Friction force microscopy as an alternative method to probe molecular interactions

Friction force microscopy was applied to study protein-carbohydrate interactions that are important in many cellular recognition processes. The expression and structure of carbohydrates can be investigated using lectins as molecular probes since they recognize different types of sugar molecules. Lectins (concanavalin A and lentil lectin, recognizing mannose-type carbohydrates) were attached to the probing tip and carboxypeptidase Y (possessing complementary carbohydrates) was immobilized on a modified glass surface using microcontact printing. The results obtained from friction force maps and dependencies on the loading rate (measured in a physiological buffer) were divided in two distinct groups. The first group of results obtained for lectin-protein complexes was assigned to molecular recognition events, whereas the other including all control measurements was attributed to nonspecific interaction. All results presented here indicate that friction force microscopy can be successfully employed to study recognition processes.