Scientists use noodle to model DNA mutation

by MIKE MARTIN, UPI Science Correspondent

LAUSANNE, Switzerland April 12 (UPI) -- Using well-cooked spaghetti,
researchers at the University of Lausanne say they have successfully
explained why knotted ropes snap more easily than straight ropes.

They say the result has implications for military exercises and
sporting events, but may also explain why strands of DNA cleave at
some points and not others, causing mutations and other genetic
diseases.

Armed with a tension meter, video camera, computer, and spaghetti
noodles, physics professor Giovanni Dietler performed the experiment,
which was based on a protocol designed by Piotr Pieranski, of Poland's
Poznan University of Technology.

Pieranski told United Press International spaghetti was the only
material suited to the experiment.

"The breaking process is very fast," Pieranski said. "Looking for
filaments on which the breaking process is slow enough to be recorded
by a camera at 1000 frames per second, we found well-cooked spaghetti
was simply the only choice."

Pieranski said he was motivated to perform the experiment because it
would resolve a simple mystery -- why knotted ropes are more prone to
breaking than unknotted ropes.

"The phenomenon is mentioned in many books on climbing and fishing,"
Pieranski said. "However, nowhere it is explained."

Knot theory is a well-established branch of topology, according to
mathematician Alain Goriely, which has wide applications.

"Knot theory is a wonderful unifying theory that has found many
different uses," Goriely told UPI from his office at the University of
Arizona. "The most beautiful application is in the theory of DNA where
problems of knotting become extremely important in replication and
transcription. Another application of knot theory is in the study of
the solar corona."

Dietler and Pieranski believe their explanation of knot cleavage
mechanics will find similar application in a variety of both routine
and esoteric pursuits -- mountain climbing, warfare, transportation,
genetic research, boating and fishing to name a few.

In the language of mathematics, knotted ropes cleave more readily
than unknotted ropes because knots induce curvatures on the filaments
that create points of weakness.

"We found the rope breaks at special points within the knots, where
the curvature is highest," Pieranski told UPI. "Our computer movie
shows two knots where colors indicate the value of the curvature. It
is highest at the red places. As the movie proves, knots break there."

Their result is schedule for publication later this month in a
journal Pieranski is not yet able to disclose. During the
pre-publication review, one referee had an unusual question.
"In our written description of the experiment, we stated that the
spaghetti was lubricated with olive oil," Pieranski said. "One of the
referees of the paper asked us why garlic was not added as well."