Erythrocytes phospholipid mobility

There is also inside-outside (transverse) asymmetry of the phospholipids. The choline-containing phospholipids (phosphatidylcholine and sphingomyelin) are located mainly in the outer molecular layer the aminophospholipids (phosphatidylserine and phos-phatidylethanolamine) are preferentially located in the inner leaflet. Obviously, if this asymmetry is to exist at all, there must be limited transverse mobility (flip-flop) of the membrane phospholipids. In fact, phospholipids in synthetic bilayers exhibit an extraordinarily slow rate of flip-flop the half-life of the asymmetry can be measured in several weeks. However, when certain membrane proteins such as the erythrocyte protein gly-cophorin are inserted artificially into synthetic bilayers, the frequency of phospholipid flip-flop may increase as much as 100-fold. 

Beaumelle, B. D., Vial, H. J., and Bienvenue, A. (1988). Enhanced transbilayer mobility of phospholipids in malaria-infected monkey erythrocytes A spin-label study. J. Cell Physiol. 135, 94-100. 

An example is given for the composition of the liver cell membrane [2], There is also a considerable difference in the proportion of phospholipids in different cell types and different species. Figure 11-1 shows the variation of sphingomyelin (S) lo phosphatidylcholine (PC) content in the total lipid fraction of erythrocytes from various species and of ox endoplasmic reticulum in various organs [2], The lateral mobility of lipids in membranes is another essential aspect [7],... 

Phospholipids were extracted from erythrocyte membranes and were analyzed along with their lipoxygenase peroxide products using a 40°C aminopropyl column. Phospholipids (phosphatidylcholine [PC], phosphatidylethanolamine [PE], phospha-tidylinositol, phosphatidylserine [PS], and sphingomyelin) were separated using a 67/22/11 acetonitrile/methanol/water (0.2% TFA) mobile phase (A = 2I0nm). Elution was complete in 30 min and excellent resolution was achieved. The peroxide forms of PC, PE, and PS were separated at the same time but monitored at k — 234 nm. All samples were stabilized with 20mg/L BHT solutions [1185]. 

Dressier V, Schwister K, Haest CWM, Deuticke B (1983) Dielectric breakdown of the erythrocyte membrane enhances transbilayer mobility of phospholipids. Bierehim Biophys Aeda 732 304—307... 

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