Mixed guanine, adenine base quartets: possible roles of protons and metal ions in their stabilization

Dominik A. Megger*, Patrick M. Lax, Jeroen Paauwe, Célia Fonseca Guerra, Bernhard Lippert

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Structural variations of the well-known guanine quartet (G4) motif in nucleic acid structures, namely substitution of two guanine bases (G) by two adenine (A) nucleobases in mutual trans positions, are discussed and studied by density functional theory (DFT) methods. This work was initiated by three findings, namely (1) that GA mismatches are compatible with complementary pairing patterns in duplex-DNA structures and can, in principle, be extended to quartet structures, (2) that GA pairs can come in several variations, including with a N1 protonated adeninium moiety (AH), and (3) that cross-linking of the major donor sites of purine nucleobases (N1 and N7) by transition metal ions of linear coordination geometries produces planar purine quartets, as demonstrated by some of us in the past. Here, possible structures of mixed AGAG quartets both in the presence of protons and alkali metal ions are discussed, and in particular, the existence of a putative four-purine, two-metal motif.

Original languageEnglish
Pages (from-to)41-49
Number of pages9
JournalJournal of Biological Inorganic Chemistry
Issue number1
Publication statusPublished - 1 Jan 2018


  • Alkali metal ions
  • DFT calculations
  • Guanine quartets
  • Mixed adenine
  • Protonated adenine


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