Antimicrobial peptides (AMPs) have been an area of great interest, due to the high selectivity of these molecules toward bacterial targets over host cells and the limited development of bacterial resistance to these molecules through evolution. The peptides are known to selectively bind to bacterial cell surfaces through electrostatic interactions, and subsequently, the peptides insert into the cell membrane and cause local disruptions of membrane integrity leading to cell death. Previous experiments showed that replacing the Leu residues in the AMP C18G with other naturally occurring hydrophobic residues resulted in side-chain-dependent activities. This work extends the investigation to non-natural hydrophobic amino acids and the effect on peptide activity. Minimal inhibitory concentration (MIC) results demonstrated that amino acid substitutions containing long flexible carbon chains maintained or increased antimicrobial activity compared to natural analogues. In solution, the peptide showed aggregation only with the most hydrophobic non-natural amino acid substitutions. Binding assays using Trp fluorescence confirm a binding preference for anionic lipids while quenching experiments demonstrated that the more hydrophobic peptides are more deeply buried in the anionic lipid bilayers compared to the zwitterionic bilayers. The most effective peptides at killing bacteria were also those which showed some level of disruption of bacterial membranes; however, one peptide sequence exhibited very strong activity and very low levels of red blood cell hemolysis, yielding a promising target for future development.

抗菌肽（AMP）一直是人们非常感兴趣的领域，因为这些分子相对于宿主细胞对细菌靶标具有高选择性，并且细菌通过进化对这些分子的耐药性发展有限。已知这些肽通过静电相互作用选择性地结合到细菌细胞表面，随后，这些肽插入细胞膜并引起膜完整性的局部破坏，导致细胞死亡。先前的实验表明，用其他天然存在的疏水残基替换 AMP C18G 中的亮氨酸残基会产生侧链依赖性活性。这项工作将研究扩展到非天然疏水氨基酸及其对肽活性的影响。最低抑菌浓度 (MIC) 结果表明，与天然类似物相比，含有长柔性碳链的氨基酸取代可维持或增强抗菌活性。在溶液中，肽仅在最具疏水性的非天然氨基酸取代时表现出聚集。使用色氨酸荧光的结合测定证实了对阴离子脂质的结合偏好，而猝灭实验表明，与两性离子双层相比，疏水性更强的肽埋藏在阴离子脂质双层中更深。杀死细菌最有效的肽也是那些对细菌膜有一定程度破坏的肽。然而，一种肽序列表现出非常强的活性和非常低水平的红细胞溶血，为未来的开发提供了一个有希望的目标。