ABSTRACT
This chapter discusses the consequences for the analysis of sedimentation velocity. It introduces qualitatively and semi-quantitatively the origin and phenomenology of the most common forms of nonideal sedimentation, such that they can be anticipated and recognized. The chapter describes how the analysis methods developed so far for determining size-distributions and characterizing macromolecular interactions can be applied or need to be adapted, respectively. Batchelor calculated the overall effect of the mutual hydrodynamic interaction of a statistical ensemble of mono-disperse hard spheres, randomly distributed through the solution, and occupying a total volume fraction Φ. Despite thorny experimental details and theoretical improvements, Batchelor's theory presents an excellent starting point for expectations of the magnitude of nonideality in sedimentation. The velocity difference of the slow material in the absence and presence of the faster material causes an increase of the slower species' concentration in the slow boundary, known as the Johnston-Ogston effect.
