Protein Crystallization Hits

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

There are so many parameters to change when optimizing crystallizations and they all need to be tried out to identify the critical parameter that improves X-ray diffraction. In this series of blog posts I've mostly discussed modulating the crystallization reaction, by adding additives, changing precipitant or protein concentration etc. However, there seems to be a simple way to optimize, keeping all other parameters constant: drop volume, temperature, all concentrations. What could it be?

Try switching the crystallization plate!

Jenny Martin describes in her recent PLOS paper with statistical rigour that different 96-well crystallization plates - formats, materials - do effect the outcome of protein crystallization experiments:

King, Gordon J., Kai-En Chen, Gautier Robin, Jade K. Forwood, Begoña Heras, Anil S. Thakur, Bostjan Kobe, Simon P. Blomberg, and Jennifer L. Martin.
Interaction between Plate Make and Protein in Protein Crystallisation Screening.
PLoS ONE 4, no. 11 (November 16, 2009): e7851

In fact, she suggests to optimize protein crystal growth by matching the protein with its optimal plate make. 

Figure: Compare different protein crystallization plates to grow optimized protein crystals.

So, here's a selection of 6 different Emerald BioSystems protein crystallization plates with different formats, well arrangements, volumes and materials that you may want to try to optimize protein crystal growth:

Clover 384 plate (COC material, 4 micro crystallization wells / reservoir)
Clover 384 plate (Polystyrene, 4 micro crystallization wells / reservoir)
Compact Clover plate (Polypropylene, 4 crystallization wells / reservoir)
Compact, Jr. plate (Polypropylene, 1 crystallization well / reservoir)
Combi Clover plate (Polypropylene, large wells, 4 crystallizations well / reservoir)
Combi Clover Jr. plate (Polypropylene, large wells, 1 crystallization well / reservoir)

Sometimes it's time to change the game.

Peter