Molecular recognition force spectroscopy of a specific lectin–carbohydrate interaction at single-molecule level

Carbohydrates are involved in many essential biological recognition processes in physiological and pathological states. Thus, it is important to understand the mechanism of protein–carbohydrate interactions at molecular level. In the present study, molecular recognition force spectroscopy was applied to investigate the interactions between RCA120, a lectin from Ricinus communis, and galactose (Gal) and asialofetuin (ASF) at the single-molecule level. RCA120 coupled to the AFM tip could specifically recognize Gal and ASF, respectively. The unbinding forces of RCA120–Gal and RCA120–ASF increase linearly with the logarithm of loading rate. The results reveal that the binding capability of RCA120 toward Gal is weaker than that of ASF, implicating a multivalent effect in the RCA120–ASF interaction.