Structure-physicochemical function relationships of 7S globulins (vicilins) from red bean (Phaseolus angularis) with different polypeptide constituents

Red bean 7S globulins (vicilins) with different polypeptide constituents or heterogeneity were fractionated using acidic extraction (at 0.5 M NaCl) and anion-exchange column chromatography. The physicochemical and conformational properties, including amino acid composition, net charge and/or surface hydrophobicity (H-0), protein solubility (PS), thermal and emulsifying properties, as well as secondary, tertiary and/or quaternary conformations, were evaluated. There were distinct differences in zeta potential, H-0, DSC characteristics, emulsifying activities and tertiary and/or quaternary conformations among the vicilins with different polypeptide constituents, but the PS and secondary conformation were slightly different. The PS as a function of pH and thermal stability were closely related to their surface charge and/or hydrophobicity. The emulsifying ability and the emulsion stability were closely dependent on the PS and H-0, and even the flexibility in tertiary and/or quaternary conformations. These results suggested good relationships between the physicochemical functions and conformational features of red bean vicilins, which could be of great help for further utilization of legume proteins as a potential functional ingredient. (C) 2010 Elsevier Ltd. All rights reserved.