SASDNX4 – Gram-negative bacteria lipid membrane mimic deposited onto silicon wafer in the presence of antimicrobial peptide WLBU2 (oriented sample anisotropic scattering)

This is a membrane mimic designed to emulate the bacterial Gram-negative inner membrane. The sample is 4 mg of Gram-negative inner membrane mimic plus WLBU2 antimicrobial peptide in a 75:1 molar ratio oriented onto a silicon wafer, hydrated fully through the vapor. The area/lipid is 0.749+/- 0.002 sq. nm. The lipid is deposited using the rock and roll procedure where the lipid (and peptide if present) is solubilized in two organic solvents - one to dissolve the lipid and the other to spread the lipid solution onto the silicon wafer. All of the organic solvent is removed under vacuum for at least two hours, after the lipid is initially dry. The sample is trimmed to a thin strip (5 mm wide) in the center of the silicon wafer. The width of the wafer is 1.5 cm and its length is 3 cm. It is 1 mm thick. The sample is fully hydrated in a thick-walled hydration chamber. The sample is rotated in the x-ray beam during the data acquisition. For more detail regarding this kind of sample please see: Kučerka, N., Liu, Y. F., Chu, N. J., Petrache, H. I., Tristram-Nagle, S. & Nagle, J. F. (2005). Structure of fully hydrated fluid phase DMPC and DLPC lipid bilayers using X-ray scattering from oriented multilamellar arrays and from unilamellar vesicles. Biophys J 88, 2626-2637. The data analysis uses liquid-crystal theory to obtain the bending modulus and the compressibility modulus. These are needed to obtain the structure factor. The form factor is then obtained as described in: Lyatskaya, Y., Liu, Y., Tristram-Nagle, S., Katsaras, J. & Nagle, J. F. (2001). Method for obtaining structure and interactions from oriented lipid bilayers. Phys Rev E Stat Nonlin Soft Matter Phys 63, 011907. The gram-negative mixture consists of a 7:2:1 molar ratio: 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(10-rac-glycerol) sodium salt (POPG), 10,30-bis-[1,2-dioleoyl-sn-glycero-3-phospho]-sn-glycerol (Cardiolipin 18:1) with the RRWVRRVRRWVRRVVRVVRRWVRR peptide.