First images described of zipper-like alignment between DNA double helices

Imaging aligned grooves on DNA surfaces in liquid

Researchers used high-resolution atomic force microscopy in liquid to image neighboring DNA double helices and resolve their major and minor grooves. The report says some helices aligned groove-to-groove in the long-hypothesized zipper arrangement.

Simulations of individual atoms suggested that doubly positively charged ions can form bridges between the helices; nickel, magnesium, and calcium were examined. The experiments involved purified DNA under controlled laboratory conditions.

The groove-to-groove “zipper” arrangement of neighboring DNA double helices had been hypothesized for more than 20 years, but the report describes no earlier direct images resolving the individual grooves in this arrangement.

The reported work moves the proposed zipper arrangement to high-resolution images of aligned purified DNA helices, with simulations offering a possible ion-bridging mechanism. It does not establish that the arrangement occurs in living cells.

The purified-DNA result does not establish the same process in cells

The images reportedly provide structural evidence for a proposed way that similarly negatively charged DNA molecules can approach one another. The finding supplies a mechanism to investigate DNA packing and the association of matching DNA regions, but it does not demonstrate genetic recombination or the same process inside cells.