System dynamics from the biochemical experiments conducted for protofibril elongation and lateral association. Experimental results for Aβ42 protofibril elongation and lateral association. A) Three concentrations of isolated protofibrils (7, 4 and 2 µM) were elongated with freshly purified Aβ42 monomers (30 µM). The reactions were monitored by ThT fluorescence. Both mature fibrils and monomers (~ 4 µM) were used as negative controls. B) Lateral association was initiated by the addition of 150 mM NaCl to the isolated protofibrils (4 µM) that was monitored by Dynamic Light Scattering instrument. Protofibrils without salt was used as a negative control. The data is plotted against count rate which is directly proportional to the hydrodynamic radius of the sample.