title: Condensation of supercoiled DNA induced by MnCl2.
abstract: Multivalent cations condense DNA in vitro, but it had been thought that a valence of at least + 3 was required in aqueous solution. We have found that Mn2+ can produce toroidal condensates of supercoiled plasmid DNA, but not of linearized plasmid. Mg2+ does not cause condensation, and neither MgCl2 nor NaCl can negate the effect of MnCl2, indicating that the condensation mechanism with Mn is not primarily electrostatic. Supercoiled MnDNA is more extensively digested than the linear form by S1 nuclease. Supercoiling appears to cooperate with Mn2+ in stabilizing helix distortions and also provides a "pressure" that enhances lateral association.
authors: Department of Biochemistry, University of Minnesota, St. Paul 55108.
authors: C
authors: C
authors: Ma
authors: V A
authors: VA
authors: Bloomfield
mesh_terms: D002712:Chlorides / Q000494:pharmacology; D004278:DNA, Superhelical / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure; D007700:Kinetics; D015636:Magnesium Chloride / Q000494:pharmacology; D017895:Manganese Compounds / Q000494:pharmacology; D008854:Microscopy, Electron; D009994:Osmolar Concentration; D010957:Plasmids / Q000737:chemistry* / Q000187:drug effects / Q000648:ultrastructure*; D015719:Single-Strand Specific DNA and RNA Endonucleases; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D002712:Chlorides; D004278:DNA, Superhelical; D017895:Manganese Compounds; D015636:Magnesium Chloride; D012965:Sodium Chloride; D015719:Single-Strand Specific DNA and RNA Endonucleases; C025340:manganese chloride