Research Of The Interaction Between Polar Dipeptides And Monovalent Metal Ions And Their DNA Cleavage Activity

Peptides, a kind of biological molecules composed by amino acid unit, widely exist in nature and exhibit a multitude of interesting biological activities. Peptides and their metal complexes attract more and more attention for their multitudinous biological activities as antiviral, antibiotic, antimicrobial, antitumor and forming hormones.On the basis of predecessor’s studies, the interaction of plasmid pUC19DNA with11polar peptides (L-Asp-L-Asp, L-Arg-L-Arg, L-Thr-L-Thr, L-Pro-L-Pro, L-His-L-Lys, L-Asp-L-Pro, L-Gln-L-Gly, L-Asp-L-Tyr, L-Glu-L-Glu, L-Tyr-L-A-rg, cyclo(L-Thr-L-Thr)) in the absence or in the presence of Cu(Ⅱ)、Zn(Ⅱ)、 Co(Ⅱ)、Ca(Ⅱ)、Mg(Ⅱ) complexes respectively were monitored by Agarose gel electrophoresis. Meanwhile, the optimum conditions on the cleavage of pUC19DNA by complexes were investigated from buffer, pH value, concentration and reaction time. The results indicated that:in the presence of Mg (Ⅱ) complex, Ca(Ⅱ) complex or Co(Ⅱ)complex, cyclo(Thr-Thr), L-Thr-L-Thr, L-Asp-L-Asp, L-His-L-Lys, L-Glu-L-Glu and L-Asp-L-Pro could act as effective catalysts for the cleavage of pUC19DNA. Especially, even in the absence of a metal complex, cyclo(Thr-Thr) could act as powerful catalysts for the cleavage of pUC19DNA under optimum conditions, and the cleavage value reached to above80%. Moreover, the hydrolytic cleavage mechanism of DNA plasmid by polar dipeptide was confirmed.The interaction of11polar dipeptides with monovalent metal ions (Li+, Na+, K+, Cs+, Ag+) was examined by HPLC and ESI-MS, and the association constants (Ka) were acquired. The results showed that the polar peptides compounds had stronger binding ability with Ag+ions than other monovalent metal ions. At the same time, the influence of mobile phase composition on association constant (Ka) has been investigated by HPLC. Due to the substituent’s of different amino acid, their binding ability of polar dipeptides with metal ions is varied greatly. Generally, the binding abilities of metal ion to L-Pro-L-Pro, L-Asp-L-Tyr, L-Gln -L-Gly and L-Glu-L-Glu are higher than other polar dipeptide. Moreover, the association constant of L-Asp-L-Tyr with Na+is about4116times the L-Tyr-L-Arg with Na+.