Frequently Asked Questions
How does the Crystal Former minimize evaporation?
When the first liquid is added to the Crystal Former, the drop fills the narrow channel with approximately 150 - 200 nL of solution. Usually, this is the protein solution since its viscosity is lower than the precipitant solution. Adding the second liquid automatically makes the good liquid to liquid interface for diffusion. The chip will be sealed with a cover strip to seal the well openings. This seal is usually good enough to prevent evaporation, but humidity is recommended for high temperature (room or higher)
If the experiment goes longer 1 – 2 weeks, there will be less evaporative losses than are seen in the vapor diffusion techniques.
Crystal Former design?
Minimum volume of both protein and precipitant to fill the channel is approximately 150 – 200 nL. Some robots are capable of dispensing this volume. At 400 – 500 nL, most robots and people are able to fill the wells without much training. We don’t need to be precise with the volumes since it is a gradient condition; NOT static as in hanging, sitting and under oil experiments.
Limitations of Screens?
In general, our customers have used all the standard commercially available crystallization screens, including the viscous conditions, for screening. If we use these screens with the Crystal Former, and compare to standard vapor diffusion techniques, we obtain substantially improved output; more crystals of good diffraction quality.
However, once a crystallization condition has been identified in the Crystal Former there is no need to transfer the condition to vapor diffusion as the crystals can be harvested directly from the device. We have collected full data for multiple different proteins from single crystals obtained in the initial screening.
Many of the commercially available dispensers have volume or viscosity limitations. In general, we are able to produce crystals with as little as 200nL of protein (more, up to 500nL, is better). The viscous precipitant conditions for manual pipetting could be higher than the robots since you would have some control over the aspiration / dispense rate of the solution. We only need 1 uL or less; enough to fill the well and make liquid contact with the protein.