The Research On The Interaction Of The Dipeptides And Calf Thymus DNA(CT-DNA) Under The Assist Of Metal Ions

As an inherently chiral molecular, desoxyribonucleic acid(DNA) has played a key role in the process of cell replication, which is helpful to the development of drugs and possible cures for disease. Owing to the special features, the interaction between peptide and DNA known as one of the potential chemotherapeutics, which have attracted us more and more attention. Therefore, it is very significant to explore the interaction mechanisms of DNA with peptide and metal ions, which is beneficial for expounding the secrets of life and enhancing the health of human beings. In this paper, experiments has investigated the interaction mechanism between 10 dipeptides and CT-DNA under the assist of metal ion by several spectroscopic techniques,meanwhile, also has studied the binding sites, binding mode and action mechanism.Firstly, in physiological condition(pH=7.40), the interaction between dipeptides and CT-DNA under the assist of metal ion have been studied by UV-Vis spectrometry.The result showed that dipeptides always form compound with metal ion at first, then the compound interact with CT-DNA. In addition, dipeptides interacted with CT-DNA in the mode of groove binding, by inserting into the major and minor grooves of CT-DNA.Secondly, the interactions of the dipeptides with CT-DNA aided by metal ions had been investigated by fluorescent quenching technique under the simulative physiological conditions. We founded that the quenching of CT-DNA-EB fluorescence by dipeptide-metal ion complex are mainly static quenching and the static quenching constant(Ksv) decreases with increasing temperature. According to the van’t Hoff equation, the thermodynamic parameters were estimated. The results indicated that dipeptides interacted with CT-DNA mainly through hydrogen interactions, and accompanied by hydrophobic interactions. The entropy increase and the free energy reducing in this combining process proved it is a spontaneous procedure. Moreover, dipeptides interacted with CT-DNA in the mode of groove binding have been fully vindicated.Thirdly, CD spectral technology was used for examining the changes in thestructure of the CT-DNA treated by dipeptides, metal ions and dipeptide-metal ion complex. Only in presence of complexes, the intensity of both the positive and negative bands decreased. This suggests that the CT-DNA binding of the complexes induces certain conformational changes. The CD spectral changes clearly demonstrate non-covalent interaction between the complexes and CT-DNA, probably via groove binding. The results were similar to UV-Vis and fluorescent spectra analysis.