DIRECT IDENTIFICATION OF WHEAT GLIADINS AND RELATED CEREAL PROLAMINS BY MATRIX-ASSISTED LASER-DESORPTION IONIZATION TIME-OF-FLIGHT MASS-SPECTROMETRY

Matrix-assisted UV laser desorption/ionization time-of-flight mass spe ctrometry (MALDI/TOF-MS) allows the detection of large proteins from h ighly complex protein mixtures such as those present in gluten prolami ns. These proteins from wheat (gliadins), barley (hordeins), rye (seca lins) and probably oats (avenins) are known to cause the mucosal damag e in coeliac disease (gluten-sensitive enteropathy), Gluten prolamins are structurally and chemically related, and their resolution into sin gle components is extremely difficult, Preliminary results are present ed based on a novel choice of analysis and identification of prolamins from unfractionated protein complex mixtures by MALDI/TOF-MS, The hig h resolution and sensitivity of this technique have allowed the elucid ation of protonated molecular masses of most of the gliadin, hordein, secalin and avenin components displaying a typical characteristic mass pattern: gliadins showed mass signals corresponding to gliadin compon ents ranging from 31 to 55 kDa; barley showed mass signals for 2-3 com ponents with 32-38 kDa; oats showed mass signals for 5-6 components wi th 30-35 kDa; and rye showed mass signals for two main components of 3 2 and 39 kDa. Analysis by this technique of gliadin-containing foods a llows the immediate identification of the characteristic gliadin mass pattern, consequently permitting easy identification of gliadins in su ch samples. In summary, MALDI/TOF-MS seems to be a useful alternative technique for the identification of these cereal prolamins with a dete ction sensitivity of similar to 50-100 ng total protein loaded.