Molecular interactions between magainin 2 and model membranes in situ.
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 degrees from the POPG bilayer normal. For the POPC bilayer, even at a much higher peptide concentration of 2.0 microM, 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 degrees 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.
Nguyen
Khoi Tan
KT
Department of Chemistry, 930 North University Avenue, University of Michigan, Ann Arbor, Michigan 48109, USA.
Le Clair
Stéphanie V
SV
Ye
Shuji
S
Chen
Zhan
Z
D000818:Animals; D023181:Antimicrobial Cationic Peptides / Q000737:chemistry*; D002462:Cell Membrane / Q000737:chemistry*; D054806:Magainins; D017550:Spectroscopy, Fourier Transform Infrared; D029867:Xenopus Proteins / Q000737:chemistry*
D023181:Antimicrobial Cationic Peptides; D054806:Magainins; D029867:Xenopus Proteins; C053301:magainin 2 peptide, Xenopus