CE-MS of zein proteins from conventional and transgenic maize

In this work, an original CE-MS method has been developed to analyze the complex zein protein fractions from maize. A thorough optimization of: (i) zein protein extraction, (ii) CE separation, and (iii) electrospray-MS (ESI-MS) detection is carried out in order to obtain highly informative CE-MS profiles of this fraction. The developed CE-MS method provides good separation of multiple zein proteins based on their electrophoretic mobilities as well as adequate characterization of these proteins based on their M(r). Zein proteins with small M(r) differences (below 100 Da) were easily separated and successfully analyzed by CE-MS. Thus, apart of the so-called 15-kDa-beta-zein and 16-kDa-gamma-zein, which are demonstrated to be formed by a heterogeneous group of proteins, numerous alpha-zeins belonging to the 19- and 22-kDa fraction were also identified for the first time in this work. The usefulness of this CE-MS method was corroborated by comparing the zein-protein fingerprints of various maize lines including transgenic and their corresponding nontransgenic isogenic lines cultivated under the same conditions.