, bound ligand is detected by addition of an avidin–peroxidase conjugate followed by a colorimetric detection step. This type of assay is particularly well suited for studying the interaction of ECM proteins with integrins. The screening of antagonists of integrin–ligand interactions in the pharmaceutical industry is an important area in which this assay is finding use.