Study On Synthesis Of Poly(pyridinium Salt)s And Their Interaction With DNA

Conjugated polymers with ?–?* electronic system and conjugated delocalized structure are a kind of polymer materials with special photoelectric properties.In recent years,the application of conjugated polymers in the field of chemical and biological sensors has received widespread attention.DNA is the carrier of genetic information and it shoulders the mission of genetic information.Taking conjugated polymer as optical signal output carrier to explore the interaction between biological molecules will help people to understand the pathogenesis of some diseases from gene level.In addition,a lot of antiviral drugs are also using DNA as the binding target,so it has important theory value and great practical prospects for constructing biological sensing platform based on conjugated polymers and systematically studies the interaction.In this thesis,we synthesized a series of water-soluble poly?pyridinium salt?s with cationic on main chain,and we used analysis methods such as UV-vis spectroscopy,fluorescence spectroscopy,circular dichroism and dynamic light scattering to study the interaction between calf thymus DNA?ctDNA?and polyelectrolyte.The work was focused on several aspects as following:1)Synthesis poly?pyridinium salt?s containing diphenyl oxide and diphenylmet-hane?named P1,P2?and study the interaction between them with ctDNAIn Tris-HCl buffer solution?2 mM,pH = 7.4?which was close to human physiological environment,we fixed the polyelectrolyte concentration and injected DNA to the system continuously.The UV-vis absorption indicated that the association constants of P1 and P2 with ctDNA are estimated to be 3.3 × 10⁵ M^-1 and 2.33 × 10⁷ M^-1,respectively.Fluorescence spectrum showed that the calculated quenched constant Ksv were estimated to be 3.39×106M^-1 and 5.10 × 106 M^-1.Thermal denaturation of ctDNA found that combination with P1,P2 increaced its melting temperature by 5 °C and 14 °C.Circular dichroism displayed that P1 and P2 had influence on double helix conformations of ct DNA.Dynamic light scattering?DLS?experiments proved that aggregation happened after polyelectrolyte P1,P2 combined with ctDNA.Therefore,we could conclude that the interaction between P1,P2 and ctDNA was mainly based on electrostatic and intercalation,and P2 combined with ctDNA more tightly when it compared with P1.2)Synthesis poly?pyridinium salt?s containing phenylphenanthridine?named P3?and study the interaction between them with ctDNAIn ethanol-Tris-HCl buffer solution?2 mM,pH = 7.4?,UV-vis titration spectra and fluorescence spectra indicated that there was strong interaction between P3 and ctDNA,forming a combination of about 1:1 stable complexes and the association constant was 2.20 ×10⁵ M^-1.In the range of pH = 6.0 to pH = 10.0,P3 had stable photophysical properties showing that it could detect DNA in a wide pH range.Thermal denaturation experiments of ctDNA found that when combined ctDNA with P3,the melting temperature increased by 13.8° C.Circular dichroism experiments further confirmed that in the process of combination,ctDNA conformation change gradually,base stacking was weaker and the double helix structure had become loose.Thus,interaction between P3 and ct DNA was mainly based on electrostatic and intercalation.3)Synthesis poly?pyridinium salt?s containing azobenzene?named P4?and study the interaction between them with ctDNAIn the aqueous solution?pH = 7.4?,UV-vis and fluorescence titration experiment preliminary confirmed the combination of P4 and ctDNA was based on static electricity.Circular dichroism experiment results showed that conformation of DNA did not change significantly after combination with P4.Dynamic light scattering experiments showed that with the increase of ctDNA concentration,the hydrodynamic diameter of P4-ctDNA complex increased from 41 nm to 824 nm.