ABSTRACT
The rheological behavior of polyvinyl alcohol (PVA) aqueous solution is crucial to optimizing the processing technology and performance of PVA products. In this paper, the dynamic rheological behavior of PVA aqueous solution was investigated in detail. PVA solution with a concentration of 10 wt% showed unnormal rheological behaviors, that is, the liquid-like behavior in the high frequency (ω) region and the solid-like behavior in the low ω region. A storage modulus (G') plateau appears in the relatively low ω region as a gel with a network structure. Different from conventional hydrogel, this plateau has a low modulus, and the corresponding size of the relaxation unit is estimated to be 554 nm, being higher than the size of a whole PVA chain. It is believed that the network mesh is formed by the intermolecular hydrogen bonding interactions among PVA chains. The relaxation time of these meshes is longer than the reptation time of a PVA chain. Based on the relaxation spectrum and calculation analysis, it is found that the destruction of intermolecular hydrogen bonds, such as by heating up, adding sodium dodecyl sulfate, and shear operation, will make the relaxation unit (mesh) larger and lead to the left shift of the intersection of G' and loss modulus (Gâ³). In a PVA solution with a high concentration, multiple meshes of various sizes could be formed and thus generate multiple relaxation peaks. The large-sized meshes mainly contribute to the left shift of the intersection of G' and Gâ³, and the small-sized meshes contribute to the high plateau modulus. The results in this paper offer a new angle to analyze polymer solutions with strong intermolecular interaction.
ABSTRACT
OBJECTIVE: To prepare polyclonal antibody against invariant chain of Muscovy duck (Cairina moschata) (MDIi) and identify its reaction with MDIi extracted from tissues of Muscovy duck. METHODS: MDIi was amplified by PCR and used to construct the prokaryotic expression vector of pET-32a/MDIi by linking with the plasmid of pET-32a. Then pET-32a/MDIi was transformed into E.coli Rosetta to induce the prokaryotic expression. After identified by SDS-PAGE, prokaryotic expression products were further purified from running gel of SDS-PAGE and injected into mice to prepare polyclonal antibody against MDIi. The titer and specificity of the polyclonal antibody against MDIi were analyzed by indirect ELISA and Western blotting, respectively. The intensity of reaction between the polyclonal antibody and MDIi extracted from tissues of Muscovy duck was also identified by indirect ELISA. RESULTS: The prokaryotic expression vector pET-32a/MDIi was successfully constructed. About 40 kD recombinant proteins of MDIi were confirmed to be expressed in the form of inclusion body in Rosetta. Polyclonal antibody against MDIi with a titer of 1:128 000 was obtained from the immunized mice and its high specificity was demonstrated by Western blotting. The titer of reaction between the polyclonal antibody and MDIi was 1:32 000. CONCLUSION: The polyclonal antibody against MDIi was successfully prepared with a high titer and specificity. It has a strong immune reaction with MDIi extracted from tissues of Muscovy duck.