3-D Magnetic Tweezers for Investigation of Mechanical Properties of Single DNA Molecules

This study reports a new three-dimensional (3-D) micromachined magnetic tweezers, fabricated using MEMS (micro-electro-mechanical systems) technology, for manipulating a single 2-nm diameter DNA molecule. The new apparatus uses magnetic forces to exert over 20-pN, with less heating compared to other methods, allowing the extension of the DNA molecule over its whole contour length to investigate its entropic and elastic regions. The important elastic modulus of DNA has been explored to be 453 pN at a low ionic strength. The force-extension curve for DNA molecules is found to be consistent with theoretical models. In addition to a single DNA stretching, this study also successfully demonstrated the stretching of two parallel DNA molecules, which was never reported previously in the literature.