Formation of a streaming convective disturbance which may occur at one gravity during preparation of samples for zone centrifugation

Zone centrifugation experiments are occasionally ruined by convective processes which occur at one gravity subsequent to layering a solution of macromolecules on a supporting density gradient. The factors which contribute to this convection have been little understood. In most of the experiments described in this communication, Blue Dextran 2000 is used as the macromolecular component. The convective disturbance may be clearly seen and accurately measured. The effects of macromolecular concentration, composition and density of the supporting gradient, diffusion coefficient of the solute, and several other variables are studied, and an empirical equation constructed to describe the phenomenon. This convective disturbance appears to be minimized or prevented by layering and fractionating in the presence of a centrifugal field.