How do you investigate the electrical properties of G-wire DNA?
James Vesenka, Tomas Marsh*
Department of Chemistry and Physics, University of New England, Biddeford, ME. 04046, USA. jvesenka@une.edu
* Department of Chemistry, University of St. Thomas, St. Paul, MN, 55105, USA tcmarsh@stthomas.edu
Jamie Vesenka recently presented a virtual conference talk at DNA Nanotechnology Mitteldeutschland. He and colleague Tom Marsh have been exploring quadruplex guanine “G-wire” DNA physical [1] and electrical properties [2] for some time. Recently ultra-high-resolution images in solution [3] revealed at least two distinct higher order structures are observed for dGGGGTTGGGG derived G-wires assembled in K+ buffer. The polymorphic nature of G-wires has been confirmed in the UNE Atomic Force Microscopy Lab [4] (Figure below) making it possible to identify two DNA conformations.
Electric Force Microscopy (EFM) can be used to evaluate the dielectric constant of materials with different dielectric constants. Ruby mica has a permittivity about 5.4 times higher than vacuum, whereas DNA and AFM estimates of double stranded DNA are about 8 times higher [5]. In principle this difference can be detected by EFM through a phase lag measured between topographic and contour hugging imaging of the biased sample. Quantitative analysis of the dielectric constant is complicated by the small size of molecules, tip and sample geometry, to name just a few. The presentation described our attempts to make progress in evaluating the dielectric constant of G-wire DNA.
Figure 1a: Ultra high resolution image of 2.2nm and 4.3 nm G-wire repeat.
Figure 1b,c: cross sections of the two helical repeats.
[1] Marsh, T.C., J. Vesenka, & E. Henderson, Nucleic Acids Research, 23;4, 696-700 (1995).
[2] Armstrong, T., J. Root, & J. Vesenka, Jena, Germany 2002, Editor: W. Fritzsche, AIP Conf. Proc. 725. pp. 59-64 (2004).
[3] Bose, K., C.J. Lech, B. Heddi, & A.T. Phan, Nat Commun 9, 1959 (2018). https://doi.org/10.1038/s41467-018-04016-y
[4] NSF Award Search: Award#1531298
[5] Cuervo, A., P. D. Dans, J. L. Carrascosa, M. Orozco, G. Gomila, & L. Fumagalli, PNAS, 111(35), E3624–E3630 (2014) https://doi.org/10.1073/pnas.1405702111