Protein Crystallization Hits

Protein Crystallization Drops: Stirred or shaken?

When you pipett your crystallization experiment, do you mix the drop? I've heard crystallizers discuss best pipetting practices ad nauseum. There's the "Always mix!" fraction on one end of the spectrum and the "let the drops just kiss" advocates on the other. Turns out that the protein/precipitant mixing regime is indeed complicated and a lot depends on it. In a timely methods paper in Cryst.Growth Des. Howard et al. describe that mixing patterns are governed by density flow, Rayleigh-Taylor instability, diffusion and fingering/layering - all of which become irrelevant to the crystallizer in the lab who takes to heart this practical tip: mix for high-reproducibility crystallization and don't mix when trying to explore crystallization space . Of course I'm a huge fan of the somewhat lazier no-mix method and enjoy the 'free ride' by letting drops do what they like.
However, my lesson learned: keep the mixing regime constant for optimization and production drops.
How do you like your crystallization drops now - stirred or just shaken a little bit?

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