23 October 2007

Making light work of DNA molecules

Scientists in Dundee have become among the first in the world to observe the effect of forces that are applied to DNA molecules as human cells divide.

When a human cell divides, its newly-duplicated chromosomes which contain all that person’s genetic information get pulled apart, separating them into new `daughter’ cells. However, the DNA of the chromosomes is held together in places by the formation of junctions, that are therefore subjected to a pulling force.

Now scientists in the universities of Dundee and Illinois can look at this process directly, studying single DNA junction molecules as they gently tug on them.

The mechanical forces involved at the molecular scale are tiny - a feather falling on a surface would be huge by comparison. Indeed, because these forces are so weak, it is difficult to detect them.

Physicists have only just learned how to measure such tiny effects. The researchers at Dundee and Illinois use light beams from a laser to apply this small force, and then detect the resulting effect upon the object's shape by the nature of fluorescent light that is emitted.

"These weak forces are actually more relevant to biology than larger ones, so the new approach is telling scientists a lot about how DNA molecules react to mechanical force," said Professor David Lilley, head of the Cancer Research UK Nucleic Acid Structure Research Group in the College of Life Sciences at Dundee.

"This is providing a greater understanding of very basic processes involved during cell division."

This work has been published in the prestigious scientific journal Science.

Experiments on single molecules have only become possible in the last few years. Molecules are tiny (about a millionth of a millimeter in size), and so this requires extraordinarily high sensitivity. But now that its possible the rewards are enormous. The laboratories of Professor Lilley in Dundee and Professor Taekjip Ha at the University of Illinois at Urbana-Champaign, USA, have been collaborating for five years in these kinds of studies.

The work in Dundee is funded by Cancer Research UK.

For media enquiries contact:
Roddy Isles
Head, Press Office
University of Dundee
Nethergate Dundee, DD1 4HN
TEL: 01382 384910
E-MAIL: r.isles@dundee.ac.uk