The Studies On Sodium Alginate Polysaccharides Of Different Molecular Weights Interaction With HSA And Pb²⁺,Cd²⁺

In this thesis, the interaction of sodium alginate with different molecular weight, metal ions and human serum albumin were studied in detail, which is aimed at increase the possibility that specific molecular weight sodium alginate remove the excess metal ions in the human body. This thesis consists of the following four parts:Part one: The physiological activity, application range and preparation of different molecular weight of sodium alginate and the harm of cadmium ionon human body were introduced briefly. The research methods about the interaction of sodium alginate and cadmium ion, lead ion with human serum albumin were also introduced.Part two: Two sodium alginate samples were obtained by controlling the degradation reaction conditions. The result of HPLC analysis showed that sodium alginate was degraded and different degradation conditions lead to degradation products with different molecular weight. FT-IR spectra of sodium alginate before and after degradation suggested that the degradation reaction only reduced the molecular weight of sodium alginate, and did not change its molecular structure. Six different degradation products were obtained by separation of the two degraded samples. HPLC method were used to determine the relative molecular weight of the six degradation products, which showed that the molecular weightof them were 3715 D, 5011 D, 7413 D, 15850 D, 23450 D, and 64650 D, respectively.Part three: The interaction of the six different relative molecular weight sodium alginate with human serum albuminwere studied through the fluorescence quenching spectrometry, uv-vis absorption spectroscopy and synchronous fluorescence spectrometry. The results shows that quenching process is a static quenching process;the interaction constant was increased with molecular weight at first, but then decreasedgradually, and reached maximum value at the molecular weight of 15850 D; the value of combining points are approximate 1;The reaction types were hydrogen bonding and van der Waals force, which is related to the large number of hydroxyl of sodium alginate; Synchronous fluorescence experiments show that when ??=15 nm the maximum emission wavelength with blue shift, when ??=60 nm the maximum emission wavelength does not change. Sodium alginate have changedthe Tyrosine environment, but not change the microenvironment of the tryptophan.Part four: The equilibrium constant of the reaction between lead ion, cadmium ion and different relative molecular weight of sodium alginate were studied by using equilibrium dialysis method.The interaction between lead ion, cadmium ion and HSA and the interaction between six kind's relative molecular weight of sodium alginate reaction and HSA in the presence of metal ions were studied using the method of fluorescence quenching and synchronous fluorescence. The results showed that: molecular weight have significant influence on the equilibrium constant, the equilibrium constant was increased with molecular weight at first, but then decreasedgradually in 310K; the quenching type is static quenching, and the equilibrium constant of the interaction of lead ion, cadmium ion with HSA were decreases with the increase of temperature. The microenvironment of the tryptophan and tyrosine are not affected by metal ions; under the condition of lead ion and cadmium ion, the equilibrium constant and binding pointswere different with the change of relative molecular weight of sodium alginateand theprocess of sodium alginate interaction with HSA is not independent but the combination of the three interactional process.Through the comparison of quenching efficiency of sodium alginate with relative molecular weight of 15850 D interaction with human serum albumin under the condition of lead ion and cadmium ion.The results shows that Lead ions and Cadmium ions effect the interaction between sodium alginate and HSA by means of synergy.sodium alginate combine with metal ionsat first,soreduce the ability to combine with HAS lead to the quenching efficiency decline.Sodium alginate forming complexes with cadmium ion and lead ions,Ultimately affect thecontent of Lead ions and Cadmium ionscombined with HSA.These results provide a theoretical basis to use a certain molecular weight of sodium alginate to remove excess lead ions and Cadmium ions.