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Radionuclide Production
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
The target is placed in a tube and heated, under a stream of argon gas, to evaporate the 76Br activity by dry distillation (Figure 4.18). A temperature gradient is applied to separate the deposition areas of 76Br and traces of co-evaporated selenide in the tube by thermal chromatography. The 76Br activity deposited on the tube wall is dissolved in small amounts of buffer or water.
Trace Metals in Growth and Sexual Maturation
Published in Owen M. Rennert, Wai-Yee Chan, Metabolism of Trace Metals in Man, 2017
Another hypothesis explaining action of selenium has been proposed. It has been suggested that selenide has a role in the electron transfer functions associated with mitochondria and smooth endoplasmic reticulum. Since mitochondria contain nonheme iron proteins, the active centers of which contain selenide, it has been tentatively suggested that the selenide might form part of a class of nonheme iron selenide proteins.
Specific Geomedical Problems in Asia
Published in Jul Låg, Geomedicine, 2017
Selenium has been established as an essential element for animals because it is specifically required for the activation of one type of glutathione peroxidase, while the other type is selenium independent. Its deficiency can lead to a number of diseases, such as “stiff limb disease” in lamb, “white muscle disease” in calves, encephalomalacia in chicks, and muscular dystrophy, which are also known as vitamin E-deficiency diseases. In certain regions of China, Keshan disease in human beings has been recorded in endemic form in rural areas and is considered to have resulted from selenium deficiency. Children less than 15 years of age and pregnant women showed clinical pathological changes in the myocardium and responded to sodium selenide treatment in dietary doses of 10 to 15 ppm selenium. A clue to this selenium-deficiency disease came from the white muscle disease prevalent in cattle in the same area.13
Biosynthesis of nano selenium in plants
Published in Artificial Cells, Nanomedicine, and Biotechnology, 2023
Jonas Verstegen, Klaus Günther
Selenium occurs in multiple oxidative states ranging from -II to + VI just like sulphur and coherently it forms analogous compounds, including selenide (Se2−), selenite (SeO32−) and selenate (SeO42−). Plants are able to take up a variety of selenium compounds, but the most abundant forms of selenium in soil are selenate in alkaline and oxic environments and selenite in anaerobic and acidic environments. Selenate uptake is catalysed by high-affinity sulphate transporters (HASTs) while phosphate transporters such as OsPt2 and aquaporin channels such as OsNIP2;1 catalyse selenite uptake [6]. Generally, the similarities between selenium and sulphur hint towards many functions of selenium in biochemistry. Selenium shows superiority to sulphur in the catalytic centre of enzymes in the form of increased catalytic activity. Due to selenium being a good nucleophile and electrophile, peroxidases containing SeCys instead of Cys can more easily regenerate throughout an oxidoreductive cycle, leading to the hypothesis that one of selenium’s functions is the prevention of irreversible oxidative inactivation [7]. Selenium’s ability to be both rapidly oxidised and reduced, also known as ‘selenium paradox' could explain why non selenium dependent species such as those within the plant kingdom may profit from low doses of selenium, as the unintentional incorporation of SeCys into the active centre of enzymes can benefit their activity.
Antibacterial carbonic anhydrase inhibitors: an update on the recent literature
Published in Expert Opinion on Therapeutic Patents, 2020
Claudiu T. Supuran, Clemente Capasso
A series of selenides bearing benzenesulfonamide moieties were also evaluated as inhibitors of BpsCAβ enzyme [120]. The series inhibited the catalyst in the nanomolar range, and thus resulted in interesting leads as antibacterials. Besides, these molecules showed excellent inhibitory selectivity for the VchCAα and BpsCAβ over the human enzymes [120].
Insights into cancer and neurodegenerative diseases through selenoproteins and the connection with gut microbiota – current analytical methodologies
Published in Expert Review of Proteomics, 2019
Ana Arias-Borrego, Belén Callejón-Leblic, Marta Calatayud, José Luis Gómez-Ariza, Maria Carmen Collado, Tamara García-Barrera
Selenium is a well-known essential element which plays key roles in medicine. The relationship between Se intake and status is not linear, but approximates more closely to a U-shape where adverse effects (e.g. on mortality and prostate cancer) are found at low and high Se intake [1]. Moreover, the bioaccessibility, essentiality or toxicity character depends not only on its narrow range of required concentration, but also on the chemical form. In this sense, there are three types of selenium containing biomolecules in the body, namely: (i) selenometabolites or selenospecies of molecular mass below 1500 Da (e.g. inorganic selenium, selenoamino acids, methylated selenium), (ii) selenium containing proteins, containing selenomethionyl residues (e.g. selenoalbumin (SeAlb)) [2] and (iii) selenoproteins, with selenocysteinyl residues incorporated by a specific codon and – SeH as the active center (e.g. glutathione peroxidase (GPx), selenoprotein P (SELENOP) and other selenoenzymes). Figure 1 illustrates the selenium metabolism in human body after intake. As can be seen, selenocysteine (SeCys) is co-translationally incorporated into certain proteins by an in-frame opal stop codon (UGA) in combination with specific stem-loop structures within the 3´-untranslated region of transcripts and a unique set of accessory factors. This aminoacid represents the 21st proteinogenic residue not included in the classical genetic code [3]. Selenide is a common intermediate metabolite in the synthesis of selenoproteins from inorganic or organic selenium precursors. Selenomethionine (SeMet) can be transformed into selenocystathionine and then to SeCys through the trans-selenation pathway (cystathionine β-synthase and cystathionine γ-lyase) to be later lysed by β-lyase to selenide. At the same time, SeMet can be used for the synthesis of selenium containing proteins by methionine-RNAt [4]. There are 25 genes encoding for about 25 human selenoproteins, the majority of them without a clear function defined. All of the selenoproteins that catalyzes redox reactions belong to the family of glutathione peroxidases (GPxs) [5], thyroid hormone de-iodinases [6] methionine-R-sulfoxide reductase [7] and thioredoxin reductase isoenzymes [8]. However, antioxidant activities have not yet been demonstrated for all selenoproteins.