Magnetic forces and DNA mechanics in multiplexed magnetic tweezers

Two-dimensional programmable manipulation of magnetic nanoparticles on-chip

A novel device is designed for on-chip selective trap and two-dimensional remote manipulation of single and multiple fluid-borne magnetic particles using field controlled magnetic domain walls in circular nanostructures. The combination of different ring-shaped nanostructures and field sequences allows for remote manipulation of magnetic particles with high-precision along any arbitrary pathway on a chip surface.

Stopped in its tracks: the RNA polymerase molecular motor as a robust sensor of DNA damage

DNA repair is often a complex, multi-component, multi-step process; this makes detailed kinetic analysis of the different steps of repair a challenging task using standard biochemical methods. At the same time, single-molecule methods are well-suited for extracting kinetic information despite time-averaging due to diffusion of biochemical components and stochasticity of chemical reaction steps. Here we discuss recent experiments using DNA nanomanipulation in a magnetic trap to study the initiation of transcription-coupled repair in a model bacterial system comprising the canonical Escherichia coli RNA polymerase and the Mfd translocase which specifically binds to it. These experiments provide kinetic insight into the reaction process, helping to explain how Mfd discriminates between transcribing RNAP and stalled RNAP. They also identify a reliably long-lived intermediate containing Mfd translocase and, potentially, RNA polymerase. This intermediate presumably serves as a platform for assembly of downstream repair components UvrAB(C).

Optical characterization of oligonucleotide DNA influenced by magnetic fields

UV-VIS spectroscopic analysis of oligonucleotide DNA exposed to different magnetic fields was performed in order to investigate the relationship between DNA extinction coefficients and optical parameters according to magnetic-field strength. The results with the oligonucleotides adenine-thymine 100 mer (AT-100 DNA) and cytosine-guanine 100 mer (CG-100 DNA) indicate that the magnetic field influences DNA molar extinction coefficients and refractive indexes. The imaginary parts of the refractive index and molar extinction coefficients of the AT-100 and CG-100 DNA decreased after exposure to a magnetic field of 750 mT due to cleavage of the DNA oligonucleotides into smaller segments.