NMR studies on the conformational change of the synthetic oligonucleotide d(TGTGCGCACA) induced by spermine

Abstract

The binding of spermine to the self-complementary DNA sequence d(TGTGCGCACA) has been studied by $^1$H and $^{31}$P NMR techniques in order to investigate the change of DNA conformation. In proton NMR studies of the free oligomer without spermine, we observed two regions of imino peaks which supported the fact that the oligomer could coexist in two forms. These two forms of oligomer predicted as normal B-form duplex and multimeric structure were totally converted to Z-form duplexes when spermine was added. The transitions were confirmed by the results of the proton and phosphorus NMR spectra about spermine-DNA complex which were consistent with characteristics of Z-form duplex.