Poster abstracts

Poster number 34 submitted by Alexander Johnson-Buck

Tracking the autonomous motion of single molecular “spiders” on a DNA origami track with total internal reflection fluorescence microscopy

Alex Johnson-Buck (Department of Chemistry, University of Michigan), Nicole Michelotti (Department of Physics, University of Michigan), Anthony Manzo (Department of Chemistry, University of Michigan), Kyle Lund, Hao Yan (Department of Chemistry and Biochemistry, Arizona State University), Steven Taylor, Milan Stojanovic (Department of Medicine, Columbia University), Nils Walter (Department of Chemistry, University of Michigan)

Abstract:
Total internal reflection fluorescence (TIRF) microscopy is used to image polycatalytic supramolecular complexes, dubbed “spiders,” moving across defined substrate tracks on tiles of DNA origami, long single-stranded DNA molecules folded into a 2-dimensional landscapes by hundreds of short DNA “staples.” Each spider is composed of a streptavidin body and three 8-17 deoxyribozyme-bearing legs which allow for motion across the single-stranded DNA substrate in a self-repelling random walk via the catalytic activity of its legs upon a site following a single RNA base in the substrate sequence. By registering the images of diffraction-limited point spread functions (PSFs) of emission from Cy3 and Cy5 labels on the spider and origami, respectively, and fitting Gaussian functions to these PSFs, spider positions on the origami track are measured with low-nanometer spatial precision to monitor the spider’s motion over time. Using this technique, individual spiders are observed to traverse 100-nm linear tracks in the presence of zinc ions, which are essential for 8-17 deoxyribozyme activity, but do not exhibit any net displacement in the absence of zinc ions. The spiders also traverse more complicated substrate tracks containing approximately 90-degree turns. These experiments are initial steps towards nanoscale control of dynamic artificial molecular assemblies. Preliminary results and future directions are discussed.

Keywords: Total internal reflection fluorescence, Single particle tracking, DNA origami