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Michealovich, Ido

PhD student
Michealovich, Ido
Research type


  • 2019- now, PhD Optical Super-Resolution Measurement of DNA Structure: from Superhelical Plasmids to Chromatin
    with Oleg Krichevsky
  • 2018- 2019, MSc Super-Resolution Scanning Fluorescence Correlation Spectroscopy Measurements of Supercoiled Plasmid Structure
    with Oleg Krichevsky

    Abstract/Description: The structure of circular DNA (plasmids) is determined by its superhelicity, a topological
    quality which can be thought of as the excess, or defficiency, of whole twist turns of the double
    helix around its axis. Since supercoiled plasmids are a few hundred nanometers in size, their
    structural details cannot be observed optically. While there have been studies to characterize
    the structure of supercoiled plasmids, none have attempted to probe the structure in a liquid
    solution, resembling physiological conditions.
    We present an in-vitro study of the structure of supercoiled plasmids in solution: Plasmids
    are labeled uniformly and covalently with minimal structural interference. A combination
    of scanning
    Fuorescent correlation spectroscopy (sFCS) and time-gated stimulated emission
    depletion microscopy (gSTED) are utilized to measure the static structure factor of plasmid
    topoisomers, and its dependence on superhelicity. By analyzing the results and comparing
    with a DNA simulation, we shed more light on the actual structure of supercoiled plasmids
    - support for a branched plectonemic structure is given, and a qualitative resemblance is
    observed between the measured and simulated gyration radii and structure factors of both
    relaxed and supercoiled plasmids.