Effects of Sodium Dodecyl Sulfate, 2-Mercaptoethanol and EDTA on the Chemical Forms of Copper and Zinc in a Soybean Protein Fraction

Abstract

The effects of sodium dodecyl sulfate, 2-mercaptoethanol and EDTA on the distribution and binding status of copper and zinc in the soybean protein fraction were examined by gel filtration on Sephadex G-100. Copper and zinc in the protein fraction were both associated primarily with the major components of >100, 000 in mol wt. The molecular distribution of zinc in the protein fraction of >100, 000mol wt differed slightly from that of copper. Gel filtration of the protein fraction on Sephadex G-100 in the presence of sodium dodecyl sulfate resulted in conversion of both copper- and zinc-binding components to lower molecular weights (30, 000 to 100, 000) accompanied by denaturation of the soybean proteins. Separation of the major protein fraction of >100, 000mol wt in the presence of 2-mercaptoethanol did not cause any significant denaturation of the large proteins but caused a shift of copper to the fraction of about 10, 000mol wt. Only a small amount of zinc was shifted by 2-mercaptoethanol. Zinc in the protein fraction was removed by EDTA in the absence and presence of sodium dodecyl sulfate and/or 2-mercaptoethanol. Copper in the fraction of about 10, 000mol wt in the presence of 2-mercaptoethanol was not affected by EDTA. The stabilization of copper binding by 2-mercaptoethanol was also observed in the presence of sodium dodecyl sulfate.