The PCT Pre-Crystallization Test is used to determine the appropriate protein concentration for crystallization screening. Sample concentration is a significant crystallization variable. Samples too concentrated can result in amorphous precipitate, while samples too dilute can result in clear drops. Precipitate and clear drops are typical crystallization screen results for reagent conditions which do not promote crystallization and are part of every crystallization screen. However, by optimizing protein concentration for the screen, the number of clear and precipitate results can often be reduced, which in turn results in more efficient sample utilization while at the same time enhancing the chances for crystallization. PCT can minimize or prevent situations where a screen results in an over abundance of precipitate or clear drops.
The PCT kit contains 4 unique, preformulated, sterile filtered reagents used to evaluate protein concentration for crystallization screening. Initially, the sample protein is mixed with two of the reagents to determine if the protein concentration is appropriate for crystallization screening. If the protein is very sensitive to salt and polymer concentration, based on initial PCT results, the protein may be evaluated using a second set of PCT reagents. PCT results will then provide insight to either the appropriate sample concentration or indicate that other diagnostic testing such as native gel electrophoresis or dynamic light scattering should be performed to demonstrate sample homogeneity appropriate for crystallization.
PCT Kit comparison table.
|24 Well Plate
|HR2-140||✓ (50 mL each)||✓ (22 mm Square)|
|HR2-141||✓ (10 mL each)|
|HR2-142||✓ (30 mL each)||✓ (22 mm Square)||✓ (5x VDX)|
|HR2-143||✓ (10 mL each)||✓ (18 mm Circle)||✓ (4x VDXm)|
30 ml bottles (4 ea), cover slides (1 pk), VDX Plates with sealant (5 ea)
10 ml tubes (4 ea), cover slides (1 pk), VDXm Plates with sealant (4 ea)
1. Crystallization and x-ray diffraction analysis of human CLEC-2. Aleksandra A. Watson and Christopher A. O’Callaghan. Acta Cryst. (2005). F61, 1094-1096.