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A library of “tweezer” receptors, incorporating a guanidinium “head group” and two peptide derived side arms has been prepared on the solid-phase using an orthogonally protected guanidinium scaffold 12. The library was screened with various tripeptide derivatives in an aqueous solvent system. A tweezer receptor 25 for the side chain protected tripeptide 19 was identified from the screening experiments. Receptor 25 was resynthesised and solution binding studies were carried out, which revealed that 25 binds to tripeptide 19 with Ka=8.2×104±2.5×104 (15 % DMSO/H2O, pH 8.75) and with appreciable selectivity over the tripeptide enantiomer 22 and the side chain deprotected tripeptide 20.

Split-and-mix libraries of resin-bound "tweezer" receptors have been prepared and screened to identify receptors for dye-labelled tripeptides. The receptors incorporate a diamidopyridine unit to serve as a specific recognition site for the CO2H group, leading to strong and selective receptors for peptide guests with a CO2H terminus. The role of the dye-label, attached to the peptide guest to allow visualisation of selective recognition events in the screening experiments, has also been examined and was found to have a significant influence on the binding selectivities.

A library of "tweezer" receptors, incorporating a guanidinium "head group" and two peptide derived side arms has been prepared on the solid-phase using an orthogonally protected guanidinium scaffold 12. The library was screened with various tripeptide derivatives in an aqueous solvent system. A tweezer receptor 25 for the side chain protected tripeptide 19 was identified from the screening experiments. Receptor 25 was resynthesised and solution binding studies were carried out, which revealed that 25 binds to tripeptide 19 with K(a)=8.2 x 10(4) +/- 2.5 x 10(4) (15 % DMSO/H(2)O, pH 8.75) and with appreciable selectivity over the tripeptide enantiomer 22 and the side chain deprotected tripeptide 20.