Abstract: Valine-Schiff base-Cu(PBP-L-Val-Cu), which is a nonenzyme DNA-cleavage complex, contains four different forms: L-CH₃, D-CH₃, L-Ph and D-Ph. To obtain the most efficient activity, we test the cleavage activity of complexes under different conditions using pUC18 from E.Coli as DNA sample. Plasmid pUC18 was cleaved by the four certain complexes seperately and the products cleaved in variance of time were examined through agarose gel electrophoresis. In this way, we compare the cleavage ability of PBP-L-Val-Cu complexes in cleaving supercoiled DNA into nicked or linear DNA product, and then we find that L-CH3 has the highest activation in cleaving supercoiled plasmid DNA. Futhermore, we purificate the linear DNA product by TIANgel Midi Purification Kit, and this linear DNA extraction could be connected again by T4 DNA ligase. Finally, we incided the linear DNA extraction with two different kinds of restriction enzyme. The results show that this complex can cleave DNA in a site-specific way. Moreover, PBP-L-Val-Cu can also cleave other plasmid DNA, such as pNQ216 from Bacillus subtilis.

Key words: Valine-Schiff base-Cu complex, Plamid DNA, Site-specific cleavage