Study On The Interaction Between Chlorogenic Acid-Nano Gold And Protein

Nanogold is one kind of precious metal nanomaterials which have been studied more mature at present.Because of its good biocompatibility,low cytotoxicity and excellent loading,it has been widely used in biomedical,material chemistry and other fields.In this paper,the purpose of research is to comply with the purpose of green environmental protection.Using a natural compound chlorogenic acid as a modifier,a series of chlorogenic acid-nano gold particles with different sizes are regulated and synthesized.The main findings can be summarized as follows:1.Controllable synthesis of chlorogenic acid-nano gold particles and evaluation of their properties.With reference to the Frens reduction method,using chlorogenic acid as a modifier,chlorogenic acid-nano gold nanoparticles with size ranging from 18.94 ±1.81 nm 48.72±6.47 nm was quickly and simply synthesized.The UV-Vis spectra showed that the characteristic peak of chlorogenic acid-nano gold particles was near 520 nm,and the absorption peak of chlorogenic acid was displayed in the range of 200～300 nm.Transmission electron microscopy(TEM)showed that chlorogenic acid-nano gold particles were mainly spherical nanoparticles,One-Way ANOVA of the average particle size was 18.94 ±1.81 nm,30.42 ±6.32 nm,37.86 ±3.80 nm,48.72±6.47 nm.High-resolution TEM and selective area electron diffraction showed that these nanoparticles were all face-centered cubic polycrystalline gold structures.The stability of chlorogenic acid-nano gold colloids with different particle diameters was measured at a fixed wavelength.The results show that chlorogenic acid-nano gold particles have good stability.The growth curves of E.coli(ATCC 25922)and S.aureus(ATCC 25923)were determined by chlorogenic acid-nano gold.The results showed that chlorogenic acid-nano gold had a certain antibacterial effect on the two kinds of bacteria.2.Study on the interaction between chlorogenic acid-nano gold particles with different sizes and human serum albumin.Simulate human physiological environment,with the increase of chlorogenic acid-nano gold particles in the system,the absorption value of human serum albumin near 280 nm gradually increases,and the absorption band becomes wider,indicating that chlorogenic acid-nano gold particles and proteins interacted with each other,and the chromophores in the human serum albumin were continuously exposed to the outside,which changed the microenvironment of human serum albumin.Fluorescence spectrum data show that chlorogenic acid-nano gold particles can well quench the endogenous fluorescence of human serum albumin,and the quenching types are static quenching.The binding constants and binding sites of two different sizes of chlorogenic acid-nanogold particles interacting with human serum albumin can be obtained according to the fluorescence spectrum data.Experimental results show that the interaction force between chlorogenic acid-nano gold particles with size of 18.94 ± 1.81 nm and human serum albumin is mainly hydrogen bond and van der Waals force,and the interaction force between chlorogenic acid-nanogold with size 48.72±6.47 nm and human serum albumin is gravity.The fluorescence changes of tryptophan and tyrosine residues in proteins after the interaction between two different sizes of chlorogenic acid-nano gold particles and human serum albumin molecules were analyzed by synchronous fluorescence spectroscopy.The results showed that both sizes of chlorogenic acid-nano gold particles could quench the fluorescence of these two amino acids.Circular dichroism showed that the secondary structure of human serum albumin was affected by the increase of concentration of chlorogenic acid-nano gold particles,which showed the increase of α-helix.3.Study on molecular interactions between chlorogenic acid-modified or unmodified gold nanoparticles and lysozyme.Spectroscopic studies of the interaction between unmodified nano-gold,chlorogenic acid-nano gold particles and lysozyme with comparable particle size,which showed that the two molecules interact and form stable complexes.Thermodynamic parameters indicate that the force between unmodified nanogold and lysozyme is electrostatic attraction,while the force between chlorogenic acid-nano gold particles and lysozyme is hydrogen bond and van der Waals force.It was found that gold nanoparticles that were synthesized using chlorogenic acid as a modifier had a stronger binding force to lysozyme and had a relatively small effect on its conformation.Therefore,the results of this study encourage attempts to use nanomaterials synthesized from natural extracts as modifiers as promising nanocarrier candidates for next-generation drug delivery applications.