“η6”-Type anion–π in biomolecular recognition

AbstractTheoretical and compelling experimental evidence indicates that the interaction between an anion and an aromatic π system when the anion is directly above the ring face (“η6”-type anion–π), can be attractive. This may play an important role in the formation and recognition of biomolecular structures. We examined high-resolution structures of proteins and nucleic acids for the presence of “η6”-type anion–π. Though less frequent than its counterpart cation–π, “η6”-type anion–π is observed unambiguously, occurring in protein/nucleic acid loops and often involving conserved/coevolving sites in proteins, suggesting it plays an important role in macromolecular folding and function