Comparison of the structural characteristics of Cu2+-bound and unbound alpha-syn12 peptide obtained in simulations using different force fields
The effects of Cu2+ binding and the utilization of different force fields when modeling the structural characteristics of alpha-syn12 peptide were investigated. To this end, we performed extensive temperature replica exchange molecular dynamics (T-REMD) simulations on Cu2+-bound and unbound alpha-syn12 peptide using the GROMOS 43A1, OPLS-AA, and AMBER03 force fields. Each replica was run for 300 ns. The structural characteristics of alpha-syn12 peptide were studied based on backbone dihedral angle distributions, free-energy surfaces obtained with different reaction coordinates, favored conformations, the formation of different Turn structures, and the solvent exposure of the hydrophobic residues. The findings show that AMBER03 prefers to sample helical structures for the unbound alpha-syn12 peptide and does not sample any beta-hairpin structure for the Cu2+-bound alpha-syn12 peptide. In contrast, the central structure of the major conformational clusters for the Cu2+-bound and unbound alpha-syn12 peptide according to simulations performed using the GROMOS 43A1 and OPLS-AA force fields is a beta-hairpin with Turn(9-6). Cu2+ can also promote the formation of the beta-hairpin and increase the solvent exposure of hydrophobic residues, which promotes the aggregation of alpha-syn12 peptide. This study can help us to understand the mechanisms through which Cu2+ participates in the fibrillation of alpha-syn12 peptide at the atomic level, which in turn represents a step towards elucidating the nosogenesis of Parkinson's disease.
effects of cu2+ temperature replica exchange free-energy surface cu2+-bound alpha-syn12 peptide solvent exposure of hydrophobic residues effects of different force fields