Fluorescence enhancement upon G-quadruplex folding: synthesis, structure, and biophysical characterization of a dansyl/cyclodextrin-tagged thrombin binding aptamer

Bioconjug Chem. 2013 Nov 20;24(11):1917-27. doi: 10.1021/bc400352s. Epub 2013 Oct 25.

Abstract

A novel fluorescent thrombin binding aptamer (TBA), conjugated with the environmentally sensitive dansyl probe at the 3'-end and a β-cyclodextrin residue at the 5'-end, has been efficiently synthesized exploiting Cu(I)-catalyzed azide-alkyne cycloaddition procedures. Its conformation and stability in solution have been studied by an integrated approach, combining in-depth NMR, CD, fluorescence, and DSC studies. ITC measurements have allowed us to analyze in detail its interaction with human thrombin. All the collected data show that this bis-conjugated aptamer fully retains its G-quadruplex formation ability and thrombin recognition properties, with the terminal appendages only marginally interfering with the conformational behavior of TBA. Folding of this modified aptamer into the chairlike, antiparallel G-quadruplex structure, promoted by K(+) and/or thrombin binding, typical of TBA, is associated with a net fluorescence enhancement, due to encapsulation of dansyl, attached at the 3'-end, into the apolar cavity of the β-cyclodextrin at the 5'-end. Overall, the structural characterization of this novel, bis-conjugated TBA fully demonstrates its potential as a diagnostic tool for thrombin recognition, also providing a useful basis for the design of suitable aptamer-based devices for theranostic applications, allowing simultaneously both detection and inhibition or modulation of the thrombin activity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aptamers, Nucleotide / chemistry*
  • DNA / chemistry*
  • Dansyl Compounds / chemistry*
  • Fluorescence*
  • G-Quadruplexes*
  • Humans
  • Models, Molecular
  • Molecular Structure
  • Nucleic Acid Conformation*
  • beta-Cyclodextrins / chemistry*

Substances

  • Aptamers, Nucleotide
  • Dansyl Compounds
  • beta-Cyclodextrins
  • thrombin aptamer
  • DNA
  • betadex