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Published June 1, 1963 | Published
Journal Article Open

Band-centrifugation of macromolecules and viruses in self-generating density gradients


This communication presents a new method of carrying out sedimentation velocity experiments. A thin lamella of a solution of macromolecules is layered onto a denser miscible liquid in a rotating ultracentrifuge cell. The macromolecules then sediment through the liquid in a narrow concentration distribution, or band, which is observed photographically as a function of time. The density gradients necessary to stabilize the system against convection are generated during the experiment by the diffusion of small molecules between the lamella and the bulk solution, and in some cases by the sedimentation of the small molecules in the bulk solution. The inhomogeneities in the solvent are usually small enough to have no observable effect on the motion of the macromolecules. Sedimentation coefficients of macromolecules may be evaluated from the motion of bands. Diffusion, hydrodynamic interactions, and chemical reactions affect the shapes of bands.

Additional Information

© 1963 National Academy of Sciences. Communiated by Norman Davidson, April 24, 1963. The authors thank J. H. Fessler, J. E. Hearst, R. F. Stewart, and H. Wayland for helpful discussions, R. P. Feynman for valuable suggestions in connection with the development of the theory, and P. Knust-Graichen, R. L. Sinsheimer, J. H. Strauss, Jr., and W. E. Studier for gifts of materials. This work was supported in part by grant HE 03394 from the U.S. Public Health Service and a grant from the National Foundation. A preliminary report of this work was presented at the National Academy of Sciences' Conference on the Ultracentrifuge, New York, June 18-20, 1962, and at the Seventh Annual Biophysical Society Meeting, February 18, 1963, New York.

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