Various Spectrum And Molecular Simulation To Explore The Mechanism Of Action Between Small Molecules And Proteins

Drugs are closely related to the health of humans and animals.After entering the human body,drugs achieve therapeutic effects by interacting with proteins in the body.By investigating the interaction between drug small molecules and proteins under different external conditions,we can obtain the force,type of burst,and change of secondary structure content between drug small molecules and serum albumin,which can provide a theoretical basis as well as a research foundation for the process of drug application in the clinic.This thesis investigates the interaction of clobetasol propionate(Clobetasol propionate,CP)and the Tesetaxel side chain(Tesetaxel,Tt)synthesised in this thesis with serum albumin and the effect of different p H and temperature on the binding of small molecules to proteins,using a variety of spectroscopic methods including UV-Vis,IR and circular dichroism,as well as differential scanning calorimetry and molecular docking.The experiments are divided into two parts,focusing on their binding mechanisms and spectroscopic properties.Part I: This part explores the interaction mechanism of CP on bovine serum albumin(BSA)under different p H conditions using multispectral,differential scanning calorimetry and molecular docking techniques.The results of UV and fluorescence spectra showed that the CP and BSA complexes produced static bursts at different p H conditions,and the highest burst rate was observed at p H=7.4;Molecular thermodynamic and molecular docking results indicate that the non-covalent binding forces of the CP-BSA complex are hydrogen bonds,electrostatic interactions and hydrophobic interactions,with hydrophobic bonds playing the most important role;Simultaneous fluorescence spectroscopy and UV-Vis spectroscopy indicate that CP and p H affect the BSA conformation,resulting in an altered microenvironment and enhanced hydrophobicity.Infrared spectroscopy,circular dichroism and denaturation temperature tests suggest that hydrophobic forces are the main cause of the increased β-fold content in BSA,which may be the result of CP binding to the hydrophobic region of the α-helical structure in BSA and inducing a shift to the β-fold,resulting in a more stable conformation;The molecular docking results show that clobetasol propionate is surrounded by hydrophobic pockets and interacts with BSA primarily through hydrophobic forces.These results provide a theoretical basis for understanding how to reduce CP and other glucocorticoid drugs for skin side effect studies.Part II: Based on the current situation that the synthesis method of the side chain of tesetaxel is complicated and costly,this part explores an efficient method for the preparation of the side chain precursor of tesetaxel.Using 3-fluoropyridine-2-carboxaldehyde and p-methylaniline as the initial raw materials,chiral products with optical purity,i.e.the C-13 side chain precursor of tesetaxel,were obtained by condensation reaction,Staudinger reaction,deprotection and enzymatic hydrolysis and splitting.After NMR spectroscopy,it was confirmed that the target product obtained was tesetaxel.then combined Tt with human serum albumin(HSA)and investigated the interaction mechanism by various spectroscopic methods,circular dichroism spectroscopy,DSC experiments and molecular docking analysis.The fluorescence spectra showed a static burst mode during the interaction of Tt with HSA,which was verified by the experimental findings of the UV-vis spectra;the binding constant Ka increased with temperature at p H = 7.4,indicating that a complex was formed between Tt and BSA,which became more stable with increasing temperature;The thermodynamic calculations showed that ΔH and ΔS were less than 0,indicating that the hydrogen bonding between Tt and HSA was predominant.ΔG < 0,indicating that the reaction was spontaneous;the simultaneous fluorescence results indicated that the interaction between Tt and HSA changed the microenvironment around the protein and the binding site was closer to the Tyr residue;Circular dichroism,infrared spectroscopy,three-dimensional fluorescence spectroscopy and differential scanning calorimetry all showed that Tt interacted with HSA to alter the secondary structure of the protein;the molecular docking results showed that the compound Tt could bind well to the protein,forming a stable complex with a binding energy of-7.35 kcal/mol,and was able to form a strong hydrogen bonding interaction with LYS-199 at the active site of the protein.This is consistent with the thermodynamic results.Further studies using molecular dynamics simulations showed that the two could form a very stable compound through spontaneous reactions,with van der Waals forces as the driving force.