Remarkably selective saccharide recognition by solid-supported peptide boronic acids

The affinity of nine different saccharides to a library of solid-supported pentapeptide diboronic acids was measured using a competitive binding assay, which employed alizarin as the chromophoric indicator. Considerable variation in carbohydrate binding strengths was observed, with association constants in the range 60-5300 M^-1 being recorded. Of particular note was the 7-fold preference for CMP over AMP shown by peptide 1. Enantioselectivity was also observed, with peptide 4 showing an 8.4-fold binding preference for l-glucose over d-glucose. The remarkably selective binding characteristics of these boronic acid-peptide hybrids suggest their potential use in carbohydrate sensors and cell-specific diagnostics and therapeutics.