An ultracentrifugal analysis of the macromolecular particles of normal and leukemic mouse spleen.

As part of a comprehensive program of isolation and comparison of the various nucleoprotein frac tions of normal and leukemic mouse spleen (10, 11), the macromolecular particles of the cyto plasm have been separated by differential centrifugation and studied in the analytical ultracentrifuge. Although these preparations contain large amounts of polydisperse material, there are also several well defined sedimentation boundaries. While the components which they represent are found only in small amounts in preparations made from normal spleen, their concentrations are markedly elevated in preparations from either transplanted or spontaneous leukemic spleen.