On The Interaction Of Losartan Potassium With Bovine Serum Albumin And Baicalin With Ache And Fluorescence Performance Of Nitrogen-doped Carbon Quantum Dots

In this paper,Experiment has investigated the interaction mechanism between protein and small molecules drug by several spectroscopic techniques.Nitrogen doped carbon quantum dots(N-CQDs)were synthesized through one-pot hydrothermal carbonization approach.Moreover,the N-CQDs present a sensitive response to Hg2+ ions.This thesis consists of four chapters.Chapter one: In this section,the structures and functions of bovine serum albumin(BSA)and acetylcholinesterase(AChE)were introduced briefly first.Then the interaction between protein with small molecules drug by fluorescence spectroscopy were reviewed.Last the synthesis process and surface-modification of N-CQDs were introduced.Their applications and development trends were also presented.Chapter two: The interaction between bovine serum albumin(BSA)and losartan potassium(LP)and the influence of rutin and baicalin were investigated under near physiological conditions by different spectroscopic techniques.The fluorescence of BSA was quenched remarkably by LP and the quenching mechanism was considered as static quenching.The results of thermodynamic parameters ?H(-134.3 kJ·mol-1),?S(-368.4 J ·mol-1.K-1)and ?G(-24.52 kJ·mol-1~-20.83 kJ·mol-1),indicate that both hydrogen bonds and Vander Waals forces play the main role in the binding process.The binding distance between BSA and LP was 3.183 nm,which indicates that the energy transfer from BSA to LP can occur with high probability.The decreased association constants and the increased binding distance of LP binding to BSA in the presence of rutin and baicalin were both due to their competitive binding to BSA.The results obtained from synchronous fluorescence and three-dimensional fluorescence spectra showed that the conformational changes of BSA during the binding process.Chapter three: Fluorescence,absorption spectroscopy,circular dichroism spectra were employed to research the spectroscopy characteristics of the interaction between AChE and baicalin,The fluorescence quenching mechanism,the number of binding sites,the binding constants,the binding distance of AChE were determined.The fluorescence of AChE was quenched remarkably by baicalin and the quenching mechanism was considered as static quenching.The results of thermodynamic parameters ?H(-174.6 kJ ·mol-1),?S(-489.9 J·mol-1.K-1)and ?G(-28.61 kJ ·mol-1 ~-23.71 kJ ·mol-1)indicate that both hydrogen bonds and Vander Waals forces play the main role in the binding process.The binding distance between AChE and baicalin was 2.85 nm.The conformational change of AChE in the prescence of baicalin were observed by synchronous fluorescence,three-dimensional fluorescence spectra and circular dichroism spectra.Last Ellman's method was used to study the changing of AChE activity by baicalin,The inhibitory activity was compared by means of calculating the half inhibitory concentration with the addition of baicalin,the IC50 value was 124?M.Chapter four: Nitrogen doped carbon quantum dots(N-CQDs)were prepared using L-serine acid and ethylenediamine as raw material through one-pot hydrothermal method.Under the excitation of 360 nm,the quantum yield of N-CQDs was 8.66%,the as-prepared N-CQDs were well dispersed in water.The morphology,structure and fluorescent properties of N-CQDs were characterized by transmission electron microscopy(TEM),High resolution transmission electron microscopy(HRTEM),Fourier transform infrared(FT-IR),absorption spectroscopy and fluorescence spectroscopy.FTIR analysis showed that the N-CQDs have hydroxyl and carboxyl groups on the surfaces.Moreover,the NCQDs present a sensitive response to Hg2+ ions,the fluorescence intensity showed a good linear relationship with the concentration of Hg2+ range from 1?M to 20?M and the detection limit was 7.33×10-5 mol·L-1(S/N = 3).The results showed that NCQDs might have a potential for the detection of Hg2+.