Screens in C3

Protein crystallisation kits (screens) are a collection of crystallisation conditions which are used together. Each condition usually consists of 2-5 chemicals, at different concentrations and pHs. This mixture of chemicals may be called a number of things, including:

  • a crystallisation condition
  • a crystallisation cocktail
  • a reservoir solution
  • a crystallant solution

Keeping it simple

We can’t predict which crystallant will crystallise any given protein, so we trial lots of them at the same time. But how many? A quick back of the envelope calculation shows there are trillions of possible chemical combinations! We’ve narrowed our selection to a few dozen screens, with a rational for screen availability being based on diversity, turnover and popularity. Old screens are chemically unreliable, so if we notice a screen is used once every 6 months we will think about removing it from our inventory. Sometime we will force change (for the better).

All of the screens used in C3 are made in C3 and contain 96 conditions

There are many commercial vendors of crystallisation products – crystallisation screens can be purchased from Hampton Research, Molecular DimensionsRigakuReagentsJena Biosciences and Qiagen amongst others. In C3 we make our own versions of the commercially available screens (we do not sell these). The reason for doing this was to create a chemically accurate transition to optimisation: The stocks used in our optimisation blocks are the same as the stocks used to create the initial screens. Other advantages include the ability to have standard naming of chemicals across all of our screens and the ability to better manage turnover and availability of the screens. We deal with legacy screens (older 24 well designs such as The Grid Screen MPD, from Hampton Research) by combining them with other limited designs to make up 96 conditions.

Screens which are created in house will have the term ‘C3’ in the name

Thus ‘JCSG+_C3’ is the JCSG+ screen, made in C3. All of our screens are made up with MilliQ water, with 0.02% sodium azide added.  This limits the microbial growth seen in crystallisation trials. If for some reason you need an azide free screen, we keep on block of each of our screens with no added azide. These screens are kept frozen, and need to be specially requested. We also have a selection of “under the counter” screens (many of the outmoded commercial screens), talk to us if the screen you desire is not readily available.

Screens readily available for use in C3 are listed in the available screens report using C6

Screen Sets

It can often be useful to set up more than one screen at the same time and we have clustered some of our screens into screen sets, for example in 1-Click Screening we use Shotgun, PACT and PS-Gradient. More screen sets used in C3 and the screens that make up the screen sets can be found on the C6 webtool – select the report “Screens group list” then the option “A Design Set”.

NEXT: Shotgun