(262b) Single Molecule Protein Dynamics and Aggregation At the Oil-Water Interface

The dynamic behavior of proteins at liquid-liquid interfaces is of fundamental interest to many applications, including complex fluids formulation, biosensing, and pharmaceutical processing and delivery. However, the methods for understanding proteins at fluid interfaces have been limited to a small number of traditional methods (such as interfacial rheology), because of the experimental complexities associated with investigating fluid interfaces.  We have recently developed methods based on single molecule total internal reflectance fluorescence (smTIRF) microscopy to investigate the dynamics and aggregation of proteins at the silicone oil-water interface.  Using high throughput single molecule tracking, we track each individual protein from adsorption to the interface, through diffusive interfacial transport and finally till desorption back into the bulk water phase.  We have discovered a rich diversity of dynamic phenomena, including reversible adsorption, diffusion and desorption correlated with aggregate state, and multiple modes of diffusion.  We have also measured the nonlinear kinetics associated with interfacial protein layer formation and modeled this process using a kinetic population balance model.  Importantly, this model includes desorption since we explicit observe it in our single molecule tracking experiments.  In this talk, I will show how using this single molecule approach has given us these new insights, many of which could not be observed using traditional ensemble averaged methods.