Dynamics and Aggregation of Proteins At Fluid Interfaces

The dynamic behavior of proteins at liquid-liquid interfaces is of fundamental interest to many applications, including complex fluids formulation, pharmaceuticals, and biosensing. However, the methods for understanding proteins at fluid interfaces are typically limited to a small number of traditional methods, such as interfacial rheology. While these methods are useful in characterizing bulk materials properties of protein films, they are of limited utility in understanding the mechanisms that lead to the formation of protein films.  In this poster, the use of single molecule TIRF has been used to characterize the dynamic behavior of proteins at the oil-water interface.  For isolated single proteins, we find that individual proteins are reversibly bound to the surface.  In fact, diffusion and desorption dynamics are characteristic of the aggregate state of an individual protein at the oil-water interface.  For protein layer formation to occur at the oil-water interface, we add many orders of magnitude of non-fluorescent protein, so that the effect of protein-protein interactions can be characterized.  By studying the dynamics of tracer fluorescent proteins, protein aggregation is found to be the primary mechanism of protein layer formation.  Furthermore, the kinetics of protein layer fomation depend on bulk protein concentration and use a kinetic population balance model to explain the non-linear concentration dependence.