The measurements reveal that DNA is significantly stiffer than previously thought and, when wound, may in fact provide enough power to be used as a sort of molecular, rubber-band motor to propel nanomachines. Although that type of application may be well in the future, the studies are significant because they offer a blueprint for measuring the contortions that DNA undergoes during replication and other key processes.

The researchers, led by Howard Hughes Medical Institute investigator Carlos Bustamante, reported their research in the July 17, 2003, issue of the journal Nature. Bustamante and the paper's two lead authors, graduate students Zev Bryant and Michael Stone, are at the University of California, Berkeley.

"This finding is important because many of the processes involved in reading the information in DNA involve distorting the DNA molecule," said Bustamante. "And to truly understand these processes, we need to understand the energy costs involved in the interaction between the protein that induces distortion and the DNA."

Almost ten years ago, Bustamante and his colleagues measured the extensional elasticity of single-strand DNA, by attaching a DNA molecule at either end to tiny beads. Using a laser "magnetic tweezers" instrument, the researchers applied a precisely known force to stretch the molecule. However, measuring the torsional stiffness of the molecule proved far more difficult.

"For almost seven years, I couldn't convince any graduate student or postdoc to do these experiments," said Bustamante. "I would tell them my idea, which I thought was really great, and they would look at me, smile and say, 'Yeah, yeah, great, nice idea next?' Fina
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Contact: Jim Keeley
keeleyj@hhmi.org
301-215-8858
Howard Hughes Medical Institute
1-Aug-2003