Characterization and differentiation of diverse transgenic and nontransgenic soybean varieties from CE protein profiles

Abstract

Nowadays, soybeans are commercialized in a wide variety of colors and tones. Moreover, some pigmented seeds are being commercialized as soybeans while, on other occasions, these seeds are labeled as mung beans, azuki beans or soybean frijoles generating confusion on their identity. In this work, CE has been applied for the first time for the characterization and differentiation of different pigmented beans commercialized as soybeans. Other seeds commercialized as azuki, mung green soybeans or soybean frijoles were also analyzed. Borate buffer (at pH 8.5) containing 20% v/v ACN was used as the separation media and solution containing ACN/water (75:25 v/v) with 0.3% v/v acetic acid was used to solubilize the proteins from the samples. A 50 cm bare fused-silica capillary was employed for obtaining adequate separations in about 12 min. The CE protein pattern observed for yellow soybeans was different from that corresponding to green and red soybeans. The seeds commercialized as black soybean presented electropherograms identical or similar to those yielded by the yellow seeds with the exception of the sample labeled as black soybeans frijoles that presented a totally different pattern. In addition, CE protein profiles obtained for azuki and mung green soybeans were very similar to those corresponding to red soybeans and green soybeans, respectively. Finally, the CE method was also applied to differentiate transgenic and nontransgenic soybean varieties. Discriminant analysis, using several protein peak areas as variable, was used to successfully classify these samples.

Modification of Resolution in Capillary Electrophoresis for Protein Profiling in Identification of Genetic Modification in Foods

“…The soybean sample was extracted with ACN/water mixture containing 0.3 % acetic acid which was already employed earlier for differentiation of various commercial soybeans. 17 In case of formerly used borate BGE for application with dendrimer additive too long migrations were observed for practical measurements. The phosphate buffer of low pH value was already employed for CE of water soluble proteins, 18 and in this work was employed with addition of DAB dendrimer and 5 % of ACN.…”

“…[14][15][16] Recently, there were several attempts to employ CE to obtain the protein profiles in extracts of maize and soybean, oriented towards finding some differences between genetically modified plant material or foods and natural variants and their food products. For this purpose both CE measurements with UV 17,18 and MS detections 19,20 were reported. Such studies were carried out for maize samples, [18][19][20] as well soybean, 17 of which GM variants are most commonly cultivated.…”

“…For this purpose both CE measurements with UV 17,18 and MS detections 19,20 were reported. Such studies were carried out for maize samples, [18][19][20] as well soybean, 17 of which GM variants are most commonly cultivated. It is well known that applied conditions of solvent extraction from plant material allow to extract different types of proteins.…”

“…19,20 For this purpose also watersoluble fraction (albumins) was used, 18 while in case of soybean extracts the fraction extracted with ACN/water mixture with acetic acid. 17 The CE measure-ments with UV detection were carried out using capillaries without any modification with borate back-ground electrolyte (BGE) with ACN addition for proteins extracted with ACN/water with acetic acid, 17 while in case of albumins extracted with water several acidic BGEs were examined, assuming 0.2 mol dm −3 solution of iminodiactetic acid of pH 2.26 was the optimum. 18 For CE determination of zeins with MS detection the capillary was modified with ethylpyrrolidine methacrylate-N,N-dimethylacrylamide, 19,20 and in both these cases BGE used was a mixture of ACN, isopropanol, formic acid and water.…”

“…18 In case of application of CE/UV to differentiation of diverse transgenic and non-transgenic soybean varieties, by applying discriminant analysis using several protein peak areas as variable, some successful differentiation between transgenic and nontransgenic soybeans was reported based on measurements at 254 and 280 nm. 17 These detection wavelengths correspond to the maximum absorption of certain common amino acids present in proteins.…”