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Biophys. J. BioFAST: First Published December 7, 2007. doi:10.1529/biophysj.107.121673
© 2007 by the Biophysical Society.

A more recent version of this article appeared on March 15, 2008.
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SPECTROSCOPY, IMAGING, OTHER TECHNIQUES

Sub-Piconewton Dynamic Force Spectroscopy Using Magnetic Tweezers

Maarten Kruithof 1, Fan-Tso Chien 1, Martijn de Jager 1 and John van Noort 1*

1 Leiden University

* To whom correspondence should be addressed. E-mail: noort{at}physics.leidenuniv.nl.

Submitted on September 11, 2007
Revised on October 1, 2007
Accepted on 5 November 2007


  Abstract
We introduce a simple method for dynamic force spectroscopy with magnetic tweezers. This method allows application of sub-piconewton force and twist control, by calibration of the applied force from the height of the magnets. Initial dynamic force spectroscopy experiments on DNA molecules revealed a large hysteresis that is caused by viscous drag on the magnetic bead and which will conceal weak interactions. Using smaller beads this hysteresis is sufficiently reduced to reveal intra-molecular interactions at sub-piconewton forces. Compared to typical quasi-static force spectroscopy a significant reduction of measurement time is achieved, allowing the real time study of transient structures and reaction intermediates. As a proof of principle nucleosome-nucleosome interactions on a sub-saturated chromatin fiber were analyzed.

Key Words: DNA, Force Spectroscopy, Magnetic Tweezers, chromatin






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Copyright © 2007 by the Biophysical Society.