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Structures retaining many of the morphological features of nuclei may be released by lysing human cells in a non-ionic detergent and 2 M NaCl. Such nucleoids contain all the nuclear DNA packaged within a flexible cage of RNA and protein. HeLa nucleoids have been spread at an air-water interface and viewed in the electron microscope. A tangled network of superhelical fibres surrounds the collapsed cage. Irradiation with gamma-rays abolishes supercoiling and treatment with the untwisting enzyme or a low concentration of ethidium reduces it. A high concentration of ethidium induces supertwisting. The nuclear DNA of higher cells can be isolated naked, supercoiled and intact.

Type

Journal article

Journal

J Cell Sci

Publication Date

10/1979

Volume

39

Pages

53 - 62

Keywords

Cell Nucleus, DNA Topoisomerases, Type I, DNA, Superhelical, Ethidium, Gamma Rays, HeLa Cells, Humans, Microscopy, Electron, Nucleic Acid Conformation