EVALUATION OF DIFFUSION COEFFICIENTS OF PROTEINS FROM SEDIMENTATION BOUNDARY CURVES

A simple and approximate equation is derived from Fujita's equation which permits evaluation of the diffusion coefficient, D, from sedimentation boundary curves. It is shown that the effect of the concentration dependence of the sedimentation coefficient on the evaluation of D decreases with decreasing the speed of the rotation, and D can be found with simple procedures under proper conditions. Diffusion coefficients of several typical proteins, both native and denatured, have been evaluated from sedimentation experiments in a synthetic boundary cell either according to the classical Lamm equation or the equation proposed here. The values of D thus obtained and the molecular weights calculated by Svedberg's equation have an uncertainty of at most 10% for native proteins and that of over 10% for denatured proteins. © 1969, American Chemical Society. All rights reserved.