Teasing apart the molecules of life

Researchers devise new technique and measure the forces required to unzip DNA

Fifty years after James Watson and Francis Crick’s publication of the structure of DNA, research in the latest issue of the Journal of Biology shows how scientists can now measure the forces needed to tear the DNA double helix apart. The work was carried out using the first successful simultaneous combination of two important techniques for looking at single molecules – single molecule fluorescence and optical trapping.
Optical trapping, or ’optical tweezers’, uses laser beams to counteract, and hence reveal, the tiny forces involved in the complex interactions between molecules. Single molecule fluorescence enables researchers to study biological systems on a molecule by molecule basis, by lighting up parts of the molecule in particular circumstances. The combination of the two methods applied to a single molecule has been impossible up until now because the light from the lasers used in conventional optical traps is too bright to allow single molecule florescence to be seen.

Matthew Lang, Polly Fordyce and Steven Block devised a new method, which uses special filters and specific fluorescence labels, to successfully combine the techniques of optical trapping and single-molecule fluorescence for the first time. They used this new method to simultaneously examine the structural and mechanical changes occurring as a small fragment of DNA was ripped apart.

The authors of this study, based at the University of Stanford, California, believe that their new technique will have a major impact in a wide range of biological investigations.

“We anticipate that this technique will have broad applicability to the study of fundamental biological questions”

Single molecule experiments allow scientists to study rare molecules that can be impossible to look at in complex mixture of chemicals found in the cells of our body. Many of these molecules may play important roles in the development of disease or are simply essential to maintenance of life. The published study provides another much-needed tool to help science improve our understanding of how our bodies work and what happens when they go wrong.

This article is available free of charge, in line with the publisher’s policy of open access to original research: http://www.biomedcentral.com/html/info/about/block01apress.html