Volume and Compressibility of Amyloid Fibrils

Abstract

Intrinsically unfolded hen lysozyme disulfide-deficient variant spontaneously forms amyloid-like fibrils. Its early assembly reversibly dissociates under high hydrostatic pressure with a partial molar volume decrease of 100 mL per monomeric unit. The partial specific volumes of the monomeric and protofibrillar states are 0.684 and 0.724 mL g^-1, respectively, and the adiabatic compressibility coefficient of these states are -7.48 and 1.35 Mbar^-1, which indicates that the protofibrillar state is highly voluminous and compressible. Pressure accelerates the dissociation of protofibrils with a negative activation volume of -50 ml mol^-1 and a negative activation compressibility of -0.013 ml mol^-1 bar^-1, which suggests that partial hydration of existing voids takes place in the transition state of dissociation reaction.