The Interaction Of Gelatin And Surfactant

The interactions of gelatin with three different types of surfactants and the influence effect of surfactants on interactions between gelatin and CAS have been studied through fluorescence and UV-vis spectroscopy, transmission electronic microscopy (TEM) after being freeze fractured and NMR technology, combined with the measurements of conductivity, pH and viscometry. Before now the method of TEM after being freeze fractured has been first applied in the study of interactions between gelatin and surfactants. This study, having some innovation can provide important information for further applications of gelatin and surfactant.(1) The interactions of gelatin with ionic surfactant CTAB (SDS).The cac1, cac2 and cmc values of CTAB (SDS) increase and the aggregation number decreases with the addition of gelatin in the CTAB (SDS)/gelatin/H2O system. The TEM image of this system after being freeze fractured show that the structure of the complex formed between CTAB (SDS) and gelatin molecules changes from linear, coiled and bead- necklace to rod-like with increasing surfactant concentration. Thecurve of fluorescence intensity, conductivity and thermodynamics function A G ofgelation/ CTAB(SDS)/ H2O find that the interaction between gelatin and CTAB is greater than that between gelatin and SDS. Different aggregation state of CTAB molecules has different effects on the critical associating concentration of gelatin and the effect of CTAB monomer is greater than that of spherical micelle. Compare with CTAB monomer and CTAB micelle, SDS monomer has the greastest effect on the critical associating concentration of gelatin.(2) The interaction of gelatin with nonionic surfactant Triton X-100.The study show there exits hydrogen bond and hydrophobic interaction between Triton X-100 and gelatin, which change the conformation of gelatin. The addition of gelatin increases the cmc of Triton X-100 slightly. The experiments of the freeze-fractured transmission electron microscopy and 1H NMR show that the presence of Triton X-100 makes gelatin chains coil first and then open, with little influence on the microenvironment of amino acid. When Triton X-100 concentration is larger than cmc,some of Triton X-100 micelles are absorbed on gelatin chain. A little amount of Triton X-100 can't have significant effect on the critical associating concentration of gelatin. When the Triton X-100 concentration is larger than 1.75%, Triton X-100 makes the associating of gelatin easier and the associating concentration of gelatin doesn't change with Triton X-100 concentration. (3) The effect of surfactant on the interactions between CAS and gelatin.CAS can decrease the fluorescence intensity of gelatin and it is a static quenching. The interactions between CAS and gelatin can be significantly influenced by temperature and the structure and concentration of surfactant. Thermodynamic parameters indicate that associating force between CAS and gelatin is hydrophobic interaction. Increasing temperature is helpful to the interaction between gelatin and CAS. The addition of surfactant can lower the A H and A S for the interaction of gelatin with CAS. When surfactant is at present, the decreasing order of the influence of structure on the effect of gelation on the CAS absorbance is CTAB, followed by SDS and then Triton X-100.