Ultrafast Excited State Dynamics Of Zinc-Bilirubin Complex

Bilirubin,one of the final products of heme catabolism,has the functions of antioxidation and anti-inflammatory.The normal content of bilirubin is benefical to the prevention of modern diseases such as cancer,diabetes and stroke,and plays an indispensable role in human health.However,elevated level of bilirubin content indicates the presence of cirrhosis,jaundice or other diseases,reduced level of bilirubin content is considered to be associated with anemia or coronary artery diseases.The bilirubin content is also generally used in clinic as an indicator to test liver function and to identify various liver diseases.Therefore,accurate analysis of bilirubin content in body fluids has significant application values.Numerous methods have been found for the bilirubin content detection in serum samples at present.Among them,the fluorescence detection method has the advantages of quick reponse and high accuracy,attracting more and more researchers' attention.In this thesis,we aim to use zinc ions to enhance the fluorescence of bilirubin and apply it to the bilirubin content detection.Firstly,the fluorescence enhancement effect of zinc ions on bilirubin has been explored with the use of UV-Vis absorption spectra and steady-state fluorescence spectra.Based on the excitation spectra of zinc-bilirubin complex at different detection wavelengths,a model of the complex with two fluorescence subunits is proposed.The transient absorption spectroscopy has been used to verify the model and it is in good agreement with the previous conclusion about Zinc ions and bilirubin coordination.By analyzing the data of steady-state spectra and timeresolved absorption spectra,not only the mechanism of zinc ions enhancing the fluorescence of bilirubin has been explained,but also the dynamics model of the complex has been given.Besides,it is also found that bilirubin and zinc ions can coordinate as the structure of zinc porphyrin.The complex produced by this way has extremely low yields,but high fluorescence quantum yield.The solvent effect is also considered on zinc ions-enhanced bilirubin fluorescence and the optical properties of the complex.It is found that the solvent has little effect on the kinetics of the complex,and there exists a slightly difference in the efficiency of zinc ions-enhanced bilirubin fluorescence.