(A) Low-angle X-ray scattering (LAXS) of oriented, fully hydrated model membranes yields bending modulus (KC) and (B) wide-angle X-ray scattering (WAXS) yields lipid chain order parameter (SX-ray).

In the questf or new antibiotics, two novel engineered cationic antimicrobialpeptides (eCAPs)h ave been rationallyd esigned. WLBU2 and D8 (all 8v alines are the denantiomer)e fficiently kill both Gram-negative and -positive bacteria, but WLBU2 is toxic and D8 nontoxict oe ukaryotic cells. We explore protein secondary structure, location of peptides in six lipid model membranes, changes in membrane structurea nd pore evidence. We suggest that protein secondary structure is not ac riticald eterminant of bactericidal activity,b ut that membrane thinning and dual location of WLBU2 and D8 in the membrane headgroup and hydro-carbonr egion may be important. While neither peptide thins the Gram-negative lipopolysaccharide outer membrane model,b oth locate deep into its hydrocarbonr egion where they are primedf or self-promoted uptake into the periplasm.T he partially a-helicals econdarys tructure of WLBU2 in ar ed blood cell (RBC) membrane model containing 50 % cholesterol, could play ar ole in destabilizingt his RBC membrane modelc ausing pore formationt hat is not observed with the D8 randomc oil, which correlates with RBC hemolysis causedb yWLBU2 but not by D8.[a] Prof. Figure 4. CD results of WLBU2i na queouss olution, pH 7and with lipidmembrane models. A) WLBU2 in G(À)I M( black trace) and WLBU2 in water (red trace), B) secondary structure results of WLBU2 in G(À)I Mmodel with decreasing WLBU2:lipid molar ratio in 15 mm PBS, (C) Secondary structure results of 10 mm WLBU2 in 15 mm PBS in six model membranes at 10:1 lipid:peptide molar ratio. R 2 indicates the goodnesso ft he fit to the Brahms and Brahmsd ata set. [49] All CD experiments were carried out at 37 8C. The errors on the percentages are 3-5 %.

characterize membrane remodeling induced by other pore forming peptides such as a mutant derivative of the bee venom peptide melittin in supported lipid bilayers (Langmuir 34: 28 (2018)). The data revealed time dynamic interconversion between membrane-thinned and pore-like states, as well as colocalization between these different modes of membrane remodeling. Here, we use AFM imaging to characterize the lipid bilayer remodeling induced by pHD108. Studies of pHD108 conducted on supported POPC bilayers at differing pH revealed pH-dependent membrane distortions including punctate pore-like features. To provide a broader mechanistic picture, single molecule AFM imaging results are placed in context with other measurements (e.g., leakage assays) performed on the same peptide/membrane system.