Conformational Transition of Alkali-Denatured Soybean 7S and 11S Globulins by Ethanol

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Abstract
Transformation depending on ethanol concentration of alkali-denatured soybean 7S and 11S globulins was studied by means of CD measurement and difference spectra. The ordered structure formation from unfolded random structure was enhanced with increasing ethanol concentration. Helical and β-structure content at pH 11.4 in 66% ethanol were 54%, 39% for the 7S and 49%, 28% for the 11S, respectively. The 7S showed more ordered structure transition than the 11S. In the condition where an alkaline dope solution showed remarkable increase of viscosity by adding ethanol, the helical transition was more predominant than others. The β-structure formation was less dependent on alcohol concentration. In conclusion, it is speculated that a three dimensional structure of the gel obtained by alkali-alcohol treatment is constructed by orientating protein molecules having ordered structures, especially α-helix. Additionally, it is likely that the tyrosine residues are not incorporated into the interior of the new ordered conformation.