Sedimentation analysis and some related problems

Abstract

AbstractWith the development of the ultracentrifuge by Svedberg there was provided a group of methods for the determination of solute molecular weight and of distribution of molecular weights in proper solutions. In addition to the sedimentation equilibrium and the sedimentation velocity experiments, there are other closely related molecular kinetic phenomena which, when taken together, form a collection of very useful tools in an area of macromolecular chemistry.The principal past use of the ultracentrifuge has been in the determination of the molecular weight and the homogeneity of proteins. In this report the attempt has been made to point the way for concerted action in the return to the original problem–that of investigating the dispersity of macromolecular and other colloidal solutions. Among other things, there is proposed in outline a combination of the sedimentation velocity and sedimentation equilibrium experiments to provide mass distribution data in macromolecular systems. While the main emphasis is devoted to the theory of the sedimentation methods and their unique usefulness to this end, there have been presented shorter discussions of diffusion and osmotic pressure as such and in their relationships to the sedimentation problems.Recognition is also made of the fact that the optical systems for the study of the redistribution of the components in the diffusion and sedimentation cells are now in a state of change, with a rapid adaptation of several interference methods to take the place of the more classical refractometric schemes. The change is being made in the interest of a greatly enhanced accuracy, even to the point that diffusion behavior in systems which contain two solutes can properly be observed.