Investigation of B-Z transitions with DNA oligonucleotides containing 8-methylguanine.

Among various Z-form DNA inducers, such as transition metal complexes, polyamines and high ionic concentrations, 8-methylguanine have received attention as efficient chemical modifications. Although it is clear that m8-modified guanine base markedly stabilizes the Z conformation of short oligonucleotides under physiological salt conditions, how sequence composition affects the preference of Z-DNA is still not well established. In this study, various oligomers of d(CG)n or d(GC)n containing either 8-methylguanine in a different position were synthesized and their capacity of stabilizing Z-DNA were evaluated by CD spectra and then compared with each other. It is was found out that the Z-DNA stabilizing effect depend on the order of arrangement of m(8)G and m(8)rG in DNA strands and the center position is the most effective to stabilize the Z-DNA and promote the B to Z transition.