A procedure for the isolation of enzymically active rat-liver nuclei

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Abstract
A method is described for the isolation of rat-liver nuclei involving homogenization in 0.32 [image]-sucrose-3 m[image] -magnesium chloride and purification in 2.2 [image]-sucrose-l m[image]-magnesium chloride. The chemical composition of these purified nuclei was compared with those isolated in 0.32 [image]-sucrose-3m[image]-magnesium chloride alone. These purified nuclei are virtually free of whole cells and erythrocytes, and have lower activities of cytochrome oxidase, NADH-cytochrome c oxidoreductase and glucose 6-phosphatase (cytoplasmic enzymes used as markers) than the unpurified preparation; glucose 6-phosphate dehy-drogenase was not detected in either preparation. The specific activiy of NAD pyrophosphorylase, expressed per unit of DNA, was the same in each preparation, but the specific activity/mg of DNA of DNA-depndent RNA polymerase was more than 3-fold greater in the purified preparation.