Synthetic receptors with antibody-like binding affinities

Antibodies are critical reagents in biological research and are increasingly being developed as therapeutic agents. They typically exhibit very high affinity and selectivity for their ligands. Synthetic protein-binding agents rarely achieve the combination of high affinity and selectivity for their target protein that is typical of a good antibody. However, significant efforts are underway to develop a new generation of protein ligands with improved properties. This article reviews progress towards this goal and suggests fruitful strategies for future research.