Open AccessOptimization of salt concentration in PEG‐based crystallization solutions
Author(s) -
Yamanaka Mari,
Inaka Koji,
Furubayashi Naoki,
Matsushima Masaaki,
Takahashi Sachiko,
Tanaka Hiroaki,
Sano Satoshi,
Sato Masaru,
Kobayashi Tomoyuki,
Tanaka Tetsuo
Publication year - 2011
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049510035995
Subject(s) - crystallization , salt (chemistry) , polyethylene glycol , peg ratio , ionic strength , protein crystallization , diffusion , chemistry , water of crystallization , salt solution , chemical engineering , materials science , chromatography , inorganic chemistry , aqueous solution , thermodynamics , organic chemistry , physics , finance , economics , engineering
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.