Nucleic Acids Research, 1988, Vol. 16, No. 1 279-289
© 1988
Articles |
Conformation of the synthetic DNA poly(amino2dA-dT) duplex in high-salt and aqueous alcohol solutions
kováInstitute of Biophysics, Czechoslovak Academy of Sciences 612 65 Brno, Czechoslovakia Central Research Institute for Chemistry, Hungarian Academy of Sciences H-1525 Budapest, Hungary
Received November 4, 1987. Accepted December 9, 1987.
It has previously been demonstrated by other workers that the duplex of a synthetic DNA poly(amino2dA-dT) undergoes a salt-induced conformational isomerization. We show in the present work using circular dichroism that the same isomerization is induced in poly(amino2dA-dT) by various alcohols. The isomerization was originally identified as the B-to-Z and then B-to-A conformational transition of DNA but we demonstrate that the high-salt or alcohol conformation of poly (amino2dA-dT) is the non Z-DNA zig-zag double helix we have previously observed with poly(dA-dT) and called X-DNA. X-DNA is a cesium cation specific conformation of poly(dA-dT) while no similar cation specificity is observed with poly(amino2dA-dT). Thus it appears that the extra amino group attached to A and cesium cations make the same thing; they probably dehydrate the double helix minor groove and relieve its conformational variability. Poly(amino2dA-dT) is exceptionally stable in X-DNA and conditions inducing it are mild, which opens the door to assess its molecular structure.