Structural And Functional Changes Of Three Proteins In Egg White During Storage

The present thesis focused on the structure and function between egg white protein structure and egg white properties. A series of experiments related to ovalbumin, lysozyme and ovomucin’structure and egg white properties has been performed. The main research contents and results are as follows:First, detect the structure changes of ovalbumin during egg storage. The results showed that endogenous fluorescence intensity of ovalbumin has increased from125to330during storage, This means that the microenvironment polarity of Trp, Tyr, and PHe in ovalbumin has declined. Combined with subsequent Fourier transform infrared spectroscopy we know that ovalbumin fluorescence decrease was mainly due to the occurrence of intermolecular aggregates. In ovalbumin β-sheet content highest, accounting for35.3%. Random coil structure of ovalbumin in storage on day0and day50were20.6%and27.5%; Random coil structure in infrared results of ovalbumin accounted for20.14%, while in50days random coil rose to24.02%; Raman results showed that, Trp of ovalbumin decreased from0.45to0.14in day0to day50; PHe intensity decreased from0.78to0.42; disulfide bond strength at505cm-1decreased from0.43to0.18; Tyr throughout the storage process the smallest decline, down only0.02units of value. Decrease in the peak intensity of disulfide means the disulfide of ovalbumin molecules has fractured.Secondly, the structure of lysozyme during egg storage has been detected. Fluorescence intensity is from52to73for lysozyme.It was mainly due to Trp residues continuously embedded into the intramolecular.0days of lysozyme is rich in a-helix and β-sheet structure, belong to the highly ordered α+β type protein.a-helix content highest in lysozyme, accounting for34.72%. Lysozyme random coil structure consists24.25%to36.52%on0day to50days of storage. Infrared results of lysozyme was similier to circular dichroism. lysozyme random coil content on day0and day50were27.62%and37.27%. In Raman spectroscopy lysozyme contains four pairs of disulfide bonds, during storage we can observed the peak displacement of disulfide, this illustrates that the disulfide linked two domains of lysozyme has fractured first.Third, we have detected the structure of ovomucin during storage. The intrinsic fluorescence intensity of ovomucin has declined from365to176. Ovomucin was a highly polymerized glycoprotein molecules, during egg storage ovomucin transition from insoluble to soluble, and the increasing collisions between molecular was the mainly reason of the decrease in fluorescence intensity. In addition, ovomucin denaturation and aggregation allowed more Trp residues move to a more polarity microenvironmen. Ovomucin molecules fall in the degree of polymerization during storage, ovomucin molecular disorder rising solution state (random coil increased from26.6%to35.8%). Infrared spectra of ovomucin shows random coil content declined during storage, showed peak area1660-1640cm-1at day0decreased from28.36%to26.34%for50days. This with its own degree of polymerization in constant decline. Compared with the circular dichroism, the solution state ovomucin was closer to the natural ovomucin, Circular dichroism changes therefore more representative ovomucin change during storage.Fourth, using an antibody specifically binding there to ovomucin to establish a fast and efficient method to detect in vivo ovomucin content with indirect ELISA. The concentration range of the standard curve was50ng/mL-1000ng/mL; other major contaminating proteins (ovalbumin, ovotransferrin, lysozyme) antibody cross-reactivity between the egg white and egg within less than0.01%, description that the method was not only high sensitivity but specificity.Finally, the emulsifying activity, emulsion stability, foaming, foam stability of three proteins and egg white, gel properties of ovomucin and egg white, melting wall activity of lysozyme and egg white were measured, and was analysised with bivariate correlation. The results showed that random coil of ovomucin and β-sheet of ovalbumin were affected egg white emulsifying activity (Significant differences <0.01), correlation coefficients were-0.936and0.919respectively; emulsion stability is mainly affected by lysozyme a-helix and random coil, the correlation coefficient is0.859and0.908, significant differences <0.05, which is a significant correlation; foaming ability of egg white was related to β-turn of ovalbumin, correlation coefficient0.914, significant differences <0.05; foam stability primarily related with lysozyme ordered structure (a-helix, β-sheet and β-turn) on which the β-turn is highly significant related, significant differences <0.01, a-helix and β-sheet significant related, difference coefficient <0.05; lywallzyme activity and gel properties of egg white were highly relevant with β-sheet of lysozyme and random coil of ovomucin respectively, significant differences were both less than0.01.