DNA And HSA Interaction Of Water-soluble Carboxyl Porphyrins And Its Metal Complexes

With the application developing of porphyrin in biology and medicine, various synthetic water-soluble porphyrins had been prepared and extensively studied. Porphyrin is mainly used as drugs to diagnosis and treat cancer in medicine, photodynamic therapy with porphyrin as photosensitizer has become an effective method of treating cancer. The interaction between porphyrins or metalloporphyrins and DNA or HSA may provide useful information for their use in medicine. Cationic water-soluble porphyrins have been studied intensively for their unique strong DNA binding and nuclease-like activity. Anionic porphyrin is proved to have better cell membrane permeability than cationic porphyrin and this may render it higher biological activity. In order to extend the biological application scope of anionic porphyrins, this thesis focused on the DNA and HSA binding and nuclease activity of anionic carboxyl porphyrin and its metal complexes. The main contents of this thesis are as follows:1. A new water-soluble anionic meso-tetrakis(carboxyl) porphyrin and its znic(II), manganese(III) and iron(III) complexes were prepared by hydrolysis of their corresponding 5,10,15,20-tetrakis(ethoxycarbonyl)porphyrin. The synthesized porphyrins were well characterized by UV-Vis, MS, NMR spectra.2. The interaction between these compounds and calf thymus DNA(ct-DNA) were studied by UV-Vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy and viscosity experiments. Results revealed that all of them bind to ct-DNA via outside binding mode with 2-Mn has the highest affinity.3. The nuclease activities of synthesized porphyrins were studied by agarose gel electrophoresis experiments. 2 displayed good photonuclease activity, but preliminary results indicate signlet oxygen or hydroxyl radical were not the reactive species; 2-Mn and 2-Fe exhibited good chemical nuclease activity in the presence of hydrogen peroxide as oxidant, and 2-Mn was performed to be a better DNA cleavage ability. Inhibitor tests suggested that hydroxyl radical was one of the species for the oxidative DNA scission.4. The in vitro inhibitory activities of synthesized porphyrins against carcinoma of human breast cells(MCF-7), human hepatocellular carcinoma cells(Hep G2) and human cervical carcinoma cells(He La) were evaluated by MTT. 2-Mn and 2-Zn exhibited considerable photocytotoxicity against Hep G2 tumor cell lines, especially 2-Mn with its IC50 reaches 39.2 μΜ.5. The interactions of HSA with porphyrins were also investigated by multi-spectroscopic techniques and molecular docking. The fluorescence quenching of HSA by compounds was a static process with moderate affinity, the number of binding sites was approximately 1. The binding site investigation was carried out using warfarin, ibuprofen and digitixon as site markers fluorescence probe, the results revealed that 2 and 2-Mn mainly bind at site I, while 2-Zn mainly bind at site II and 2-Fe mainly bind at site III. Synchronous fluorescence, UV-Vis absorption and CD spectroscopy showed that the interaction of HSA with porphyrins induced a conformational and microenvironment change of protein. The non–radiation energy transfer was occurred between porphyrins and HSA, and the major acting force were hydrogen bond force for 2, while electrostatic interaction and hydrophobic ineraction for 2-Zn, 2-Mn and 2-Fe, respectively. The molecular docking results coincide well with the aforementioned thermodynamic analysis and competitive binding experiments. The order of binding strength is as follows: 2-Mn > 2-Fe >2-Zn > 2.