Novel biosurfactants: Rationally designed surface-active peptides and in silico evaluation at the decane-water interface

Biosurfactants are surface-active molecules obtained from natural sources and potential substitutes for various applications where their petrochemical counterparts dominate. Different efforts have been made to produce tailored and efficient biosurfactants, including rational design. However, there is limited information about the rational design of peptide-based biosurfactants and their interfacial behavior at the molecular level. In this work, the interfacial activity of two novel rationally designed peptides (Surf-UAC1 and Surf-UAC2) was evaluated by means of molecular dynamics (MD) simulations. Both peptides were in silico designed based on the properties of the amino acids. Their stabilities, conformations, mass density profiles, orientation, interaction energies, and average interfacial tension were assessed at the decane-water interface. Results were compared to those obtained with the widely used surfactant Tween 20®, simulated under the same conditions. Here, a new methodology based on a sequence of MD simulations is proposed. Results show that this methodology provides accurate interfacial tension data for the decane-water interface. The peptides are randomly adsorbed at low concentrations, but as the concentration increases, the interface becomes saturated, and an irregularly shaped peptide cluster is formed. This behavior strongly suggests that an adsorption barrier prevents the peptides from reaching the interface after interfacial saturation. Reorganization at the interface was evidenced.