Probing synaptic vesicle fusion by altering mechanical properties of the neuronal surface membrane

Because synaptic vesicle exocytosis is a nano-mechanical process, it should be influenced by the mechanical properties of the cell membrane to which the vesicle fuses. By dissolving surfactants at various concentrations in the neuronal membrane, we have perturbed mechanical properties of the membrane and have found that dissolved surfactants lower the probability that a synaptic vesicle will open its fusion pore when the fusion machinery of the vesicle is activated by binding calcium. By using standard theories from the physics and chemistry of surfaces, we can account for this decrease in fusion probability and can infer that a vesicle, when activated, opens its fusion pore ≈3 times out of 4 and that the area of the fusion pore is ≈4 nm 2 .