Metal-mediated aggregation of DNA comprising 2,2′-bipyridine nucleoside, an asymmetrically substituted chiral bidentate ligand

Abstract

The incorporation of an artificial 5-methyl-2,2′-bipyridine nucleoside at the 5′ terminus of an otherwise self-complementary oligonucleotide sequence opens up the opportunity of metal-mediated aggregation of DNA double helices triggered by the addition of the respective metal ions. Interestingly, two-dimensional aggregates (DNA monolayers) are formed in the presence of nickel(II), whereas copper(II) leads to the formation of three-dimensional disc-shaped structures. With iron(II), a coexistence of both types of aggregates had been observed previously. Models are proposed in which these observations are explained based on geometrical considerations. The artificial nucleoside itself represents a rare example for a C₁-symmetric chiral derivative of 2,2′-bipyridine, enabling the formation of four isomeric octahedral complexes.