Effects of Storage Time and Hydrogen Peroxide on the Formation of Soy Globulin 15S in 11S Dilute Solutions Investigated by Analytical Ultracentrifu-gation
Two soy protein 11S fractions with differ-ent surface sulfhydryl contents were pre-pared.Utilizing analytical ultracentrifuga-tion,the effects of storage time and hydro-gen peroxide at different concentrations(0.5-100 mmol/L)on the two 11S fractions were investigated.Results show that after removing 2-mercaptoethanol(2-ME)by size exclusion chromatography,the 1 1S fraction with high surface sulfhydryl content(2.0 mol sulfhydryl/mol 11S)progressively formed 15S and 21S in dilute solutions during storage at 4 ℃ for 82 days.While,the 11S fraction with low surface sulfhydryl content(0.2 mol sulfhydryl/mol 11S)was stable under the same condition.Moreover,after treating the 11S with high surface sulfhydryl content with 1 mmol/L H2O2,the weight percentage of 15S reached the maximum value of 20％.The 15S induced by air and H2O2 could be totally con-verted to 11S with the addition of 10 mmol/L 2-ME,which could be attributed to that the disulfide bond linking two 11S molecules is on the surface of the 15S and easily accessible to the reducing agent 2-ME.This study helps us to deeply understand the formation mechanism of 15S and the stability of 1 1S.
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