Two-dimensional electrophoresis of proteins of citric acid nuclei prepared with aid of a Tissumizer

Nuclei prepared from normal rat liver and Novikoff hepatoma ascites cells with the aid of a Tissumizer® in media containing 0.5 and 5 % citric acid were compared on the basis of electron microscopic appearance, DNA, RNA and protein content. Electron microscopy revealed better preservation of the nucleolar and nuclear morphology in the nuclei isolated in 0.5 % citric acid than in nuclei isolated in 5 % citric acid. Moreover, losses of protein and DNA from liver nuclei prepared by the sucrose-Ca²⁺ procedure were significantly less in nuclei treated with 0.5 % citric acid than in nuclei treated with 5 % citric acid. The preservation of nuclear morphology and the retention of the majority of types of nuclear protein were significantly better with the procedure using 0.5 % citric acid than with the procedure using 5 % citric acid. The 5 % citric acid treatment was found to alter nuclear morphology and extract specific nuclear proteins, as demonstrated by two-dimensional polyacrylamide gel electrophoresis of the proteins.