An application of the Rayleigh optics of the ultracentrifuge to molecular weight determinations by the Archibald method

For Archibald molecular weight calculations measurements are made along a single Rayleigh fringe. The displacement of the fringe measured as a function of the radial distance, x, is used to obtain the concentration gradient dc/dx by fitting a second-degree polynomial in x, extrapolating and differentiation. Good agreement with published values of the molecular weight was obtained with solutions of RNAase and of bovine serum albumin.

Also described is a graphical method for obtaining dc/dx from a tangent to the fringe drawn upon a photographic enlargement.