title: Investigations of the interactions between synthetic antimicrobial polymers and substrate-supported lipid bilayers using sum frequency generation vibrational spectroscopy.
abstract: Sum frequency generation (SFG) vibrational spectroscopy was used to analyze interactions between solid-supported lipid bilayers acting as models for cellular membranes and several membrane-active random copolymers with different lipophilic side chains, named 0R (no group), 33Me (methyl group), 11Bz (benzyl group), and 33Bu (butyl group), according to both the identity and percentage of the side chains within the polymer. Biological tests of the minimum inhibitory concentration (MIC) and hemolytic concentration were performed. The inherent surface sensitivity of SFG allowed for independent monitoring of isotopically labeled lipid bilayer leaflets as a function of concentration to study polymer-bilayer interaction mechanisms. Concentrations at which each bilayer leaflet was disrupted were quantitatively determined for each copolymer. Spectroscopic evidence of interaction with the bilayer below the critical concentrations was observed for the 11Bz polymer. The lipophilic butyl side chain of the 33Bu polymer was found to be oriented parallel to the surface normal. This research shows that SFG is a useful analytical technique which provides unique details regarding the interaction mechanisms of these membrane-active copolymers and lipid bilayers.
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Avery
authors.forename: Edmund F
authors.initials: EF
authors.lastname: Palermo
authors.forename: Amanda
authors.initials: A
authors.lastname: McLaughlin
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kuroda
authors.forename: Zhan
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology* / Q000633:toxicity; D002462:Cell Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000378:metabolism*; D010715:Phosphatidylglycerols / Q000378:metabolism; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D013057:Spectrum Analysis; D014732:Vibration
chemical_list: D000890:Anti-Infective Agents; D008051:Lipid Bilayers; D010715:Phosphatidylglycerols; D011108:Polymers; D000644:Quaternary Ammonium Compounds; C030345:1,2-dipalmitoylphosphatidylglycerol