Rapid molecular mass determination by sedimentation velocity experiments and direct fitting of the concentration profiles

Abstract

We present a method for the direct molecular mass determination from sedimentation velocity experiments. It is based on a non-linear least-squares fitting procedure of the radial concentration profiles and simultaneous estimation of the sedimentation coefficient and the ratio of sedimentation/diffusion coefficients considering approximate solutions of the Lamm equation. Different model functions from Faxén as well as Archibald type derived by Fujita [4] were used to describe the sedimentation behavior of macro-molecules during the centrifugation. By means of a computer program, LAMM sedimentation and diffusion constants of some proteins were determined. The method presented here appears to be useful for the rapid molecular mass determination of proteins large than 10 kDa. One of the equations of the Archibald type is also suitable for substances of low molecular mass of about 1 kDa. The model function neither requires the existence of a plateau region nor a meniscus region free of solute.