REVERSAL OF THE Z-CONFORMATION TO B-CONFORMATION OF POLY(DA-DT)CENTER-DOT-POLY(DA-DT) INDUCED BY NETROPSIN AND DISTAMYCIN-A

Poly(dA-dT). poly(dA-dT) which adopts the Z-form at 5 M NaCl in presen ce of 95 mM Ni(2+)ions is reversed to the B-conformation by the nonint ercalating drugs netropsin (Nt) and distamycin A (Dst). The drug-induc ed reversal from the Z-to B-form of poly(dA-dT). poly(dA-dT) is eviden ced by CD spectral changes at characteristic wavelengths around 295 nm and 248 nm. The drug-induced conformational transition is accompanied by a slow kinetic process. The results suggest the preference of thes e AT-specific drugs for the B-form and the inability of Nt and Dst to form a stable complex with the Z-form of poly(dA-dT). poly(dA-dT>.