Opioid peptide interactions with lipid bilayer membranes

Varadarajan Ramaswami, Ronald C. Haaseth, Terry O. Matsunaga, Victor J. Hruby, David F. O'Brien

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The interaction of the δ-opioid receptor selective peptides, cyclic [d-Pen2, d-Pen5]-enkephalin [DPDPE] and its acyclic analog, DPDPE(SH)2, with neutral phospholipid bilayer membranes was examined by permeability and calorimetry measurements. The permeabilities were accomplished by entrapping either peptide inside of unilamellar liposomes (composed of a mixture of a molar ratio 65:25:10 phosphatidylcholine/prosphatidylethanolamine/cholesterol) then monitoring the peptide efflux through the bilayer. The initial permeability of DFDPE (first 12 h) averaged over four experiments was (0.91 ± 0.47) · 10-12 cm s-1. In contrast the average permeability of the acyclic DPDPE(SH)2 was (4.26 ± 0.23) · 10-12 cm s-1. The effect of these peptides on the phase transition, Tm, of 1,2-dipalmitoylphosphatidylcholine (DPPC) bilayers was examined by high sensitivity differential scanning calorimetry. The Tm, the calorimetric enthalpy, and the van 't Hoff enthalpy of DPPC were not significantly altered by the presence of DPDPE, whereas the calorimetric data for DPPC with DPDPE(SH)2 showed a small, yet significant, increase (0.2°C) in the Tm with a 30% decrease in the cooperative unit. Both the permeability and calorimetry data reveal a stronger peptide-membrane interaction in the case of the more flexible acyclic peptide.

Original languageEnglish (US)
Pages (from-to)195-202
Number of pages8
JournalBBA - Biomembranes
Issue number2
StatePublished - Aug 24 1992


  • DSC
  • Membrane permeability
  • Opioid peptide
  • Peptide-membrane interaction
  • Quasi-clastic light scattering

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology


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