The impact of maculatin 1.1 (Mac1) on the mechanical properties of supported lipid membranes derived from exponential growth phase (EGP) and stationary growth phase (SGP) E. coli lipid extracts was analysed by surface plasmon resonance and atomic force microscopy. Each membrane was analysed by quantitative nanomechanical mapping to derive measurements of the modulus, adhesion and deformation in addition to bilayer height. Image analysis revealed the presence of two domains in the EGP membrane differing in height by 0.4 nm. Three distinct domains were observed in the SGP membrane corresponding to 4.2, 4.7 and 5.4 nm in height. Using surface plasmon resonance, Mac1 was observed to bind strongly to both membranes and then disrupt the membranes as evidenced by a sharp drop in baseline. Atomic force microscopy (AFM) topographic analysis revealed the formation of domains of different height and confirmed that membrane destruction was much faster for the SGP derived bilayer. Moreover, Mac1 selectively disrupted the domain with the lowest thickness, which may correspond to a liquid ordered domain. Overall, the results provide insight into the role of lipid domains in the response of bacteria to antimicrobial peptides.

中文翻译：

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抗菌肽对细菌脂质膜的影响取决于生长阶段

maculatin 1.1 (Mac1) 对来自指数生长期 (EGP) 和固定生长期 (SGP)大肠杆菌的支撑脂质膜机械性能的影响通过表面等离子共振和原子力显微镜分析脂质提取物。通过定量纳米力学映射分析每个膜，以得出除双层高度外的模量、粘附和变形的测量值。图像分析显示 EGP 膜中存在高度相差 0.4 nm 的两个域。在 SGP 膜中观察到三个不同的域，对应于 4.2、4.7 和 5.4 nm 的高度。使用表面等离子体共振，观察到 Mac1 与两个膜强烈结合，然后破坏膜，基线急剧下降证明了这一点。原子力显微镜 (AFM) 形貌分析揭示了不同高度区域的形成，并证实 SGP 衍生的双层膜破坏速度要快得多。而且，Mac1 选择性地破坏了厚度最小的域，这可能对应于液体有序域。总体而言，结果提供了对脂质结构域在细菌对抗菌肽反应中的作用的深入了解。