Investigation of the structural changes of bovine serum albumin caused by two antimicrobial drugs using multi-spectroscopic approaches

Structural changes of bovine serum albumin( BSA) caused by sulfamethoxazole( SMX) and sulfamethazine( SMZ) were studied using fluorescence quenching spectroscopy,Synchronous fluorescence spectroscopy,three-dimensional fluorescence spectroscopy,UV-vis absorption spectroscopy and circular dichroism spectroscopy( CD). The experiment results obtained from fluorescence quenching spectra data indicated that the fluorescence intensity of BSA was quenched by the gradual addition of SMX /SMZ; Experimental results obtained from the Synchronous fluorescence spectroscopy,three-dimensional fluorescence spectroscopy and UV-vis absorption spectroscopy qualitatively confirmed that the secondary structure of BSA was altered in the presence of SMX /SMZ in aqueous solution,and the quenching mechanisms of SMX /SMZ and BSA were both static quenching process confirmed by UV-vis absorption spectroscopy. Furthermore,the bindings of SMX /SMZ to BSA caused the changes of protein secondary structures,with the loss of α-helical stabilities. The calculating results exhibited reductions of α-helix structures from 53. 77%to 51. 82%and 53. 77%to47. 59%at molar ratios SMX /SMZ to BSA of 4 ∶1,respectively.