Direct visualization of supercoiled DNA molecules in solution.

摘要: The shape of supercoiled DNA molecules in solution is directly visualized by cryo-electron microscopy vitrified samples. We observe that: (i) adopt an interwound rather than a toroidal form, (ii) the diameter superhelix changes from about 12 nm to 4 upon addition magnesium salt and (iii) partition linking deficit between twist writhe can be quantitatively determined for individual molecules.