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Studies of DNA organization in hydrated spermidine-condensed DNA toruses and spermidine-DNA fibres.

Authors
  • Marx, K A
  • Ruben, G C
Type
Published Article
Journal
Journal of biomolecular structure & dynamics
Publication Date
Mar 01, 1984
Volume
1
Issue
5
Pages
1109–1132
Identifiers
PMID: 6400814
Source
Medline
License
Unknown

Abstract

We have investigated in vitro spermidine-condensed DNA preparations by both biochemical and freeze-etch electron microscopic approaches. These studies lead us to the conclusion that the reversibly condensed preparations, qualitatively described by Manning's counterion condensation theory, contain disk-like torus structures largely comprised of unidirectional, circumferentially wrapped DNA. Stereoscopic measurements on stereomicrographs of DNA torus and fibre objects have demonstrated the feasibility of directly measuring DNA writhe or, for that matter, mapping any secondary, tertiary or quaternary structure features of a hydrated macromolecular array in which the features can be differentially highlighted by low replica metal shadow levels.

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