title: A bacterial monorhamnolipid alters the biophysical properties of phosphatidylethanolamine model membranes.
abstract: This work presents a biophysical study on the interactions of a monorhamnolipid (monoRL) produced by Pseudomonas aeruginosa MA01 with model dielaidoylphosphatidylethanolamine (DEPE) membranes. Incorporation of monoRL into DEPE shifts the onset temperature of the Lβ-to-Lα and the Lα-to-HII phase transitions toward lower values. Incorporation of monoRL into DEPE indicates the coexistence of lamellar and hexagonal-HII phases in rhamnolipid-containing samples at 60°C, at which pure DEPE is lamellar. Thus, both techniques show that monoRL facilitates formation of the hexagonal-HII phase in DEPE, i.e. it destabilizes the bilayer organization. The phase diagram for the phospholipid component indicates a near-ideal behavior, with better miscibility of monoRL into DEPE in the fluid phase than in the gel phase. The various vibrational mode bands of the acyl chains of DEPE were studied by FTIR spectroscopy, focusing on the CH2 symmetric stretching mode. Incorporation of monoRL into DEPE shifts the frequency of this band to higher wavenumbers, at temperatures both below and above the main gel to liquid-crystalline phase transition. Examination of the CO stretching band of DEPE indicates that monoRL/DEPE interactions result in an overall dehydration effect on the polar headgroup of DEPE. These results are discussed in light of the possible role of rhamnolipids as bilayer stabilizers/destabilizers during cell membrane fluctuation events.
authors: Department of Chemical Engineering, Jundi-Shapur University of Technology, Dezful, Iran.
authors: Habib
authors: H
authors: Abbasi
authors: Francisco J
authors: FJ
authors: Aranda
authors: Kambiz Akbari
authors: KA
authors: Noghabi
authors: Antonio
authors: A
authors: Ortiz
mesh_terms: D006017:Glycolipids / Q000737:chemistry* / Q000302:isolation & purification; D008051:Lipid Bilayers / Q000737:chemistry*; D044367:Phase Transition; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D055672:Static Electricity; D013696:Temperature; D014867:Water
chemical_list: D006017:Glycolipids; D008051:Lipid Bilayers; D010714:Phosphatidylethanolamines; C418382:rhamnolipid; D014867:Water
keywords: Dielaidoylphosphatidylethanolamine; Differential scanning calorimetry; FTIR; Phospholipid vesicle; Rhamnolipid; SAXD