Electric-Field Induced Modulation of Amorphous Protein Aggregates: Polarization, Deformation, and Reorientation

Proteins in their native state are only marginally stable and tend to aggregate. However, proteinmisfolding and condensation are often associated with undesired processes, such as pathogenesis, orunwanted properties, such as reduced biological activity, immunogenicity, or uncontrolled materialsproperties. Therefore, controlling protein aggregation is very important, but still a major challengein various fields, including medicine, pharmacology, food processing, and materials science. Here,flexible, amorphous, micron-sized protein aggregates composed of lysozyme molecules reduced bydithiothreitol are used as a model system. The preformed amorphous protein aggregates are exposedto a weak alternating current electric field. Their field response is followed in situ by time-resolvedpolarized optical microscopy, revealing field-induced deformation, reorientation and enhancedpolarization as well as the disintegration of large clusters of aggregates. Small-angle dynamiclight scattering was applied to probe the collective microscopic dynamics of amorphous aggregatesuspensions. Field-enhanced local oscillations of the intensity auto-correlation function are observedand related to two distinguishable elastic moduli. Our results validate the prospects of electric fieldsfor controlling protein aggregation processes