Boundary spreading in sedimentation-velocity experiments. 5. Measurement of the diffusion coefficient of bovine albumin by Fujita's equation

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Abstract
The use of Fujita''s theory for the con-centration-dependent sedimentation of a single solute is discussed and illustrated with experiments on bovine plasma albumin. With this theory, the diffusion coefficient of bovine albumin has been measured from experiments with the velocity ultracentrifuge. The values obtained for D were in agreement within experimental error ([plus or minus] 5%) with the value known from Gosting''s diffusion studies. As the theory shows, the correction of apparent diffusion coefficients for the dependence of S on c is large. Previous work, in which this correction was ignored, should be re-evaluated. The main component of one sample of bovine albumin showed measurable heterogeneity in sedimentation behavior. A method for calculating sedimentation coefficients is discussed. The method takes into account the dependence of S on c and the effect on S of the uncertainty in measuring the photographic plates. Sedimentation coefficients of bovine albumin measured from 6 experiments fit the equation S25, w = 5.01 (10.054c-0.004c2) with a standard deviation of 0.14%.