Sulfur Dioxide Promotes the Formation of Amyloid Fibrils through Enhanced Secondary Nucleation: A Molecular Dynamics Study

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Air pollution is a common phenomenon in developing countries, and pollutants are suggested to be essential reasons to produce various diseases, such as cancers, neuro-degenerative diseases and so on. In present work, the effects of sulfur dioxide on the dissociation of Aβ17~42 peptides from core region of Aβ fibril were studied with umbrella sampling method. It is found that the free energy penalty related to the dissociation processes would decrease for larger concentrations of sulfur dioxide. The detailed interactions between peptides and sulfur dioxide are analyzed based on contact statistics. It is suggested that the destabilization of the Aβ fibril is realized by the binding of sulfur dioxide with the peptide backbone as well as the side chains of charged residues, which results in the decrease of hydrophobic interaction and blockage of the electrostatic interactions between charged residues. Furthermore, the positive contribution of such a marginal destabilization on the growth of fibril is also discussed with a nonlinear master equation, which is consistent with the medical knowledge. Through these computations, we disclose the characteristics of the interactions between air pollutants and protein molecules. We expect that these results could help to assess the effect of air pollutants on human health.