Spectroscopic Study On The Interaction Of Meloxicam With Several Enzymes And Albumin

In recent years,the study of the interaction between exogenous small molecular drugs and proteins has become an important research topic.Meloxicam?MEL?is a widely used oral drug.When meloxicam is taken into the human body,it will come into contacting with a variety of proteins in the body and interact with each other.In this paper,meloxicam and pepsin?PEP?,trypsin?TRP?,porcine pancreatic lipase?PPL?,?-amylase??-AMS?,lysozyme?LYSO?and bovine serum albumin?BSA?were studied.Six binding systems were studied by fluorescence spectroscopy,synchronous fluorescence spectroscopy,UV-vis spectroscopy,circular dichroism spectroscopy and molecular docking methods.Chapter one:Several spectral methods and molecular docking techniques used in the research were reviewed,MEL and several model protein molecules involved in MEL were summarized,and the development in the field of drug-protein research was described and prospected.Chapter two:Study on the interaction between MEL and PEP by spectroscopy.The binding constant K_a,the number of binding sites n and other experimental parameters were obtained by fluorescence experiments,which indicated that the stable compound at 1:1 was formed by static quenching.The UV-vis absorption spectrum experiment showed that the binding changed the conformation of PEP.Through the discussion of thermodynamic parameters,it was known that the hydrophobic force and hydrogen bond were the main forces driving the binding of MEL to PEP.The molecular docking experiment can further explain this conclusion.The docking results also showed that the binding changed the microenvironment at the active center of PEP,which thus had an impact on the catalytic function of PEP.The binding rate model of the system was established based on the data of spectral experiments.under the experimental conditions at 310 K,the drug binding rate of the binding system was2.97%¹.39%,and the protein binding rate was 2.97%⁴8.30%.Combined with the discussion of molecular docking,it could be speculated that patients taking MEL will have a certain effect on the digestive function of the stomach,which was consistent with the side effects of the stomach caused by taking drugs in MEL drug instructions.Chapter three:The interaction between MEL and TRP was discussed under the condition of pH=7.40.Fluorescence experiments showed that MEL and TRP formed a stable compound at 1:1 by static quenching.?G<0 indicates that the binding was spontaneous,and the hydrophobic force and hydrogen bond were the main forces driving the binding reaction.Synchronous fluorescence spectra and circular dichroism spectra experiments showed that the binding changed the microenvironment of TRP.At the experimental temperature,the binding distance r<7 nm,indicating that there was a non-radiative energy transfer between MEL and TRP molecules.Molecular docking simulation showed that the best binding site of MEL and TRP was located at the catalytic active site of TRP,indicating that the binding would affect the microenvironment of amino acid residues at the catalytic active site and it would affect the catalytic function of TRP.Chapter four:The interaction between MEL and PPL was studied by synchronous fluorescence spectroscopy.The experimental results showed that MEL and PPL combined spontaneously in the form of static quenching and the hydrophobic interaction and hydrogen bond were the main forces of the binding system.The quenching ratio of tryptophan?Trp?residue in lipase(N_SFQR?Trp?)was larger than that of tyrosine?Tyr?residue(N_SFQR?Tyr?),indicated that the position of the binding reaction was closer to the Trp residue.The synergistic study of the binding system showed that there was no synergistic effect between MEL and PPL.Molecular docking showed that the binding changed the microenvironment near the active center of PPL and affected the catalytic activity of PPL.The binding rate study described the changes of free contents of Trp and Tyr residues in drugs and proteins after binding,which showed that the binding of MEL and PPL basically did not affect the efficacy,but it would affect the digestion and absorption of fatty substances in human body.Chapter five:Under the condition of pH=6.80,the binding between MEL and?-AMS was studied by spectroscopy and molecular docking methods.MEL and?-AMS spontaneously formed a stable system at 1:1 in the form of static quenching under hydrophobic interaction and hydrogen bond driving.Synchronous fluorescence experiments and UV-vis absorption spectra experiments showed that the binding could change the conformation of?-AMS,make it hydrophobic and tend to fold.Molecular docking experiments showed that the best binding site of the binding system was near the catalytic active center of?-AMS,and the binding might affect the catalytic activity of?-AMS.In the study of system binding rate,the changed of free content of MEL and?-AMS was discussed deeply,and it was shown that the binding effect would affect the digestion and absorption of starch.Chapter six:Using LYSO as a model protein,the interaction between MEL and LYSO was studied by multispectral method under the condition of pH=7.40.The results showed that MEL reacted with LYSO to form a stable compound at 1:1 in the form of static quenching,and the conformation of LYSO was changed by the combination of MEL and LYSO.The discussion of thermodynamic parameters showed that hydrophobic interaction and hydrogen bond were the main binding forces of the driving system,and the results of molecular docking further illustrated this point of view.On this basis,molecular docking experiments also showed that the binding site was near the active center of LYSO.The binding rate was analyzed according to the content of LYSO in human plasma environment and the oral dosage of MEL.It is suggested that after oral administration of MEL,the effects on the anti-inflammatory and bactericidal ability of LYSO and the concentration of free MEL can be ignored.Chapter seven:Under the condition of pH=7.40,the quenching mechanism between MEL and BSA was studied by fluorescence experiment.The results showed that MEL and BSA formed a stable compound at 1:1 in the form of static quenching.?G<0 indicated that the binding was spontaneous,and the hydrophobic force and hydrogen bond were the main forces driving the binding reaction.The conformational study of the binding system was carried out by synchronous fluorescence experiment and UV-vis absorption spectrum experiment.The results showed that the binding enhanced the hydrophobicity of BSA microenvironment and made the protein tend to fold state.At the experimental temperature,the binding distance?r?between MEL and BSA was less than 7 nm,indicating that there was a non-radiative energy transfer between MEL and BSA.