Biology Reference
In-Depth Information
A. COMPLEX LIPID INTERACTIONS
Lipid Affinities
A basic hallmark of all biological membranes is their extreme heterogeneity. This topic will
come up over and over again in discussions of lipid
protein interactions.
Since a single biological membrane is composed of hundreds or even thousands of different
lipid molecular species, it is logical to assume that they will exhibit different affinities for one
another. Each lipid may prefer to be in the company of one type of lipid while avoiding that
of another type. One well studied example of this is the lipid raft. Lipid rafts (discussed in
Chapter 8) are enriched in sphingolipids and cholesterol, the components responsible for
the raft's basic physical properties. In fact, cholesterol is believed to be the molecular
'glue' that holds rafts together. Rafts are destroyed upon the addition of cyclodextrin,
(
Figure 10.1
) a family of cyclic glucose oligosaccharides that are often used to extract choles-
terol from membranes
[1]
.
Through the years cholesterol has probably received more attention than any other
membrane lipid. Cholesterol was first identified in 1769 as a solid in gallstones by Fran¸ois
Poulletier de la Salle. However, the man most associated with early cholesterol studies was
the French chemist Eugene Chevreul (
Figure 10.2
). Chevreul was an early pioneer on lipid
lipid and lipid
e
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FIGURE 10.1
a
-Cyclodextrin. Courtesy of RDI Division of Fitzgerald Industries Intl
