In general, thermodynamic stability is defined by the concentration of different species in equilibrium, e.g., folded, and unfolded states for protein conformational stability (Equation ). Similarly, the thermodynamic stability of amyloid fibrils can be defined by the concentration of soluble precursors (herein termed monomers) in equilibrium with the insoluble fibrils. At sufficiently high total concentration, the equilibrium concentration of monomer is independent of the molar concentration of fibrils and relates to fibril stability according to Equation .