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(from left to right) Vittoria Finazzi, Davide Luca Janner, Daniel Cavalcanti and Tristán Valenzuela
(from left to right) Vittoria Finazzi, Davide Luca Janner, Daniel Cavalcanti and Tristán Valenzuela

ICFO in Physics Focus

Giovanni Volpe and Prof. Dmitri Petrov demonstrate a new technique to detect molecule-scale torque

November 25, 2006
ICFO researcher Giovanni Volpe and Prof. Dmitri Petrov have conceived a new technique to measure torque using statistical methods similar to what researchers use for linear force measurements. Compared to other measurements, this method achieves ten times higher torque sensitivity and it could be applied to proteins, DNA, or even synthetic nanomotors developed for futuristic devices.

To test their method, Petrov and Volpe trapped a 1-micron-wide polystyrene bead with a red laser beam and at the same time nudged it with a green laser. Only when the researchers calculated the correlation functions were they able to measure a miniscule torque of 4 x 10-21 newton-meters, which matched their predictions and was ten times smaller than the smallest torque measured before.

Even though many protein molecules, such as those that process DNA, execute twisting motions, until now researchers have only managed to measure the torques in a few cases. Often the random thermal jiggling of water molecules makes rotation hard to detect. With this new analysis technique, it will be easier to reveal a hidden torque.

The new method was reported in the 24 November Physical Review Letters issue and has been recently highlighted by the Physical Review Focus, a service of the American Physical Society that selects physics research published in the APS journals, which stands out for its educational value and intrinsic interest to non-specialists.
(from left to right) Irina Soboleva, Ellie Kim, Xavier Menino and Susana Santos