The mechanism of action of antimicrobial peptides (AMPs) has been debated over many years, and various models have been proposed. In this work we combine small angle X-ray/neutron scattering (SAXS/SANS) techniques to systematically study the effect of AMPs on the cytoplasmic membrane of Escherichia coli bacteria using a simplified model system of 4 : 1 DMPE : DMPG ([1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine] : [1,2-dimyristoyl-sn-glycero-3-phospho-(10-rac-glycerol)]) phospholipid unilamellar vesicles. The studied antimicrobial peptides aurein 1.2, indolicidin, LL-37, lacticin Q and colistin vary in size, charge, degree of helicity and origin. The peptides insert into the bilayer to various degrees, and are found to accelerate the dynamics of phospholipids significantly as seen by time resolved SANS (TR-SANS) measurements, with the exception of colistin that is suggested to rather interact with lipopolysaccharides (LPS) on the outer membrane of E. coli. We compare these results with earlier published data on model systems based on PC-lipids (phosphatidylcholines), showing comparable effect with regards to peptide insertion and effect on dynamics. However, model systems based on PE-lipids (phosphatidylethanolamine) are more prone to destabilisation upon addition of peptides, with formation of multilamellar structures and morphological changes. These properties of PE-vesicles lead to less conclusive results regarding peptide effect on structure and dynamics of the membrane.

中文翻译：

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抗菌肽对大肠杆菌模拟脂质模型膜的影响：使用散射方法关联结构和动态效应

抗菌肽 (AMPs) 的作用机制多年来一直存在争议，并提出了各种模型。在这项工作中，我们结合小角度 X 射线/中子散射 (SAXS/SANS) 技术，使用 4:1 DMPE :DMPG ([1, 2-二肉豆蔻酰-sn-甘油-3-磷酸乙醇胺]：[1,2-二肉豆蔻酰-sn-甘油-3-磷酸-(10- rac-甘油)]) 磷脂单层囊泡。所研究的抗菌肽 aurein 1.2、indolicidin、LL-37、lactin Q 和多粘菌素在大小、电荷、螺旋度和来源方面有所不同。通过时间分辨 SANS (TR-SANS) 测量可以看出，这些肽以不同程度插入到双层中，并被发现显着加速磷脂的动力学，但建议与脂多糖 (LPS) 相互作用的粘菌素除外。大肠杆菌的外膜. 我们将这些结果与早期发表的基于 PC 脂质（磷脂酰胆碱）的模型系统的数据进行比较，在肽插入和对动力学的影响方面显示出相当的效果。然而，基于 PE 脂质（磷脂酰乙醇胺）的模型系统在添加肽后更容易不稳定，形成多层结构和形态变化。PE-囊泡的这些特性导致关于肽对膜结构和动力学的影响的不确定性结果。