Glass beads increase the formation kinetics of beta-lactoglobulin amyloid fibrils

Abstract

In this study beta-lactoglobulin solutions were processed with glass beads in an orbital shaker at high temperatures and low pH value to identify the effect of mechanical stressing and surfaces on amyloid aggregation kinetics. The information will provide a better understanding on how specific mechanical factors provide a nucleation supporting effect on the assembling of building blocks for a more efficient production of functional amyloid aggregates. Because aggregate morphologies vary at pH 2 (semiflexible) or pH 3.5 (worm-like), examination at both pH values gives information about their specific formation and stability characteristics. Different diameters of glass beads (20–1000 μm), and different shaking frequencies (0 - 280 min−1) were used to vary mechanical stress energy, which was quantified by CFD-DEM simulations. To investigate surface effects, the hydrophobicity and surface roughness of glass beads was altered by modification with stearic acid. Amyloid aggregates and bead surfaces were analysed by ThT-assay, AFM and ATR-FTIR.Hydrophobic beads with high surface roughness affected the aggregation negatively. The use of non-hydrophobic beads increased the formation kinetics of fibrils but not of worm-like aggregates, although, both morphologies had a reduced mean length.