Spectroscopic study of conformation changes of bovine serum albumin in aqueous environment

The secondary structural changes of bovine serum albumin (BSA) aqueous solutions with and without calcium cations were investigated by attenuated total reflection-Fourier transform infrared (ATR-FTIR) technology. The spectra of BSA solution and BSA dry powder were mainly reflected the formation of hydrogen bonds between water and BSA. Further investigation indicated that the concentrations of calcium cations in BSA aqueous solution also affected the secondary structural change of the protein. Amide I band was red shifted and amide II band was blue shifted in aqueous environment compared with the dry BSA powder, and the addition of calcium cations further changed the amide bands position, which led to the change of the secondary structure. The result was coinciding with the Raman spectroscopy.

FTIR-ATR study for adsorption of trypsin in aqueous environment on bare and TiO2 coated ZnSe surfaces

Undesired adsorption of proteins brings big troubles to marine structures.The settled proteins change the physical and chemical properties of the surfaces,which allow marine fouling organisms to settle down on the structures.Therefore,to understand the adsorption mechanism of proteins is very helpful to find an environment-friendly solution against biofouling.Many approaches have been developed to study protein adsorption,but most of them are insufficient to give the chemical interaction information between proteins and surfaces.Fourier transform infrared spectroscopy with attenuated total reflection(FTIR-ATR)is an efficient,fast and non-destructive method for in situ surface measurement,which greatly minimizes the interference of water to infra red spectra,because of the very small depth of penetration of the evanescent wave.In this paper,an in situ FTIR-ATR technology was used to investigate the adsorption process of trypsin on a bare ZnSe surface and on a TiO2 coated ZnSe surface,and the effect of calcium cation strength and ultraviolet light irradiation on the secondary structure of trypsin were also evaluated.FTIR spectra of trypsin showed that Amide I band red shift and AmideⅡband blue shift in aqueous environment on both surfaces compared with the dry trypsin powder,and the addition of calcium cations further changed the Amide bands position,which indicated that the change of the secondary structure could be interfered by the environment.The hydrogen bond formation between water and trypsin,the interaction between surface and trypsin,the interaction between hydrated calcium cations and trypsin,are major facto rs to change the secondary structure of trypsin,and UV light irradiation also showed its influence for the secondary structure.

ATR-FTIR study of Bacillus sp. and Escherichia coli settlements on the bare and Al_2O_3 coated ZnSe internal reflection element

Marine microorganism accumulated on the surface of ships or pipelines would accelerate fouling organisms, such as mussels and barnacles, adhered on the surface. It was significant to understand the bio-interaction between the microorganisms and the surface. Attenuated total reflection(ATR) Fourier transform infrared(FTIR) spectroscopy was used to study the initial stages of marine microorganism adhering to surfaces, because it could probe the microorganism interaction to the surface regardless of the water interference. Bacillus sp. and Escherichia coli were selected to study the initial attachment on different surfaces, because they were typical fouling microorganisms and showed opposite Gram stain results. The assays were conducted respectively in dried and settled bacteria on two different surfaces(ZnSe, Al2 O3 coated on ZnSe). IR spectra of settled bacteria showed amide I band red shift and amide II band blue shift in aqueous environment on both surfaces compared with the dry bacteria. The reasons of amide bands shift were investigated and it was discovered that the hydrogen bond between the water and the protein of the bacteria led to the protein secondary structure change. ATR-FTIR provided an approach to study the attachment process and showed dynamic changing process on the surface, and it could be an appropriate approach to study the interaction between proteins and chemicals.