Cereal Chem 45:203 - 224. | VIEW
Internal Structure of 7S and 11S Globulin Molecules in Soybean Proteins.
D. Fukushima. Copyright 1968 by the American Association of Cereal Chemists, Inc.
The internal structure of soybean protein molecules (7S and 11S) was investigated by optical rotary dispersion (ORD), UV difference spectra, infrared absorption spectra, and other techniques. The native soybean globulins of 7S and 11S possess bo values, near zero in the Moffitt-Yang equation, and their ao values increased in the negative direction without accompanying changes in bo values, upon urea denaturation. The far-UV ORD curve indicated a positive peak at 200-201 micron and a negative trough at 233-235 micron, but the shoulder near 210 micron was not observed. Levorotation near the negative trough increased upon urea denaturation. The infrared spectrum measurements, the amide I bands, were observed at 1,650-1,655 (shoulder), 1,638 (main peak), and 1,685 cm.-1 (weak shoulder); the amide II bands, at 1,520-1,535 cm.-1; and the amide V bands, at 698, 660, and 620 cm.-1 (weak), in both proteins. UV difference sprectra indicated that tyrosine (7S), or tyrosine and tryptophan (11S), are buried in the water- impenetrable hydrophobic regions. The denaturing abilities of various alcohols on these proteins completely depended upon the hydrophobicities of the alcohols used. The native protein molecules are quite compact, and were not hydrolyzed by proteinase without disruption of the internal structure.