The effect of curcumin on the stability of Aβ dimers.

A beta oligomers are potential targets for the diagnosis and therapy of Alzheimer's disease (AD). On the other hand, the molecule curcumin has been shown to possess significant therapeutic potential in many areas. In this paper, we use all-atom explicit solvent molecular dynamics simulations to study the effect of curcumin on the stability of A beta amyloid protein oligomers. We observed that curcumin decreases the beta-sheet secondary structural content within the A beta oligomers without reducing the contacts between the monomers. The breaking of the beta-sheet is found to be preceded by a deformation of the beta-sheet structure due to hydrophobic interaction from the nearby curcumin. Furthermore, the pi-stacking interaction between curcumin (keto ring and enol ring) and the aromatic residues of A beta, which exists throughout the simulations, has also contributed to the diminishing of the beta-sheet structure. Our analysis of the underwrapped amide-carbonyl hydrogen bonds reveals several stable dehydrons of the oligomer, especially the dehydron pair 34L and 41I, which curcumin tends to hover over. We have examined the paths of curcumin on the A beta proteins and determined the common routes where curcumin lingers as it traverses around the A beta. In consequence, our study has provided a detailed interaction picture between curcumin and the A beta oligomers.