Study On The Interaction Between Human Serum Albumin And Berberine Hydrochloride

Human serum albumin?HSA?,the most abundant protein in human blood plasma,can bind various exogenous and endogenous compounds,which are also transpoted and stored in it.So it plays an significant role in biological and pharmacological functions.Berberine hydrochloride?BBR?is a common medication that is usually used to treat inflammation.We studied the spectral characteristics of human serum and its changes after adding berberine hydrochloride,in order to evaluate the interaction between them and the changes in its secondary structure.Through simulating human physiological pH condition,we studied the interaction between berberine hydrochloride and human serum albumin and secondary structure of the protein molecules by using fluorescence spectra and ATR-FTIR spectra.The results showed that when excitation wavelength was 280 nm,the maximum emission peak occurred at 334.8 nm,when the HSA concentration was 1.0×10^-6 mol L^-1,and the fluorescence intensity was 734.0.With the addition of berberine hydrochloride,the fluorescence intensity of human serum albumin gradually decreased,indicating that fluorescence quenching occurred between berberine hydrochloride and human serum albumin.And the results indicated that the interactions between berberine hydrochloride with human serum albumin led to the fluorescence quenching of human serum albumin.Synchronous fluorescence spectra and three-dimensional fluorescence spectra indicated that adding berberine hydrochloride to human serum albumin decreased the intensities of fluorescent peak,but had no effect on the position of fluorescent peak.ATR-FTIR spectra indicated that the secondary structure of human serum albumin molecules had no changes after binding to berberine hydrochloride molecules.The quenching mechanism between BBR and HSA is considered as mainly static quenching.We calculated the binding equilibrium constant K_A and numbers of binding sites n at different temperature and conditions.We also calculated the changes of thermodynamic parameters.It was calculated that static quenching occurred between berberine hydrochloride and human serum albumin,and the binding site was approximately equal to1.And it also showed that electrostatic interaction plays a key role in stabilizing the complex.According to the theory of F?rster energy transfer,we calculated the distance between the two is 4.51nm.