Chemistry Reference
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Figure 10.1
Schematic illustration of different liquid crystalline phases. [Reprinted
with permission from Barauskas and Nylander (2008). Copyright 2008 by Woodhead
Publishing.]
chain length (
l
). The packing parameter for a particular environment will be
refl ected in the curvature of the lipid aqueous interface and thus the particular
phase. It is important to bear in mind that the packing parameter is not a
constant parameter but is dependent on the environment (e.g., water content,
ionic strength, pH, temperature, and pressure). In a generalized picture shown
in Figure 10.1, the liquid crystal structures mirror at the lamellar phase (L
α
),
where bilayers of lipid molecules alternate with water layers, and it corre-
sponds to a packing parameter close to unity. At lower lipid concentration, the
lipids form the oil-in-water structures: bicontinuous cubic (V
1
), hexagonal
(H
1
), cubic (I
1
), and micelles (L
1
). At higher lipid concentration, the lipid
phases reverse its curvature and form water-in-oil phases: the reversed bicon-
tinuous cubic (V
2
), reversed hexagonal (H
2
), reversed cubic (I
2
), and reversed
micelles (L
2
). The reversed bicontinuous cubic (V
2
) phase formed by curved
lipid bilayers can be further broken down into three types according to the
infi nite periodic minimal surface (IPMS) characterization of the midplane of
the lipid bilayers (Hyde, 1996; Hyde et al., 1984; Kaasgaard and Drummond,
2006): gyroid (G, Ia3d), diamond (D, Pn3m), and primitive (P, Im3m). A less
common phase, called sponge phase (L
3
), can also occur adjacent to the lamel-
lar phase. The sponge phase forms a bicontinuous disordered structure by
dividing into two unconnected volumes like the bicontinuous cubic phase.
These interesting lipid phases have the potential to be used as templates
and reservoirs. The easiest way to handle and use these structures is to make
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