Single Molecule Studies of Tau Protein in the Abel Trap

Tau protein is an intrinsically disordered protein that stabilizes microtubules of neurons mainly in the central nervous system. Abnormalities in Tau are thought to be involved in Alzheimer's disease. The aggregation process of monomeric Tau into an oligomeric species and the intermediate conformational states that may facilitate aggregation are of particular interest. To investigate the disordered nature and aggregation of Tau protein, single, solution-phase Tau proteins and oligomers were isolated in a microfluidic trap, called the Anti-Brownian Electrokinetic (ABEL) Trap. The ABEL trap cancels Brownian motion of a molecule of interest via electrokinetic and/or electroosmotic flow, allowing prolonged examination of a single, fluorescently-labeled analyte in solution. Combining this technique with fluorescence anisotropy enabled studies into how monomer structure and aggregation changes with cellular conditions known to accelerate aggregation, including concentration effects, solution viscosity, heparin, and cellular crowding. Characteristics of disordered Tau were compared with those of a globular protein of similar size, microbial transglutaminase (MTG). The ultimate goal is to provide the missing link between non-aggregated, monomer Tau protein and the toxic species that result in devastating disease, offering insight into how this pathway may be upset.