We recently discovered that peptide dendrimers such as G3KL ((KL)₈(KKL)₄(KKL)₂KKL, K = branching l-lysine) exert strong activity against Gram-negative bacteria including Pseudomonas aeruginosa, Acinetobacter baumannii, and Escherichia coli. Herein, we report a detailed mechanistic study using fluorescence labeled analogs bearing fluorescein (G3KL-Fluo) or dansyl (G3KL-Dansyl), which show a similar bioactivity profile as G3KL. Imaging bacterial killing by super-resolution stimulated emission depletion (STED) microscopy, time-lapse imaging, and transmission electron microscopy (TEM) reveals that the dendrimer localizes at the bacterial membrane, induces membrane depolarization and permeabilization, and destroys the outer leaflet and the inner membrane. G3KL accumulates in bacteria against which it is active; however, it only weakly penetrates into eukaryotic cells without inducing significant toxicity. G3KL furthermore binds to lipopolysaccharide (LPS) and inhibits the LPS induced release of TNF-α by macrophages, similarly to polymyxin B. Taken together, these experiments show that G3KL behaves as a potent membrane disruptive antimicrobial peptide.

中文翻译：

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抗菌肽树状聚合物G3KL对细菌的杀灭作用的荧光成像。

我们最近发现，肽树状聚合物，例如G3KL（（KL）₈（K KL）₄（K KL）₂ K KL，K =支链l-赖氨酸）对革兰氏阴性细菌（包括铜绿假单胞菌，鲍曼不动杆菌和大肠杆菌。在这里，我们报告了详细的机制研究，使用带有荧光素（G3KL-Fluo）或dansyl（G3KL-Dansyl）的荧光标记类似物，它们显示出与G3KL类似的生物活性。通过超分辨率激发发射耗尽（STED）显微镜，延时成像和透射电子显微镜（TEM）对细菌杀死进行成像显示，树状大分子位于细菌膜上，引起膜去极化和透化，并破坏外部小叶和内膜。G3KL积聚在对其具有活性的细菌中；然而，它仅微弱地渗入真核细胞而不会引起明显的毒性。与多粘菌素B相似，G3KL还与脂多糖（LPS）结合并抑制巨噬细胞通过LPS诱导的TNF-α释放。综上所述，这些实验表明，G3KL发挥了强大的膜破坏性抗菌肽的作用。