Molecular interactions between magainin 2 and model membranes in situ

Khoi Tan Nguyen, Stéphanie V. Le Clair, Shuji Ye, Zhan Chen

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In this paper, we investigated the molecular interactions of magainin 2 with model cell membranes using sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). Symmetric 1-palmitoyl-2-oleoyl-sn-glycero-3-[Phospho- rac-(1-glycerol)] (POPG) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers, which model the bacterial and mammalian cell membranes, respectively, were used in the studies. It was observed by SFG that magainin 2 orients relatively parallel to the POPG lipid bilayer surface at low solution concentrations, around 200 nM. When increasing the magainin 2 concentration to 800 nM, both SFG and ATR-FTIR results indicate that magainin 2 molecules insert into the POPG bilayer and adopt a transmembrane orientation with an angle of about 20° from the POPG bilayer normal. For the POPC bilayer, even at a much higher peptide concentration of 2.0 μM, no ATR-FTIR signal was detected. For this concentration on POPC, SFG studies indicated that magainin 2 molecules adopt an orientation nearly parallel to the bilayer surface, with an orientation angle of about 75° from the surface normal. This shows that SFG has a much better detection limit than ATR-FTIR and can therefore be applied to study interfacial molecules with a much lower surface coverage. This magainin 2 orientation study and further investigation of the lipid bilayer SFG signals support the proposed toroidal pore model for the antimicrobial activity of magainin 2.

Original languageEnglish (US)
Pages (from-to)12358-12363
Number of pages6
JournalJournal of Physical Chemistry B
Issue number36
StatePublished - Sep 10 2009

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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