Studies on left-handed DNA:B to Z conformation transition of double strand oligo-d(G-C)6

Abstract: Synthetic oligo-d(G-C)6 was induced to undergo B-Z conformation transition by appropriate high-salt solution as shown by ultraviolet and circular dichroism spectroscopy. Among the salts tested, MgCl2 had the most potent ability to induce the conformation transition of oligo-d(G-C)6, NaClO4 (5mol/L) could also induce the full transition and NaCl (5mol/L) induced only an incomplete transition (Ca. 70%). The effect of temperature on the B-Z conformation transition of oligo-d(G-C)6 varied with the kind of salts used. On the basis of the observation, duodecandeoxyribonucleotide-d(GpCpGpCpGpCpGpCpGpCpGpC) was the minimal sequence that would support left-handed conformation in aqueous salt solution. And the results show that, oligo-d(G-C)6, or oligo-d(C-G)6 in 4mol/L MgCl2 solution, the process of its conformation transition might be: BZX, "X", an unknown conformation form is present, it is may very helpful to make a complete search for the Biological function of Z-DNA..