Study On The Interaction Between Nitrofuran And Bovine Serum Albumin

As a broad-spectrum antibiotic,nitrofuran drugs can effectively inhibit the activity of enzymes in microorganisms.Nitrofuran drugs are widely used in livestock and Aquaculture because they have good therapeutic effect on most diseases caused by protozoa and fungal pathogens.Studies have shown that nitrofuran drugs and their metabolites may have carcinogenic and teratogenic effects on the human body although nitrofuran drugs have low prices and good efficacy.As a most abundant protein in human and animal plasma,SA could interact with drug and affect the distribution and concentration,Therefore,studying the mechanism of the interaction between drugs and SA has certain research significance for understanding the toxicity of drugs.A variety of spectroscopic methods were used to study the interaction between two nitrofurans,nitrofurantoin?NFT?and nitrofurazone?NFZ?and bovine serum albumin?BSA?.This has a certain reference significance for in-depth understanding of the transportation and distribution of nitrofurans in living organisms,and to clarify the mechanism of action between nitrofurans and biological macromolecules.The research of this article is mainly divided into four parts:1.The interaction mechanism of NFT and its metabolite1-amino-hydantoin hydrochloride?AHD?in the individual presence condition and mixing of BSA was studied by fluorescence,UV-vis and time-resolved fluorescence under simulated physiological conditions?pH=7.4?.The experimental results show that the quenching mechanisms of NFT and AHD on BSA were mainly static quenching.The binding constants K_A of NFT and AHD and BSA were 6.02×10⁴ L mol^-1 and 4.94×10⁴ L mol^-1,respectively,and the number of binding sites n were 1.28 and 1.43,indicating that NFT/AHD both can form compound with BSA in the ratio of 1:1.It can be seen that van der Waals force and hydrogen bonding were the main forces between NFT/AHD and BSA from the thermodynamic parameters?H<0,?S<0.The working distance between NFT and BSA was 2.67 nm,and the working distance between AHD and BSA was 2.69 nm according to F?rster's non-radiative energy transfer theory,which indicated that there was a high possibility of energy transfer between BSA and NFT/AHD.The results of ultraviolet-visible absorption spectroscopy and simultaneous fluorescence spectroscopy showed that NFT/AHD can induce the conformational change of BSA.BSA has only one binding site with NFT/AHD,which was located at Site I of BSA subdomain II A.2.The metabolite AHD of NFT can affect the interaction mechanism between the parent NFT and BSA.The quenching constant K_sv of NFT for BSA increased to 7.91×10⁴ L mol^-1,and the binding constant K_A increased to6.72×10⁴ L mol^-1 when AHD was present.It shows that under the influence of metabolite AHD,the degree of quenching of BSA by NFT was enhanced.The combination of AHD and NFT with BSA has an additive effect under coexistence conditions.3.A variety of spectroscopic methods were used to study the characteristics of the NFZ and BSA combination reaction under simulated human physiological conditions.Studies have shown that:the complex,which formed by NFZ and BSA,caused the endogenous fluorescence quenching of BSA.The quenching methods are mainly static quenching and non-radiative energy transfer.The binding constants and the number of binding sites under different temperatures were obtained according to the Stern-Volmer equation.According to the Van't Hoff equation and thermodynamic formula,the thermodynamic constants of the interaction between NFZ and BSA were obtained,and the interaction force types of NFZ and BSA were determined as hydrogen bonding and van der Waals force.The conformational changes of BSA before and after interaction with NFZ were studied by ultraviolet-visible absorption spectroscopy and synchronous fluorescence spectroscopy.The site competition experiment was used to determine the binding position of NFZ on BSA,which is located at Site I of BSA subdomain II A.4.The effect of metal ions on the interaction between NFZ and BSA was studied.The experimental results show that when coexisting with metal ions Zn²⁺and Mg²⁺,the quenching constant K_sv and the binding constant K_A of NFZ to BSA will decrease.This indicates that the presence of Zn²⁺and Mg²⁺can weaken the degree of NFZ quenching BSA fluorescence,and reduce the binding ability of NFZ and BSA.Neither Zn²⁺nor Mg²⁺can affect the conformational change of NFZ-BSA.