Simple Synthetic Lectin Binds Glucose

Carbohydrate recognition in aqueous solutions is difficult, even for the carbohydrate-binding proteins known as lectins, because the hydroxyl-rich carbohydrates blend in with the water background. Synthetic molecules that mimic those proteins have tended to be complicated and hard to make. Now, Anthony P. Davis and coworkers at the University of Bristol, in England, report a synthetic water-soluble macro­cyclic lectin that they can synthesize in five steps at 23% overall yield, compared with 20 steps and 0.1% overall yield for an earlier version (Nat. Chem., DOI: 10.1038/nchem.1409). The new lectin has a simpler structure than the earlier one but similar recognition properties. It is selective for glucose relative to other common monosaccharides, with an affinity for glucose 50 times that for galactose. In addition, because it includes anthracene units, the new lectin has a built-in fluorescence-signaling mechanism. The molecule’s fluorescence intensity changes in response to the addition of glucose. The lectin is sensitive to glucose at concentrations relevant for blood glucose monitoring.