# Minimal frictional coefficient

The equivalent radius is the radius of an anhydrous sphere of equivalent volume to a given protein. Given Mr and vbar, a vbar-dependent equivalent radius can be computed. An empirical packing radius can also be computed from Mr alone according to an average estimating formula worked out by Teller (Ref. 28 33). Sednterp automatically calculates the equivalent radius when Mr is computed. It also calculates the minimal frictional coefficient for both the empirical and vbar dependent equivalent radius. From this minimal frictional coefficient the values of Smax (maximum sedimentation coefficient), and Dmax (maximum diffusion coefficient) are also calculated. On the main form, the equivalent radius is reported in text box R. The radius reported is either that from the Teller or the vbar method, depending on the method selected on the Results form. To see both equivalent radii values and their corresponding estimates, choose Results (r shortcut keystroke) to make the Results form visible.

The formulae and assumptions involved in the calculation of the equivalent radius and associated estimates are found in Calculating the Equivalent Radius section and the sections immediately following that section of this help file. Following the calculation of the equivalent radius, other estimates of physical properties of the sample can be calculated. These are discussed generally in Calculating Estimates of Hydration and Asymmetry, file in the theory section: Calculating the Equivalent Radius section and the sections immediately following that section of this help file and more particularly in the help sections dealing with the individual boxes on the Results form.