Molecular Dynamics of Peptide Folding and Aggregation at the Vapor-Water Interface

Abstract

Hyrophobic-hydrophilic interfaces such as the water-vapor or other liquid-liquid or solid-liquid interfaces have large effects on the secondary structure formation and aggregation processes of amphiphilic peptides. Due to the dual nature of these peptides, they are surface active or tend to self assemble to minimize the exposed fraction of unsolvable surface. In our study, we investigate representatives of two different families of amphiphilic peptides in solution and at the vapor-water interface: β-sheet forming peptides (containing repetitive sequences of hydrophobic/hydrophilic residues), which self-assemble into monolayers at the air−water interface [1], and an anionic α-helical amphiphilic cell penetrating peptide (CPP) [2]. The aggregated acidic β-sheet peptides can serve as a template to promote mineralization processes taking place at an interface. Whereas the studied CPP GALA belongs to a relatively small class of anionic helix building peptides. The CPPs are promising tools for targeting intracellular proteins and might be useful in the development of new delivery systems for therapeutics. We investigate the coupling between secondary structure formation, partitioning at the interface, and self-aggregation at the microscopic level in atomistic molecular dynamics simulations with the aim of gaining insight into the interactions which govern the structure formation at the local scale. Since processes taking place at longer time scales or larger system sizes are hardly accessible to atomistic simulations, we utilize the information gathered from atomistic simulations to develop a fragment-based coarse-grained model which can be applied to inhomogeneous systems with interfaces.