Stability and liquid-liquid phase separation in mixed saturated lipid bilayers.
The phase stability of a fluid lipid bilayer composed of a mixture of DC(18)PC, (DSPC), and a shorter DCn(s) PC, with n(s) from 8 to 17, has been studied using a self-consistent field theory that explicitly includes molecular details and configurational properties of the lipid molecules. Phase separation between two liquid phases was found when there was a sufficient mismatch between the hydrophobic thicknesses of the two bilayers composed entirely of one component or the other. This occurs when n(s) <or = 12 and there is a sufficient concentration of the shorter lipid. The mixture separates into a thin bilayer depleted of DSPC and a thick bilayer enriched in DSPC. Even when there is no phase separation, as in the cases when there is either insufficient concentration of a sufficiently short lipid or any concentration of a lipid with n(s) > 12, we observe that the effect of the shorter lipid is to increase the susceptibility of the system to fluctuations in the concentration. This is of interest, given that a common motif for the anchoring of proteins to the plasma membrane is via a myristoyl chain, that is, one with 14 carbons.
Longo
Gabriel S
GS
International School for Advanced Studies, Trieste, Italy.
Schick
M
M
Szleifer
I
I
D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry*; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry / Q000302:isolation & purification; D013500:Surface Tension; D013696:Temperature
D008051:Lipid Bilayers; D010713:Phosphatidylcholines