Self-organization and phase structure of ternary lipid membranes: A spin label EPR study

Лившиц, В. А.; Demisheva, I. V.; Marsh, Derek

doi:10.1134/s199507801009003x

Cited by 2 publications

(2 citation statements)

References 22 publications

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“…The phase diagrams of the DPPC/DOPC/cholesterol (Veatch et al 2004), palmitoyl-SPM/POPC/cholesterol (Livshits et al 2010), and DSPC/DOPC/cholesterol (Zhao et al 2007, Heberle et al 2010) lipid systems are comparable to the phase diagram of our system, because of the lipid similarities and the existence of phase boundaries and tie-lines for the L o + L d coexistence region. The closed coexistence regions (i.e.…”

Section: Resultssupporting

confidence: 54%

Dynamics and ordering of lipid spin-labels along the coexistence curve of two membrane phases: An ESR study

Smith¹,

Freed²

2012

Chemistry and Physics of Lipids

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An analysis of electron spin resonance (ESR) spectra from compositions along the liquid-ordered (L o ) and liquid-disordered (L d ) coexistence curve from the brain-sphingomyelin/ dioleoylphosphatidylcholine/cholesterol (SPM/DOPC/Chol) model lipid system was performed to characterize the dynamic structure on a molecular level of these coexisting phases. We obtained 200 continuous-wave ESR spectra from glycerophospholipid spin-labels labeled at the 5, 7, 10, 12, 14, and 16 carbon positions of the 2 nd acyl chain, a sphingomyelin spin-label labeled at the 14 carbon position of the amide-linked acyl chain, a headgroup-labeled glycerophospholipid, a headgroup-labeled sphingomyelin, and the cholesterol analogue spin-label cholestane all within multi-lamellar vesicle suspensions at room temperature. The spectra were analyzed using the MOMD (microscopic-order macroscopic-disorder) model to provide the rotational diffusion rates and order parameters which characterize the local molecular dynamics in these phases. The analysis also incorporated the known critical point and invariant points of the neighboring threephase triangle along the coexistence curve. The variation in the molecular dynamic structures of coexisting L o and L d compositions as one moves toward the critical point is discussed. Based on these results, a molecular model of the L o phase is proposed incorporating the "condensing effect" of cholesterol on the phospholipid acyl chain dynamics and ordering and the "umbrella model" of the phospholipid headgroup dynamics and ordering.

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Section: Resultssupporting

confidence: 54%

Dynamics and ordering of lipid spin-labels along the coexistence curve of two membrane phases: An ESR study

Smith¹,

Freed²

2012

Chemistry and Physics of Lipids

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“…This is perhaps due to the difficulties inherent in analyzing ESR spectra that are a superposition of Ld and Lo phase components near a critical point, where the coexisting phases have nearly identical physical properties. Moreover, ESR determinations of the critical point location in PSM/POPC/Chol are also shifted to higher fractions of low-Tm lipid [21,23]. …”

Section: Discussionmentioning

confidence: 99%

Phase behavior and domain size in sphingomyelin-containing lipid bilayers

Petruzielo

Heberle

Drazba

et al. 2013

Biochimica et Biophysica Acta (BBA) - Biomembranes

113

153

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Membrane 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.

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Self-organization and phase structure of ternary lipid membranes: A spin label EPR study

Cited by 2 publications

References 22 publications

Dynamics and ordering of lipid spin-labels along the coexistence curve of two membrane phases: An ESR study

Dynamics and ordering of lipid spin-labels along the coexistence curve of two membrane phases: An ESR study

Phase behavior and domain size in sphingomyelin-containing lipid bilayers

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