Study On Interaction Of Cefixime With BSA And Determination Of Microbial Activity By Spectrofluorimetry

In this dissertation, the study of the interaction between cefixime and bovine serum albumin was discussed and a new method for the determination of microbial activity in environmental samples was proposed.The first section of the dissertation briefly introduced the structure, functions of protein and serum albumin’s composition, structural characteristics, physiological functions. The contents and methods of interaction of small ligands with bovine serum albumin were reviewed in detail.The second section of the dissertation studied the mutual interaction between cefixime and BSA by means of fluorescence spectra, UV-visible absorption spectra and circular dichroism spectra. The physical and chemical parameters were optimized. The experimental results showed that cefixime can quench fluorescence of BSA under simulative physiological conditions. According to spectroscopic data, quenching mechanism between cefixime and BSA was analyzed. The binding site numbers, the binding constants and corresponding thermodynamic parameters at different temperatures were calculated. Bsaed on Forster theory of non-radiation energy transfer, the binding distance and the energy transfer efficiency between drug and BSA were obtained. The action force could be able to infer from the thermodynamic parameters. Moreover, several methods including UV-visible absorption spectra, synchronous fluorescence spectra, three dimension fluorescence spectra and circular dichroism spectra were used to investigate the effects of cefixime on the conformation of BSA.The third section of the dissertation proposed the spectrofluoremetric method for measuring microbial activity in environmental samples. The proposed method was based on the principle in which colorless FDA is hydrolyzed by non-specic esterases including proteases, lipases, and esterases releasing a colored end product fluorescein which can be measured by spectrofluorimetry. Acetone (50%v/v) was used to terminate the hydrolysis reaction. The sensitivity of fluoremetric method was improved by means of optimizing physical and chemical parameters. Under optimized experiment conditions, the linear range was2-2000μg/L (R=0.9971) and detection limit (3σ) was3.1×10μg/L. The relative standard deviation was2.8%for the same soil samples in5repeated measurements. The proposed method was successfully applied to determination of microbial activity in soil samples with a recovery between90.6%and104%. In addition, the method was applied to the determination the distribution of microbial activity in profiles of soil samples and obtained satisfactory results.The last section was the summary of the experiment. The prospects of the study of the interaction between cefixime and BSA and the method for the determination of microbial activity in environmental samples were described.