AFM force-clamp spectroscopy captures the nanomechanics of the Tad pilus retraction

We use a novel platform combining force-clamp spectroscopy with a fluorescence-based piliated cell selection to study the nanomechanics and dynamics of the retraction of the Caulobacter crescentus Tad pilus.

Force-clamp spectroscopy identifies a catch bond mechanism in a Gram-positive pathogen

Physical forces have profound effects on cellular behavior, physiology, and disease. Perhaps the most intruiguing and fascinating example is the formation of catch-bonds that strengthen cellular adhesion under shear stresses. Today mannose-binding by the Escherichia coli FimH adhesin remains one of the rare microbial catch-bond thoroughly characterized at the molecular level. Here we provide a quantitative demonstration of a catch-bond in living Gram-positive pathogens using force-clamp spectroscopy. We show that the dock, lock, and latch interaction between staphylococcal surface protein SpsD and fibrinogen is strong, and exhibits an unusual catch-slip transition. The bond lifetime first grows with force, but ultimately decreases to behave as a slip bond beyond a critical force (~1 nN) that is orders of magnitude higher than for previously investigated complexes. This catch-bond, never reported for a staphylococcal adhesin, provides the pathogen with a mechanism to tightly control its adhesive function during colonization and infection.

Force clamp approach for characterization of nano-assembly in amyloid beta 42 dimer

Atomic force microscopy force clamp approach was used for probing Aβ42 dimer that enabled us to measure stability and binding pattern within the dimer.