Research On Structural Stability Of Selenoprotein In Natural Selenium-enriched Soybean

By comparing the extracted six kinds of soybean protein-ordinary soy isolate protein(OSPI), selenium-rich soy isolate protein(SSPI),ordinary conglycinin(O-7S), Se-conglycinin(S-7S) and glycinin ordinary(O-11S), Se glycinin(S-11S), which was obtained by the classic isolate method of protein soluble in alkali and precipitated in acid and incorporated with centrifugal separation,the physical and chemical properties and secondary structure of the six protein will be discussed.Moreover, based on the study about effect on six protein by adding acrolein and peroxide free radicals, the Se-proteins capacity of antioxidant and the mechanism of which aerobic would effcet on morphology of selenoproteins.The results showed that two composition-proteins and fat are prominent in ordinary soyprotein and Se-enriched protein while a slight higher protein and a slight decrease fat content in Se-enriched one.Moreover,we also find out that S-11 S and SSPI owe the highest content of protein and selenium,respectively. By comparing the content of Se between Se-enriched and ordinary isolate protein, the content in SSPI is 10 times as the ordinnary ones while 3 times in S-7S and 11 times in S-11 S. Amino acid analysis showed a similar composition in six isolate protein,which glutamic acid and aspartic acid are the highest content amino acid and sulfur acid for the five proteins(except OSPI) is the first limiting amino acids. Furthermore, SDS-PAGE was also done to research the substructure further, the results reveal 6 kinds of proteins with clear stripe and high purity; FTIR results showed that the major soy protein secondary structure are α- helix and β-fold and the relevant propeties revealed that the best /worst capacity of holding water is O-7S, S-11 S, respectivily while the best/worst capacity of holding oil is SSPI and S-7S.In this study, peroxyl radical generated by thermal decomposition of 2, 2’–azobis(2-amidinopropane) dihydrochloride(AAPH) under aerobic condition was selected as representatives of free radicals derived from lipid peroxidation. The effects of AAPH on the propeties and structure of Se-enriched soy protein will be discussed.The results were as follows: the number of structure-α-helix、β-bend and random structure was getting larger while fewer β-sheet with the increasing AAPH.Based on SDS-PAGE, surface hydrophobicity, emulsification, emulsion stability share a same tendency, which increased firstly and then decreased. However, the protein solubility and content of free thiols decreased while protein carbonyl increased. Fluorescence emission maxim um(λmax) showed blue shift and the fluorescence intensity increased firstly and decresed. Above all, SSPI showd a better propeties than OSPI on account for a higher content of Se.Meanwhile, the effects of acrolein on the propeties and structure of Se-enriched soy protein will be discussed.With a tendency of grown-up content of acrolein,the results of FTIR、SDS-PAGE、propeties of isolate protein were as follows: FTIR illustrated a cutting-down tendency of β-bend; The subunit of SPI aggregated by SDS-PAGE and the content of protein carbonyl increased; The propeties of solubility showed worse and the free thiols was getting decresed while surface hydrophobicity, emulsification, emulsion stability suggested the tendency of increasing firstly and decreasing then;An excellent capacity of antioxidant activity was obtained in SSPI again,but the mechanism would be reported in future.