Direct measurement of single molecule DNA bend-stiffness with nano-magnetic torque balance

The tight-bending of DNA plays a key role in many biological contexts, from nucleosome formation to DNA packaging in viral capsids. Despite its biological significance, questions remain about the mechanical properties of DNA on sub-persistence-length scales. Using magPI, a novel approach for measuring the position and orientation of magnetic nanoparticle probes, we perform a torque-balance measurement on short dsDNA molecules to directly measure the DNA bending free energy. We expect the magPI approach will be widely applicable to other biological systems where long-duration probe-orientation tracking is critical.