A bacterial monorhamnolipid alters the biophysical properties of phosphatidylethanolamine model membranes

作者：Abbasi Habib; Aranda Francisco J; Akbari Noghabi Kambiz; Ortiz Antonio^*

来源：Biochimica et Biophysica Acta-Biomembranes, 2013, 1828(9): 2083-2090.

DOI：10.1016/j.bbamem.2013.04.024

• Rhamnolipid
• Dielaidoylphosphatidylethanolamine
• Phospholipid vesicle
• Differential scanning calorimetry
• FTIR
• SAXD

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 L-beta-to-L-alpha and the L-alpha-to-H-II phase transitions toward lower values. Incorporation of monoRL into DEPE indicates the coexistence of lamellar and hexagonal-H-II, phases in rhamnolipid-containing samples at 60 degrees C, at which pure DEPE is lamellar. Thus, both techniques show that monoRL facilitates formation of the hexagonal-H-II 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 C=O 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.

• 出版日期2013-9