(706b) The Effects of Salt on the Thermodynamics of Protein Folding

Protein structure and conformation determines its physical property and biological function. Many human pathologies including Alzheimer’s, Parkinson’s diseases and type 2-diabetes are due to protein misfolding and aggregation associated with the formation of insoluble β-sheet amyloid fibrils. However, earlier efforts to understand protein folding and aggregation often fail to take into account the presence of salt ions in solution, which is ubiquitous under physiological conditions. Salt ions play a critical role in many biological processes including protein solubility, stability, denaturation and aggregation, as well as regulate neuron activities. Here classical molecular dynamics (MD) simulations coupled with metadynamics simulations were conducted to elucidate the effects of salt ions on the mechanisms, dynamics and the free energy surfaces during protein folding, unfolding and aggregation. Here the folding and unfolding of a protein proxy poly (N-isopropylacrylamide) as well as lysozyme in the presence and absence of salt ions were investigated. Salt ions were found to alter the dynamics as well as the free energy landscape during the folding and unfolding processes.