Unsaturated lipids, effects biomembranes

From the modelling results for bilayers composed of unsaturated lipids one can begin to speculate about the various roles unsaturated lipids play in biomembranes. One very well-known effect is that unsaturated bonds suppress the gel-to-liquid phase transition temperature. Unsaturated lipids also modulate the lateral mobility of molecules in the membrane matrix. The results discussed above suggest that in biomembranes the average interpenetration depth of lipid tails into opposite monolayers can be tuned by using unsaturated lipids. Rabinovich and co-workers have shown that the end-to-end distance of multiple unsaturated acyl chains was significantly less sensitive to the temperature than that of saturated acyls. They suggested from this that unsaturated... 

The effect of double bonds on both transfection and phase behavior is well illustrated by the pair C18 1/C10-EPC and C18 0/C10-EPC. These two lipids differ by one double bond only. However, the unsaturated lipid is over ten times more efficient as transfection agent than the saturated one [112]. The superior efficiency of C18 1/C10-EPC relative to C18 0/C10-EPC is also implied by the phases that evolve in membrane lipid formulations upon mixing with these two cationic lipids. A biomembrane-mimicking lipid formulation DOPC/DOPE/DOPS/Chol 45 20 20 15 remained lamellar in mixtures with C18 0/C10-EPC in contrast, the more efficient C18 1/C10-EPC induced a lamellar-nonlamellar phase conversion in this mixture, which was taking place at physiological temperature (Fig. 27). 

C. butyricum appears to regulate the stability of the bilayer arrangement of membranes by altering the ratio of ether versus acyl ethanolamine phospholipids in response to changes in the degree of lipid unsaturation of the membranes. Experiments with bacteria indicate that substitution of plasmenylethanolamine for phosphatidylethanolamine in biomembranes would have only small effects on lipid melting transitions, whereas the tendency to form non-lamellar lipid structures would be significantly increased. 

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