Interaction of antimicrobial peptides with lipopolysaccharides.
We study the interaction of antimicrobial peptides with lipopolysaccharide (LPS) bilayers to understand how antimicrobial peptides interact with the LPS monolayer on the outer membrane of Gram-negative bacteria. LPS in water spontaneously forms a multilamellar structure composed of symmetric bilayers. We performed X-ray lamellar diffraction and wide-angle in-plane scattering to study the physical characteristics of LPS multilayers. The multilayer alignment of LPS is comparable to phospholipids. Thus, it is suitable for the application of oriented circular dichroism (OCD) to study the state of peptides in LPS bilayers. At high hydration levels, the chain melting temperature in multilamella detected by X-ray diffraction is the same as that of LPS aqueous dispersions, as measured by calorimetry. LPS has a strong CD, but with a careful subtraction of the lipid background, the OCD of peptides in LPS is measurable. The method was tested successfully with melittin. It was then applied to two representative antimicrobial peptides, magainin and protegrin. At peptide concentrations comparable to the physiological conditions, both peptides penetrate transmembrane in LPS bilayers. The results imply that antimicrobial peptides readily penetrate the LPS monolayer of the outer membrane.
Department of Physics and Astronomy, Rice University, Houston, Texas 77251-1892, USA.
Lai
L
Ding
Lin
L
Yang
Thomas M
TM
Weiss
Alan J
AJ
Waring
Robert I
RI
Lehrer
Huey W
HW
Huang
D023181:Antimicrobial Cationic Peptides / Q000378:metabolism*; D002942:Circular Dichroism; D008051:Lipid Bilayers; D008070:Lipopolysaccharides / Q000378:metabolism*; D011485:Protein Binding; D014961:X-Ray Diffraction
D023181:Antimicrobial Cationic Peptides; D008051:Lipid Bilayers; D008070:Lipopolysaccharides