Protein Sample Requirements for Crystallization Trials

  • Pure as assessed by SDS-PAGE.
  • Homogeneous, i.e., devoid of truncated proteins, isomorphs, or incorrectly folded molecules. Evaluation utilizes size exclusion chromatography (SEC), Circular Dichroism spectroscopy (CD), Mass Spectrometry (MS), or Dynamic Light Scattering (DLS).
  • A reproducible source of several milligrams of the pure protein.
  • The protein should be at an optimal concentration, in the range of 10-40mg/ml, as determined in a precrystallization trial by the crystallization unit. The salt concentration should be as low as possible, the buffer concentration should be 20-50mM, at a pH close to neutral, and potassium should be avoided if possible.
  • For each of 96 crystallization conditions (one plate regardless of the crystallization method used) 25μl of protein is needed. 150μl of protein is needed for initial screening.