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

Peptide is a kind of important biomolecule. It is composed by amino acid units,and plays a key role in the process of life. It is found that the interaction of peptideand metal ion often relates to diverse biological activities, such as antibiotic,antibacterial, antivirus, anticancer, immunity regulation and ion carrier. Now, peptideshave received considerable attention for their potential applications in the fields ofmolecular biological technology and pharmacological research due to their diversebiological activities. Moreover, peptides often take effect on many biology processes,and the studies on the peptides attract more and more attentions from different fields.In this dissertation, the cleavage activity of8nonpolar linear dipeptides tosupercoiled pUC19DNA was investigated in the presenceor or absence of Cu(II)、Zn(II)、Co(II)、Ca(II)、Mg(II) by agarose gel electrophoresis. The results indicated thatnonpolar dipeptides had hardly any cleavage activities by themselves. However, thecleavage activities of nonpolar dipeptides coupled with metal ions were improvedobviously. Moreover, the optimal conditions for these peptides and metal ionscleaving the pUC19DNA were investigated on buffer, metal ion, pH value,concentration of dipeptides and their reaction time. The results showed that in thepresence of Co(II), nonpolar peptides could act as powerful catalysts for the cleavageof pUC19DNA, and the cleavage value reached to above80%. The optimalconditions for DNA cleavage by nonpolar dipeptides and Co2+is in the Tris-HClbuffer solution, pH6.8-7.0, and12h.The optimal concentrations of dipeptidesshowed diversity for their different solubility and side chain. For example, Gly-Glycould cleave the DNA at0.2mM, while L-Phe-L-Phe was at1mM, and theconcentrations of L-Ala-L-Ala had no influence on the cleavage activities. In addition,the results suggested that nonpolar dipeptides cleave DNA via the hydrolysispathway.By ESI-MS and HPLC, the interaction of nonpolar dipeptides with monovalentmetal ions(Na+、K+、Li+、Cs+、Ag+) was examined, and the association constants(Ka)were calculated. The results obtained by ESI-LC-MS were in good agreement withthose obtained by HPLC. It was found that L-Phe-L-Phe and L-Met-L-Met hadstronger binding ability to the monovalent metal ions, while the L-Pro-L-Pro had theweakest ability. For the five metal ions, it is easier for Ag+to conjugate to thenonpolar dipeptides than that for Na+、K+、Li+or Cs+.The influence of different anions on the combining ability between nonpolar dipeptides and monovalent metal ions wasalso investigated. And the results indicated that in the presence of anion H2PO4-, theassociation constants of nonpolar dipeptides and monovalent metal ions were theleast.The study reveals important theoretical significances and application value inclarifying the molecule recognition and the structure relations between nonpolardipeptides and metal ions. Meanwhile, according to our experimental results,difference of the action force of metal ions to dipeptides can apply to the future studyof molecular recognition.