title: Optimization of salt concentration in PEG-based crystallization solutions.
abstract: Although polyethylene glycol (PEG) is the most widely used precipitant in protein crystallization, the concentration of co-existing salt in the solution has not been well discussed. To determine the optimum salt concentration range, several kinds of protein were crystallized in a 30% PEG 4000 solution at various NaCl concentrations with various pH levels. It was found that, if crystallization occurred, the lowest effective salt concentration depended on the pH of the protein solution and the pI of the protein molecule; that is, higher salt concentrations were required for crystal growth if the difference between pH and pI was increasing. The linear relationship between the charge density of the protein and the ionic strength of the crystallization solution was further verified. These results suggested that the lowest effective concentration of salt in a crystallization solution can be predicted before performing a crystallization experiment. Our results can be a tip for tuning crystallization conditions by the vapor-diffusion method.
authors.affiliation: Confocal Science Inc., Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Yamanaka
authors.forename: Koji
authors.initials: K
authors.lastname: Inaka
authors.forename: Naoki
authors.initials: N
authors.lastname: Furubayashi
authors.forename: Masaaki
authors.initials: M
authors.lastname: Matsushima
authors.forename: Sachiko
authors.initials: S
authors.lastname: Takahashi
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sano
authors.forename: Masaru
authors.initials: M
authors.lastname: Sato
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D019747:Aldose-Ketose Isomerases / Q000737:chemistry; D003460:Crystallization / Q000379:methods*; D004058:Diffusion; D006863:Hydrogen-Ion Concentration; D009113:Muramidase / Q000737:chemistry; D009994:Osmolar Concentration; D011092:Polyethylene Glycols / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry*; D012996:Solutions; D000516:alpha-Amylases / Q000737:chemistry
chemical_list: D012996:Solutions; D011092:Polyethylene Glycols; D012965:Sodium Chloride; D000516:alpha-Amylases; D009113:Muramidase; D019747:Aldose-Ketose Isomerases; C023298:xylose isomerase