High-resolution carbon-13 nuclear magnetic resonance study of the soybean 7S storage protein fraction in solution

Abstract

The molecular structure and dynamics of soybean 7S storage proteins were investigated by highresolution 13C NMR at high fields (7.05 and 11.75 T). The spectrum of the alkali-denatured proteins (pH 12.0) is well-resolved, and tentative assignments of 53 peaks are given. At pH 12.0 and 12 mM ionic strength the proteins dissociate into partially unfolded subunits that exhibit fast local motion (10"9-10"10 s), while they maintain a relatively immobile hydrophobic core. The spectra of "native", multisubunit proteins consist of broad peaks as a result of the slower protein tumbling in solution and the expected chemical shift nonequivalence. There is evidence that Phe residues are in the hydrophobic subunit core, whereas Tyr residues are found at the subunits' interface. No major spectral differences were observed between pH 7.6 and 10.3 (at 0.5 M ionic strength, where proteins exist as trimers) or between 13 mM ionic strength and 0.5 M NaCl (at pH 10.2, where a trimer-hexamer interconversion occurs). Potential applications of these results, and of the 13C NMR techniques, in general, include quality control of soy protein isolates in food engineering and the analysis of complex foods that include soy protein ingredients.

Relationship between the Method of Obtention and the Structural and Functional Properties of Soy Proteins Isolates. 1. Structural and Hydration Properties

“…There is, however, a great heterogeneity among the minor components (Iwabuchi and Yamauchi, 1987a,b). Both glycinin and /3-conglycinin are very complex oligomeric proteins, their association/dissociation state and thermal stability being highly dependent on the pH and ionic strength (Badley et al, 1975;Kitamura et al, 1976;Utsumi et al, 1981;Thanh and Shibasaki, 1979;Kakalis and Baianu, 1990;Iwabuchi et al, 1991a,b;Fukushima, 1991a,b). The structural similitude among the constituent domains of the subunits of these globulins leads to a tendency to association among some of the subunits (Yamauchi et al, 1991).…”

Synthesis of bio-adhesives from soybean flour and furfural: Relationship between furfural level and sodium hydroxide concentration

“…The peaks associated to the pure soy flour are assigned as follows: 173.1 ppm to the amino acid carbonyls, 130.3 ppm to phenylalanine C−H bond, 105.2 ppm to the C-1 anomeric carbons of the carbohydrates, 72.6 ppm to the C-5 carbons of the carbohydrates, 62.5 ppm to the C-6 carbons of the carbohydrates, 53.9 ppm to the αC−H bonds of amino acids, 40.4 ppm to the βC−H 2 groups of amino acids, 30.1 ppm to the βC−H and βC−H 2 groups of amino acids and 25.5 ppm to the βC−H 2 carbon of the glutamine[21][22][23]. The peak at 239.3 ppm has not been assigned and could be from a cooking residue in the flour.…”

Preparation and Characterization of a Robust, High Strength, and Mildew Resistant Fully Biobased Adhesive from Agro-Industrial Wastes

“…As depicted in Figure c, the solid-state 13 C-NMR analysis was performed to further confirm that the presence of EXL and SM mediated the formation of a crosslinked network. The peaks associated with the pure SM adhesive are assigned as follows: 172.64 ppm to the amino acid carbonyls, 130.30 ppm to phenylalanine C–H bonds, 105.20 ppm to the C-1 anomeric carbons of the carbohydrates, 72.40 ppm to the C-5 carbons of the carbohydrates, 60.97 ppm to the C-6 carbons of the carbohydrates, 54.03 ppm to the αC–H bonds of amino acids, 40.68 ppm to the βC–H 2 groups of amino acids, 29.87 ppm to the βC–H and βC–H 2 groups of amino acids, and 24.91 ppm to the βC–H 2 carbon of the glutamine. − Moreover, the triple peaks at 28.90, 24.10, and 20.68 ppm are assigned to the βC–H and βC–H 2 groups of amino acids with nonpolar sidechains, such as proline, leucine, alanine, glutamine, and valine . Additionally, a new peak belonging to the peak formed after the reaction of EXL with amino groups on soybean protein appeared at 64.46 ppm, which became stronger at 21.20 ppm.…”