Stokes radius

The Stokes radius (also often called the hydrodynamic radius) is the radius of a spherical particle that has the same frictional coefficient, f, as that of the current sample (and therefore this spherical particle would also have the same diffusion coefficient as the current sample). Many biochemists believe that the Stokes radius is directly measured by size exclusion (gel filtration) chromatography. However, the Stokes radius can only be estimated by chromatography, while it can be determined exactly via a measurement of the diffusion coefficient, or a measurement of the sedimentation coefficient if the molecular weight is also known.