Vesicle fusion rate decreases with time.

<p>Vesicles loaded with ATP are added to the chamber containing an intact lipid bilayer. As the vesicles fuse to the bilayer, their contents are delivered to the bottom chamber. The concentration of ATP in the bottom chamber was sampled 1, 2, and 3 minutes after the addition of the vesicles (n = 3). ATP without vesicles was added to ensure the ATP delivery to the bottom chamber was dependent on vesicle fusion. The inset is a standard curve generated using known amounts of ATP.</p>