The effect of different alcohols on the Asp23-Lys28 and Asp23-Ala42 salt bridges of the most effective peptide in Alzheimer's disease: Molecular dynamics viewpoints

The beta-amyloid peptide A beta 1-42 is the most effective peptide in the process of forming plaque and creating Alzheimer's. After the separation of A beta 1-42 from APP membrane protein, the membrane surface is transmitted to the extracellular environment, which is a crowded environment. On the other hand, stability of salt bridges Asp23-Lys28 and Lys28-Ala42 is important for monomer toxicity and fibrillation formation. In this work, the effects of ethanol, propanol, butanol, pentanol, hexanol, heptanol and octanol on the Asp23-Lys28 and Lys28-Ala42 salt bridges of the A beta 1-42 have been investigated by molecular dynamics simulation. The radial distribution function of the oxygen atoms of the water around the atoms C-gamma-Asp23, N-xi-Lys28 and O-Ala42 was calculated in the presence of the alcohols. The results show that the peak height of the radial distribution function around the C-gamma-Asp23 atom is larger than the other two atoms. Also, the numbering of water molecules in the interval corresponding to the first peak in the radial distribution function for all atoms involved in the two salt bridges Asp23-Lys28 and Lys28-Ala42 was calculated. The results show that the obtained coordinate numbers are within the range of experimental numbers reported for water. The results also show that the order of water molecules around the O-Ala42 is lower. The results of solvent accessible surface area of A beta 1-42 show that the Lys28-Ala42 Salt bridge stability is more important for toxicity of monomer. (C) 2018 Elsevier Inc. All rights reserved.