Comparison of lipid/gramicidin dispersions and cocrystals by Raman scattering

Biochemistry. 1987 Jan 27;26(2):557-62. doi: 10.1021/bi00376a030.


Gramicidin crystals, dimyristoylphosphatidylcholine (DMPC)/gramicidin dispersions, and DMPC/gramicidin cocrystals were examined by Raman scattering to determine lipid/gramicidin stoichiometries and lipid organization. Calibrations of the choline (716-cm-1) and tryptophan (756-cm-1) peaks indicate that the cocrystals contain two lipids for each gramicidin monomer, a result confirmed by chemical analyses of washed crystals. In dispersions with high lipid/gramicidin ratios (e.g., 25:1), the lipid is ordered but becomes increasingly disordered as the gramicidin content is increased. Paradoxically, the DMPC/gramicidin cocrystals have highly ordered lipids that possibly contain no gauche bonds at all, despite their low lipid/gramicidin ratio. In addition, the polypeptide amide I peak position near 1670 cm-1 is found to be independent of the lipid/gramicidin ratio in the complexes and may indicate a beta-helix-type secondary structure at all ratios. However, the amide I peak broadens significantly at low lipid/gramicidin ratios and broadens still further in the cocrystals, suggesting that protein-protein interactions may induce band-broadening distortions of the polypeptide structure.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Choline
  • Crystallization
  • Dimyristoylphosphatidylcholine*
  • Gramicidin*
  • Kinetics
  • Liposomes*
  • Models, Biological
  • Molecular Conformation
  • Protein Conformation
  • Spectrum Analysis, Raman / methods
  • Tryptophan


  • Liposomes
  • Gramicidin
  • Tryptophan
  • Choline
  • Dimyristoylphosphatidylcholine