Li Yu-feng

Direct quantitative speciation of selenium in selenium-enriched yeast and yeast-based products by X-ray absorption spectroscopy confirmed by HPLC-ICP-MS

Selenium (Se)-enriched yeast has probably been the most widely investigated food supplement and the literature on Se speciation in the Se-enriched yeast is fairly abundant, however, the strategy for Se speciation commonly requires complicated pretreatment procedures such as digestion and stepwise extraction. The present study was carried out to apply X-ray absorption spectroscopy (XAS) for the direct speciation of Se species with minimal pretreatment steps. By comparison of the XAS spectra of Se-enriched yeast samples with that of the standard Se species, organic R–Se–R (represented by selenomethionine) was found to be the main chemical form of Se. Quantitative speciation through principal component analysis (PCA) and least-squares linear combination (LC) fitting the Se-enriched yeast samples found 83%, 85% and 81% of R–Se–R (probably selenomethionine which is known to exist in yeast) for SelenoPrecise® yeast, SelenoPrecise® tablets, and Xiweir® tablets, respectively, which is in agreement with those from HPLC-ICP-MS analysis. More broadly, XAS can also be applied to other Se-enriched products with the merit of minimal pretreatment. However since XAS, specifically XANES, can only identify the chemical type rather than specific molecules, other methods like HPLC-ICP-MS are necessary to give not only the coordination environment of Se but also the identity of the Se species.

Analysis of Small Molecular Selenium Species in Serum Samples from Mercury-Exposed People Supplemented With Selenium-Enriched Yeast by Anion Exchange-Inductively Coupled Plasma Mass Spectrometry

Abstract A hyphenated technique was optimized to simultaneously determine different selenium species, including Se(IV), Se(VI), selenocysteine (SeCys), and selenomethionine (SeMet), by anion exchange chromatography (AEC)-inductively coupled plasma mass spectrometry (ICP-MS). Ammonium citrate and methanol were used as mobile phase. Mobile phase A is composed of 0.5 mM ammonium citrate + 2% ( V/V ) methanol, and mobile phase B is 100 mM ammonium citrate + 2% ( V/V ) methanol. When 93% A + 7% B were used, the four Se species can be separated in 7.5 min. The detection limits for SeCys, Se(IV), SeMet and Se(VI) were 0.34, 0.67, 1.38 and 0.63 μg L −1 , respectively, according to three times standard deviation of the blank criterion. The recoveries of spiked Se(IV) in serum samples were between 93% and 107%, and the RSDs were less than 9% ( n = 3). This method was applied to analyze serum samples from long-term mercury-exposed people supplemented with selenium-enriched yeast. The concentrations of total Se and Se(IV) in serum samples were found to be increased after Se supplementation. The method is simple, rapid, sensitive, repeatable, and suitable for speciation analysis of small molecular weight seleno-compounds in different biological samples.

Study of Selenium Speciation in Selenized Rice Using High-Performance Liquid Chromatography-Inductively Coupled Plasma Mass Spectrometer

On the basis of Osborne fractionation, albumin, globulin, prolamine, and gluletin in selenium (Se) rich rice were extracted with water, 2% NaCl solution, 70% alcohol, and 0.5% alkaline solution subsequently. The content of Se in these protein extracts was determined by inductively coupled plasma mass spectrometry (ICP-MS). The chemical forms of Se in albumin extract and enzymatic digests of rice were analyzed with a hyphenated technique of high performance liquid chromatography and ICP-MS. The Se content in four types of extracts shows an order of gluletin > prolamine > albumin > globulin. The protein with molecular weight of 12.6 kDa is the primary Se-containing protein in extracts of albumin, and the Se from selenocysteme is approximately 30% of the total Se present in the selenized rice.

Effect of Ar+ Implantation and Maize Genome DNA on Autotetraploid Rice

The effect of Ar+ beam implantation and maize genome DNA on autotetraploid rice is studied. Better mutation types and higher mutation rates were discovered in M2 of T3 with ion implantation and immersion in maize genome DNA. In the five agronomic categories investigated, the mutation rate of the seed setting rate was 9.1%, and the total mutation rate was 14.8% in the T3. However, the total mutation rate was 2.1% with the treatment of only ion implantation and 1.3% with the treatment of only immersion in maize genome DNA. Mutant FA36(4) was discovered in M1 with ion beam implantation and immersion in maize genome DNA. Its RuBPCase activity, PEPCase activity and seed setting rate were 32%, 153%, and 36.79%, respectively, higher than its parent IR36(4). Rapid analysis of polymorphicDNA (RAPD) analysis of three M2 plants of FA36(4) (FM1, FM2, FM3) and two controls (purple maize and IR36(4)) were also conducted with 40 random primers. S5-3 was RAPD fragment amplified with a template of purple maize, FM2 and FM3 genome DNA using primer S5. There was no S5-3 in the RAPD pattern of IR36(4) or FM1.