Weak
molecular interactions drive processes at the core of
living systems, such as enzyme-substrate interactions, receptor-ligand binding, and
nucleic acid replication.
Single-molecule force spectroscopy is a remarkable tool for revealing molecular scale energy landscapes of noncovalent bonds, by exerting a mechanical force directly on an individual molecular complex and tracking its survival as a function of time and applied force. In principle,
force spectroscopy methods can also be used for highly specific molecular recognition
assays, by directly characterizing the strength of bonds between probe and target molecules. However, complexity and low
throughput of conventional
force spectroscopy techniques render such biosensing applications impractical. Here we demonstrate a straightforward
single-molecule approach, suitable for both
biophysical studies and molecular recognition
assays, in which a approximately 3 nm
silicon nitride nanopore is used to determine the bond lifetime spectrum of the biotin-neutravidin complex. Thousands of individual molecular complexes are captured and dissociated in the solid-state
nanopore under constant applied forces, ranging from 400 to 900 mV, allowing us to extract the location of the
energy barrier that governs the interaction, mapped at Deltax approximately 0.5 nm. These results highlight the capacity of a solid-state
nanopore to detect and characterize intermolecular interactions and demonstrate how this could be applied to rapid, highly specific molecular detection
assays.
