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Hydrogen selenide (H2Se) is a central metabolite in the biological processing of selenium for incorporation into selenoproteins, which play crucial antioxidant roles in biological systems. Despite being integral to proper physiological function, this reactive selenium species (RSeS) has received limited attention. We recently reported an early example of a H2Se donor (TDN1042) that exhibited slow, sustained release through hydrolysis. Here we expand that technology based on the P═Se motif to develop cyclic-PSe compounds with increased rates of hydrolysis and function through well-defined mechanisms as monitored by 31P and 77Se NMR spectroscopy. In addition, we report a colorimetric method based on the reaction of H2Se with NBD-Cl to generate NBD-SeH (λmax = 551 nm), which can be used to detect free H2Se. Furthermore, we use TOF-SIMS (time of flight secondary ion mass spectroscopy) to demonstrate that these H2Se donors are cell permeable and use this technique for spatial mapping of the intracellular Se content after H2Se delivery. Moreover, these H2Se donors reduce endogenous intracellular reactive oxygen species (ROS) levels. Taken together, this work expands the toolbox of H2Se donor technology and sets the stage for future work focused on the biological activity and beneficial applications of H2Se and related bioinorganic RSeS.

Matrix isolation infrared spectroscopy has been employed to study the reaction of laser-ablated boron atoms with hydrogen selenide in a 5 K solid argon matrix. On the basis of the isotopic shifts as well as the theoretical frequency calculations, triatomic molecule BSe2 and its anion BSe2- were identified. Both BSe2 and BSe2- were predicted to have D∞h symmetric structures with nearly identical structure parameters and bond strengths by quantum chemical calculations. Whereas the observed antisymmetric B-Se stretching frequency of BSe2 is much lower than that of BSe2-, the anomalously low antisymmetric B-Se stretching frequency of BSe2 is attributed to a pseudo-Jahn-Teller effect due to the mixing of the X2Πg ground state with the A2Πu excited state. In addition, H2BSe, HBSe, and HSeBSe molecules were produced in the reaction.

The adsorption performance of hydrogen selenide (H2Se) on the Zn/P-, Cd/P-, and Hg/P-modified graphitic carbon nitride (gCN) was theoretically investigated. The results of calculations revealed that with adsorption of H2Se on the modified gCN materials, the electrical conductivity, magnetic moments, electron transfer, and optimized structures of these systems considerably modulated. The calculated adsorption energy of H2Se on the Zn/P-, Cd/P-, Hg/P-modified, and P-doped gCN materials was −1.502, −2.141, −2.917, and −0.378 eV, respectively. The obtained results displayed that with modification of gCN by Zn/P, Cd/P, and Hg/P elements, the adsorption abilities of gCN remarkably improved. Furthermore, it was found that with the adsorption of H2Se and also embedding of Zn, Cd, Hg, and P elements, the conductance of gCN materials significantly increased. This phenomenon is attributed to the created new impurity energy levels close to the Fermi level. In addition, the results of total magnetization displayed that with adsorption of H2Se over the Hg-modified gCN material, the magnetic moment of the system remarkably changed. Also, the results of electron density and Lowdin charges analysis revealed that the adsorption energy of H2Se over the Hg/P-modified gCN is higher than the other gCN materials. Therefore, it can be deduced that the Hg/P-modified gCN is a promising candidate for detecting and removing of H2Se from the atmosphere. On the other hand, it can be concluded that the Hg/P-modified gCN system with the highest adsorption energy can be effectively used for gas sensor application.

The trace element selenium is known to manifest antitumor activity. There is a relationship between the development of cancer and selenium content in food. Recent data demonstrated the necessity of increasing selenium consumption for the prevention and treatment of oncological diseases. Certain features of cancer cells and potential targets of selenium therapy are discussed. Both natural forms of selenium, namely, element Se, sodium selenite, L-selenocystine, L-selenomethionine, and L-methylselenocysteine, and synthetic ones, methylseleninic acid and imidoselenocarbamate derivatives, which display antitumor activity due to the generation of methylselenol and hydrogen selenide, the main anticarcinogenic metabolites, are reviewed. New promising anticancer selenium compounds, diacetophenonyl selenide, 2-methylselanyl-1-phenylethanol, and amino acids 2-amino-3-selanyl butanoic acid and 2-amino-3-(methylselanyl) butanoic acid are discussed.

New reagents for the synthesis of substituted selenazoles, 3-amino-N-cyclopropyl-3-selanylidenepropanamide and methyl 3-amino-3-selanylidenepropanoate, were obtained by reactions of 2-cyano-N-cyclopropylacetamide and methyl 2-cyanoacetate with hydrogen selenide. The structure of the products was confirmed by IR, 1H and 13C NMR, and mass spectra.

Gaseous hydrogen selenide (H2Se) generated by the addition of sodium tetrahydroborate (NaBH4) into an acidic aqueous sample was collected using an aqueous ammonia solution. The selenium (Se) concen...

Sodium selenite has alleviating effects on liver fibrosis; however, its therapeutic molecular mechanism remains unclear. Herein, hydrogen selenide, a major metabolite of Na2SeO3, was tested to uncouple the sulfilimine bond in collagen IV, the biomarker of liver fibrosis. A mouse model of liver fibrosis was constructed via a CCl4-induced method, followed by the administration of 0.2 mg kg−1 Na2SeO3 via gavage three times per week for 4 weeks. Changes in H2Se, NADPH, and H2O2 levels were monitored in real time by using NIR-H2Se, DCI-MQ-NADPH, and H2O2 probes in vivo , respectively. H2Se continuously accumulated in the liver throughout the Na2SeO3 treatment period, but the levels of NADPH and H2O2 decreased. The expression of collagen IV was analyzed through Western blot and liquid chromatography-mass spectrometry. Results confirmed that the sulfilimine bond of collagen IV in the fibrotic mouse livers could be broken by H2Se with the Na2SeO3 treatment . Therefore, the therapeutic effect of Na2SeO3 on liver fibrosis could be mainly attributed to H2Se that uncoupled the sulfilimine bond to induce collagen IV degradation. This study provided a reasonable explanation for the molecular mechanism of the in vivo function of Na2SeO3 and the prevention of liver fibrosis by administering inorganic selenium.

Selenium (Se) contamination as a result of anthropogenic activity (i.e. mining, power generation, and oil & gas refining) is becoming a global concern due to its associated aquatic toxicity concerns. Herein, heterogeneous nanoscale photocatalysts were synthesized by depositing noble metal nanoparticles (gold (Au), silver (Ag), platinum (Pt) and palladium (Pd)) onto titanium dioxide (TiO2), which demonstrated work-function dependent bimodal selectivity of final products during the photocatalytic reduction of selenate to elemental Se (Se0) or hydrogen selenide gas (H2Se). The Se-noble metal-TiO2 (Se-NM-TiO2) photocatalytic system is structured in a direct Z-scheme arrangement when Au, Ag or Pt are used, allowing for high selectivity towards H2Se. In contrast, Pd acted as an electron sink which decreased reducibility of the photogenerated electrons, ultimately causing a higher selectivity towards Se0. Au–TiO2 offers the largest H2Se selectivity of all catalysts tested, while Pd–TiO2 offers the highest selectivity to solid Se0 generation. This study elucidates electron transport mechanisms and Fermi level equilibration via quantized double-layer charging effects of the Se-NM-TiO2 system and sheds light on advanced reduction processes using nanoscale heterogeneous catalysts. Finally, tunability of the Se reduction product is key to designing a sustainable treatment approach with a potential for Se capture and reuse.

Selenium (Se) is an essential micronutrient required by organisms of diverse lineage. Dietary Se is converted to hydrogen selenide either enzymatically or by endogenous antioxidant proteins. This convergent biochemical step crucially underlies the subsequent biological activity of Se and argues for inclusion of hydrogen selenide as the fourth endogenous gasotransmitter alongside nitric oxide, carbon monoxide and hydrogen sulfide.Endogenously generated hydrogen selenide is incorporated into numerous ‘selenoprotein’ oxidoreductase enzymes, essential for maintaining redox-status homeostasis in health and disease. Direct effects of endogenous hydrogen selenide on cellular and molecular targets are currently unknown. Given exogenously, hydrogen selenide acts as a modulator of metabolism via transient inhibition of mitochondrial cytochrome C oxidase. Here we provide an overview of Se biology, its impact on several physiological systems (immune, endocrine, cardiovascular and metabolic) and its utility as a supplement in acute and critical illness states. We further explore the evidence base supporting its role as the fourth gasotransmitter and propose a strategic case towards generation of novel selenomimetic therapeutics.

Functions of selenium are diverse as antioxidant, anti-inflammation, increased immunity, reduced cancer incidence, blocking tumor invasion and metastasis, and further clinical application as treatment with radiation and chemotherapy. These functions of selenium are mostly related to oxidation and reduction mechanisms of selenium metabolites. Hydrogen selenide from selenite, and methylselenol (MSeH) from Se-methylselenocyteine (MSeC) and methylseleninicacid (MSeA) are the most reactive metabolites produced reactive oxygen species (ROS); furthermore, these metabolites may involve in oxidizing sulfhydryl groups, including glutathione. Selenite also reacted with glutathione and produces hydrogen selenide via selenodiglutathione (SeDG), which induces cytotoxicity as cell apoptosis, ROS production, DNA damage, and adenosine-methionine methylation in the cellular nucleus. However, a more pronounced effect was shown in the subsequent treatment of sodium selenite with chemotherapy and radiation therapy. High doses of sodium selenite were effective to increase radiation therapy and chemotherapy, and further to reduce radiation side effects and drug resistance. In our study, advanced cancer patients can tolerate until 5000 μg of sodium selenite in combination with radiation and chemotherapy since the half-life of sodium selenite may be relatively short, and, further, selenium may accumulates more in cancer cells than that of normal cells, which may be toxic to the cancer cells. Further clinical studies of high amount sodium selenite are required to treat advanced cancer patients.

A straightforward method for measuring two aquatic inorganic species of selenium, selenate, Se(VI), and selenite, Se(IV), was developed in this study. Selenium toxicity and bioaccumulation in food chain are strongly dependent on its speciation. Therefore, it is important to measure selenium species as part of any selenium risk assessment practice. In this method, total selenium was first measured using graphite furnace atomic absorption spectrometry, and then, chemical procedures in the literature were used to reduce selenite, Se(IV), to hydrogen selenide (H2Se). Total selenium of the same solution was measured again with the analytical instrument after stripping H2Se from the solution. The difference of total selenium measured gave Se(IV) concentration. The two main species in natural waters are Se(VI) and Se(IV). Therefore, it can be assumed that after removing Se(IV) from the solution, the remaining total selenium is Se(VI). The two inorganic selenium species of (IV) and (VI) in purified waters and synthetic irrigation waters both spiked with Se(VI) and Se(IV) were determined using this method. Recovery of spiked samples in diluted synthetic irrigation water was 97% for Se(VI) and 99% for Se(IV). Detection limits of the method were 0.32 µg L−1 for Se(VI) and 0.11 µg L−1 for Se(IV). The advantages of the method developed in this study are that it employs a straightforward simple chemical reaction combined with acidification and stripping, requires only one instrument (graphite furnace atomic absorption spectrometry), and does not require extensive sample pretreatment.

The electrochemical oxidation of aqueous solutions of hydrogen selenide (HSe−) and of hydrogen polyselenide ions (HSex−) on glassy carbon electrodes at pH = 9.2 is reported. In both cases, the oxidation leads to deposits of selenium. The role of polyselenides as intermediates in the process is demonstrated. At 25 °C amorphous selenium is formed whereas at 70 °C crystalline selenium is deposited. The possible use of selenium films for technological purposes is discussed.

The work presents a review devoted to the metabolism and the mechanism of toxicity of seleniumcontaining supplements: elemental selenium, sodium selenite, diacetophenonyl selenide, selenopyrane, ebselen, dimethyl dipyrasolyl selenide and selenium-containing amino acids used for correction of selenium deficiency. Elemental selenium penetrating through cell walls, but not through transport channels demonstrates poorly predicted and difficultly regulated bioavailability. Sodium selenate is known to be the most toxic form of selenium in food. The metabolism of xenobiotic diacetophenonyl selenide resembles that of sodium selenide. The xenobiotic reacts with thiols, for instance, with the reduced form of glutathione leading to the formation of hydrogen selenide. Ebselen is not considered to be a well bioavailable form of selenium and thus possesses low toxicity. Xenobiotic selenopyrane eliminates selenium only in processes of xenobiotic liver exchange, and in our investigations - partially in acid-catalyzed hydrolysis. The metabolism of xenobiotic dimethyl dipyrasolyl selenide having low toxicity is poorly investigated. The toxicity of high doses of selenomethionine is determined by the possibility of incorporation in proteins and vitally important enzymes with dramatic changes of protein quaternary structure. The toxicity of high doses of methylselenocysteine seems to be caused by the lack of an exchange pool in the body and quick regeneration of hydrogen selenide from methylselenol which is formed as a result of enzymatic destruction of this amino acid. Also the issue of the most prospect selenium donor is discussed. The physiological compatibility, the low toxicity, the presence of an exchangeable pool in the organism, the antioxidantal properties and the simplicity of production indicate selenocystine as an optimal selenium donor.

The mechanism for the reaction of hydrogen selenide (H2Se) with the OH radical is examined using the "gold standard" CCSD(T) method along with the correlation consistent basis sets up to aug-cc-pV5Z. For the Se atom, the corresponding basis sets are combined with the core relativistic pseudopotential, designated as aug-cc-pVnZ-PP (n = D, T, Q, and 5). The predicted geometries and vibrational frequencies for reactants and products agree well with the available experimental results. For the entrance complex, the two-center three-electron hemibonded H2Se···OH structure (RC-B) is predicted to be the lowest. This structure lies 5.1 kcal/mol below the separated reactants H2Se + OH without zero-point energy correction. For the analogous H2S and H2O reactions, the entrance complexes lie 3.3 and 5.7 kcal/mol, respectively, below the reactants. The relative energies of the transition states are -1.7 (H2Se), +0.1 (H2S), and +9.5 (H2O) kcal/mol with respect to the appropriate reactants. The three reaction exoergicities are 40.8 (H2Se), 29.5 (H2S), and 0.0 (H2O) kcal/mol. Compared to the separated products XH + H2O (X = O, S, and Se), the exit well depths are 2.1 (Se), 2.9 (S), and 5.7 (O) kcal/mol. Intrinsic reaction coordinate analysis indicates that all stationary points were correctly identified. Several other stationary points were identified and analyzed. Finally, 29 density functional theory methods were tested systematically to explore their ability in describing the potential energy surface of the H2Se + OH reaction. The hemibonded H2Se···OH entrance complex should be observable, initially via matrix isolation spectroscopy.

Selenium is essential to human physiology and has recently shown potential in the treatment of common pathophysiological conditions ranging from arsenic poisoning to cancer. Although the precise metabolic and chemical pathways of selenium incorporation into biomolecules remain somewhat unclear, many such pathways proceed through hydrogen selenide (H2Se/HSe-) formation. Despite this importance, well-characterized chemistry that enables H2Se release under controlled conditions remains lacking. Motivated by this need, we report here the development of a hydrolysis-based H2Se donor (TDN1042). Utilizing 31P and 77Se NMR experiments, we demonstrate the pH dependence of H2Se release and characterize observed reaction intermediates during the hydrolysis mechanism. Finally, we confirm H2Se release using electrophilic trapping reagents, which not only demonstrates the fidelity of this donor platform but also provides an efficient method for investigating future H2Se donor motifs. Taken together, this work provides an early example of an H2Se donor that functions through a well-defined and characterized mechanism.

Structural, electronic, binding energies and magnetic properties of aluminum-doped and single vacancy blue phosphorene interacting with pollutant molecules are investigated using the density functional theory (DFT) with periodic boundary conditions. Acetylene, ozone, sulfur trioxide, hydrogen selenide, and sulfur dichloride molecules are considered to show the efficiency and enhancement of the sensing properties in comparison with the pristine blue phosphorene. Acetylene, sulfur trioxide, hydrogen selenide, and sulfur dichloride show chemisorption (> 0.5 eV/molecule) when interacting with the aluminum-doped system, but the ozone molecule dissociates in all configurations and symmetry sites. On the other hand, the acetylene, ozone, and sulfur trioxide with the single vacancy blue phosphorene exhibit chemisorption, the hydrogen selenide molecule exhibit a weak interaction energy, and the sulfur dichloride dissociates in all configurations and symmetry sites. In all the cases, the enhancement in the interaction energy was achieved when compared to other results for the same molecules. Finally, the single vacancy blue phosphorene shows a magnetic moment of ~1 μB/supercell, as induced by the vacancy.

Two Series of organochalcogen compounds were prepared. The first series was prepared by the reaction of 2-chloro-N-arylacetamide (where aryl is benzyl, phenyl, o-toluene, or p-toluene) with sodium hydrogen selenide (prepared in situ) to give diorganyl selenide compounds (R2Se). The second series was prepared by reaction of N-benzyl-2-chloro-N-(2-chloroacetyl)acetamide with sodium chalcogenate , Na2E (where E= S, Se, and Te) to give the corresponding cyclic chalcogenide compounds. Diiodo derivatives of cyclic selenide and telluride were also prepared. The thermal stability of the new selenium compounds (R2Se) were decomposed at 300oC. Thermogram showed a phase transfer point between 120-150oC indicating that these compounds may act as liquid crystal compounds. All new compounds were characterized by CHN elemental analysis, UV-Visible, FT-IR and 1H NMR spectroscopic data.

Hydrogen selenide (H2Se) is a colorless, nonmetallic, and hazardous air pollutant. It is a hydrogen chalcogenide that exists in gaseous form. The contamination of this gas may thereupon cause respirational disorder, liver disorder, other severe health effects, and antagonistic ecological effects. Being flammable in nature, H2Se presents a severe fire hazard and mandates the evaluation of any probable risks. Hence, the chapter discusses the potential risk assessment and management techniques involved in H2Se toxicity. This chapter also critically assesses the hydrogen selenide toxicity and its hazardousness on humans and the environment.