Thermodynamic studies of base pairing involving 2,6-diaminopurine

Abstract

The thermal stabilities of oligodeoxyribonucleotide duplexes containing 2,6-diaminopurine (D) matched with each of the four normal DNA bases were determined by optical melting techniques. Comparison of optical melting curves yielded relative stabilities for the D-containing standard base pairs in an otherwise identical base-pair sequence. The D:T pair was found to be more stable than the A:T pair in dC3DG3dC3TG3, as stable as the A:T in dCT3DT3G:dCA3TA3G, and less stable than the A:T in dCA3DA3G:dCT7G. The order of stabilities for X:Y in the DNA duplex dCA3XA3G:dCT3YT3G is:(A:T)>(T:D)≃(D:T)≥(T:A)>(C:D)≃(D:A)≃(D:G)≥(D:C)≃(G:D)≃(D:D)≥(A:D).Implications of these results for design of DNA oligonucleotide probes are discussed. © 1988 IRL Press Limited.