Characterization of density gradients prepared by freezing and thawing a sucrose solution.

Density gradients of sucrose can be prepared in large numbers by successive freezing and thawing of sucrose solutions. Gradients of other solute molecules, such as salt and detergents, also form and this could affect subsequent sedimentation behavior of some molecules. However, the sedimentation behavior of native and denatured DNA of bacteriophage lambda was essentially isokinetic under the conditions used thus making these gradients comparable with ones prepared manually, at least for preparative sedimentation work with nucleic acids.