N-Succinyldioleoylphosphatidylethanolamine: structural preferences in pure and mixed model membranes

Rajiv Nayar, Colin P S Tilcock, Michael J. Hope, Pieter R. Cullis, Alan J. Schroit

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

The structural preferences of the pH-sensitive phospholipid, N-succinyldioleoylphosphatidylethanolamine (N-succinyl-DOPE), have been examined alone and in mixtures with DOPE by 31P-NMR, fluorescence energy transfer, and freeze-fracture techniques. The basic polymorphic behavior of pure N-succinyl-DOPE and DOPE/N-succinyl-DOPE lipid systems and the influence of calcium and pH were investigated. It is shown that, similar to other negatively charged acidic phospholipids, N-succinyl-DOPE adopts the bilayer organization upon hydration. This structure is maintained at both pH 7.4 and 4.0 in the presence or absence of calcium. In the mixed lipid system, N-succinyl-DOPE can stabilize the non-bilayer lipid, DOPE, into a bilayer structure at both pH 7.4 and 4.0 at more than 10 mol% N-succinyl-DOPE, although a narrow 31P-NMR lineshape is observed at acidic pH values. This corresponds to the presence of smaller vesicles as shown by quasi-elastic light scattering measurements. Addition of equimolar calcium (with respect to N-succinyl-DOPE) to the DOPE/N-succinyl-DOPE systems induces the hexagonal HII phase at both pH values. In unilamellar systems with similar lipid composition the addition of Ca2+ results in membrane fusion as indicated by fluorescence energy-transfer experiments. These findings are discussed with regard to the molecular mechanism of the bilayer to hexagonal HII phase transition and membrane fusion and the utility of N-succinyl-DOPE containing pH-sensitive vesicles as drug-delivery vehicles.

Original languageEnglish (US)
Pages (from-to)31-41
Number of pages11
JournalBBA - Biomembranes
Volume937
Issue numberC
DOIs
StatePublished - 1988

Keywords

  • Freeze-fracture
  • Hexagonal H phase
  • Liposome
  • Model membrane
  • Phosphatidylethanolamine
  • Resonance energy transfer

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Cell Biology

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