The New Toxicity Evaluation Of Five Typical Contaminants Target To Bovine Serum Protein

Environmental pollution is still one of the most important global problems at present. The environmental contaminants not only create destructions to the world ecology, but also threaten human survival and health seriously. The contaminants can enter organisms through respiratory tract inhalation, digestive tract intake and skin contact, and then damage the organs and tissues by interaction with biological macromolecule (protein, nucleic acid and so on). Thereforem, study on the mechanism of the contaminants toxicity to functional biological macromolecules is very essential. In this field, biological toxicity experiment is primary research technique, but this method is difficult to explain the toxicity mechanism of contaminants to biological macromolecules.Protein is an important functional molecule in vivo, and its denaturation may cause functional or structural damage to life body. The main reason of many diseases (such as cataract, mad cow disease and diabetes) is protein denaturation. Recent research shows that contaminants in environment have toxic effect on organism protein and lead to protein denaturation. Therefore, study on toxicity mechanism of environment contaminants to protein has been a hot topic in field of environmental pollution and healthy.In the research, we studied the toxicity mechanism of five typical contaminants targeted to bovine serum albumin (BSA) in molecule level by the methods of resonance light scattering (RLS) spectroscopy, fluorescence spectroscopy, ultraviolet-visible (UV-vis) absorption spectroscopy, circular dichroism (CD) spectroscopy and transmission electron microscopy, and a new method for evaluating the toxicity of contaminants is founded.The five contaminants choosen in the research are all ionic compounds, except nanoAg. But nanoAg prepared in our study aslo has electric charges. So this paper is helpful to the regularity research of contaminants toxicity.This study has six chapters, just as follows: Chapter1: The main contaminants toxicity evaluation methods, the survey for target protein molecular, the related research about contaminants toxicity and the experiment techniques are introduced in this part.Chapter2: By using the technique of resonance light scattering (RLS), we studied the toxicity mechanism of anionic surfactant sodium dodecyl benzene sulfonate (SDBS) targeted to bovine serum albumin (BSA) and found pH value was an important factor controlling the interaction. Furthermore, we made an in-depth research on the mechanism of the interaction by the techniques of UV absorption spectra, transmission electron microscopy (TEM) and circular dichroism spectra (CD).Chapter3: By using the technique of resonance light scattering (RLS), we studied the toxicity of the complex system composed by cetyl trimethyl ammonium bromide (CTMAB) and acid flavine G targeted to bovine serum albumin (BSA).The results show that the blended system increasing transformation of RLS spectrum proves this conclusion which joining cationic surfactant CTMAB and acid flavine G in the BSA solution could form ionic aggregation, while Protein structure has also undergone a marked change. Furthermore, we made an in-depth research on the mechanism of the interaction by the techniques of UV absorption spectra, transmission electron microscopy (TEM) and circular dichroism spectra (CD).Chapter4: By using the spectroscopic techniques of fluorescence spectroscopy, synchronous fluorescence spectroscopy, UV absorption spectroscopy, circular dichroism (CD) spectroscopy, we studied the toxicity mechanism of Pb²⁺ targeted to bovine serum albumin (BSA) in vitro condition. Pb²⁺ can cause the fluorescence quenching of BSA, which indicated that lead changed the skeleton group of BSA and caused the stepwise exposure of aromatic amino acid residues (Trp, Tyr, Phe) in the internal hydrophobic region of BSA. When the concentration of Pb²⁺ was up to 1.0×10^-4mol/L, the BSA would be completely denatured. The excess lead ion would react to the aromatic amino acid residues of BSA exposed in the impregnant, which leaded to the enhanced fluorescence quenching.Chapter5: By spectroscopy techniques, the toxicity mechanism of nanoAg to organism was thoroughly studied from the level of bovine serum albumin (BSA) molecule. Results showed that nanoAg had obvious toxic effects to BSA: nanoAg can increase the helix and decrease the Beta, leading to the skeleton structure of BSA loose; the exposal of internal hydrophobic amino acids enhanced, the characteristics fluorescence of BSA was obviously quenches. When the ratio of nanoAg and BSA increased to 1:96 (calculate in quality), the impacts of nanoAg to the fluorescence spectroscopy and resonance light scattering spectroscopy went to stabile. The result of resonance light scattering spectrum, TEM, circular dichroism spectra and electrophoresis experiments showed that BSA had destroyed the double-layer structure and covered in the surface, then generated to the BSA-nanoAg complex body because of the force among moleculars and electrostatic force.Chapter6: Conclude the research parts and analyze the development direction of this new method for contaminants toxicity evaluation.This study has enriched the research of contaminants toxicity mechanism, and provided some reference gists for contaminants toxicity prevention and treatment.