In meso Approaches to Membrane Protein Crystallization - Molecules: Nucleation, Aggregation and Crystallization - page 269

exhibits no long-range order. The transformation of the cubic to the
sponge phase may occur when some small additional molecules like those
of a polar solvent such as dymethyl sulfoxide, propylene glycol, or poly-
ethylene glycol (MW 400) are added (Engstroem et al ., 1998). A major

reason for such transformation is the reduced bending rigidity of the
membranes. A schematic representation of the L 3 phase is shown in Fig. 5.
It is interesting to note that as in the case of the cubic phase there have
been a number of studies exploring possible applications of the sponge
phase for studying intracellular membranes like the endoplasmic reticulum
(Lindblom et al ., 1988), the Golgi apparatus or as drug transport vesicles
(Alfons et al ., 1998).
There are two reports in the literature on the crystallization of mem-
brane proteins in the sponge phase (Cherezov et al ., 2006; Wadsten et al .,
2006). In one of the papers the appearance of the sponge phase was
proven by “visual inspection, small-angle X-ray scattering and NMR

≈

Fig. 5. A schematic representation of the sponge L 3 phase [modified from McGrath et al .

(1997)].