Probing and controlling single-molecule interactions with force spectroscopy

Atomic force microscopy and dynamic force spectroscopy techniques provide the means to explore the spatial distribution of membrane surface receptors and their dynamic interactions with ligands. In this work, we investigated several ligands including integrins at different loading rates. We found a linear relationship between the binding strength of ligand-receptor and the logarithmic loading rate, suggesting that the unbinding process follows the Bell-Evans two-state transition model. Using the energy landscapes constructed from dynamic force measurements and the Kramers escape rate from bound to unbound state under an external force, we evaluated kinetic and thermodynamic parameters, including the potential energy barrier height, kinetic off rate, and the width of the potential well, governing the ligand-receptor transitions between the two states. We discuss the potential of adjusting these parameters to influence the specificity, affinity, and stability of the single-molecule interactions.