Phase behavior and domain size in sphingomyelin-containing lipid bilayers

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Journal titleBiochimica et Biophysica Acta - Biomembranes
Pages13021313; # of pages: 12
Subject2 oleoyl 1 palmitoylphosphatidylcholine; cholesterol; dioleoylphosphatidylcholine; sphingomyelin; analytic method; animal cell; article; artificial membrane; brain cell; cell function; differential scanning calorimetry; Forster resonance energy transfer; in vivo study; lipid bilayer; molecular size; molecular stability; neutron scattering; nonhuman; phase separation; priority journal; sensitivity analysis; swine; Calorimetry, Differential Scanning; Cholesterol; Fluorescence Resonance Energy Transfer; Lipid Bilayers; Neutrons; Phosphatidylcholines; Scattering, Radiation; Sphingomyelins; Sus
AbstractMembrane raft size measurements are crucial to understanding the stability and functionality of rafts in cells. The challenge of accurately measuring raft size is evidenced by the disparate reports of domain sizes, which range from nanometers to microns for the ternary model membrane system sphingomyelin (SM)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/cholesterol (Chol). Using Förster resonance energy transfer (FRET) and differential scanning calorimetry (DSC), we established phase diagrams for porcine brain SM (bSM)/dioleoyl-sn-glycero-3-phosphocholine (DOPC)/Chol and bSM/POPC/Chol at 15 and 25 C. By combining two techniques with different spatial sensitivities, namely FRET and small-angle neutron scattering (SANS), we have significantly narrowed the uncertainty in domain size estimates for bSM/POPC/Chol mixtures. Compositional trends in FRET data revealed coexisting domains at 15 and 25 C for both mixtures, while SANS measurements detected no domain formation for bSM/POPC/Chol. Together these results indicate that liquid domains in bSM/POPC/Chol are between 2 and 7 nm in radius at 25 C: that is, domains must be on the order of the 2-6 nm Förster distance of the FRET probes, but smaller than the ~ 7 nm minimum cluster size detectable with SANS. However, for palmitoyl SM (PSM)/POPC/Chol at a similar composition, SANS detected coexisting liquid domains. This increase in domain size upon replacing the natural SM component (which consists of a mixture of chain lengths) with synthetic PSM, suggests a role for SM chain length in modulating raft size in vivo. © 2012 Elsevier B.V. All rights reserved.
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AffiliationNational Research Council Canada (NRC-CNRC); NRC Canadian Neutron Beam Centre (CNBC-CCFN)
Peer reviewedYes
NPARC number21269620
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Record identifierfc863045-1748-40a4-afe4-8d16fc526021
Record created2013-12-13
Record modified2016-05-09
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