WHEAT CULTIVAR DISCRIMINATION BY CAPILLARY ELECTROPHORESIS OF GLIADINS IN ISOELECTRIC BUFFERS

A modified method is reported for screening of wheat cultivars: capill ary zone electrophoresis of gliadins in isoelectric buffers. Previousl y published procedures recommended a 100 mM phosphate buffer, suppleme nted with 0.05% hydroxypropylmethylcellulose and 20% acetonitrile, in uncoated capillaries. Due to the very high conductivity of such a buff er (4.7 mmhos at 25 degrees C) high speed separations (10-12 min analy sis time at 800 V/cm) could only be elicited in 20 mu m internal diame ter (ID) capillaries, at the expense of sensitivity. In the present re port, we optimized the background electrolyte as follows: 40 mM aspart ic acid (pH = pI = 2.77) in the presence of 7 M urea and 0.5% short-ch ain hydroxyethylcellulose (M-n 27000 Da; apparent pH 3.9 in 7 M urea). As an alternative recipe, the same isoelectric buffer can be suppleme nted with a mixed organic solvent composed of 4 M urea and 20% acetoni trile (apparent pH 3.66). Due to the much lower conductivity (0.7 mmho s), separations can be carried out at 1000 V/cm in only 10 min, but in larger bore capillaries (50 mu m ID), ensuring a five-times higher se nsitivity. The gliadin patterns thus obtained are species-specific and allow easy identification of all cultivars tested of both durum and b read wheat. No adsorption of proteins to the silica wall seems to occu r and high reproducibility in peak areas and transit times is obtained .