Phosphodiester hydrolysis and specific DNA binding and cleavage promoted by guanidinium-functionalized zinc complexes

Two new Zn(II) complexes containing guanidinium groups, [Zn(L1)Cl2](ClO4)2 · H2O · CH3OH (1) and [Zn(L2)Cl2](ClO4)2 · 0.5H2O (2), were synthesized and characterized (L1 = 5,5′-di[1-(guanidyl)methyl]-2,2′-bipyridyl bication and L2 = 6,6′-di[1-(guanidyl)methyl]-2,2′-bipyridyl bication). Both complexes are able to catalyze bis(p-nitrophenyl) phosphate (BNPP) hydrolysis efficiently. Obtained kinetic data reveal that both 1 and 2 show nearly 300- and 600-fold rate enhancement of BNPP hydrolysis, respectively, compared to their simple analogue without the guanidinium groups [Zn(bpy)Cl2] (bpy = 2,2′-bipyridy) (3). Enhanced acceleration for cleavage of BNPP could be attributed to cooperative interaction between the Zn(II) ion and the guanidinium groups by electrostatic interaction and H-bonding. Studies on inhibition of sequence-specific endonucleases (DraI and SmaI) by complexes show that 1 and 2 are able to recognize nucleotide sequence, -TTT^AAA-, and highly effectively cleave the plasmid DNA in the presence of hydrogen peroxide, while 3 has no specific binding to the DNA target sequences and only shows low DNA cleavage activity.