Synthetic Receptors for the Differentiation of Phosphorylated Peptides with Nanomolar Affinities

Artificial ditopic receptors for the differentiation of phosphorylated peptides varying in i+3 amino acid side chains were synthesized, and their binding affinities and selectivities were determined. The synthetic receptors show the highest binding affinities to phosphorylated peptides under physiological conditions (HEPES, pH 7.5, 154 mm NaCl) reported thus far for artificial systems. The tight and selective binding was achieved by high cooperativity of the two binding moieties in the receptor molecules. All receptors interact with phosphorylated serine by bis(Zn-II-cyclen) complex coordination and a second binding site recognizing a carboxylate or imidazole amino acid side chain functionality.