Scientists Visualize How Metal Ions Help DNA Zip Together
- Scientists have visualized DNA double helices pairing up for the first time, capturing images that confirm long-held hypotheses about how genetic material aligns before cell division.
- Researchers at the University of Sheffield used atomic force microscopy to examine short strands of DNA as they paired up.
- Because DNA strands possess a negative electrical charge, they naturally repel each other, making the alignment of twin double helices difficult.
Scientists have visualized DNA double helices pairing up for the first time, capturing images that confirm long-held hypotheses about how genetic material aligns before cell division. Published September 9 in Nucleic Acids Research, the findings reveal how charged metal ions assist the zipping process required to match chromosomes in eggs and sperm.
Visualizing DNA Pairing with Atomic Force Microscopy
Researchers at the University of Sheffield used atomic force microscopy to examine short strands of DNA as they paired up. Microscopist Thomas Catley explained the mechanics of the technique, noting that the specialized microscope operates similarly to a traditional record player. A very sharp-tipped needle is dragged across a surface containing molecules the researchers want to examine. We detect how that tip moves, and we turn that into an image signal, basically the same way that you get sound from a record player. Pink stars and green triangles in the microscopic images highlight an alternating arrangement of grooves where attraction between positively charged metal ions and negatively charged DNA holds the helices together.
Computer Simulations Confirm the DNA Zipper Model
Because DNA strands possess a negative electrical charge, they naturally repel each other, making the alignment of twin double helices difficult. Previous hypotheses suggested that positively charged ions could bridge this gap to facilitate zipping. Following the microscopy work, Agnes Noy and colleagues at the University of York conducted computer simulations to map the underlying mechanism. The simulations indicate that positively charged metal ions settle inside the grooves of the spiral staircases where information-carrying bases sit. These ions form bridges with the negatively charged ridges of the DNA backbone. The computer models suggest the DNA strands stagger so that positive and negative charges alternate, generating an attraction that draws the strands together.
Implications for Bioengineering and Disease Research
The combined images and simulations validate the established DNA zipper model. Understanding this process of matching chromosomes—which allows them to exchange information and prevents them from going astray during cellular division—carries broad applications. Researchers indicate the insights may assist bioengineers in refining folds for DNA origami structures utilized in targeted drug delivery, while also deepening the understanding of biological malfunctions involved in certain cancers.
