Structure And Function Of β-casein From Human Milk And Microstructure Of β-casein Micelle

Formula-fed that based on the bovine milk infants are not in the minority at the present,so the difference between the human milk and bovine’s milk,especially differences in terms of p-casein is very important,it can direct to modify and process the bovine β-casein,provided a theoretical basis for the bovine milk based formula,which is more suitable for the intestinal absorption of the infant.In this study,fresh human milk was the research object,human milkβ-casein was separated by anion exchange chromatography and identified by Western-Blot eluent.Microscopic morphology of human milk β-casein were observed by using transmission electron microscopy,scanning electron microscopy,confocal electron microscopy,The tertiary structure of human milk β-casein was observed by Cryo-electron microscopy and the three-dimension was reconstructed by Chimera software.Surface hydrophobicity of the human and bovineβ-casein was studied by the Fluorescence spectroscopy,the secondary structure of the two samples was analysised by the Infrared Spectroscopy.And compared the emulsifying properties,foaming,solubility,thermal absorption properties,thiol content of the two samples,,you can get the following conclusions based on the experimental results of this study:(1)Established a method to separate the human milk β-casein by DEAE-Sepharose Fast Flow anion exchange chromatography,the purity of eluate was identified by SDS-PAGE and the P-casein eluate peak was identified by Western-Blot.The results show that it can react with the rabbit anti-human β-casein antibody that recognized the protein as the target protein.(2)Confocal,transmission and scanning electron microscopy was used to describe the form of human milk p-caseine micelles in the natural state.We found the minimum diameter of the micelles was about 20 nm by the Cryo-electron microscopy,Micellar interior is very loose by restructed the three-dimension of the micelles.(3)We analysis the structure and features information of β-casein in human and bovine milk used circular dichroism spectroscopy,infrared spectroscopy,fluorescence spectroscopy.The result shows that human milk β-casein has a flexible micelle-like conformation in the natural state,human milk β-casein had less secondary structure,more loose and open micelles tertiary structure and lower surface activity than the bovine milk β-casein.