Atomic Force Microscopy and Quartz Crystal Microbalance Study of the Lectin–Carbohydrate Interaction Kinetics

Two analytical methods, atomic force microscopy and quartz crystal microbalance, were applied to the study of the reaction kinetics occurring between concanavalin A and carboxypeptidase Y, presenting the specific lectin–carbohydrate recognition. The dissociation rate constants for concanavalin A–carboxypeptidase Y complex obtained using both atomic force microscopy and quartz crystal microbalance were of the same order of magnitude: kdiss = 0.170±0.060 s−1 and kdiss = 0.095±0.002 s−1, respectively. In addition, each method alone aided in determining other parameters characterizing the studied interaction. Quartz crystal microbalance permitted us to estimate the association rate (kass = (5.6±0.1)×10 M−1 s−1) and the equilibrium (Ka = (0.59 ± 0.01) × 10 M−1) constants for the binding process occurring between concanavalin A and mannose residues of carboxypeptidase Y under given experimental conditions. Atomic force microscopy in force spectroscopy mode enabled the determination of the energy barrier position of r = 2.29±0.04 Å characterizing the dissociation of concanavalin A– carboxypeptidase Y molecular complex. The presented results show that both atomic force microscopy and quartz crystal microbalance can be used to determine quantitative parameters characterizing the specific molecular interaction. Both methods can be easily combined for complementary and/or alternative studies of a chosen molecular interaction. By preparing the samples in the same manner the direct comparison between the data obtained via atomic force microscopy and quartz crystal microbalance can be made.