Solvation shell

The solvation shell number of a dissolved electrolyte can be linked to the statistical component of the activity coefficient of the electrolyte and to the ratio between the apparent molar volume of a dissolved electrolyte in a concentrated solution and the molar volume of the solvent (water):

${\displaystyle \ln \gamma _{s}={\frac {h-\nu }{\nu }}\ln \left(1+{\frac {br}{55.5}}\right)-{\frac {h}{\nu }}\ln \left(1-{\frac {br}{55.5}}\right)+{\frac {br(r+h-\nu )}{55.5\left(1+{\frac {br}{55.5}}\right)}}}$[1]

The hydration shell (also sometimes called hydration layer) that forms around proteins is of particular importance in biochemistry. This interaction of the protein surface with the surrounding water is often referred to as protein hydration and is fundamental to the activity of the protein.[2] The hydration layer around a protein has been found to have dynamics distinct from the bulk water to a distance of 1 nm. The duration of contact of a specific water molecule with the protein surface may be in the subnanosecond range while molecular dynamics simulations suggest the time water spends in the hydration shell before mixing with the outside bulk water could be in the femtosecond to picosecond range,[2] and that near features conventionally regarded as attractive to water, such as hydrogen bond donors, the water molecules are actually relatively weakly bound and are easily displaced.[3] Solvation shell water molecules can also influence the molecular design of protein binders or inhibitors.[4]

With other solvents and solutes, varying steric and kinetic factors can also affect the solvation shell.

• Activity coefficient
• Metal ions in aqueous solution
• Ion transport number
• Ionic radius
• Water model
• Poisson-Boltzmann equation
• Hydration energy
• Solvation