Dynamic combinatorial development of a neutral synthetic receptor that binds sulfate with nanomolar affinity in aqueous solution.

Using dynamic combinatorial disulfide chemistry we have developed a new generation of neutral synthetic receptors for anions, based on a macrobicyclic peptide structure. These receptors show an exceptional affinity and selectivity for sulfate ions in aqueous solution [log K(a) = 8.67 in 41 mol% (67 volume%) acetonitrile in water]. The high affinity depends on a delicate balance between rigidity and flexibility in the structure of the receptor.