Single-Bond Association Kinetics Determined by Tethered Particle Motion: Concept and Simulations.

Tethered particle motion (TPM), the motion of a micro- or nanoparticle tethered to a substrate by a macromolecule, is a system that has proven to be extremely useful for its ability to reveal physical features of the tether, because the thermal motion of the bound particle reports sensitively on parameters like the length, the rigidity, or the folding state of its tether. In this article, we survey the applicability of TPM to probe the kinetics of single secondary bonds, bonds that form and break between the tethered particle and a substrate due, for instance, to receptor/ligand pairs on particle and substrate. Much like the tether itself affects the motion pattern, so do the presence and absence of such secondary connections.

Mechanical signaling coordinates the embryonic heartbeat.

In the beating heart, cardiac myocytes (CMs) contract in a coordinated fashion, generating contractile wave fronts that propagate through the heart with each beat. Coordinating this wave front requires fast and robust signaling mechanisms between CMs. The primary signaling mechanism has long been identified as electrical: gap junctions conduct ions between CMs, triggering membrane depolarization, intracellular calcium release, and actomyosin contraction.