In meso Approaches to Membrane Protein Crystallization - Molecules: Nucleation, Aggregation and Crystallization - page 276

numerous failed attempts to crystallize a ligand-binding GPCR, one has
to accept that this represents a considerable success of the method
under discussion.
Towards a General Method of Membrane
Protein Crystallization
New approaches to crystallization from lipid bilayers (or rather, from
membranes) have led to a breakthrough in the field of structural biology
of membrane proteins. Major progress has been due to the application of
the lipidic cubic phase approach. Nevertheless, there is evidence that
three other methods described in this chapter may have a more general
application.
Unfortunately, the number of membrane proteins of known structure
is still growing slowly and crystallization of membrane proteins remains
a challenge. One of the major problems is that there have been no
systematic experimental and theoretical studies of all crystallization
events in the course of membrane protein crystallization. In other words
we do not understand sufficiently well the systems that are used for crys-
tallization; we cannot answer important questions. For instance, we do not
know why all the above-mentioned in meso systems give rise to layer type
(type I) membrane protein crystals. Does this mean that there is something
important in common in all four cases?
A rational design of a crystallization experiment is not possible with-
out in-depth knowledge about the systems used. A complimentary
approach to the studies of complex fluids used for crystallization is
of great importance for the development of more general and efficient
methods of membrane protein crystallization. Physics with such power-
ful experimental methods as neutron and X-ray scattering as well as
theoretical tools may play a key role in the further development of
crystallization methods. Future success will have a high impact on our
understanding of the molecular mechanisms underlying the function of
living matter.