Measuring forces in the DNA molecule

DNA, our genetic material, normally has the structure of a twisted rope ladder. Experts call this structure a double helix. Among other things, it is stabilized by stacking forces between base pairs. 

Scientists at the Technical University of Munich (TUM) have succeeded at measuring these forces for the very first time on the level of single base pairs. This new knowledge could help to construct precise molecular machines out of DNA.

Over 60 years ago, the researchers Crick and Watson identified the structure of deoxyribonucleic acid, which is more commonly known as DNA. They compared the double helix to a rope ladder that had been twisted into a spiral. The rungs of this ladder consisted of guanine/cytosine and thymine/adenine base pairs. But what keeps the DNA strands in that spiral structure?

Prof. Hendrik Dietz from the Chair of Experimental Biophysics uses DNA as construction material to create molecular structures. Hence, he is greatly interested in gaining a better understanding of this material.

The forces measured by the researchers were in the range of piconewtons. "A newton is the weight of a bar of chocolate," explains Dietz. "What we have here is a thousandth of a billionth of that, which is practically nothing." Forces in the range of two piconewtons are sufficient to separate the bond created by stacking forces.

Furthermore, the scientists also observed that the bonds spontaneously broke up and formed again within just a few milliseconds. The strength and the lifetime of the interactions depends to a great extent on which base pairs are stacked on each other.