Real-time Monitoring Excitation Dynamics of Human Telomeric Guanine Quadruplexes: Effect of Folding Topology, Metal Cation, and Confinement by Nanocavity Water Pool

J Phys Chem Lett. 2019 Dec 19;10(24):7577-7585. doi: 10.1021/acs.jpclett.9b02932. Epub 2019 Nov 26.

Abstract

Guanine(G)-rich human telomeric (HT) DNA repeats, crucial to maintenance of genome stability, readily form G-quadruplexes (GQs) with various folding topologies. Research on excitation dynamics of HT-GQs is, however, scarce. Herein, we report a femtosecond time-resolved fluorescence coupled with transient absorption investigation on HT-GQ with the basket-type structure in Na+ solution. The result unveils an unusual multichannel nonradiative mechanism dominated by states with varying character of charge transfer lasting ten and hundreds of picoseconds, accounting altogether for an overwhelming ∼85% of the overall deactivation involving proton transfer. Our comparative study shows that encapsulating the GQ in nanocavity water pool or changing it into hydrid-type topologies with the presence of K+ ions alter differently energies and lifetimes of these states, yet without affecting the nature of the electronic excitation involved. The finding of this work underscores a leading role of structural rigidity in regulating the interplay with the microenvironment of photoexcited monomolecularly folded HT-GQs.

MeSH terms

  • Base Sequence
  • Cations / chemistry
  • DNA / chemistry*
  • Fluorescent Dyes / chemistry
  • G-Quadruplexes*
  • Humans
  • Hydrophobic and Hydrophilic Interactions
  • Kinetics
  • Light
  • Metals / chemistry*
  • Nanostructures / chemistry*
  • Photochemical Processes
  • Spectrometry, Fluorescence / methods
  • Telomere / chemistry*
  • Water / chemistry

Substances

  • Cations
  • Fluorescent Dyes
  • Metals
  • Water
  • DNA