Magnetic modulation of the unbraiding dynamics of pairs of DNA molecules to model the system as an intermittent oscillator

Abstract

We present a new method to measure mechanical properties of braided DNA molecules constrained between a superparamagnetic dumbbell and a glass surface. The molecules were braided using magnetic tweezers and subsequently allowed to unbraid in presence of a weak static magnetic field. For braids with high catenation numbers, the initial stages of the unbraiding process were not affected by the field. However, after releasing some energy, the static field introduced a sinusoidal perturbation on the system and the unbraiding plots showed oscillatory behavior. We demonstrated that in this regime, the system behaves as a phase oscillator. Adopting this model, we estimated the magnitudes of the torque generated by the DNA molecules and that exerted by the field. The modulated signal is sensitive to changes in the torque exerted by DNA. Torque calculations involved the average of several cycles of the modulated signal.