The Phase Behavior and Organization of Sphingomyelin/Cholesterol Membranes: A Deuterium NMR Study
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| Authors: | Keyvanloo, A; Shaghaghi, M; Zuckermann, MJ; Thewalt, JL |
| Year: | 2018 |
| Journal: | Biophys. J. 114 Article Link (DOI) PubMed |
| Title: | The Phase Behavior and Organization of Sphingomyelin/Cholesterol Membranes: A Deuterium NMR Study |
| Abstract: | We have studied the dependence of the phase and domain characteristics of sphingomyelin (SM)/cholesterol model membranes on sterol content and temperature using deuterium nuclear magnetic resonance. NMR spectra of N-palmitoyl(D31)-D-erythro-sphingosylphosphorylcholine (PSM-d31) were taken for temperatures from 25 to 70 degrees C and cholesterol concentrations of 0-40%. Analogous experiments were performed using 1-palmitoyl, 2-palmitoyl(D31)-sn-glycero-3-phosphocholine (DPPC-d31)/cholesterol membranes to carefully compare the data obtained using palmitoyl chains that have similar "kinked" conformations. The constructed phase diagrams exhibit both solid-ordered (so) + liquid-ordered (lo) and liquid-disordered (ld) + lo phase-coexistence regions with a clear three-phase line. Macroscopic (micron-sized) coexistence of ld and lo phases was not observed; instead, line-broadening in the ld+lo region was characterized by intermediate exchange of lipids between the two types of domains. The length scales associated with the domains were estimated to be 75-150 nm for PSM-d31/cholesterol and DPPC-d31/cholesterol model membranes. |
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