Interpretation of amperometric kinetics of content release during contacts of vesicles with a lipid membrane.

The exocytotic pathway of secretion of molecules from cells includes transport by vesicles, tether-mediated fusion of vesicles with the plasma membrane accompanied by pore formation, and diffusion-mediated release of their contents via a pore to the outside. In related basic biophysical studies, vesicle-content release is tracked by measuring corresponding amperometric spikes. Although experiments of this type have a long history, the understanding of the underlying physics is still elusive. The present study elucidates the likely contribution of line energy, membrane tension and bending, osmotic pressure, hydration forces, and tethers to the potential energy for fusion-related pore formation and evolution. The overdamped Langevin equation is used to describe the pore dynamics, which are in turn employed to calculate the kinetics of content release and to interpret the shape of amperometric spikes.