Probing DNA's interstrand orientation with gold nanoparticles

The interstrand orientation of a DNA duplex plays a pivotal role in its biological and chemical functions. Therefore, developing an efficient way to determine (control and monitor) the parallel or antiparallel conformation of a DNA duplex is of great significance, which, however, remains a big challenge under some circumstances. In this work, we demonstrate that gold nanoparticles tagged on DNA are especially useful in trapping and detecting a special interstrand orientation of a DNA double helix, based on inherent electrostatic and steric repulsions between nanoparticles which will affect their self-assembly into a large structure. More importantly, some of the conformations revealed by the gold nanoparticle assay may even not be thermodynamically preferred and thus will be hard to detect using currently available methods. This simple, straightforward, and efficient methodology capable of dictating and probing a special DNA duplex structure provides a useful tool for conformational analyses and functional explorations of biomolecules as well as biophysical and nanobiomedical research.