pH is an effective solubility, stability and crystallization variable because most proteins demonstrate pH dependent solubility minima and will solubilize, precipitate, or crystallize at particular pH values or in the presence of specific buffers. The solubility minima may correspond with the isoelectric point (pI) of the protein, but this is not always the case. The solubility minima and maxima is often complex and may depend on other chemical and physical variables in the crystallization experiment.
Using PEG/pH, PEG/pH 2, or PEG/pH HT one isolates pH, buffer type and relative supersaturation from other chemical and physical variables to screen the effect that pH and buffer type have on the solubility, stability, homogeneity, monodispersity and crystallization of the sample. Varying the pH can alter the protonation state and charge of amino acid residues in the protein, generating different species of the protein for solubility and crystallization screening. The change in pH can have a dramatic effect on inter and intramolecular contacts in the protein and can manipulate how the protein interacts with itself, the surrounding solvent and chemicals in the drop. By screening buffer type and pH in a low ionic strength environment of Polyethylene glycol, PEG/pH simultaneously delivers as a solubility and a crystallization screen for proteins.
Designed as a 96 reagent screen, but offered as two sets of 48 x 10 ml reagents or a single 96 x 1 ml reagent block, PEG/pH, PEG/pH 2, and PEG/pH HT samples Polyethylene glycol 4,000 versus 20 different buffers, at 0.2 M, while sampling pH 3.5 - 9.6.
PEG/pH 1 samples 20% w/v Polyethylene glycol 4,000 versus pH 3.5 - 7.4 in 0.2 M buffer. PEG/pH is supplied in a 48 x 10 ml tube format. PEG/pH is compatible with vapor diffusion, free interface diffusion, and microbatch crystallization methods. For research use only.
PEG/pH 2 samples 20% w/v Polyethylene glycol 4,000 versus pH 6.4 - 9.6 in 0.2 M buffer. PEG/pH 2 is supplied in a 48 x 10 ml tube format. PEG/pH 2 is compatible with vapor diffusion, free interface diffusion, and microbatch crystallization methods. For research use only.
PEG/pH HT samples 20% w/v Polyethylene glycol 4,000 versus pH 3.5 - 9.6 in 0.2 M buffer. PEG/pH HT is supplied in a 96 x 1 ml block format. PEG/pH HT is compatible with vapor diffusion, free interface diffusion, and microbatch crystallization methods. For research use only.
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