The Role of Oil in Protein Crystallization - Molecules: Nucleation, Aggregation and Crystallization - page 136

Fig. 3. Application of oil to improve vapour diffusion experiments: (a) set-up of a hang-
ing drop experiment containing an oil barrier, (b) thaumatin crystals grown overnight in a
standard hanging drop, and (c) thaumatin crystals grown over eight days under the same
conditions as in (b), the only difference being the presence of 500 microlitres of oil (equal
volumes of paraffin and silicone) over the reservoir. Scale: 1.5 cm = 0.25 mm.
Cleanliness of trials
Control of nucleation requires extremely clean solutions. In microbatch
where the drops are maintained under oil the samples are never exposed to
air and are therefore protected from airborne contamination. The combina-
tion of filtration methods, which allow the removal of particles as small as
100 nm from small volumes with dispensing and incubating of trials under
oil, provides an ideal environment for controlled heterogeneous nucle-
ation experiments (Blow et al ., 1994; Chayen, 1996; Chayen et al ., 1993).