Entropy of water and the temperature-induced stiffening of amyloid networks

TL;DR

This study investigates how water-induced stiffening of alpha-synuclein fibril networks occurs with temperature, attributing it to hydrophobic interactions, and quantifies the associated thermodynamic parameters using experimental data and scaling theory.

Contribution

It introduces a model linking network elasticity to reversible hydrophobic crosslinking, providing quantitative insights into the thermodynamics of fibril interactions.

Findings

Stiffening of fibril networks increases with temperature.

Hydrophobic contacts are key to reversible network stiffening.

Quantified binding enthalpy and hydrophobic patch size.

Abstract

In water, networks of semi-flexible fibrils of the protein $\alpha$-synuclein stiffen significantly with increasing temperature. We make plausible that this reversible stiffening is a result of hydrophobic contacts between the fibrils that become more prominent with increasing temperature. The good agreement of our experimentally observed temperature dependence of the storage modulus of the network with a scaling theory linking network elasticity with reversible crosslinking enables us to quantify the endothermic binding enthalpy and an estimate the effective size of hydrophobic patches on the fibril surface.