Cereal Chem 65:215-222   |  VIEW ARTICLE

Characterization of Zeins Fractionated by Reversed-Phase High-Performance Liquid Chromatography.

J. W. Paulis and J. A. Bietz. Copyright 1988 by the American Association of Cereal Chemists, Inc. 

Zein, the major alcohol-soluble protein of corn endosperm, was extracted with 55% 2-propanol. It was then fractionated by preparative reversed-phase (C18) high-performance liquid chromatography (RP-HPLC) with an acetonitrile-trifluoroacetic acid gradient. FRom 15 to 17 peaks resulted for native or reduced and alkylated (R-A) zeins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed early eluting HPLC fractions of native zein to be primarily monomers; later-eluting fractions increasingly tend to be or to form oligomers. SDS-PAGE showed that for R-A Zeins, all RP-HPLC fractions are monomers. Acidic urea PAGE and isoelectric focusing showed native zeins in each RP-HPLC fraction to contain 3-10 components, compared to 1-5 for R-A zein. Proteins differing in hydrophobicity frequently had similar electrophoretic mobilities, emphasizing zein's heterogeneity. Amino acid compositions of all RP-HPLC fractions were similar, suggesting marked homology of zein polypeptides. Preparative RP-HPLC was also useful for isolating zeins for further studies.