A Comparative Study of Thermodynamic Properties of Hydration Layer of the Amyloid Precursors of Alzheimer’s Disease and Type II diabetes using Dielectric Relaxation Spectroscopy

Recent reports suggest a biological link between Alzheimer’s disease (AD) and Type 2 diabetes (T2D). AD and T2D involves the aggregation of amyloidogenic peptides of amyloid beta 42 (Aβ42) and human islet amyloid polypeptide (hIAPP). During aggregation process, the biological water at their surface tends to redistribute itself. The thermodynamic changes accompanying this redistribution provides better insight into the understanding of the correlation between amyloidogenesis of Aβ42 and hIAPP peptides. Here, we present the variations in thermodynamic parameters of activation entropy, enthalpy, Gibbs free energy, and heat capacity for Aβ42 and hIAPP precursors as a function of incubation time (0-24 h) and temperature (133K- 283K) using dielectric relaxation spectroscopy over the frequency domain of 10^-3-10⁷ Hz. The dielectric processes corresponding to different amyloid aggregates of Aβ42 and hIAPP showed closely related values of enthalpies and entropies, indicating a lesser degree of hydrogen bonding for the bound water than bulk water. Our results showed a thermodynamic correspondence in the behaviors of Aβ42 and h-IAPP peptides which further support the relationship between AD and T2D.