National Academy of Sciences, Proceedings of the National Academy of Sciences, 14(116), p. 6594-6601, 2019
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Significance Protein–ligand interactions are commonly described in terms of a two-state or a lock-and-key mechanism. To provide a more detailed and dynamic description of receptor–ligand bonds and their (un)binding path, we combined high-speed force spectroscopy and molecular dynamics simulations to probe the prototypical streptavidin–biotin complex. The excellent agreement observed, never used for force-field refinement, provides the most direct test of the “computational microscope.” The so-far largest dynamic range of loading rates explored (11 decades) enabled accurate reconstruction of the free-energy landscape. We revealed velocity-dependent unbinding pathways and intermediate states that enhance rebinding, explaining the long lifetime of the bond. We expect similar behavior in most receptor–ligand complexes, implying unbinding pathways governed by transient, timescale-dependent induced fits.