Supercoil

Supercoiling
Further information: DNA supercoil
DNA can be twisted like a rope in a process called DNA supercoiling. With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.

Supercoiled DNA
Double-stranded circular DNA in which either overwinding or underwinding of the duplex makes the circle twist.

Supercoiled plasmid. The predominant in vivo form of plasmid, in which the plasmid is coiled around histone-like proteins.

The supercoiled arrangement of DNA in eukaryotic nuclear chromosomes produced by coiling the continuous string of nucleosomes (about 7 nucleosomes per turn).
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This relaxes the torsional strain needed to maintain supercoiling, producing the familiar form of plasmid. (See Plasmid.) NIH. See National Institutes of Health. Nitrocellulose.

Less than one picogram of linear or supercoiled DNA is analyzed in under 3 minutes. Sizing range has been extended down to 287 base pairs. Efforts continue to extend the upper limit beyond 167,000 bases.

- The protein responsible for relaxing the tension on the double helix owing to supercoiled twists brought about by the unwinding of the double helix without rotation; also called helix-unwinding protein
DNA ligase ...

Tetramer units pack together laterally to form a sheet of eight parallel protofilaments that are supercoiled into a tight bundle.

DNA gyrase A topoisomerase that catalyzes the ATP-driven introduction of negative supercoils into DNA. Also called topoisomerase II.

See also: DNA, Trans, Sequence, Protein, Molecule