Poly(d2NH2A-dT): effect of 2-amino substituent on the B to Z transition

The effect of 2-amino substitution in adenosine (which permits formation of three hydrogen bonds to T) on the B to Z transition was examined in synthetic DNA of alternating purine-pyrimidine sequence. Results of CD, IR, and 31P NMR experiments show that (d2NH2A-dT)n undergoes a cooperative transition to a different helical structure under the same conditions as the B to Z transition of (dG-dC)n.