by Peter Nollert
July 11, 2009 02:47
The optimization of a single protein crystallization hit is conceptually simple: start with the reagent cocktail in hand and vary one component after another, leaving the other component concentrations constant. With the typical 3 chemical reagents in a single formulation and protein concentration as a variable you're already dealing with a 4 dimensional optimization problem. The 'Reichert optimization' schema does a good job to do this systematically on a single 96 well crystallization tray.
But what can you do when you've got two different crystallization hits?
Well, a simple thing to do is preparing a set of mixtures of the cocktails that yielded the crystallization hits and use them as well solutions. How would that work? Say, you'd get crystals with cocktail A and also with cocktail B. In a single row one would fill in well A1 cocktail A only and in well A11 only cocktail B only. The wells in between would contain mixtures of A and B: 90%A+10%B, 80%A+20%B etc.
Then of course you'd reproduce your hit in A1 and A11 and check what happens in between.
I think Enrico Stura came up with this simple schema in the 90s and this is somewhat related to his 'reverse screening' approach.
Thanks Enrico!
Peter