228 research outputs found
Phenomenological Model and Phase Behavior of Saturated and Unsaturated Lipids and Cholesterol
We present a phenomenological theory for the phase behavior of ternary
mixtures of cholesterol and saturated and unsaturated lipids, one which
describes both liquid and gel phases, and illuminates the mechanism of the
behavior. In a binary system of the lipids, the two phase separate when the
saturated chains are well ordered, as in the gel phase, simply due to packing
effects. In the liquid phase the saturated ones are not sufficiently well
ordered for separation to occur. The addition of cholesterol, however,
increases the saturated lipid order to the point that phase separation is once
again favorable. For the system above the main chain transition of the
saturated lipid, we can obtain phase diagrams in which there is liquid-liquid
phase separation in the ternary system but not in any of the binary ones, while
below that temperature we obtain the more common phase diagram in which a gel
phase, rich in saturated lipid, appears in addition to the two liquid phases.Comment: 16 pages, 2 figure
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