The Aβ16-22 hexamer’s aggregation under a co-effect of EGCG compound and low-pH concentration

Abstract

One of the most common forms of dementia is Alzheimer’s disease (AD), and its relationship with β-amyloid plaques. The deposition of amyloid beta (Aβ) oligomers is proved to be a damage cause for AD patients in which the mechanism of Aβ16-22 fragments is believed to keep an important role in the fibrils’ aggregations due to its’ β-contents. Many previous searches showed that the more β-contents formed the more Aβ-fibrillary conformations created. In a previous study, the Aβ16-22 hexamer configuration under the inhibition of the epigallocatechin-3-gallate (EGCG) compound, which attenuated the production of β-sheet structure formation, was successfully constructed. However, the environment controlled 6Aβ16-22 association change was neglected. So, in this scheme we are motivated to make an atomistic investigation via two molecular dynamic simulations (MD): Aβ16-22 hexamer and EGCG complex, one in normal condition pH = 7.0 and the other in lower one pH = 5.5, respectively. The received data provides evidence to determine, the environmental difference does not change the number of H-bond between EGCG and Aβ fragment in which asserted that EGCG becomes a potential prospect in treating AD. Besides that, the results of simulations by using the DSSP tool of Gromacs package demonstrated that the averaging number of random-coil structure didn’t change too much and received similar values of 24.4 and 24.6, and the decreasing of β-contents under the co-operative interaction of low pH and EGCG inhibitor. The Aβ16-22 free energy has slightly increased from -14,3 kcal.mol-1 to -13,8 kcal.mol-1 when pH concentration is reduced from normal pH = 7.0 to low on pH = 5.5. Finally, the computational results are in agreement with the experimental investigation, our observation adds a physical insight into the picture of the computational aided drug design in Aβ treatment.