Previously, we described the design and synthesis of three nine‐residue AMPs, P9Nal(SS), P9Trp(SS), and P9Nal(SR), showing high stability in serum and broad spectrum antimicrobial activity. The peptides P9Trp(SS) and P9Nal(SR) differ from P9Nal(SS) for the replacement of the two 2Nal residues with Trp residues and for the replacement of the two Cys (StBu) with Cys (tBu) residues, respectively. These changes led to peptides with a lower hydrophobicity respect to the P9Nal(SS). Interestingly, the three peptides have very similar activity against Gram‐negative bacteria. Instead, they exhibit a significant difference towards Gram‐positive bacteria, being P9Nal(SS) the most active. In order to evaluate the impact of amino acids substitution on membranotropic activity and rationalize the observed effects in vivo, here, we report the detailed biophysical characterization of the interaction between P9Nal(SR) and P9Trp(SS) and liposomes by combining differential scanning calorimetry, circular dichroism, and fluorescence spectroscopy. The comparison with the results for the previously characterized P9Nal(SS) peptide reveals similarities and differences on the interaction process and perturbation activities. It was found that the three peptides can penetrate at different extent inside the bilayer upon changing their conformation and inducing lipid domains formation, revealing that the formation of lipid domains is fundamental for the activity against Gram‐negative bacteria. On the contrary, the dissimilar activity against Gram‐positive bacteria well correlate with the different affinity of peptides for the lipoteichoic acid, a component selectively present in the cell wall of Gram‐positive bacteria.

中文翻译：

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三种非天然抗菌肽的促膜作用的异同。

先前，我们描述了三种九残基AMPs P9Nal（SS），P9Trp（SS）和P9Nal（SR）的设计和合成，它们在血清中具有很高的稳定性，并具有广谱抗菌活性。肽P9Trp（SS）和P9Nal（SR）与P9Nal（SS）的区别在于分别用Trp残基替换两个2Nal残基和用Cys（t Bu）残基替换两个Cys（S t Bu）。。这些改变导致相对于P9Nal（SS）具有较低疏水性的肽。有趣的是，三种肽对革兰氏非常类似的活动-阴性细菌。相反，它们对革兰氏阳性细菌表现出显着差异，它们是最活跃的P9Nal（SS）。为了评估氨基酸替代对膜活性的影响并合理化体内观察到的影响，在这里，我们结合差示扫描量热法报告了P9Nal（SR）和P9Trp（SS）与脂质体之间相互作用的详细生物物理特征，圆二色性和荧光光谱。与先前表征的P9Nal（SS）肽的结果进行比较，揭示了相互作用过程和摄动活动的异同。发现三种肽在改变其构象并诱导脂质结构域形成时可以在双层内以不同程度渗透，揭示脂质结构域的形成对于抵抗革兰氏阴性细菌的活性至关重要。相反，对革兰氏阳性细菌的不同活性与肽对脂蛋白的酸的不同亲和力密切相关，脂蛋白是一种选择性存在于革兰氏阳性细菌细胞壁中的成分。