Curvatures in the most probable rupture force (f*) versus log-loading rate (log r(f)) observed in dynamic force spectroscopy (DFS) on biomolecular complexes are interpreted using a one-dimensional free energy profile with multiple barriers or a single barrier with force-dependent transition state. Here, we provide a criterion to select one scenario over another. If the rupture dynamics occurs b...

In atomic force microscopy (AFM) a sharp cantilever tip is used to scan surfaces at the atomic level. One further application is force spectroscopy, in which force-distance curves between binding partners located on the cantilever and substrate surface are determined. This requires specifically immobilized molecules. Herein we describe the covalent binding of single adenosine and thymidine nucl...

Dynamic force spectroscopy (DFS) makes it possible to investigate specific interactions between two molecules such as ligand-receptor pairs at the single-molecule level. In the DFS method based on the Bell-Evans model, the unbinding force applied to a molecular bond is increased at a constant rate, and the force required to rupture the molecular bond is measured. By analyzing the relationship b...

A theory of the unzipping of double-stranded DNA is presented and is compared to recent micromanipulation experiments. It is shown that the interactions that stabilize the double helix and the elastic rigidity of single strands simply determine the sequence-dependent approximately 12-pN force threshold for DNA strand separation. Using a semimicroscopic model of the binding between nucleotide st...

Type IV pili play an important role in bacterial adhesion, motility, and biofilm formation. Here we present high-resolution atomic force microscopy (AFM) images of type IV pili from Pseudomonas aeruginosa bacteria. An individual pilus ranges in length from 0.5 to 7 microm and has a diameter from 4 to 6 nm, although often, pili bundles in which the individual filaments differed in both length an...

Kinetic partitioning is predicted to be a general mechanism for proteins to fold into their well defined native three-dimensional structure from unfolded states following multiple folding pathways. However, experimental evidence supporting this mechanism is still limited. By using single-molecule atomic force microscopy, here we report experimental evidence supporting the kinetic partitioning m...

Background: A traumatic diaphragm rupture presents a unique obstacle to a minimally invasive surgical approach; most repairs are performed during an emergency laparotomy. Diaphragm injuries are diagnosed in the acute phase of blunt-force trauma in only 10% of cases, and a high index of suspicion must be maintained to avoid strangulation of the abdominal organs that have herniated into the thora...

Force probe techniques such as atomic force microscopy can directly measure the force required to rupture single biological ligand receptor bonds. Such forces are related to the energy landscape of these weak, noncovalent biological interactions. We report unbinding force measurements between complementary strands of DNA as a function of temperature. Our measurements emphasize the entropic cont...

The prevalence of Achilles tendon (AT) injury is high in various sports, and AT rupture patients have been reported to have a 200-fold risk of sustaining a contralateral rupture. Tendon adaptation to different exercise modes is not fully understood. The present study investigated the structural properties of the AT in male elite athletes that subject their AT to different exercise modes as well...

A young adult male pedestrian was struck by a car and sustained a closed complete rupture of both heads of the biceps brachii muscle belly, among other injuries. Rupture of the biceps brachii muscle belly is a rare injury, and complete muscle belly rupture of both long and short heads from direct blunt force trauma has not been reported outside of military parachutists. We describe the findings...