The chain order of binary unsaturated lipid bilayers modulated by aromatic-residue-containing peptides: An ATR-FTIR spectroscopy study

Abstract

In this study, we described the chain order change of binary unsaturated lipid bilayers by studying pure 2-oleoyl-1-pamlitoyl-sn-glyecro-3-phosphocholine (POPC) bilayers, 2-oleoyl-1-pamlitoyl-sn-glyecro-3-glycerol (POPG) bilayers, and POPC/POPG bilayers. The interactions between the POPC/POPG membrane and three model peptides containing basic, aromatic, and hydrophobic residues were studied to investigate the effects of the peptide orientation on the acyl chain order of the POPC/POPG bilayers. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic studies showed that the acyl chain order of the POPC/POPG bilayers decreased as compared to that of the pure POPC or POPG bilayers. The chain order of the POPC/POPG bilayers significantly decreased when Gravin was added as compared to that when Vamp2 or Antp was added. Fluorescence spectroscopic measurements further show that the tryptophan of the three peptides may interact with the hydrophobic region of the POPC/POPG bilayers, thus resulting in a change in the conformational order of the POPC/POPG acyl chains. This study may provide valuable insight into the dynamics and flexibility of lipid bilayers with different lipids and highlights the importance of aromatic residues in peptide binding to the membrane.