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

Two new Zn(II) complexes containing guanidinium groups, [Zn(L 1)Cl 2](ClO 4) 2 · H 2O · CH 3OH ( 1) and [Zn(L 2)Cl 2](ClO 4) 2 · 0.5H 2O ( 2), were synthesized and characterized (L 1 = 5,5′-di[1-(guanidyl)methyl]-2,2′-bipyridyl bication and L 2 = 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)Cl 2] (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.