The Role of Oil in Protein Crystallization - Molecules: Nucleation, Aggregation and Crystallization - page 131

many of which were not suitable due to their interaction with the crys-
tallization trials (e.g. causing precipitation of proteins). The IMPAX
software facilitates rapid design and execution of experiments. (Chayen
et al ., 1990, 1992, 1994). Delivery from a fine tip under oil cleanly
removes the delivered volume as the tip is drawn out from the oil, and
eliminates “carry-over.”
The mechanism of crystallization under oil
Figure 1 illustrates the mechanism of dispensing a crystallization trial under
oil. A crystallization drop (which contains the macromolecule to be crystal-
lized and the crystallizing agents) is dispensed either manually or automat-
ically, into a container, under the surface of a thick layer of oil. As the
dispensing tip is withdrawn from the oil, the drop detaches from it and the
tip is wiped clean by the oil, thereby preventing any carry-over from one
trial to another. The aqueous drop sinks to the bottom of the vessel since it
Fig. 1. The mechanism of dispensing a crystallization trial under oil. A crystallization
drop (which contains the macromolecule to be crystallized and the crystallizing agents)
is dispensed into a container, under the surface of a layer of oil. As the pipette tip is with-
drawn from the oil, the aqueous drop detaches from it and sinks to the bottom of the
vessel.