title: The effect of ergosterol on dipalmitoylphosphatidylcholine bilayers: a deuterium NMR and calorimetric study.
abstract: We have studied the effect of ergosterol, an important component of fungal plasma membranes, on the physical properties of dipalmitoylphosphatidylcholine (DPPC) multibilayers using deuterium nuclear magnetic resonance ((2)H NMR) and differential scanning calorimetry (DSC). For the (2)H NMR experiments the sn-1 chain of DPPC was perdeuterated and NMR spectra were taken as a function of temperature and ergosterol concentration. The phase diagram, constructed from the NMR spectra and the DSC thermograms, exhibits both solid-ordered (so) + liquid-ordered (lo) and liquid-disordered (ld) + lo phase coexistence regions with a clear three-phase line. This is the first demonstration that lo domains exist in liquid crystalline membranes containing ergosterol. The domain sizes in the ld+lo phase coexistence region were estimated by analyzing the exchange of labeled DPPC between the two regions, and depend on ergosterol concentration. The DPPC-ergosterol phase diagram is similar to that of the DPPC-cholesterol multibilayer system except that the so+lo and ld+lo phase coexistence regions are considerably broader.
authors.affiliation: Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada, V5A 1S6.
authors.forename: Ya-Wei
authors.initials: YW
authors.lastname: Hsueh
authors.forename: Kyle
authors.initials: K
authors.lastname: Gilbert
authors.forename: C
authors.initials: C
authors.lastname: Trandum
authors.forename: M
authors.initials: M
authors.lastname: Zuckermann
authors.forename: Jenifer
authors.initials: J
authors.lastname: Thewalt
mesh_terms: D002152:Calorimetry, Differential Scanning; D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine / Q000032:analysis / Q000737:chemistry*; D004875:Ergosterol / Q000032:analysis / Q000737:chemistry*; D008051:Lipid Bilayers / Q000032:analysis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008560:Membrane Fluidity; D008968:Molecular Conformation; D044367:Phase Transition; D012996:Solutions; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D012996:Solutions; D003903:Deuterium; D004134:Dimyristoylphosphatidylcholine; D004875:Ergosterol