Chapter

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 ap-plied force from the height of the magnets. Initial dynamic force spectroscopy experiments on DNAmolecules revealed a large hysteresis that is caused by viscous drag on themagnetic bead and which will conceal weak interactions. Using smaller beads this hysteresis is sufficiently re-duced to reveal intra-molecular interactions at sub-piconewton forces. Compared to typical quasi-static force spectroscopy a significant reduction of measurement time is achieved, al-lowing 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 ana-lyzed