Supercoiled DNA More Dynamic Than Watson-Crick Double Helix, 3D Imaging Reveals
13 October 2015, 7:43 am EDT
By Katherine Derla Tech Time
The images show the structure of the DNA calculated with the supercomputer simulations (in color) superimposed on the cryo-electron tomography data (in white or yellow). (There is no superimposition onto cryo-electron tomography data for the purple figure-8 shape.) The familiar double helix has been either simply bent into a circle or twisted into a figure 8. ( Thana Sutthibutpong )
However, a complete human DNA set contains approximately 3 billion base pairs. Watson and Crick's DNA double helix is but a small fraction of a human genome. Long DNA segments become increasingly complex when viewed under wide-angle lens.
A group of researchers from Britain and the United States learned that, apart from being more complex, long DNA strands seem to "wiggle" at a regular pace and shift shapes.
Dr. Sarah Harris of the University of Leeds believes that 3D images of the "supercoiled" DNA strands will benefit scientists in improving medications. She explained that Watson and Crick described just one turn of the double helix shape.
The recent study looked at hundreds of base pairs, a much bigger scale.
Harris added that the increase in scale is but a modest one, but it can help scientists study DNA's molecular behavior better. The study's large samples are more than a meter long when uncoiled.
"This is because the action of drug molecules relies on them recognizing a specific molecular shape — much like a key fits a particular lock," said Harris, who led the study's computer simulation of the DNA strands. She is confident about the increasing role of supercomputers in the development of drugs.
Linear DNA, of course, cannot simply be coiled, explains study co-author Dr. Lynn Zechiedrich of the Baylor College of Medicine.
"We had to make circles so the ends would trap the different degrees of winding," the author added.
The researchers published their findings in the Nature Communications journal on Oct. 12.
Here's an example of a supercomputer simulation showing how the dynamic motion of the supercoiled DNA causes its shape to change constantly to form a myriad of structures.
(Credit: Thana Sutthibutpong)
