by Peter Nollert
May 4, 2010 19:10
There's a lot of lab folklore going around in protein crystallization labs. These are stories such as: "the only thing that every worked for my protein XY is this odd trick" followed by a description of an exotic crystallization trick. Understood, often it is difficult to reconcile what exactly is going on in a particular crystallization experiment. Sometimes, however there's evidence that seemingly weird crystallization tricks do work - check out this example, where seaweed made the difference. As much as we like to get experimentally tested evidence, in general this rule should hold: 'who crystallizes is right'.
Along these lines, Ivana Tomcova and Ivana Smatanova have come across an interesting case of crystallization dependence that they call 'cross-crystallization'. In their paper
CROSS-CRYSTALLIZATION AS A NEW OPTIMIZATION TOOL OF CRYSTALLIZATION PROCEDURES
Materials Structure, vol. 14, no. 1 (2007)
they describe the crystallization of cytochrome c4 from anaerobic purple sulphur bacterium Thiocapsa roseopersicina. They used the Emerald BioSystems CombiClover Crystallization plate
(thank you very much!) in a special way: all crystallization chambers were filled with a different additive (chloride salts of copper, cadmium, cobalt and barium) and protein was only added to the cupric chloride containing chamber. They optimized this recipe (5 mM CuCl2, ammonium sulfate, citric acid buffer pH5) to a point where the neighboring crystallization chambers were required to contain metal salts (CdCl2, BaCl2, CoCl2), otherwise crystals would not show up.
Fig: Clover Crystallization Plates
There's not much to say other than: apparently it works.
Cheers,
Peter