Adducts giving Nuclease Activity to Polymers

The Co(m)-complex of cyden, Co(m)Cyc, is one of the most effedive synthetic catalysts discovered so far for the hydrolysis of supercoiled DNAs [59]. The hydrolytic nature of DNA cleavage by the Co(m) complexes of polyamines including cyden has been well documented [57, 58]. The mechanism illustrated in 25 has been proposed [57] for the catalytic action of the Co(m) complexes. Given the remarkable enhancement of proteolytic activity of Cu(n)Cyc upon attachment to PCD [49], we tested the activity of Co(m)Cyc in phosphodiester hydrolysis to see if it is also enhanced greatly upon attachment to PCD derivatives [61, 62]. 

Dicerium complex 24 took 24 h at 37 °C or 5 h at 55 °C to yield hydrolysis products of a 192-base pair DNA [60], Conversely, PCD-based Co(m)Cyc derivatives degraded the linear DNA duplex into small fragments in a few hours at 25 °C. The facile DNA hydrolysis by the PCD-based Co(m)Cyc was due to the activation of Co(m)Cyc upon attachment to PCD rather than to cooperation among two or more catalytic centers or facilitation of complex formation between DNA and the PCD-supported catalyst. 

---