Comparison of Lipid/Gramicidin Dispersions and Cocrystals by Raman Scattering

Kurt W. Short, B. A. Wallace, Richard A. Myers, Stephen P. Fodor, A. Keith Dunker

Research output: Contribution to journalArticle

19 Scopus citations


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 β-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.

Original languageEnglish (US)
Pages (from-to)557-562
Number of pages6
Issue number2
StatePublished - Jan 1 1987
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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