Anesthetic-Enhanced Membrane Fusion Examined Using Two-Photon Fluorescence Correlation Spectroscopy

Vesicle fusion has been used as a model for viral fusion with cells, but measuring the kinetics of the process simultaneously with vesicle size has been elusive. In this study, we describe the use of two-photon excitation fluorescence cross-correlation spectroscopy (TPE-XCS) to measure simultaneously the kinetics and structural changes occurring early in the process of vesicle fusion. We have shown that in the presence of a novel fusion agent, halothane, unilamellar vesicles of dioleoylphosphatidylcholine fuse at rates slower than the diffusion limit. We postulate that halothane works as a gentle perturbation agent by increasing the disorder in the phospholipid bilayer. Moreover, under the conditions used in the present study, this process appears to be complete when approximately six vesicles have fused.