The Interaction Of Novel Naphthalimides With DNA

DNA intercalators represent one of the most important drug classes in cancer therapy. DNA intercalators,naphthalimides constitute an important class of drugs in anticancer therapy which have been the research hotspot in resent years.The studies of the interaction of DNA targeting antineoplastic agents with DNA is not only helpful to developing novel DNA probes,artificial nuclease,antiviral agents and antitumor agents,but also contributes to understanding the reaction mechanism of the molecule as a antineoplastic agent.A novel series of mono and bisnaphthalimides were synthesized by our lab.From combination of absorption titration,fluorescence titration and circular dichroism(CD) spectra, the binding of the series of mono and bisnaphthalimides with calf thymus DNA(ctDNA) were analysized.Further more,their antitumor activities were evaluated against four tumor cell lines.The ablities of cleaving pBR322 DNA by these compouds were investigated.And their ablitities of inhibiting the catalytic activity of DNA topoisomerase I were studied.This master degree thesis consisted of two sections as follows:(1) The DNA binding abilities of the novel naphthalimides sNIT-2,sNIT-3,sNIT-6, dNIT-2,dNIT-3 and dNIT-6,were studied by fluorescence quenching method using EB as fluorescence probe.And the mechanism of the interaction between six momo and bis naphthalimides linked by methyl-isothiourea cation ctDNA was studied by absorption titration,fluorescence titration and CD spectra.The results showed that the naphthalimides containing the isothiourea group have higher DNA binding abilities than the ones containing the thiourea group,the compounds with longer linker have higher DNA binding abilities than the ones with shorter linker;All the novel naphthalimides could intercalate into DNA base pairs;There were no electrostatic interactions between dNIT-3,dNIT-6 and ctDNA except dNIT-2;The equilibrium constants of the novel naphthalimides with ctDNA were determined by the double reciprocal method;Comparing the equilibrium constants of these naphthalimides,we found that the longer the side chains(monomer) or the linkers(dimer) of these naphthalimides,the higher DNA equilibrium constant of them.It was also confirmed that the mechanism of the fluorescence quenching of novel naphthalimides by ctDNA was static quenching except dNIT-3. (2) The catalytic cleavage of pBR322 DNA by these novel naphthalimides containing the isothiourea group was investigated using gel electrophoresis.The novel naphthalimides' antitumor activities and the ablitities of inhibiting the catalytic activity of DNA topoisomerase I were studied.The experimental results indicated that all they had no ablities to cleave pBR322 DNA.Compared with the mono-naphthalimides,the bis-naphthalimides had much higher cytotoxicity against cancer cells and dNIT-6 had the highest cytotoxicity among these compouds.At the concentrations 80μM,all the novel naphthalimides showed the DNA topoisomerase I inhibiting abilities.Especially,dNIT-6 could inhibit the activity of DNA topoisomerase I at the concentrations 40μM.This indicated that DNA topoisomerase I may be the target of these novel naphthalimides in vivo.