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The Pi-Screens were developed at the MRC Laboratory of Molecular Biology (Cambridge, UK) for efficient crystallization screening of soluble proteins (Pi-minimal Screen) and integral membrane proteins (Pi-PEG Screen). The approach is based on incomplete factorial design.

The unique formulation was generated following a strategy named Pi sampling [1] in order to create novel combinations of precipitants, buffers and additives across a standard 96-condition plate layout. Thus, the diversity amongst the crystallization conditions is ideal for initial screening.

The Pi-minimal Screen includes 36 components, i.e. 12 precipitants, 12 buffers systems and 12 salts. Buffers employed in the Pi-minimal screen are buffer systems (acid-base pairs, e.g. HEPES and HEPES sodium salt). Consequently, pH can be adjusted by mixing 2 stock solutions at different ratios during later optimizations.
The efficiency of the Pi-minimal Screen was demonstrated by the crystallization of 10 proteins before its commercialization [1].

The Pi-PEG Screen includes various polyethylene glycol mixtures, additives and buffers covering a pH range from 4,0 – 9,5 and hence is suitable for integral membrane proteins as well as for soluble proteins.
The efficiency of the Pi-PEG screen was demonstrated by the crystallization of a G-protein coupled receptor (GPCR) when quality crystals could not be produced with other commercially available screens [1].


Bulk – 4 x 24 screening solutions in 10 ml aliquots
HTS – 96 screening solutions delivered in a deep-well block, 1.7 ml per well


BIOZ Product Citations

Please click the arrow on the right to expand the citation list. Click publication title for the full text.

Further Selected Literature Citations of Pi-Screens

  • Michalska et al. (2018) Functional plasticity of antibacterial EndoU toxins. Molecular Microbiology 109:509.
  • Luong et al. (2018) Structural Basis of a Thiol-Disulfide Oxidoreductase in the Hedgehog-Forming Actinobacterium Corynebacterium matruchotii. J. Bacteriol. DOI:10.1128/JB.00783-17.
  • Kampatsikas et al. (2017) In crystallo activity tests with latent apple tyrosinase and two mutants reveal the importance of the mutated sites for polyphenol oxidase activity. Acta Cryst. F 73:491.
  • Gorrec (2016) Protein crystallization screens developed at the MRC Laboratory of Molecular Biology. Drug Discov. Today 21:819.
  • Ohashi et al. (2016) Characterization of Atg38 and NRBF2, a fifth subunit of the autophagic Vps34/PIK3C3 complex. Autophagy 12:2129.
  • Omari et al. (2014) Pushing the limits of sulfur SAD phasing: de novo structure solution of the N-terminal domain of the ectodomain of HCV E1. Acta Cryst. D 70:2197.


[1] Gorrec et al. (2011) Pi sampling: a methodical and flexible approach to initial macromolecular crystallization screening. Acta Cryst. D67:463.

Available online at http://journals.iucr.org/d/issues/2011/05/00/bw5391/index.html

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