Selenium speciation in low molecular weight fraction of Se-enriched yeasts by HPLC-ICP-MS: detection of selenoadenosylmethionine†
In this study, selenium speciation in low molecular weight (LMW) fraction of Se-enriched yeasts was investigated assuming the presence of selenoadenosylmethionine (AdoSeMet). In order to minimize the risk of species decomposition, the pretreatment procedure consisted of homogenization of fresh cells and precipitation of proteins with perchloric acid at 0 °C. The species separation was achieved by ion pairing HPLC (hexanesulfonic acid) with UV (254 nm) and ICP-MS detection. The assignment of chromatographic peaks was by spiking the sample with both the commercial and synthesized standards. The synthesis of AdoSeMet and selenoadenosylhomocysteine (AdoSeHcy) was performed and their structures confirmed by ES-MS analysis. These two selenium species were identified in yeasts extract and the presence of Se-cystine was also observed. Significantly lower ratio between AdoSeMet and AdoSeHcy was observed in yeast extracts as compared to the ratio between sulfur analogs. This observation could contribute to further understanding of the selenium role in biomethylation processes.