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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 44: Complex Fluids, Colloids, Micelles and Vesicles (joint session CPP/DY)

CPP 44.6: Talk

Thursday, March 21, 2024, 17:00–17:15, H 0110

Protein cluster formation in protein-polymer mixtures — •Anusha Hiremath, Fajun Zhang, and Frank Schreiber — Institut für Angewandte Physik, Universität Tübingen, Germany

Understanding protein cluster formation is crucial for unraveling the mechanisms behind diseases like Alzheimer's and Parkinson's, which are linked to specific protein aggregation. Protein clusters, serving as precursors in protein crystallization [1], are also essential to comprehend the nature of protein aggregation. In this study, static and dynamic light scattering (SLS and DLS) are employed to investigate Bovine Serum Albumin cluster formation driven by depletion interactions [2] in the presence of Polyethylene Glycol (PEG) with varying sizes and concentrations. Using a two-exponential fit model, we illustrate the decreasing diffusion coefficient trend with increasing PEG concentration and size, marking the transition from a dilute to a semi-dilute regime [2]. This decrease in diffusion coefficients suggests an increased attractive potential between proteins, indicating the formation of small clusters. The apparent molecular weight from SLS indicates the formation of protein clusters above a threshold PEG concentration, which decreases with increasing PEG size. Furthermore, we find that larger PEGs accelerate cluster formation. This work demonstrates that the depletion attraction by adding PEG can balance the electrostatic repulsion, leading to the cluster formation in protein solutions. [1] Zhang, F., J Phys Condens Matter, 29, 443002(2017). [2] Zosel, F. et al., PNAS, 117, 13482(2020).

Keywords: Protein cluster; Polymer; Dynamic Light Scattering (DLS); Depletion Interaction; BSA-PEG