Studies Of The Interaction Between Metal Complexs And L-Cysteine And DNA By Spectrofluorimetry And Its Applications

For cysteine detection, the mechanism between small molecule fluorescent probe andnucleic acid, the quick method of nucleic acid detection, the paper’s main work issummarized as follows:In Britton-Robinson buffer solution of pH7.5, Cu²⁺could form the Cu²⁺-calceincomplex, calcein fluorescence quenched. When Zn²⁺was added, the fluorescence intensityincreased a little. However, the presence of cysteine, owing to cysteine could reduce Cu²⁺to Cu+. Meanwhile, the release of calcein from the complex could combine with Zn²⁺andthe fluorescence increased. So we established a new fluorescence method of cysteinedetection. Under the optimum conditions, the increase in signal intensity was linear therange from3.0×10^-7to1.2×10^-5mol L^-1and the limit of detection was4.0×10-8mol L^-1.The method was successfully applied to the determination of cysteine in human serumsamples and the recovery was satisfactory.the fluorescence and absorption spectra of DNA-Tb³⁺-PUFX were studied by usingTb³⁺-PUFX fluorescent probe. The results indicated that the fluorescence intensity ofTb³⁺-PUFX could be greatly enhanced by DNA, and the fluorescence intensity was inproportion to the concentration of DNA. Accordingly, a new method of DNA detectionwas established and the fluorescence enhancement mechanism was discussed. Under theoptimum conditions, the dynamic ranges of hsDNA and ctDNA were3.0×10^-9—1.0×10^-6g mL^-1,5.0×10^-9—8.0×10^-7g mL^-1and the limits of detection were2.1×10^-9g mL^-1,2.9×10^-9g mL^-1, respectively. The method was applied to the DNA determination insynthetic samples and the result was satisfactory.The interaction between Cu²⁺-PUFX and DNA was investigated, using the NeutralRed dye as a spectral probe by UV-vis absorption and fluorescence spectroscopy. Theresult indicated that Cu²⁺-PUFX complex could bind to DNA and the major binding modewas intercalative binding. The binding constants K and number of binding sites n ofCu²⁺-PUFX complex with DNA and the thermodynamic parameters were calculated fromthe Stern-Volmer graph at different temperatures. The result showed that the mode ofquenching between Cu²⁺-PUFX and DNA was static quenching. The negative value of ΔGrevealed the interaction process was spontaneous, while the negative ΔH and positive ΔS values indicated that the hydrophobic interaction played a major role in the intercalativebinding between Cu²⁺-PUFX and DNA.