Identification of maize lines via capillary electrophoresis of zeins in isoelectric, acidic buffers

Modified capillary zone electrophoresis of zeins in strongly acidic, isoelectric buffers is reported for screening of maize (Zea mays L.) lines. The optimized background electrolyte contained 40 mM aspartic acid (pH = pI = 2.77), 8 M urea and 0.5% short-chain hydroxyethylcellulose (Mn 27000 Da) (apparent pH in 8 M urea: 3.9). Due to the low conductivity of such a buffer (0.7 mmhos), separations can be carried out at 800 V/cm, even in relatively large bore capillaries (50 microm ID), ensuring good sensitivity. The zein patterns thus obtained are species-specific and allow easy identification of all maize lines tested. No adsorption of proteins to the silica wall is observed and high reproducibility in peak areas and transit times is obtained. The relatively slow migration time (ca. 30 min), even under such a high voltage gradient, is attributed to the paucity of basic amino acid residues typical of zeins, leading to an unfavorable charge/ mass ratio due to the modest net positive charge at the operative pH.