Rules of Thumb (module)

The Rules of Thumb module is based on Walter Stafford's rules of thumb for analytical ultracentrifugation. In transport sedimentation experiments this module provides estimations of the Stoke's radius from mass, the sedimentation coefficient, and the diffusion coefficient. In equilibrium experiments it provides estimations of the time to equilibrium, molecular weight, and rotor speed from various combinations of speed, the sedimentation coefficient, sigma, Stoke's radius, and molecular weight.

Transport experiments

Given a shape (sphere or random coil), degree of hydration (0.0 or 0.3), a molecular weight in K daltons, or both a sedimentation coefficient in Svedbergs and a diffusion coefficient in Ficks, this module can estimate the molecule's Stoke's radius. For convenience, when s and D are provided the molecular weight is also estimated. When only M is provided, the sedimentation coefficient is also estimated.

Equilibrium experiments

Estimates of various outputs from their respective inputs are tabulated below:

Input	Output
Speed, sedimentation coefficient	Time to equilibrium
Speed, Stoke's radius, MW	Time to equilibrium
Speed, sigma	MW
Sigma, MW	Rotor speed

Speed is specified in K rpm. The sedimentation coefficient is specified in Svedbergs. The Stoke's radius is specified in nanometers. The molecular weight is specified in K daltons.

Important notes

This module provides estimations only. All calculations assume a density of 1.00 g/cc and a v-bar of 0.725 cc/g.

External links

• Walter Stafford's Rules of Thumb: http://www.bbri.org/faculty/stafford/Thumb-8.html