The primary screening variables are PEG, ion type, ionic strength, and pH. More than 60% of the published crystallizations utilized PEG as a primary crystallization reagent and in approximately 50% of those reports, the PEG was combined with an ion as a secondary crystallization reagent. PEG/Ion reagents are formulated without a buffer and are not pH titrated.

PEG/Ion 2 is an extension to the fundamental crystallization strategy in PEG/Ion. PEG/Ion 2 reagents cover the monodisperse, high purity Polyethylene glycol 3,350 and an array of neutralized and pH adjusted organic acids, multivalent ions, a novel Citrate BIS-TRIS propane buffer system and pH (4 – 8.8). The formulation of PEG/Ion 2 was developed at Hampton Research. Each of the 48 reagents in PEG/Ion 2 contains PEG 3,350 as the polymer (precipitant). The concentration of PEG is varied from 12% w/v to 20% w/v depending upon the type and concentration of buffer/salt paired with the polymer. Thirteen of the forty-eight PEG/Ion 2 reagents contain a separate buffer component. The remaining PEG/Ion 2 reagents are buffered by the titrated organic acid salt. Six of these thirteen conditions feature a novel Citric acid BIS-TRIS propane (CBTP) buffer. The CBTP buffer uses Citric acid and BIS-TRIS propane as the acid base pair to create a two component buffer system effective across pH 2.5 to 9.5. The ratio of Citric acid to BIS-TRIS propane determines the solution pH. Thirty-five of the forty-eight PEG/Ion 2 reagents contain a neutralized or pH adjusted organic acid in the presence of the polymer. Neutralized organic acids are highly effective crystallization salts.¹ Four PEG/Ion 2 reagents feature polyvalent cations. Two of these reagents contain cation mixes, saving sample by screening six different cations with only two reagents. Tryptone, a casein digest combinatorial library of peptides, is included in PEG/Ion 2. PEG/Ion 2 reagents 1-30, 42, 45-47 are formulated without a buffer and are not pH titrated.

PEG/Ion contains 48 unique reagents, 10 ml each.

PEG/Ion 2 contains 48 unique reagents, 10 ml each.

PEG/Ion HT contains 1 ml of each reagent from PEG/Ion and PEG/Ion 2 in a single Deep Well block format.

Ready-to-use reagents are sterile filtered and formulated with ultra-pure Type 1 water, using the highest purity salts, polymers, organics and buffers. Individual reagents are available through the Hampton Research Custom Shop.

PEG/Ion Screen

PEG/Ion 2 Screen

PEG/Ion HT

1. Expression, purification, crystallization and preliminary X-ray diffraction analysis of Bifidobacterium adolescentis xylose isomerase. C. V. dos Reis, A. Bernardes and I. Polikarpov. Acta Cryst. (2013). F69, 588-591.

2. A comparison of salts for the crystallization of macromolecules. Alexander McPherson. Protein Science (2001), 10:418-422.

3. Searching for silver bullets: An alternative strategy for crystallizing macromolecules. Alexander McPherson and Bob Cudney. Journal of Structural Biology Volume 156, Issue 3 , December 2006, Pages 387-406.

4. Mechanisms for Glycolipid Antigen-Driven Cytokine Polarization by Valpha14i NKT Cells. Sulliivan et al, The Journal of Immunology, 2010, 184, 141 -153. (PEG/Ion 2)

5. Optimization of salt concentration in PEG-based crystallization solutions. Yamanaka M, Inaka K, Furubayashi N, Matsushima M, Takahashi S, Tanaka H, Sano S, Sato M, Kobayashi T, Tanaka T. J Synchrotron Radiat. 2011 Jan;18(1):84-7. doi: 10.1107/S0909049510035995. Epub 2010 Nov 5.

6. Crystallization and preliminary X-ray crystallographic analysis of importin-[alpha] from Neurospora crassa. N. E. Bernardes, A. A. S. Takeda, F. Z. Freitas, M. C. Bertolini and M. R. M. Fontes. Acta Cryst. (2014). F70, 501-504 [ doi:10.1107/S2053230X14005068 ]

Hampton Research, first in crystallization since 1991, developing and delivering crystallization and optimization screens, reagents, plates, and other tools for the crystallization of biological macromolecules, including proteins (antibody), peptides (insulin), and nucleic acids (DNA).

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