Research Of The Interaction Between Aromatic Dipeptides With Monovalent Metal Ions And Their Dna Cleavage Activity

Peptides, a kind of biological molecules is made up of amino acid unit, widely exist in nature and exhibit a large number of fascinating biological activities. As the smallest molecular in peptides, dipeptide is found that has diverse biological activities, such as antibiotic, antibacterial, antivirus, anticancer, immunity regulation and ion carrier. Moreover, the oxidation resistance and antimicrobial properties of some small peptide could be improved by combining with metal ions; at the same time, metal ions can also improve its bioavailability. The research on metal ion-protein interaction has been an important content of life science researches. Metal ions interact with protein using a great variety of mechanisms to regulate protein functions. Because of the structure complexities of proteins, it is extremely difficult to investigate directly. It has been common practice to use dipeptides as model compounds since they make up of the protein structures. So there is important theoretical significance and academic value to carry out researches on molecular recognition of dipeptides with metal ions.In this dissertation, the cleavage activity of 10 aromatic linear dipeptides to supercoiled p UC19 DNA was investigated in the presence of Cu(II), Zn(II), Co(II), Ca(II) and Mg(II) by agarose gel electrophoresis. The experimental results indicate that aromatic dipeptides had hardly any cleavage activities by the absent metal ions,and the cleavage activities could markedly enhanced when Co(II) was added to the solution. The optimum conditions on the cleavage of p UC19 DNA by dipeptides and metal ions were investigated from p H value, concentration and reaction time.The results show that the optimal conditions for DNA cleavage by dipeptides and Co(II) is p H 6.5 or 6.8, concentration 0.2- 0.3 m M, and time 48 h. Moreover, the cleavage mechanism of aromatic dipeptide on NDA was confirmed by experiment, it is hydrolytic.The interaction mode of DNA and aromatic dipeptide was studied by circular dichroism absorption spectroscopy. From the circular dichroism spectra between dipeptides-metal ion and DNA, it was concluded that dipeptides-metal ion can interact with DNA, and the groove binding mode was mainly existed.The interactions of aromatic dipeptides with monovalent mental ions were studyed by HPLC, and the binding constants(Ka) were acquired. It was found that L-His-L-His had stronger binding ability to the monovalent metal ions than other aromatic dipeptides and the affinity of aromatic dipeptides to Ag+ are higher than that of Li+, Na+, K+ and Cs+.