Coformational switch of oligonucleotide induced by spermine.

Conformational change of nucleic acids induced by a small molecule is essential for many biological reactions and useful for biotechnology. To construct a spermine-responsive nucleic acid, we designed DNA sequences which can potentially form a unimolecular hairpin loop structure and a bimolecular duplex by itself. On the basis of UV melting and native PAGE experiments, we found four DNA oligomers of d16cg, d14cg, d12cg, and d14ta adopting different secondary structures depending on the spermine concentration. Their dissociation constants (Kd) with spermine were estimated in the order of 10(-6).