Crystallization of Proteins: Principles and Methods - Molecules: Nucleation, Aggregation and Crystallization - page 124

Bulk dialysis
This procedure is carried out in a large dialyzing bag. Although this method
is very convenient for successive re-crystallization, the major drawback is
that large volumes of the sample are required (Ducruix, Giege, 1999).
Microdialysis
The microdialysis method is an adaptation working on the same principle
of bulk dialysis but was designed to use very small sample volumes thus
overcoming the drawback of the earlier method (Fig. 8). Microdialysis
with Zeppezauer cells are capillary tubes closed with dialysis tubes or
polyacrylamide gel plugs. Microdialysis is carried out using commercially
available dialysis buttons (Fig. 9). The buttons come in varying sizes and
are provided with a chamber in which the sample to be crystallized is
placed. A dialysis membrane with an appropriate molecular weight cut off
is placed over the top of the button and held by an O-ring. The button
Fig. 8. Dialysis cell for protein crystallization. In the microdialysis method, the sample
is separated from the “precipitant” by a semi-permeable membrane which allows small
reagent molecules to pass but prevents biological macromolecules from crossing.