Capillary electrophoretic analyses of tryptic digests of water-soluble proteins from Bt-transgenic and non-transgenic maize species in strongly acidic volatile background electrolytes

Abstract

Transgenic Bacillus thuringiensis (Bt) maize belongs to insect-resistant genetically modified organisms (GMOs), which are expanding rapidly worldwide. Bt hybrids with the event MON 810 were constructed by introducing the cry1Ab gene from Bacillus thuringiensis, in order to produce its own insecticide, δ-endotoxin, for European corn borer (Ostrinia nubilalis). Due to the public concern on GMOs role in the environment and food and feed safety, the development, growth and use of GMOs are under regulation in many countries, especially in the EU. In order to fulfill these regulations, reliable and powerful analytical methods to detect and quantify GMOs and/or their products in foods are needed. Besides the detection of transgenic DNA, protein analysis represents an alternative way to detect GMOs. Protein fractions from transgenic Bt and non-transgenic maize varieties were analyzed by perfusion and monolithic RP-HPLC. Capillary zone electrophoresis (CZE) is being increasingly used for protein analysis and peptide mapping, but up to now, rather limited research has been oriented on the development of CZE methods for separation of the water-soluble proteins from crops. The aim of this study was to test separation conditions for analysis of tryptic digests of water-soluble proteins (albumin fraction) from the maize flours of transgenic Aristis-Bt and non- transgenic Aristis and Coventry maize varieties by CZE with UV-absorption detection and potentially with subsequent mass spectrometry detection. Hence, strongly acidic volatile background electrolytes (BGEs) composed of highly concentrated weak acids, 0.5–2.0 mol/L acetic and formic acids and their mixtures were tested. CZE analyses were performed in a home-made CE analyzer equipped with UV-absorption detector at 206 nm. Significant qualitative and quantitative differences among CZE-UV profiles of tryptic digests of water-soluble proteins from different maize species have been found and will be in detail discussed in this contribution.