🧬 Scientists Just Watched Two DNA Molecules “Zip” Together

DNA has a basic physics problem.

Every DNA molecule carries a negative electrical charge. Put two of them next to each other, and they should repel.

Yet inside cells, DNA molecules somehow come close enough to recognize matching regions — an interaction relevant to genome organization, recombination and gene regulation.

Now researchers from the Universities of York and Sheffield have directly imaged how this may happen.

Using high-resolution atomic force microscopy, they observed two DNA double helices aligning with remarkable precision, with their grooves matching groove-to-groove. Atom-by-atom simulations suggest the trick comes from positively charged metal ions such as magnesium, calcium and nickel: the ions settle into DNA’s grooves and form tiny electrostatic bridges between the two helices.

The interaction is not completely random. Certain DNA sequences form stronger contacts than others, creating potential “pairing hotspots.” In some simulations, the ion bridges propagate along the molecules, producing something that looks remarkably like a molecular zipper.

The idea that DNA helices could align this way has existed for around two decades. What was missing was direct structural evidence.

Now we can actually see it.

There is an important caveat: these experiments used short DNA fragments under controlled laboratory conditions. Researchers have not shown that this exact mechanism alone explains how long chromosomes find matching sequences inside living cells.

Still, it reveals something surprisingly elegant:

DNA may recognize DNA not only through the information written in its bases —

but through the physical shape of the molecule itself.

#DNA #Genetics #MolecularBiology #Biophysics #Genome #Science

https://academic.oup.com/nar/article/54/16/gkag817/8769959