A----Z transition in the synthetic hexanucleotide (dCdGfl)3.

500 MHz proton NMR and NOE measurements on (dCdGfl)3 show that at very low ionic strength the hexanucleotide adopts an A-DNA conformation, whereas at high salt concentrations a Z-form is found. At intermediate salt concentrations the two species are in slow exchange on the proton NMR time scale. This transition was also observed by characteristic changes in the CD spectra.