MB vs VD

Microbatch and vapor diffusion methods both have their advantages and

disadvantages. While microbatch is faster and more "precise", each droplet

in the vapor diffusion experiment passes through a whole range of

reagent/protein/etc concentrations. In essence, it would appear that

traditional microbatch scans a point of the phase diagram, whereas vapor

diffusion scans through a vector. Both methods are useful, and I usually

start with vapor diffusion or microdialysis methods and then continue

with microbatch if necessary.

Artem Evdokimov, Weizmann Institute, Israel

Patrick's Comment:

The scanning effect with VD is not always as significant as is generally believed. For example, Luft and DeTitta found (Acta Crystallogr [D] 1995, 51: 1099-1102) that a droplet containing PEG8000 took 12 weeks to reach equilibrium. Even when 0.4 M NaCl was added, this was only reduced to 10 days. Crystallization would normally have taken place before this. In other words VD may often sample a point rather than a line in the phase diagram in practice.