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Issue 2, 2008
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Formation of the liquid-ordered phase in fully hydrated mixtures of cholesterol and lysopalmitoylphosphatidylcholine

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Abstract

The role of cholesterol (Chol) in promoting lamellar phase formation in mixtures with 1-palmitoyl-2-hydroxy-sn-glycero-3-phosphocholine (Lyso-PPC) in excess water was investigated using multinuclear solid-state NMR and X-ray scattering. It was found that mixtures containing Chol and Lyso-PPC form a liquid-ordered (Lo) lamellar phase over a range of temperatures and concentrations, as previously observed in mixtures of Chol with various diacylphospholipids. The maximum quadrupolar splitting of the 2H-NMR powder patterns for samples containing per-deuterated Lyso-PPC were 40–50 kHz which is strongly indicative of an Lo phase. This evidence was supported by wide angle X-ray scattering data which showed a characteristic diffuse peak centred at 4.2 Å. The Lo phase coexists with an isotropic Lyso-PPC phase at Chol concentrations up to 70 mol% Chol, and with Chol crystals at Chol concentrations above this value. Below 70 mol% Chol, an increase in the concentration of Chol in the system caused a corresponding increase in the proportion of the Lo phase present compared with the amount of isotropic Lyso-PPC. The chemical-shift anisotropy (CSA) of the static 31P-NMR spectra of the Lo phase showed the symmetry of a lamellar phase, but the linewidth, Δσ, was much narrower than CSA powder patterns obtained for diacylphospholipids in similar conditions, being ∼20 ppm as opposed to ∼40 ppm, respectively.

Graphical abstract: Formation of the liquid-ordered phase in fully hydrated mixtures of cholesterol and lysopalmitoylphosphatidylcholine

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Publication details

The article was received on 13 Jul 2007, accepted on 18 Oct 2007 and first published on 09 Nov 2007


Article type: Paper
DOI: 10.1039/B710726A
Citation: Soft Matter, 2008,4, 263-267
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    Formation of the liquid-ordered phase in fully hydrated mixtures of cholesterol and lysopalmitoylphosphatidylcholine

    D. L. Gater, J. M. Seddon and R. V. Law, Soft Matter, 2008, 4, 263
    DOI: 10.1039/B710726A

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