Buffer and Solute Solution Parameters

vbar ρ and η are needed for further interpretation of s* and σ: s* and σ are directly accessible from sedimentation data. However, more often than not, it is the anhydrous molecular weight Mr and the frictional coefficient f that are of interest to the experimenter since these are required to learn about the size and shape of a molecule. Rearrangement of equation 4 yields: equation 5.

which shows that calculation of Mr from σ will require vbar, ρ, ω^2 and T. Similarly, rearrangement of equation 3 shows that vbar and ρ are required to determine f from and s. Further interpretation of f requires that the solvent viscosity η be taken into account and that estimates of f be made for anhydrous spheres of identical molecular weight and density. These calculations permit, through still more calculations, the estimation of the limits on a protein's hydration and asymmetry. While none of the calculations is difficult, Sednterp assembles all of them into one program to facilitate data interpretation. This not only eliminates the tedium associated with routine analysis, it also provides a consistent and reliable means of evaluating hydrodynamic observations.