Balancing Length and Hydrophobicity in Cationic Amphipathic Peptides: Insights From Biological Analysis and Molecular Simulation

Cationic amphipathic antimicrobial peptides (AMPs) have garnered attention for their dual antibacterial and anticancer activities. However, the structural determinants underlying their selective bioactivity remain incompletely defined. In this study, we investigate the structure–function relationships of four representative peptides: MPCK , LTX315 , CnAMP1 , and its C‐terminally amidated analog, CAP , through a combination of experimental assays and molecular dynamics (MD) simulations. CAP exhibited enhanced helicity relative to CnAMP1 , yet neither peptide showed significant anticancer or antibacterial activity, suggesting that increased helicity alone is insufficient for potency. In contrast, LTX315 displayed strong activity, likely driven by its higher net charge and hydrophobicity. MPCK demonstrated the most potent anticancer effect, potentially due to its extended length and stable helical structure, but was less active against bacteria and more hemolytic than LTX315 . Molecular dynamics simulations further demonstrated how structural parameters govern lipid selectivity and membrane perturbation. Our findings highlight that balancing peptide length and hydrophobicity provides a rational basis for developing potent anticancer and antimicrobial peptides with improved selectivity.