A topological classification of G-quadruplex structures.

@article{Esposito2007ATC,
  title={A topological classification of G-quadruplex structures.},
  author={Veronica Esposito and Aldo Galeone and Luciano Mayol and Giorgia Oliviero and Antonella Virgilio and Loredana Randazzo},
  journal={Nucleosides, nucleotides & nucleic acids},
  year={2007},
  volume={26 8-9},
  pages={1155-9}
}
A topological classification of most quadruplex structures is proposed, based on two main characteristics: 1) the relative orientation of the strands and 2) the nature of the loops connecting the strands.