Electrostatic Polarization Effect on Cooperative Aggregation of Full Length Human Islet Amyloid.

Amyloid aggregation initiates from a slow nucleation process, where the association of monomers is unfavorable in energetics. In principle, the enthalpy change for aggregation should compensate the entropy loss as new monomers attach to formed oligomers. However, the classical force fields with fixed point charges failed to yield the correct enthalpy change due to the lack of electrostatic polarization effect on amyloid aggregation. In this work, we performed molecular dynamics simulation for the full-length human islet amyloid using the polarized protein-specific charges and calculated the electrostatic interaction energy for amyloid oligomers. The results of molecular dynamics simulation show that the aggregates simulated with polarized charges have larger enthalpy change than that with fixed charges. The large enthalpy change mainly originates from the electrostatic polarization, which makes a significant contribution to the cooperative effect of aggregation and facilitates the nucleation process of amyloids.