To further elucidate if binding of protein to the fibril surface can be distinguished from amyloid elongation, we investigated the characteristic QCM-D response from fibril growth and protein. We exposed α-synuclein amyloid fibrils to 1% Human Serum Protein (HsP) that binds to the fibrils causing a decrease in frequency of -12 Hz, while the dissipation increases only 0.3 10 -6 giving a distinctly different response from fibril growth (Fig. A, the HsP binding is not unspecific binding to the sensor surface, see Fig. ). As a result, when fibrils are exposed to a 1% HsP 50 µM α-synuclein solution, fibril growth can be monitored through the dissipation response, which remains constant throughout the measurement. Meanwhile the frequency response is convoluted by protein binding to the fibrils and fibril growth.