Search

This study reports new three-dimensional (3D) micromachined magnetic tweezersconsisting of micro-electromagnets and a ring-trap structure, fabricated using MEMS(micro-electro-mechanical systems) technology, for manipulating a single 2 nm diameterDNA molecule. The new apparatus uses magnetic forces to exert over 20 pN with lessheating, allowing the extension of the DNA molecule over its whole contour length toinvestigate its entropic and elastic regions. To improve the localized DNA immobilizationefficiency, a novel ring-trapper structure was used to handle the vertical movement ofmagnetic beads which were adhered to the DNA molecules. One extremity of theDNA molecule, which was bound to the thiol-modified magnetic bead, could beimmobilized covalently on a gold surface. The other extremity, which was bound toanother unmodified magnetic bead, could be manipulated under a magnetic fieldgenerated by micro-electromagnets. The important elastic modulus of DNA hasbeen explored to be 453 pN at a low ionic strength. This result reveals that DNAbecomes more susceptible to elastic elongation at a low ionic strength due toelectrostatic repulsion. The force–extension curve for DNA molecules is found to beconsistent with theoretical models. In addition to a single DNA stretching, thisstudy also successfully demonstrates the stretching of two parallel DNA molecules. [ABSTRACT FROM AUTHOR]