Equivolumetric gradients for zonal rotors: Separation of ribosomes

We have described a gradient shape for zonal rotors in which the volume through which a particle migrates is proportional to time and to the sedimentation coefficient of the particle. Such gradients are the sectorial analogs of the isokinetic gradients of swinging-bucket rotors. We propose to call these equivolumetric gradients. We have tested resolution in these gradients with Euglena ribosomal subunits and polysomes, and found it superior to that of comparable isometric or linear gradients. Broadening of particle zones is independent of particle size and the volumetric distance migrated, but depends on the time of centrifugation and on the concentration of particles above certain limiting values.