Detection and Measurement of Unlabeled Lipid Transmembrane Movement

López‐Montero, Iván; Vélez, Marisela; Devaux, Philippe F.

doi:10.1002/9781118120118.ch2

Cited by 1 publication

(1 citation statement)

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“…Several methods have been developed to track the movement of spin-labeled and fluorescently labeled lipids in vesicles and planar supported lipid bilayers. , Kinetic rates for labeled lipid flip-flop were measured to be on the order of hours or days using these techniques. Techniques that do not require lipid probes, such as SFVS, atomic force microscopy (AFM), and small-angle neutron scattering (SANS), have also been used to measure lipid translocation. − These label-free techniques have reported values for lipid flip-flop on the order of minutes to hours. Measuring the rate of native (or unlabeled) lipid flip-flop is essential in developing an understanding of the complex molecular interactions between components of the plasma membrane like phospholipids and sterols.…”

Section: Introductionmentioning

confidence: 99%

Structural Origins of Cholesterol Accelerated Lipid Flip-Flop Studied by Sum-Frequency Vibrational Spectroscopy

2016

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The unique structure of cholesterol and its role in modulating lipid translocation (flip-flop) were examined using sum-frequency vibrational spectroscopy (SFVS). Two structural analogues of cholesterol--cholestanol and cholestene--were examined to explore the influence of ring rigidity and amphiphilicity on controlling distearoylphosphocholine (DSPC) flip-flop. Kinetic rates for DSPC flip-flop were determined as a function of sterol concentration and temperature. All three sterols increased the rate of DSPC flip-flop in a concentration-dependent manner following the order cholestene > cholestanol > cholesterol. Rates of DSPC flip-flop were used to calculate the thermodynamic activation free energy barrier (ΔG(‡)) in the presence of cholesterol, cholestanol, and cholestene. The acyl chain gauche content of DSPC, mean lipid area, and membrane compressibility were correlated to observed trends in ΔG(‡). ΔG(‡) for DSPC flip-flop showed a strong positive correlation with the molar compression modulus (K*) of the membrane, influenced by the type and concentration of the sterol added. Interestingly, cholesterol is distinctive in maintaining invariant membrane compressibility over the range of 2-10 mol %. The results in this study demonstrate that the compression modulus of a membrane plays a significant role in moderating ΔG(‡) and the kinetics of native, protein-free, lipid translocation in membranes.

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