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#lipid movement

3 public questions tagged with this topic.

Properties of Plasma Membrane

Which lipid movement occurs the fastest in a membrane?

Biological membranes support diverse motions separated by orders of magnitude based on activation energy required to traverse hydrocarbon core. Lateral diffusion within same leaflet requires only breaking weak van der Waals contacts and creating small free volume achieving diffusion coefficient about ten to minus eight centimeters squared per second meaning lipid circumnavigates Escherichia coli in microseconds and mammalian cell in seconds. Axial rotation and wobbling of acyl chains are even faster nanoseconds observed by ESR. In contrast flip flop forcing zwitterionic or anionic headgroup th

Ref: Alberts et al., MBOC 7th ed., Chapter 10: Rates of lipid movement lateral vs transverse.

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Properties of Plasma Membrane

Which experimental technique is used to study lipid movement in membranes?

Experimental investigation of lipid dynamics in plasma membranes of living cells requires fluorescence techniques capable of micrometer spatial resolution and millisecond temporal. FRAP fluorescence recovery after photobleaching involves incorporating fluorescent lipid analogs NBD-phosphatidylethanolamine BODIPY-phosphatidylcholine DiI dialkylcarbocyanine into bilayer at low mole fraction, or fluorescent protein fusions GFP-tagged for proteins. Focused laser beam bleaches circular spot one to four micrometer diameter irreversible photodestruction, subsequent recovery of fluorescence intensity

Ref: Axelrod et al., Fluorescence Recovery After Photobleaching FRAP Method, Biophys J 1976.

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Properties of Plasma Membrane

Which type of lipid motion requires enzymatic activity?

Lipid mobility modes illustrate fluid dynamics of membranes. Four motions described: lateral diffusion random walk within leaflet plane diffusion coefficient ten to minus eight centimeters squared per second for phospholipids measured by FRAP single particle tracking; rotational diffusion around long axis nanosecond timescale; trans-gauche isomerization flexing of acyl tails picosecond; transverse flip-flop movement of entire lipid from one leaflet to opposite requiring polar headgroup passage through hydrocarbon interior large activation barrier twenty to fifty kilocalories per mol depending

Ref: Kol et al., Flip-Flop and Enzymatic Lipid Transport, Nature Reviews Mol Cell Biol 2004.

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