2-Amino-7-deazaadenine forms stable base pairs with cytosine and thymine

2-Amino-7-deazaadenine (ADA) was incorporated into oligodeoxynucleotides (ODN) and their base-pairing properties with natural nucleobases were investigated. In melting temperature (Tm) experiments, the duplex containing an ADA/C base pair showed a high stability comparable to that containing ADA/T base pair. Destabilization of the duplex usually observed for existing degenerate bases was not observed. However, the incorporation efficiency of dCTP was only 1.8% for TTP in single-nucleotide insertion reactions using polymerase.