Characterization of Polymeric Proteins from Vitreous and Floury Sorghum Endosperm

Authors

B. Ioerger
S. R. Bean
M. R. Tuinstra
Jeffrey F. Pedersen, University of Nebraska-LincolnFollow
J. Erpelding
K. M. Lee
T. J. HerrmanFollow

Document Type

Article

Date of this Version

11-17-2007

Comments

Published in J. Agric. Food Chem. 2007, 55, 10232–10239.

Abstract

Differences in protein content and composition between vitreous and floury endosperm were investigated using a number of different techniques. Differences in protein cross-linking between vitreous and floury endosperm were investigated using differential solubility, size exclusion chromatography (SEC), and analysis of sulfhydryl content and composition. Vitreous endosperm was found to have higher levels of total protein and kafirins, but floury endosperm had a higher proportion of γ-kafirins than the vitreous. Floury endosperm was found to have higher levels of SDS-soluble proteins than SDS-insoluble proteins extracted using sonication than vitreous endosperm. Conversely, vitreous endosperm had a greater proportion of the insoluble proteins. SEC analysis of the polymeric proteins revealed that the insoluble proteins had more polymeric proteins than did the soluble proteins, indicating greater cross-linking and a larger M_w distribution. Vitreous endosperm was also found to have a greater percentage (i.e., a higher ratio of disulfide to total sulfhydryls) of disulfide bonds than floury endosperm. These results show that the proteins in vitreous endosperm have a higher degree of cross-linking and a greater M_w distribution than those found in floury endosperm.