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Completed Project

Investigating Intermolecular Forces of Pseudohyperphosphorylated Tau

Zofia E. Siwicka, Vassar College ’18 and Prof. Zachary Donhauser
Tau is a microtubule-associated protein found in neuronal cells that helps stabilize and regulate the spacing between microtubules. However, hyper- phosphorylated tau has a higher propensity to aggregate and therefore lose function resulting in neurofibrillary tangles found in many neurodegenerative disorders. To observe the characteristics of phosphorylated tau we have created a pseudo-phosphorylated tau by replacing seven amino acids in the protein with the negatively charged acidic residues (S199E, S202E, T205E, T231E, S235D, S396E, S404E), which mimics hyper-phosphorylated tau that can found in a cell. In order to look at the interactions exhibited between phosphorylated tau we use a form of surface quantification and atomic force microscopy. In the surface quantification we immobilized tau on mica to mimic its interactions with microtubules and measured the ionic strength of an aqueous solution required to remove the tau from the mica, and found that pseudophosphorylated protein is more easily removed from the surface than wild-type tau, indicating that the electrostatic forces between mica and phosphorylated tau are weaker. Through atomic force microscopy it appears that the interactions between pseudophosphorylated tau are similar to those between wild type tau. These insights help us better understand the intermolecular forces present in phosphorylated tau as compared to those present in wild-type tau, and future work may lead to a better understanding of aggregation and malfunction in phosphorylated taus.