To explain the observed changes in frequency in the QCM-D results, we created kinetic models of several different possible scenarios at the molecular level (Fig. ). Each of these models makes different assumptions on how full length monomers can interact with amyloid fibrils (with and without flanks), and how those interactions translate into changes in growth rate observed in the QCM-D experiments. The null model (Model 0), describes elongation of non-modified amyloid fibrils. Model A is the simplest model, which describes amyloid fibril elongation without the repulsive charges of the fuzzy coat. The growth rate very quickly returns to baseline as recruited monomer reintroduces charges to the fibril ends. In addition to elongation, Model B also allows monomers to bind to the surface when no disordered flanks are present, leading to an acute increase in surfaceassociated mass, and an initial increase in fibril elongation rates. In Model C, surface binding enables secondary nucleation and subsequent growth on the shaven fibril surface. After every proteinase K degradation step new nucleation-viable binding sites become available, which leads to a sustained increase in growth rate in subsequent growth phases. Notably, fibril growth accelerates throughout the growth phase, as new fibrils nucleate. Model D assumes that protofilaments can be proteolytically fragmented by Proteinase K degradation leading to an increase in the number of fibril ends during the shaving period as the newly accessible proto-filament ends are capable of recruiting monomers.