For many reasons, Crystal Former users may wish to follow-up on a condition identified in the Crystal Former by translating that condition into sitting drop or hanging drop formats for vapor diffusion. For most proteins, this is a fairly straight-forward goal to achieve.
An important consideration
Many users ask if the position of crystals along the channel indicates the starting concentration of precipitant for the translation of conditions to vapor diffusion. The short answer is that it does not. Why is this so? The mixing kinetics of vapor diffusion and the Crystal Former are significantly different, thus variations of the individual components of a crystallization condition through grid screening is essential. As a rule of thumb, most of our users report using higher concentrations of precipitant in vapor diffusion than were necessary in the Crystal Former.
The first step to translation
Consider the listed crystallization condition as the starting point for translation (and optimization). Vary the components against one another, as you would for a standard grid screen in vapor diffusion, being sure to consider concentrations of components that are both higher and lower than the starting condition.
Crystallization of SA0802 from S. aureus using the Crystal Former.
Crystallization screening with the Crystal Former identified two new crystallization conditions for SA0802:
(A) Smart Screen H6 (10% PEG 8000, 0.1 M HEPES pH 7.5, 8% ethylene glycol)
(B) SmartScreen G1 (20% PEG 8000, 0.1 M CHES pH 9.5).
The SmartScreen H6 condition was then translated to three crystallization variants in hanging drop:
(C) 8% PEG 8000, 0.1 M Tris-Cl pH 7.0, 8% ethylene glycol;
(D) 8% PEG 8000, 0.1 M sodium cacodylate pH 7.0, 8% ethylene glycol;
(E) 8% PEG 8000, 0.1 M MES pH 7.0, 8% ethylene glycol.
(F) The SmartScreen G1 condition was translated to 18% PEG 8000, 0.05M CAPSO pH 9.6 in hanging drop vapor diffusion.