Watson–Crick and Hoogsteen tri-base pairing: a co-crystal structure of a 2 : 1 complex of 6-isopropyluracil and adenine nucleobases

Abstract

The formation of a tri-base pairing from free nucleobases is rare. A co-crystal structure obtained from an equimolar mixture of 6-isopropyluracil and adenine shows the formation of a tri-base pairing, where one molecule of free adenine is adhered to two molecules of the free pyrimidine nucleobase, involving both Watson–Crick and Hoogsteen base-pairing interactions.