Metal binding sites, molecular recognition

The design of most protein probes involves the incorporation of a molecular substrate as a pendant into a metal complex. The recognition of the substrate by the protein host is then revealed by changes of the photophysical properties of the probe. However, metal complexes without a specific molecular substrate have also been employed the recognition is usually on the basis of hydrophobic interactions. As can be seen in the examples mentioned in Sect. 4, the hydrophobic nature of protein matrix, in particular the substrate-binding sites, provides opportunities in the development of new probes. 

This enhancement of a metal coordination binding site with the potential for molecular recognition via other intermolecular forces allows the synthesis of anion receptors with novel anion selectivities. 

---