Some Fluorescence Quenching Spectral Analysis Interacted With Bio-related Molecules

In recent years, analytical instruments and bio-science have seen rapid development, and the fluorescence spectroscopy for chemical analysis has become a very important tool, which has been widely applied to the determination of biological substances, inorganic substances, and drugs, etc.The first part of this paper inclueded the preparation of gold sol solution of spherical nanoparticle with 12nm by chemical reduction and chracterization with transmission electron microscopy (TEM). The fluorescence quenching caused by the interaction of gold nanoparticles with c-MYC oncogene protein has been investgated in PBS buffer solution (pH = 7.40) with an excitation wavelength of 295nm and an emission wavelength of 450nm. The quenching mechanism has been examined by theoritical calculation, indicating that the quenching constant was 6.291×10⁸L·mol^-1, the binding constant was 1.93×10⁶L·mol^-1, and the binding sites was 0.9969, so the quenching interaction belonged to static quenching. There was a linear relationship between c-MYC protein concentration and fluorescence intensity, and the detection limit could reach 2.51×10^-10μmol/L. The presented method had good reproducibility and stability with a recovery of 94.29-107.14%, so the approach for detection of c-MYC oncogene protein is feasible, showing its promising application on biomedical and molecular bioscience.In the second part, a fluorescence spectrophotometry based on o-methoxyl tetraphenylporphyrin (o-OCH3TPP) for analysis of trace amount of cadmium ion in environmental waste water with a high sensitivity and high selectivity bas been discussed in this paper. When the optimal concentration of the porphyrin was fixed as 5.0×10^-5mol/L and the optimal pH value was adjusted to 8.81 using Tris-HCl-tetrahydrofuran buffer solution, the fluorescence extinction value was proportional to the logarithmic value of Cd²⁺ concentration with the range of 5.0×10^-8 to 1.0×10^-6 mol/L, and the correlation coefficient was 0.9974 (n=10). The detection limit for Cd²⁺ could be evaluated to be 4.07×10^-8mol/L. In addition, no obvious interferences from some common metal ions were observed. Also, the presented fluorescence spectrophotometry possessed a very nice reproducibility and stability with a recovery rate of 98.20 102.00%, indicating that it was of feasibility for determination of trace amount of Cd²⁺ in environmental waste water, showing its promising application on people's health living and environmental protection.The third part of this paper related to detection of quercetin in drugs. Quercetin could make the BSA fluorescence quenching, and this is the principle for determination of quercetin content. The conditions of the experiment is under PBS buffer solution (pH = 7.40) with an excitation wavelength of 288 nm and an emission wavelength of 356nm. The calculation showed that the quenching constant was 5.233×10⁴L·mol^-1, the binding constant was 4.47×10⁶L·mol^-1, and the binding sites was 0.5362, so the quenching interaction belonged to static quenching. There was a linear relationship between the quercetin concentration and fluorescence intensity, with a detection limit of 2.43×10^-6μmol/L. This method had good reproducibility and stability with a recovery of 99.37 - 102.29%, which can be well applied to the determination of the quercetin in drug samples, showing its promising application in pharmaceutical industry.