Analysis by Isopycnic centrifugation of isolated nucleoids of Escherichia coli
- 1 January 1975
- journal article
- Published by Oxford University Press (OUP) in Nucleic Acids Research
- Vol. 2 (9) , 1559-1568
- https://doi.org/10.1093/nar/2.9.1559
Abstract
The isolated, formaldehyde-fixed nucleoid of E. coli has been analyzed by isopycnic centrifugation in CsCl density gradients. The membrane-free nucleoid bands at a density of 1.69 +/- 0.02 g/cm3. The membrane-associated nucleoid bands at a density of 1.46 +/- 0.02 g/cm3. Both species sediment to equilibrium as nearly monodisperse bands in CsCl, suggesting that the nucleoid components of DNA, RNA and protein are present in relatively constant ratios. These ratios are constant regardless of the position of the nucleoids in the heterogeneous sedimentation profile of a preparative sucrose gradient. The fixed nucleoids remain condensed during isopycnic centrifugation and there is no detectable loss of RNA from the nucleoid.Keywords
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