Polyphenolic self-association accounts for redirecting a high-yielding amyloid aggregation

Abstract Among the various methods used to induce protein amyloid aggregation in vitro (quiescent/agitated/shaken incubation) and different strategies of modulating the aggregation, the quiescent incubation of an amyloidogenic protein (AP) solution at a defined temperature, and using polyphenolic small molecules, are most common. Using a typical ThT fluorescence assay, we have shown that at the lowest percentage of DMSO used, the thermomixer-shaken incubation of AP solution results in a high-yielding aggregation. Under these conditions, some polyphenols such as curcumin and quercetin are unable to redirect the process except at higher concentrations, as shown by CD spectroscopy and TEM. Based upon NMR experiments and MD simulations, we suggest that polyphenolic self-association is the main cause. Because of the different properties of n -mer particles of these polyphenols formed through self-association, the redirection of AP aggregation occurred differently. To prove the involvement of self-association, rosmarinic acid with a much lower tendency to self-associate was examined. It was unable to redirect the process even at concentrations two and three times those of the other two.