Layer formations of dipalmitoylphosphatidylcholine liposomes in the pretransition range

Attila Bóta, Tamás Drucker, Manfred Kriechbaum, Zsolt Pálfia, Gábor Réz

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Abstract

Destroyed lamellar and chain packing arrangements of the dipalmitoylphosphocholine-water (30% w/w) system are formed in the pretransition range (31-35.5 °C) under quasi-equilibrium conditions observed by means of simultaneous small- and wide-angle X-ray scattering method. The peak profiles of the scattering curves detected in the pretransition range were modeled as the superpositions of the fitted profiles of the Lβ′ and Pβ′ phases corresponding to the one-dimensional layer arrangements and the subcells in the chain packing. On the basis of the fitted profiles the ratios of the phases can be given as a function of the temperature. It can be stated that (i) both the Lβ′ and Pβ′ phases are present in the temperature range of the pretransition and (ii) in the Pβ′ phase the layer arrangements and chain packing do not change to the same extent. The maximum loss in the layer arrangement was observed around 33 °C. The accumulation of the defect structures appears to be highly permanent as it was observed after sequential heat treatments, i.e., quenching to the temperature domain of the Lβ′ phase (28 °C) and then reheating above the pretransition range to the temperature domain of the Pβ′ phase (38 °C). A memory effect occurs in the sense that the destroyed structures are restored in the temperature range of phase Pβ′ after the formation of a largely reconstructed phase Lβ′. The destroyed layer structures formed in the pretransition and in the rippled phase temperature domains are not identical, as observed by freeze-fracture electron microscopy.

Original languageEnglish
Pages (from-to)3101-3108
Number of pages8
JournalLangmuir
Volume15
Issue number9
DOIs
Publication statusPublished - Apr 27 1999

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ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Spectroscopy
  • Electrochemistry

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