RAPID-DETERMINATION OF MOLAR-MASS IN MODIFIED ARCHIBALD EXPERIMENTS USING DIRECT FITTING OF THE LAMM EQUATION

A new method is described that allows measurement of the molar mass of the solute within 15 to 30 min after start of a conventional long-col umn sedimentation equilibrium experiment. A series of scans of the con centration distribution in close vicinity of the meniscus, taken in ra pid succession after the start of the centrifuge run, is analyzed by d irect fitting using the Lamm equation and the Svedberg equation. In ca se of a single solute, this analysis of the initial depletion at the m eniscus reveals its buoyant molar mass and sedimentation coefficient w ith an accuracy of approximately 10% and provides gross information ab out sample heterogeneity. This method can be used to study macromolecu les that do not possess the prolonged stability needed in conventional sedimentation equilibrium experiments and it can increase the efficie ncy of sedimentation equilibrium experiments of previously uncharacter ized samples.