Lipid lateral diffusion in bilayers with phosphatidylcholine, sphingomyelin and cholesterol

Lindblom, Göran; Orädd, Greger; Филиппов, А. В.

doi:10.1016/j.chemphyslip.2006.02.011

Cited by 105 publications

(86 citation statements)

References 41 publications

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“…Additional measurements by us (data not shown) and other studies42 of perdeuterated cholesterol in PSM/POPC/cholesterol mixtures display an intermediate ordering between those of PSM/cholesterol and POPC/cholesterol, in contrast to the results for the chain-perdeuterated lipids. In line with recent pulse-field-gradient NMR studies of similar systems,41 this implies that cholesterol is involved in exchange between the different membrane regions that is fast on the NMR time scale (milliseconds to microseconds). Nonetheless, it should be noted that preferential affinity of the sterol for the sphingolipid probably appears at small cholesterol mole fractions and low temperatures, as shown here for PSM- d 31 /POPC with X C = 0.20 below 25 °C.…”

Section: Discussionsupporting

confidence: 77%

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State ²H NMR Spectroscopy

et al. 2008

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Sphingomyelin is a lipid that is abundant in the nervous systems of mammals, where it is associated with putative microdomains in cellular membranes and undergoes alterations due to aging or neurodegeneration. We investigated the effect of varying the concentration of cholesterol in binary and ternary mixtures with N-palmitoylsphingomyelin (PSM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) using deuterium nuclear magnetic resonance ( 2 H NMR) spectroscopy in both macroscopically aligned and unoriented multilamellar dispersions. In our experiments, we used PSM and POPC perdeuterated on the N-acyl and sn-1 acyl chains, respectively. By measuring solidstate 2 H NMR spectra of the two lipids separately in mixtures with the same compositions as a function of cholesterol mole fraction and temperature, we obtained clear evidence for the coexistence of two liquid-crystalline domains in distinct regions of the phase diagram. According to our analysis of the first moments M 1 and the observed 2 H NMR spectra, one of the domains appears to be a liquidordered phase. We applied a mean-torque potential model as an additional tool to calculate the average hydrocarbon thickness, the area per lipid, and structural parameters such as chain extension and thermal expansion coefficient in order to further define the two coexisting phases. Our data imply that phase separation takes place in raftlike ternary PSM/POPC/cholesterol mixtures over a broad temperature range but vanishes at cholesterol concentrations equal to or greater than a mole fraction of 0.33. Cholesterol interacts preferentially with sphingomyelin only at smaller mole fractions, above which a homogeneous liquid-ordered phase is present. The reasons for these phase separation phenomena seem to be differences in the effects of cholesterol on the configurational order of the palmitoyl chains in PSM-d 31 and POPC-d 31 and a difference in the affinity of cholesterol for sphingomyelin observed at low temperatures. Hydrophobic matching explains the occurrence of raftlike domains in cellular membranes at intermediate cholesterol concentrations but not saturating amounts of cholesterol.

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Section: Discussionsupporting

confidence: 77%

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State ²H NMR Spectroscopy

et al. 2008

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“…This result is consistent with a number of studies, concluding that the structural details of SM may play an important role in membrane spatial organization. An NMR study of ternary mixtures consisting of a natural SM with DOPC and Chol found a broader compositional range of liquid phase coexistence for eSM than for bSM, and no liquid coexistence for milk-SM [66]. Farkas has reported significantly higher chain order in GUVs comprising SSM mixtures, compared to bSM mixtures [67].…”

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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“…4) D surface Х 2 ϫ 10 Ϫ7 cm 2 ⅐s Ϫ1 . It should be pointed out that the diffusion coefficient of lipid molecules within a pure lipid bilayer typically is smaller (31). Therefore, the exchange of protons can be expected to occur via collisions of fluorescein with DOPA only to a minor extent.…”

Section: Resultsmentioning

confidence: 99%

Localized proton microcircuits at the biological membrane–water interface

Brändén

Sandén

Brzezinski

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

137

136

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Cellular processes such as nerve conduction, energy metabolism, and import of nutrients into cells all depend on transport of ions across biological membranes through specialized membranespanning proteins. Understanding these processes at a molecular level requires mechanistic insights into the interaction between these proteins and the membrane itself. To explore the role of the membrane in ion translocation we used an approach based on fluorescence correlation spectroscopy. Specifically, we investigated exchange of protons between the water phase and the membrane surface, as well as diffusion of protons along membrane surfaces, at a single-molecule level. We show that the lipid head groups collectively act as a proton-collecting antenna, dramatically accelerating proton uptake from water to a membraneanchored proton acceptor. Furthermore, the results show that proton transfer along the surface can be significantly faster than that between the lipid head groups and the surrounding water phase. Thus, ion translocation across membranes and between the different membrane protein components is a complex interplay between the proteins and the membrane itself, where the membrane acts as a proton-conducting link between membranespanning proton transporters.diffusion ͉ fluorescence ͉ membrane protein ͉ pH ͉ proton transfer E nergy metabolism in living organisms involves translocation of protons across biological membranes through specific membrane-spanning proton transporters, thereby generating a proton-motive force (⌬p)where ⌬ is the electrical potential, R is the gas constant (J⅐K Ϫ1 ⅐mol Ϫ1 ), T is the absolute temperature (K), F is the Faraday constant (C mol Ϫ1 ), and ⌬pH is the pH difference between the two bulk solutions on either side of the membrane. The proton-motive force is used, e.g., by ATP synthase to produce ATP. It originally was proposed that ⌬p only depends on the solution properties and that the membrane only acts as a passive barrier isolating the two compartments (1). Over the years, evidence has accumulated indicating that the scenario is more complicated and also that the membrane surface and the water layer near the surface play major roles in the process (for a recent review, see ref.2). One important finding in this respect is the alkaliphilic bacteria, which live in environments having 2-3 units higher pH than that of the bacterial cytosol. Assuming a passive role of the membrane, these bacteria would in principle not be able to maintain a ⌬p large enough to account for their ATP production (3). To resolve this apparent paradox, the idea of a localized proton circuit along the membrane surface, originally proposed by Williams (4), has been exploited (2, 5-7) (see also ref. 8 for a theoretical analysis as well as refs. 9 and 10). According to this idea, protons ejected by a membrane-spanning proton transporter are transferred along the membrane to the proton acceptor (e.g., ATP synthase) faster than they are released to the bulk solution. Most likely, this process is facilitated by surface-b...

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Lipid lateral diffusion in bilayers with phosphatidylcholine, sphingomyelin and cholesterol

Cited by 105 publications

References 41 publications

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State ²H NMR Spectroscopy

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State ²H NMR Spectroscopy

Phase behavior and domain size in sphingomyelin-containing lipid bilayers

Localized proton microcircuits at the biological membrane–water interface

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Lipid lateral diffusion in bilayers with phosphatidylcholine, sphingomyelin and cholesterol

Cited by 105 publications

References 41 publications

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State 2H NMR Spectroscopy

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State 2H NMR Spectroscopy

Phase behavior and domain size in sphingomyelin-containing lipid bilayers

Localized proton microcircuits at the biological membrane–water interface

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Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State ²H NMR Spectroscopy

Raftlike Mixtures of Sphingomyelin and Cholesterol Investigated by Solid-State ²H NMR Spectroscopy