The concentration of protein sample is a significant crystallization variable. High concentration sample can cause an amorphous precipitate and too dilute sample can also result in clear drops. To overcome this problem, a strategy called pre-crystallization test (PCT) is performed to select and optimize the appropriate protein concentration for crystallization screening. Besides clear drops, precipitate resulted from reagent conditions is another obstacle for crystallization screening.
Creative Biostructure’s PCT can help you to determine an appropriate protein concentration for your next crystallization screening. By optimizing the protein concentration for screen, the number of clear and precipitate results can often be reduced, which in turn results in more efficient sample utilization and enhance the chances for crystallizationat the same time.PCT can minimize or prevent the situations that a screen results in an overabundance of precipitate or clear drops.
The PCT kit includes 2 reagents (CB 1/2) which are used to evaluate protein concentration for crystallization screening. Initially, the sample protein is mixed with these two reagents to determine if the protein concentration is appropriate for crystallization screening.
The sample should not contain phosphate, borate or carbonate buffers. Typical sample concentration for crystallization should be not less than 5 mg/ml or more than 100 mg/ml but averages 15 mg/ml. PCT can assist in determining the appropriate sample concentration for crystallization screening so there is no required sample concentration for using PCT. Simply concentrate the sample to a level reasonable for crystallization (5 to 20 mg/ml).
Creative Biostructure offers various custom UniCrys™ membrane protein crystallization services. Please feel free to contact us for a detailed information.
A. A. Watson and C. A. O'Callaghan. (2005). Crystallization and X-ray diffraction analysis of human CLEC-2. Acta. Crystallogr. Sect. F. Struct. Biol. Cryst. Commun., 61(Pt 12): 1094-1096.