Selenium speciation profiles in selenite-enriched soybean (Glycine Max) by HPLC-ICPMS and ESI-ITMS

Abstract

Soybean (Glycine Max) plants were grown in soil supplemented with sodium selenite. A comprehensive selenium profile, including total selenium concentration, distribution of high molecular weight selenium and characterization of low molecular weight selenium compounds, is reported for each plant compartment: bean, pod, leaf and root of the Se-enriched soybean plants. Two chromatographic techniques, coupled with inductively coupled plasma mass spectrometry (ICPMS) for specific selenium detection, were employed in this work to analyze extract solutions from the plant compartments. Size-exclusion chromatography revealed that the bean compartment, well-known for its strong ability to make proteins, produced high amounts (82% of total Se) of high molecular weight selenospecies, which may offer additional nutritional value and suggest high potential for studying proteins containing selenium in plants. The pod, leaf and root compartments primarily accumulate low molecular weight selenium species. For each compartment, low molecular weight selenium species (lower than 5 kDa) were characterized by ion-pairing reversed phase HPLC-ICPMS and confirmed by electrospray ionization ion trap mass spectrometry (ESI-ITMS). Selenomethionine and selenocystine are the predominant low molecular weight selenium compounds found in the bean, while inorganic selenium was the major species detected in other plant compartments.

A metallomics approach discovers selenium-containing proteins in selenium-enriched soybean

“…In the soluble portion, low-molecular-weight molecules (<5,000 Da) were removed by the molecular weight cutoff membrane. The total Se in the dissolved proteins was then measured by ICPMS, which accounts for 25% of the total Se in the bean, 75±5 μg g −1 as reported in the previous study [27]. Since 82% of the total Se is high-molecular-weight Se in the bean [27], the Se in water-soluble proteins takes its 30% (25%/82%).…”

“…The mature plants were cleaned and freeze-dried before being ground into a fine powder. The details for these procedures are described elsewhere [27]. Only the bean compartment was used in this study.…”

“…In the algae Chlamydomonas reinhardtii, a UGA opal codon was found decoded to SeCys, indicating the presence of an essential selenoprotein [21]. More interestingly, high-molecular-weight Se species were consistently found in various types of plants when sizeexclusion chromatography (SEC) was used in Se speciation [27][28][29][30][31]. Despite the progress made in yeast and algae, the presence of Se-containing proteins in land plants remains an area for investigation.…”

“…A previous study elucidated that 82% of the Se in the bean of Se-enriched soybean (Glycine max) was highmolecular-weight Se species, and the major Se metabolites were SeMet and SeCys, the building blocks for Secontaining proteins [27]. Since about 40% of the soybean dry weight is protein [32], the Se-enriched soybean is a good candidate for searching Se-containing proteins.…”

Comparative Studies Involving Transgenic and Non-Transgenic Soybean: What is Going On?

“…These data showed that the soybean plants convert selenite (used to enrich the plant) to high molecular weight species, which, according to the authors, can add nutritional value to the plant. Another work from the same group [108] used reversed phase coupled to ICP-MS to study the Se-Hg antagonism, and they found that in plants enriched with Hg, more Se was assimilated, indicating a possible protective response mechanism to the Hg.…”