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Modifying the N-terminus of polyamides: PyImPyIm has improved sequence specificity over f-ImPyIm
Bioorganic and Medicinal Chemistry (2008)
  • Toni Brown
  • Hilary Mackay
  • Mark Turlington
  • Arden Sutterfield
  • Traci Smith
  • Alan Sielaff
  • Laura Westrate
  • Chrystal D. Bruce, John Carroll University
  • Jerome Kluza
  • Caroline O'Hare
  • Binh Nguyen
  • W. David Wilson
  • John A. Hartley
  • Moses Lee
Abstract

Seven N-terminus modified derivatives of a previously published minor-groove binding polyamide (f-ImPyIm, 1) were synthesized and the biochemical and biophysical chemistry evaluated. These compounds were synthesized with the aim of attaining a higher level of sequence selectivity over f-ImPyIm (1), a previously published strong minor-groove binder. Two compounds possessing a furan or a benzofuran moiety at the N-terminus showed a footprint of 0.5μM at the cognate ACGCGT site (determined by DNase I footprinting); however, the specificity of these compounds was not improved. In contrast, PyImPyIm (4) produced a footprint of 0.5μM but showed a superior specificity using the same technique. When evaluated by thermal melting experiments and circular dichroism using ACGCGT and the non-cognate AAATTT sequence, all compounds were shown to bind in the minor-groove of DNA and stabilize the cognate sequence much better than the non-cognate (except for the non-amido-compound that did not bind either sequence, as expected). PyImPyIm (4) was interesting as the ΔTm for this compound was only 4°C but the footprint was very selective. No binding was observed for this compound with a third DNA (non-cognate, ACCGGT). ITC studies on compound 4 showed exothermic binding with ACGCGT and no heat change was observed for titrating the compound to the other two DNA sequences. The heat capacity (ΔCp) of the PIPI/ACGCGT complex calculated from the hydrophobic interactions and SASA calculations was comparable to the experimental value obtained from ITC (−146calmol−1K−1). SPR results provided confirmation of the sequence specificity of PyImPyIm (4), with a Keq value determined to be 7.1×106 M−1 for the cognate sequence and no observable binding to AAATTT and ACCGGT. Molecular dynamic simulations affirmed that PyImPyIm (4) binds as a dimer in an overlapped conformation, and it fits snugly in the minor-groove of the ACGCGT oligonucleotide. PyImPyIm (4) is an especially interesting molecule, because although the binding affinity is slightly reduced, the specificity with respect to f-ImPyIm (1) is significantly improved.

Disciplines
Publication Date
May 1, 2008
Citation Information
Toni Brown, Hilary Mackay, Mark Turlington, Arden Sutterfield, et al.. "Modifying the N-terminus of polyamides: PyImPyIm has improved sequence specificity over f-ImPyIm" Bioorganic and Medicinal Chemistry Vol. 16 Iss. 9 (2008)
Available at: http://works.bepress.com/chrystal_bruce/6/