Clear drops

Clear drops

might seem like a negative result, but this is not necessarily the case (see point 3 below). There are three reasons why you can get clear drops.

  1. You (or the robot) didn’t add the protein.
  2. The drop is undersaturated. The protein concentration needs to be higher. Check that the protein concentration really is what you think it is. Did you measure the absorbance at 280? Check with an orthogonal method, like Bradford. You might not have anywhere near the concentration that you think you have.
  3. The drop is supersaturated, but in the metastable zone. In other words, the supersaturation level is high enough to support crystal growth, but not high enough to initiate it.

Clear drop

 

Phase diagram

showing where clear drops can appear. Coming soon.