Direct visualization of supercoiled DNA molecules in solution.
The shape of supercoiled DNA molecules in solution is directly visualized by cryo-electron microscopy of vitrified samples. We observe that: (i) supercoiled DNA molecules in solution adopt an interwound rather than a toroidal form, (ii) the diameter of the interwound superhelix changes from about 12 nm to 4 nm upon addition of magnesium salt to the solution and (iii) the partition of the linking deficit between twist and writhe can be quantitatively determined for individual molecules.
Adrian
M
M
Laboratoire d'Analyse Ultrastructurale (LAU), Université de Lausanne, Switzerland.
ten Heggeler-Bordier
B
B
Wahli
W
W
Stasiak
A Z
AZ
Stasiak
A
A
Dubochet
J
J
D004278:DNA, Superhelical / Q000648:ultrastructure*; D015636:Magnesium Chloride / Q000494:pharmacology; D009690:Nucleic Acid Conformation; D012996:Solutions; D013237:Stereoisomerism
D004278:DNA, Superhelical; D012996:Solutions; D015636:Magnesium Chloride