Large-scale speciation of selenium in rice proteins using ICP-MS assisted electrospray MS/MS proteomics

Abstract

A Se-targeted bottom-up proteomics approach was developed for the identification of Se-containing proteins in rice grown naturally on seleniferous soils. The proteins were separated by 2D gel electrophoresis. The position of Se-containing spots was tentatively identified by the correlation between the 1D isoelectrofocusing (IEF) and 1D SDS electropherograms of a sample aliquot and confirmed by (78)Se imaging in the 2D gel. The method was complemented by the ICP-MS assisted shotgun proteomics approach. The proteins were identified by capHPLC with the dual ICP MS and electrospray Orbitrap MS detection. The first ever comprehensive study of rice selenoproteome revealed the presence of selenium, as both selenomethionine (SeMet) and selenocysteine (SeCys) residues, in a dozen proteins including a 19 kDa globulin, granule-bound starch synthase, and the family of glutelin-type seed storage proteins.

Evaluation of selenium in dietary supplements using elemental speciation

“…Specifics vary among studies, but in general, inorganic forms of selenium (iSe) are absorbed less effectively than the organic forms, with the latter being slightly less toxic (Dietary Reference Intake (DRI), 2000; Tiwary, Stegelmeier, Panter, James, & Hall, 2006). Selenocysteine (SeCys) and SeMet have been shown to be incorporated into proteins in humans and plants (Cheajesadagul, Bianga, Arnaudguilhem, Lobinski, & Szpunar, 2014). To our knowledge, SeCys is not commercially available as a standard or dietary supplement.…”

Application of hyphenated analytical techniques in the investigation of selenium speciation of different plants

“…However, considering the recent development in bioinorganic chemical research, it is increasingly important to gain molecular information of the analyzed species. Nowadays, in complex biochemical research, ICP-MS is mostly used to assist sample preparation (Szpunar and Łobiński 2002) and to detect Se in trace quantities (Cheajesadagul et al 2014), while the qualitative analysis of the species is usually based on molecular mass spectrometric techniques.…”

“…For example, the above mentioned multidimensional HPLC separations are assisted by ICP-MS detection, while the identification of selenocompounds from the adequately purified and concentrated fractions is delivered by ESI-MS techniques (Dernovics et al 2007a). Another interesting application of these techniques is the detection of selenium containing proteins on two-dimensional gels by laser ablation (LA) ICP-MS, then the identification of these proteins by high resolution ESI-MS , Cheajesadagul et al 2014. In speciation analysis mass spectrometric detection is always preceded by some kind of separation that enables the qualitative and quantitative analysis of the different species by separating them from each other and also from matrix interferences.…”

“…Nowadays, Se speciation studies predominantly focus on qualitative analysis, thus the application of HPLC-ICP-MS and LA-ICP-MS became a complementary tool for the detection of Se compounds before their qualitative identification by molecular mass spectrometric techniques , Cheajesadagul et al 2014. The introduction of different coupled molecular mass spectrometric techniques to Se speciation is summarized in Table 2.1.…”

“…Plants from the Allium and Brassica genera like garlic, green onion, radish, broccoli or different kinds of cabbages contain a variety of selenium species depending on the Se content of the soil. These characteristics made them the ideal targets for biofortification in order to provide dietary Se from natural sources (Ogra et al 2005, Larsen et al 2006, Kápolna and Fodor 2007, Cheajesadagul et al 2014).…”