PEG/Ion, developed by Hampton Research, is a crystallization screen designed to evaluate monodisperse, high purity Polyethylene glycol 3,350 and 48 unique salts representing a very complete range of anions and cations frequently used in the crystallization of biological macromolecules.
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.
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 ]