Figure 3.

Effects of chaotropic and kosmotropic salt ions on lysozyme hydration. (A) Mean hydrodynamic radius R_H of lysozyme in the presence of various salts with predominately chaotropic or kosmotropic salt ions. R_H values were derived from the measured free particle diffusivity D₀ (see Fig. 1) and corrected for the salt- and temperature-dependent changes in water viscosity (see Fig. 2 and Table 1). R_H values for different concentrations of the same salt were averaged because they displayed no discernible systematic variations (B). For comparison, the thickness of a monolayer of water is ∼0.26–0.28 nm. (B) Hydrodynamic radius R_H of lysozyme in the presence of MgCl₂ at different solution temperatures T, and for MgCl₂ concentrations ranging from 50 mM to 1 M. The lack of any systematic variation with temperature or salt concentration is representative for our measurements with any salts, and at all salt concentrations and solution temperatures.