A metal-coordinating DNA hairpin mimic

Abstract

A self-complementary oligodeoxynucleotide containing a 6,6″- substituted terpyridine was found to adopt a highly stable, hairpin-like structure. In addition to serving as a hairpin-loop mimic, the terpyridine can act as a coordination site for metals. Thus, the binding of several divalent transition metals (Zn2+, Co2+, Ni2+, Cu 2+ and Pd2+) to the terpyridine hairpin mimic was investigated. The terpyridine-modified hairpin mimic forms a stable secondary structure in the presence of these metals. The stability of the metal-coordinated hairpin mimic was found to be lower than in the absence of metal. Furthermore, the Tm of the metallohairpin is strongly influenced by the type of the bound metal, with Tm's increasing in the order Co2+ ∼ Ni2+ < Zn2+ < Cu2+ < Pd2+. Model considerations suggest that a conformational change of the terpyridine ligand is required to allow coordination of the metal.