Selenium-enriched plants, such as hyperaccumulative phytoremediation plants (Astragalus praleongus, 517 micrograms g-1 Se, and Brassica juncea, 138 micrograms g-1 Se in dry sample), yeast (1200, 1922 and 2100, micrograms g-1 Se in dry sample), ramp (Allium tricoccum, 48, 77, 230, 252, 405 and 524 micrograms g-1 Se in dry sample), onion (Allium cepa, 96 and 140 micrograms g-1 Se in dry sample) and garlic (Allium sativum, 68, 112, 135, 296, 1355 micrograms g-1 Se in dry sample) were analyzed by HPLC-ICP-MS for their selenium content and speciation after hot water and enzymatic extractions. Reference samples with natural selenium levels, such as onion and garlic controls, cooking garlic powder, baking yeast powder and a commercial garlic supplement were also analyzed. Selected samples were also examined by HPLC-electrospray ionization (ESI)-MS. HPLC was mostly carried out with 0.1% heptafluorobutanoic acid (HFBA) as ion-pairing agent in 1 + 99 v/v methanol-water solution, but 0.1% trifluoroacetic acid (TFA) in 1 + 99 v/v methanol-water solution was also utilized to permit chromatography for compounds that did not elute with HFBA. More than 75% of the total eluting selenium compounds, based upon element specific detection, were identified from retention time data and standard spiking experiments, and between 60 and 85% of compounds were identified by MS, with up to 25% of the total eluting molecular selenium species being unidentified as yet. Limits of quantification (LOQ, defined as the concentration giving an S/N of 10) for HPLC-ICP-MS were in the range 2-50 ng mL-1 Se in the injected extracts for the selenium-enriched samples and 2-10 ng mL-1 Se for the natural selenium level samples. LOQ values for HPLC-ESI-MS were ca. 100 times higher than those measured by HPLC-ICP-MS.

A recent human intervention trial showed that daily supplementation with selenized yeast (Seyeast) led to a decrease in the overall cancer morbidity and mortality by nearly 50%; past research has also demonstrated that selenized garlic (Se-garlic) is very effective in mammary cancer chemoprevention in the rat model. The goal of this study was to compare certain biological activities of Se-garlic and Se-yeast and to elucidate the differences based on the chemical forms of selenium found in these two natural products. Characterization of organic selenium compounds in yeast (1922 µg/g Se) and garlic (296 µg/g Se) was carried out by high-performance liquid chromatography with inductively coupled plasma mass spectrometry or with electrospray mass spectrometry. Analytical speciation studies showed that the bulk of the selenium in Se-garlic and Se-yeast is in the form of γ-glutamyl-Se-methylselenocysteine (73%) and selenomethionine (85%), respectively. The above methodology has the sensitivity and capability to account for >90% of total selenium. In the rat feeding studies, supplementation of Se-garlic in the diet at different levels consistently caused a lower total tissue selenium accumulation when compared to Se-yeast. On the other hand, Se-garlic was significantly more effective in suppressing the development of premalignant lesions and the formation of adenocarcinomas in the mammary gland of carcinogen-treated rats. Given the present finding on the identity of selenomethionine and γ-glutamyl-Se-methylselenocysteine as the major form of selenium in Se-yeast and Se-garlic, respectively, the metabolism of these two compounds is discussed in an attempt to elucidate how their disposition in tissues might account for the differences in cancer chemopreventive activity.

No abstract

No abstract

No abstract

PC, "Identification of the principal selenium compounds in seleniumenriched natural sample extracts by ion-pair liquid chromatography with inductively coupled plasma-and electrospray ionization-mass spectrometric detection" (1999 Selenium-enriched garlic and yeast sample extracts and digests were analyzed using ion-pair high performance liquid chromatography (HPLC) with on-line inductively coupled plasma-mass spectrometric (ICP-MS) and electrospray ionization-mass spectrometric (ESI-MS) detection. The principal selenium compounds in these samples were identified as selenomethionine, and Se-adenosyl-selenohomocysteine in yeast, and g-glutamyl-Se-methyl-selenocysteine and possibly g-glutamyl-selenomethionine in garlic. The compounds identified account for 85 and 90% of the total selenium content of the yeast and the garlic samples, respectively. On-line HPLC-ESI-MS selected ion chromatograms (SIC) and mass spectra of selenium compounds extracted from selenium enriched samples are presented. Limits of quantification (LOQ, defined as S/N = 10) for HPLC-ICP-MS were in the range 10-50 ng mL 21 Se in the injected extracts. LOQ values for HPLC-ESI-MS were ca. 100 times higher than those of HPLC-ICP-MS.

Abstractb-2-Microglobulin (b2m) is deposited as amyloid fibrils in the bones and joints of patients undergoing long-term dialysis treatment as a result of kidney failure. Previous work has shown that biologically relevant amounts of Cu(II) can cause b2m to be converted to amyloid fibrils under physiological conditions in vitro. In this work, dynamic light scattering, mass spectrometry, and size-exclusion chromatography are used to characterize the role that Cu plays in the formation of oligomeric intermediates that precede fibril formation. Cu(II) is found to be necessary for the stability of the dimer and an initial form of the tetramer. The initially formed tetramer then undergoes a structural change to a state that no longer binds Cu(II) before progressing to a hexameric state. Based on these results, we propose that the lag phase associated with b2m fibril formation is partially accounted for by the structural transition of the tetramer that results in Cu(II) loss. Consistent with this observation is the determination that the mature b2m amyloid fibrils do not contain Cu. Thus, Cu(II) appears to play a catalytic role by enabling the organization of the necessary oligomeric intermediates that precede b2m amyloid formation.

6 Atomic Magneto-optical Rotation Spectrometry 7 Chemical Vapour Generation 7.1. Hydride Generation Analysis by atomic spectrometry was one of the first instrumental analytical techniques to be developed. It might be expected that this maturity would be reflected in a slowing down in the pace of development. That this has not happened is attributable to the symbiotic relationship that exists between demand and development with each feeding continually on the other. Recent catalysts in this cycle have been the development of hybrid techniques and chemometrics which both enhance the information content of analytical procedures and provide means for its extraction and interpretation. Thus, as the nature of the source material changes, so must these Update Reviews in order to provide a balanced view of progress. For this reason, this Atomisation and Excitation Update has been pruned slightly with inorganic mass spectrometry being transferred and combined with X-ray spectrometry to form a new Update that will appear in the next issue of JAAS.