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Solubility of Lysozyme in the Presence of Aqueous Chloride Salts: Common-Ion Effect and Its Role on Solubility and
 

Summary: Solubility of Lysozyme in the Presence of Aqueous Chloride
Salts: Common-Ion Effect and Its Role on Solubility and
Crystal Thermodynamics
Onofrio Annunziata,* Andrew Payne,
and Ying Wang
Department of Chemistry, Texas Christian UniVersity, Fort Worth, Texas 76129
Received June 6, 2008
Abstract: Understanding protein solubility is important for a rational design of the conditions of protein
crystallization. We report measurements of lysozyme solubility in aqueous solutions as a function of NaCl,
KCl, and NH4Cl concentrations at 25 C and pH 4.5. Our solubility results are directly compared to
preferential-interaction coefficients of these ternary solutions determined in the same experimental conditions
by ternary diffusion. This comparison has provided new important insight on the dependence of protein
solubility on salt concentration. We remark that the dependence of the preferential-interaction coefficient
as a function of salt concentration is substantially shaped by the common-ion effect. This effect plays a
crucial role also on the observed behavior of lysozyme solubility. We find that the dependence of solubility
on salt type and concentration strongly correlates with the corresponding dependence of the preferential-
interaction coefficient. Examination of both preferential-interaction coefficients and second virial coefficients
has allowed us to demonstrate that the solubility dependence on salt concentration is substantially affected
by the corresponding change of protein chemical potential in the crystalline phase. We propose a simple
model for the crystalline phase based on salt partitioning between solution and the hydrated protein crystal.

  

Source: Annunziata, Onofrio - Department of Chemistry, Texas Christian University
Benedek, George B. - Department of Physics, Massachusetts Institute of Technology (MIT)

 

Collections: Chemistry; Physics