Biology Reference
In-Depth Information
Fig. 7. The GCB available from Hampton Research (HR3-194) and Triana Science &
Technology (GCB-A-20) consists of three parts made of polystyrene: the box body con-
sisting of a narrow box open on one side, the capillary holder that fits into the body, and
the cover lid that closes the box. The box body has been designed to be small enough for
experiment stowage and transport. It can hold up to six different crystallization experi-
ments. The box is very narrow and transparent, allowing microscopic observation of
experiments.
Dialysis
Dialysis is among the oldest, most useful and most effective techniques
for dynamically altering the degree of supersaturation of a protein solu-
tion and in accomplishing crystal growth. It is a variation of a typical
vapor diffusion method and utilizes the principle of slow diffusion by
selective permeability. This method allows for an easy variation of the dif-
ferent parameters which influence the macromolecular crystallization
process (Ducruix, Giege, 1999). The macromolecule solution to be crys-
tallized is equilibrated against a large volume of precipitant using a semi-
permeable membrane, allowing free passage of small molecules and ions
but preventing circulation of macromolecules by the small pore size of the
membrane. Equilibration against the solvent facilitates supersaturation,
eventually resulting in crystallization.
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