Thermal expansivity of amyloid beta(16-22) peptides and their aggregates in water

Temperature dependence of the volumetric and structural properties of Abeta(16-22) peptides (wild type and pathogenic forms) and their aggregates in water was studied by simulations. The intrinsic thermal expansion coefficient alpha(p) of peptides was evaluated by taking into account the difference between the volumetric properties of hydration and bulk water. Single peptides show mainly positive values of alpha(p) that correlates with the increasing number of intrapeptide hydrogen bonds upon heating. Negative values of alpha(p) found for large peptide aggregates may be attributed to the shrinking of voids inside aggregates with increasing temperature or to their rubber-like elasticity. The peptide surface exposed to water becomes more hydrophobic with increasing aggregate size that appears in decreasing density of hydration water and evidences a hydrophilic character of aggregation.