Understanding the helical stability of charged peptides

Cationic helical peptides play a crucial role in applications such as anti-microbial and anticancer activity. The activity of these peptides directly correlates with their helicity. In this study, we have performed extensive all-atom molecular dynamics simulations of 25 Lysine-Leucine co-polypeptide sequences of varying charge density (lambda$$ \lambda $$) and patterns. Our findings showed that, an increase in the charge density on the peptide leads to a gradual decrease in the helicity up to a critical charge density lambda c$$ {\lambda}_c $$. Beyond lambda c$$ {\lambda}_c $$(,) a complete helix to coil transition was observed. The decrease in the helicity is correlated with the increased number of water molecules in first solvation shell, solvent-exposed surface area, and a higher value of the radius of gyration of the peptide.