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Chem Phys Lipids. 2014 Dec;184:1-6. doi: 10.1016/j.chemphyslip.2014.08.002. Epub 2014 Aug 27.

Membrane properties of cholesterol analogs with an unbranched aliphatic side chain.

Author information

1
Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany.
2
Department of Chemistry and Biochemistry, Queens College of CUNY, Flushing, NY 11367-1597, USA.
3
Institute of Biology/Biophysics, Humboldt University Berlin, Invalidenstr. 42, D-10115 Berlin, Germany.
4
Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany; Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India.
5
Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany. Electronic address: holger.scheidt@medizin.uni-leipzig.de.

Abstract

The interactions between cholesterol and other membrane molecules determine important membrane properties. It was shown that even small changes in the molecular structure of cholesterol have a crucial influence on these interactions. We recently reported that in addition to alterations in the tetracyclic ring structure, the iso-branched side chain of cholesterol also has a significant impact on membrane properties (Scheidt et al., 2013). Here we used synthetic cholesterol analogs to investigate the influence of an unbranched aliphatic side chain of different length. The (2)H NMR order parameter of the phospholipid chains and therefore the molecular packing of the phospholipid molecules shows a significant dependence on the sterol's alkyl side chain length, while, membrane permeation studied by a dithionite ion permeation assay and lateral diffusion measured by (1)H MAS pulsed field gradient NMR are less influenced. To achieve the same molecular packing effect similar to that of an iso-branched aliphatic side chain, a longer unbranched side chain (n-dodecyl instead of n-octyl) at C17 of cholesterol is required. Obviously, sterols having a branched iso-alkyl chain with two terminal methyl groups exhibit altered cholesterol-phospholipid interactions compared to analogous molecules with a straight unbranched chain.

KEYWORDS:

Cholesterol; Diffusion; Domain formation; Lipid membrane; Order parameter; Permeability

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