Analysis of wheat gluten proteins by matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) was used to analyze the protein composition in several common and durum wheat varieties. Mass spectra were obtained directly from crude and partially purified wheat gliadin and reduced glutenin subunit fractions. Mass spectra of the gliadins and the low molecular weight (LMW) glutenin subunits show a complex pattern of proteins in the 30-40 kDa range. The observed gliadin patterns may be suitable for differentiation between wheat varieties, but the complexity of the mass spectra precludes the use of MALDI/MS as a stand-alone technique for the identification of most individual gliadin components. The mass spectra of the high molecular weight (HMW) glutenin subunits are much simpler and the complete HMW subunit profile can be determined directly from a single mass spectrum. This may prove particularly useful in wheat breeding programs for rapid identification of lines containing subunits associated with superior quality. The correspondence between previously identified HMW subunits and the mass spectral peaks was established with MALDI measurement's of HPLC-separated subunits. Delayed extraction proved effective in improving the mass resolution for the monomeric gliadins and LMW glutenin subunit fractions, with masses less than 40 kDa. However, it gave little improvement for the MMW glutenin subunits which have masses of similar to 80 kDa. (C) 1998 John Wiley & Sons, Ltd.