Rational Protein Crystallization Optimization Schema
Posted by Peter Nollert on Tue, Jun 23, 2009 @ 10:57 AM
What's a good systematic way to vary all components of a crystallization hit in a single 96-well crystallization tray? For a typical 3 component formulation, Paul Reichert a crystallographer at Schering-Plough, has worked out a remarkably useful schema. Here's what he came up with:
At first divide the 96 well tray into 4 quadrants, with 24 wells in each quadrant:
Reichert systematic optimization quadrant schema for optimizing protein crystallization. Starting point is a single, 3 component hit.
The image above tells much of the story: In quadrant II (beige) the pH and salt concentration are varied systematically in a gradient-like fashion while the precipitation concentration is kept constant. In quadrant III (green) the precipitation and salt concentration is varied while the pH is kept at its original pH and, in quadrant IV (orange) the precipitation concentration and pH are varied while the salt concentration is kept constant. What about quadrant I? Here only the precipitation concentration is changed, keeping pH and salt constant. These are not conditions to be tested in triplicates but allow to assay three different protein concentrations.
Applying this scheme to single crystallization hits provides a lot of meaningful data because it isolates 4 different crystallization factors: (i) pH, (ii) protein, (iii) salt and (iv) precipitant concentration. While not perfect, this is an efficient schema that has often resulted in greatly improved crystal quality.
Since this has worked so well, Emerald provides this type of customized optimization screen as "Reichert Optimization Screen". This is one of several optimization screen services we offer. Just tell us about your hit condition and we'll design, prepare and send you the screen.
Enjoy your crystals,
Peter
P.S. We have recently incorporated this optimization schema into Escreen Builder, a free online tool to calculate an optimization screen using this tool.
