British scientists capture alignment of two DNA helices for the first time — ScienceAlert

Researchers at the Universities of Sheffield and York in the United Kingdom have for the first time obtained detailed images of two DNA double helices positioned side by side with aligned grooves. This structure resembles the teeth of a zipper and confirms a hypothesis proposed more than 20 years ago, ScienceAlert reports.

DNA grooves observed in liquid

The team used high-resolution atomic force microscopy to examine the surface of molecules in a liquid environment. The method made it possible to distinguish the major and minor grooves that spiral along DNA and record cases of their close alignment in two molecules.

The most detailed images of individual grooves were obtained in the presence of nickel ions. The researchers also studied the interaction of molecules with magnesium and calcium ions over larger areas, and used computer modeling to analyze how this close approach forms.

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Ions form bridges between molecules

DNA has a negative electric charge, so its molecules repel one another. According to the modeling results, ions with a double positive charge can form salt bridges between neighboring helices. The strongest contacts arose when the minor grooves aligned: ions could interact with both molecules across the gap between them.

The stability of such contacts was also affected by the DNA sequence. In particular, in the presence of nickel ions, especially stable interactions were linked to the short GTAC sequence. Modeling showed that magnesium and calcium can also stabilize aligned pairs, although the networks of ion bridges differed for different ion types.

The study's authors believe that this mechanism may help investigate DNA compaction in cells and the initial stages of corresponding regions coming together during genetic recombination. At the same time, the experiments were conducted with purified DNA under controlled laboratory conditions, and the role of such interactions in living cells has yet to be established. The study was published in the journal Nucleic Acids Research.