G-quadruplex vs. duplex-DNA binding of nickel(II) and zinc(II) Schiff base complexes

Abstract Novel nickel(II) ( 1 ) and zinc(II) ( 2 ) complexes of a Salen-like ligand, carrying a pyrimidine ring on the N,N′ bridge, were synthesized and characterized. Their interaction with duplex and G-quadruplex DNA was investigated in aqueous solution through UV–visible absorption, circular dichroism and viscometry measurements. The results obtained point out that, while the zinc(II) complex does not interact with both duplex and G-quadruplex DNA, the nickel(II) complex 1 binds preferentially to G-quadruplex respect to duplex-DNA, with values of the DNA-binding constants, K b , 2.6 × 10 5  M − 1 and 3.5 × 10 4  M − 1 , respectively. Molecular dynamics simulations provided an atomic level model of the top-stacking binding occurring between 1 and hTelo (a 22-mer sequence oligonucleotide) in G-quadruplex conformation.