Se Molecules Research Articles

S-Se-S type molecule: A bactericidal promoter against H<sub>2</sub>S-induced antibiotic resistance

<p>The hydrogen sulfide (H<sub>2</sub>S)-induced defense system is a crucial bacterial pathway that leads to antibiotic resistance. Herein, a unique S-Se-S molecule, namely, 2,2’-(selenobis(sulfanediyl))diacetic acid (Se-Acid), is first reported to relieve H<sub>2</sub>S-induced antibiotic resistance by acting as a hydrogen selenide (H<sub>2</sub>Se) donor. The S-Se-S molecular structure was formed using the carboxyl terminal as an electron acceptor. After being endocytosed by cells, Se-Acid effectively released H<sub>2</sub>Se molecules by reacting with glutathione (GSH). The released H<sub>2</sub>Se increased the endocytosis of antibiotics by promoting bacterial membrane permeability. Moreover, H<sub>2</sub>Se effectively reactivated the bacterial respiratory flux by functioning as an H<sub>2</sub>S disguiser. The synergistic effect of Se-Acid and Gentamicin (Gm) on H<sub>2</sub>S-induced antibiotic-resistant MRSA was proven on MRSA<sup>S+</sup> wound infection model. Our results establish S-Se-S type molecules as potential tools for addressing the challenge of H<sub>2</sub>S-induced antibiotic resistance and reducing the risk of antibiotic resistance.</p>

Antiproliferative Effect of Inorganic and Organic Selenium Compounds in Breast Cell Lines.

Triple-negative breast cancer (TNBC) is an aggressive, fast-growing tumor that is more likely to spread to distant organs. Among women diagnosed with breast cancer, the prevalence of TNBC is 20%, and treatment is currently limited to chemotherapy. Selenium (Se), an essential micronutrient, has been explored as an antiproliferative agent. Therefore, this study aimed to evaluate the effects of exposure to organic (selenomethionine, ebselen, and diphenyl diselenide) and inorganic (sodium selenate and sodium selenite) Se molecules in different breast cell lines. The compounds were tested at 1, 10, 50, and 100 μM for 48 h in the non-tumor breast cell line (MCF-10A) and TNBC derivatives cell lines (BT-549 and MDA-MB-231). The effects of Se on cell viability, apoptotic and necrotic processes, colony formation, and cell migration were analyzed. Exposure to selenomethionine and selenate did not alter the evaluated parameters. However, selenomethionine had the highest selectivity index (SI). The exposure to the highest doses of selenite, ebselen, and diphenyl diselenide resulted in antiproliferative and antimetastatic effects. Selenite had a high SI to the BT cell line; however, the SI of ebselen and diphenyl diselenide was low in both tumoral cell lines. In conclusion, the Se compounds had different effects on the breast cell lines, and additional tests are needed to reveal the antiproliferative effects of Se compounds.

Seleno-Metabolites and Their Precursors: A New Dawn for Several Illnesses?

Selenium (Se) is an essential element for human health as it is involved in different physiological functions. Moreover, a great number of Se compounds can be considered potential agents in the prevention and treatment of some diseases. It is widely recognized that Se activity is related to multiple factors, such as its chemical form, dose, and its metabolism. The understanding of its complex biochemistry is necessary as it has been demonstrated that the metabolites of the Se molecules used to be the ones that exert the biological activity. Therefore, the aim of this review is to summarize the recent information about its most remarkable metabolites of acknowledged biological effects: hydrogen selenide (HSe−/H2Se) and methylselenol (CH3SeH). In addition, special attention is paid to the main seleno-containing precursors of these derivatives and their role in different pathologies.

Oriented loading and enduring confinement endow long-life-span Se cathode based on chemical affinity

Reversible electrochemical conversion between selenium (Se) and lithium selenide (Li2Se) can be achieved in the carbonate-based electrolytes through a solid-solid phase transformation, avoiding the fatal shuttle effect of intermediate products in the ethter-based electrolytes. However, the solid-solid conversion puts forward more stringent requirements on the initial distribution state of active Se, which cannot be satisfied by the existing physical methods for Se loading. Herein, a novel in-situ oxidization strategy is developed to construct an ideal Se/dual-carbon composite (marked as Gr@Se⊂HC). In the process, under the guidance of the N/O heteroatoms, Se molecules oxidized from the pre-embedded ZnSe are orientedly deposited inside of the hollow carbon (HC) boxes that are implanted on the 3D graphene scaffold. More impressively, the durable chemical confinement effect from the N/O functional groups during the overall lithiation/delithiation process and the fast electron transfer path provided by the delicate graphene (Gr) framework contribute to the suppressive micro-structure degradation and rapid interfacial charge transfer. Thereby, Gr@Se⊂HC delivers the ultra-long cycle life and the outstanding high-rate capability. This work proposes an original strategy for the synthesis of Se cathode and opens a new route for propelling the development of the long-life-span Li-Se batteries.

Trimodal hierarchical porous carbon nanorods enable high-performance Na-Se batteries.

Technical bottlenecks of polyselenide shuttling and material volume variation significantly hamper the development of emerging sodium-selenium (Na-Se) batteries. The nanopore structure of substrate materials is demonstrated to play a vital role in stabilizing Se cathodes and approaching superior Na-ion storage properties. Herein, an ideal nanorod-like trimodal hierarchical porous carbon (THPC) host is fabricated through a facile one-step carbonization method for advanced Na-Se batteries. The THPC possesses a trimodal nanopore structure encompassing micropores, mesopores, and macropores, and functions as a good accommodator of Se molecules, a reservoir of polyselenide intermediates, a buffer for volume expansion of Se species during sodiation, and a promoter for electron/ion transfer in the electrochemical process. As a result, Na-Se batteries assembled with the Se-THPC composite cathode realize high utilization of Se, fast redox kinetics, and excellent cyclability. Furthermore, the Na-ion storage mechanism of the well-designed Se-THPC composite is profoundly revealed by in situ visual characterization techniques.

Multi-wafer-scale growth of WSe2 films using a traveling flow-type reactor with a remote thermal Se cracker

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) have demonstrated superior electrical and optical characteristics and are expected to replace silicon in semiconductor materials. However, in practice the use of TMDCs remains a challenge due to the lack of a suitable method for the large-scale synthesis of TMDCs. Herein we demonstrated a multi-wafer-scale growth method to obtain very uniform and continuous 2D WSe2 films by combining the selenization of the W metal using thermally cracked Se molecules, a metal-agglomeration-suppressed growth technique, and a traveling flow-type reactor. The usefulness of the traveling flow reactor must be attributed to the self-saturated selenization of a very thin W metal precursor film on a large-area substrate. The number of 2D WSe2 layers was easily controlled by varying the thickness of the W precursor. Raman scattering and thickness measurements showed that WSe2 films grew uniformly on three 4-inch Si wafers at once, at both 530 and 600 °C. The average Hall mobility and carrier concentration of 6-nm-thick p-type WSe2 films on the three wafers were 22.8 cm2 V−1 s−1 and 3.69 × 1016 cm−3, respectively. The field effect (FE) transistor with the 6-nm WSe2 channel and SiO2 back gate insulator also showed p-type transfer characteristics. The formation of a WSe2/MoSe2 vertical heterostructure also demonstrated the usefulness of the method proposed herein.

STM study of selenium adsorption on Au(111) surface**Project supported by the Direct Grant for Research of CUHK, China (Grant Nos. 4053306 and 4053348)

Adsorption of chalcogen atoms on metal surfaces has attracted increasing interest for both the fundamental research and industrial applications. Here, we report a systematic study of selenium (Se) adsorption on Au(111) at varies substrate temperatures by scanning tunneling microscopy. At room temperature, small Se clusters are randomly dispersed on the surface. Increasing the temperature up to 200 °C, a well-ordered lattice of Se molecules consisting of 8 Se atoms in ring-like structure is formed. Further increasing the temperature to 250 °C gives rise to the formation of Se monolayer with Au(111)- lattices superimposed with a quasi-hexagonal lattice. Desorption of Se atoms rather than the reaction between the Se atoms and the Au substrate occurs if further increasing the temperature. The ordered structures of selenium monolayers could serve as templates for self-assemblies and our findings in this work might provide insightful guild for the epitaxial growth of the two-dimensional transition metal dichalcogenides.

Noncovalent Interactions in Complexes Involving the Cyclic C2H2X (X=O, S, Se) Molecules and the Lewis Acids YF (Y=F, Cl, Br, H)

AbstractA computational study of the cyclic Lewis bases C2H2X (X=O, S, Se) interacting with the Lewis acids YF (Y=F, Cl, Br, H) in model C2H2X…YF dyads was undertaken. It was shown that the noncovalent X…Y interaction in these binary complexes increases with increasing YF dipole moment for the C2H2O complexes, but not for the C2H2S and C2H2Se complexes, where instead the X…Y interaction increases with increasing X/Y electronegativity difference. This suggests that electrostatic forces dominate the binding in the former, whereas polarization effects dominate in the latter complexes. These explanations were supported by natural bond orbital (NBO) and atoms in molecules (AIM) analyses of the electron density, as well as interaction energy decomposition analyses. A subsequent study of the cooperative effect of an additional hydrogen bond in the model triads, FH…C2H2X…YF and C2H2X…YF…HF, found that the X…Y interaction in the dyads is weakened in the former and strengthened in the latter, with the trends identified in the dyads persisting in both triads.

Mercury and selenium levels, and Se:Hg molar ratios in freshwater fish from South Louisiana

Ample historical evidence has demonstrated the neurotoxicity of organic Hg. However, several studies have suggested that Se effectively sequesters MeHg. The affinity of Hg is up to ≈106 times higher for Se molecules than for comparable sulfur molecules, most of which are components of brain enzymes. The neurotoxicity of MeHg is associated with its binding to Se and the resultant interference with selenoenzymes (Ralston & Raymond, Global Advances in Selenium Research from Theory to Application, 2016). Therefore, having ample Se reserves is an effective way to mitigate MeHg’s toxicity. When the molar ratios of Se to Hg in fish exceed 1.0, ingestion of the fish is unlikely to deplete Se reserves. The goal of this study was to determine the Hg and Se levels, and the Se:Hg molar ratios in freshwater fish from south Louisiana and the implications of those ratios with respect to fish consumption and Hg advisories. Five waterbodies were surveyed (University lake, Calcasieu lake, Toledo Bend, the Atchafalaya River and Henderson Lake). The sampled species included black drum (Pogonias cromis), catfish sp., largemouth bass (Micropterus salmoides) and bluegill (Eupomotis macrochirus). All fish were assayed for total Hg and Se. The average Hg concentration was 0.001 µmol g−1 (0.21 ppm), and all concentrations were below the 1 ppm US FDA action level (from 3.1 × 10–5 to 0.003 µmol g−1). Se concentrations exceeded Hg concentrations in most cases. The average Se concentration was 0.003 µmol g−1 (0.27 ppm), all concentrations were around or less than 1.0 ppm (from 3.7 × 10–4 to 0.017 µmol g−1). Hence, the Se:Hg molar ratios were >1 in all fish except largemouth bass from Henderson Lake. In general, Se was detected in sufficient amounts to sequester Hg, but consumption of largemouth bass from Henderson Lake would pose no risk only if anglers followed the posted Hg advisory. For advisory purposes, perhaps, both Hg and Se levels and Se:Hg molar ratios should be considered. In general, the results indicated that risk assessment will require consideration of both the fish species and body of water, because both can influence Se and Hg concentrations and Se:Hg molar ratios.

Selenium targets resistance biomarkers enhancing efficacy while reducing toxicity of anti-cancer drugs: preclinical and clinical development.

Selenium (Se)-containing molecules exert antioxidant properties and modulate targets associated with tumor growth, metastasis, angiogenesis, and drug resistance. Prevention clinical trials with low-dose supplementation of different types of Se molecules have yielded conflicting results. Utilizing several xenograft models, we earlier reported that the enhanced antitumor activity of various chemotherapeutic agents by selenomethione and Se-methylselenocysteine in several human tumor xenografts is highly dose- and schedule-dependent. Further, Se pretreament offered selective protection of normal tissues from drug-induced toxicity, thereby allowing higher dosing than maximum tolerated doses.These enhanced therapeutic effects were associated with inhibition of hypoxia-inducible factor 1- and 2-alpha (HIF1α, HIF2α) protein, nuclear factor (erythyroid-derived 2)-like 2 (Nrf2) and pair-related homeobox-1 (Prx1) transcription factors, downregulation of oncogenic- and upregulation of tumor suppressor miRNAs. This review provides: 1) a brief update of clinical prevention trials with Se; 2) advances in the use of specific types, doses, and schedules of Se that selectively modulate antitumor activity and toxicity of anti-cancer drugs; 3) identification of targets selectively modulated by Se; 4) plasma and tumor tissue Se levels achieved after oral administration of Se in xenograft models and cancer patients; 5) development of a phase 1 clinical trial with escalating doses of orally administered selenomethionine in sequential combination with axitinib to patients with advanced clear cell renal cell carcinoma; and 6) clinical prospects for future therapeutic use of Se in combination with anticancer drugs.

Synthesis of enantiomerically pure glycerol derivatives containing an organochalcogen unit: In vitro and in vivo antioxidant activity

We describe here the synthesis of enantiomerically pure chalcogenoethers obtained through the reaction of nucleophilic species of chalcogen (S, Se and Te), generated in situ from the respective diorganyl dichalcogenides, with (R)- and (S)-tosyl solketal. Furthermore, some of the chalcogenoethers were treated with acidic cation exchange resin Dowex-(H+) leading to the respective deprotected enantiomerically pure 3-phenylchalcogenyl-1,2-diols. In order to explore the biological potential of these molecules, the antioxidant activity of some organochalcogens was evaluated by several in vitro assays. Overall, the chalcogenoethers containing Te were better scavengers of DPPH and ABTS+ radicals, had higher ferric reducing capacity and prevented lipid peroxidation. To analyze the effects of these compounds in vivo, we used the alternative model Caenorhabditis elegans. Chalcogenoethers treatment, especially (S)- and (R)-2,2-dimethyl-4-(phenylselanylmethyl)-1,3-dioxolane, conferred protection against the mortality-induced by hydrogen peroxide. Accordingly, these chalcogenoethers were able to modulate the antioxidant enzyme catalase. Notably, the compounds did not present toxicity in worm’s reproduction. To sum up, our study demonstrated that Te- containing chalcogenoethers were promising in vitro scavengers, while Se molecules were more prone to protect against a stressor in vivo. In this sense, the antioxidant activity of chalcogenoethers, especially with Se and Te, indicates that these molecules may have biological application in an attempt to reduce the oxidative stress.

A new energy storage system: Rechargeable potassium-selenium battery

A new reversible and high-performance potassium-selenium (K-Se) battery, using confined selenium/carbonized-polyacrylonitrile (PAN) composite (c-PAN-Se) as cathode and metallic potassium as anode, is reported in this work. The PAN-derived carbon matrix could effectively confine the small Se molecules and provide a sufficient buffer for the volume changes. The reversible formation of small-molecule trigonal Se (Se1, P3121) phase could essentially inhibit the formation of polyselenides and account for outstanding electrochemical performance. The carbonate-based electrolyte further synergistically diminishes the shuttle effect by inhibiting the formation of polyselenides in the meantime. The as-prepared K-Se battery shows a reversible capacity of 1904mAhcm−3 after 100 cycles at 0.2C and rate retention of 89% from 0.1 to 2C. In addition, the charge-discharge mechanism is also investigated via the combination of in-situ and ex-situ synchrotron X-ray diffraction (XRD), and Raman spectroscopy analysis. The results reveal that the introduction of K+ ions leads to the cleavage of C-Se bonds, the rearrangement of selenium atoms, and the final formation of the main product K2Se. Moreover, the reversible formation of trigonal Se (Se1, P3121) phase was detected in the reaction with K+. These findings not only can advance our understanding of this family of batteries, but also provide insight into chemically-bonded selenium composite electrodes, which could give guidance for scientific research and the optimization of Se and S electrodes for the K-S, Na-S, Li-S, Na-Se, and Li-Se batteries.

Graphitic Nanocarbon–Selenium Cathode with Favorable Rate Capability for Li–Se Batteries

A well-organized selenium/carbon nanosheets nanocomposite(Se/CNSs) is prepared by confining chain-like Sen molecules in hierarchically micromesoporous carbon nanosheets. A unique two-dimensional morphology and high graphitization degree of carbon nanosheets benefits fast Li+/e- access to the active Se, which guarantees a high utilization of Se during the(de)lithiation process. Besides, the chain-like Se molecules confined in the carbon matrix could alleviate the shuttle effect of polyselenides and promise a stable electrochemistry. Therefore, the resultant Se/CNSs delivers a highly reversible capacity, a long cycle life and favorable rate capabilities. Furthermore, a Li-Se pouch cell built from a metallic Li anode and the as-prepared Se/CNSs cathode exhibits an excellent electrochemical performance, demonstrating the potential of Se/CNSs in serving future energy storage devices with high energy density.

The Electrochemistry with Lithium versus Sodium of Selenium Confined To Slit Micropores in Carbon.

Substitution of selenium for sulfur in the cathode of a rechargeable battery containing Sx molecules in microporous slits in carbon allows a better characterization of the electrochemical reactions that occur. Paired with a metallic lithium anode, the Sex chains are converted to Li2Se in a single-step reaction. With a sodium anode, a sequential chemical reaction is characterized by a continuous chain shortening of Sex upon initial discharge before completing the reduction to Na2Se; on charge, the reconstituted Sex molecules retain a smaller x value than the original Sex chain molecule. In both cases, the Se molecules remain almost completely confined to the micropore slits to give a long cycle life.

Flexible one-dimensional carbon–selenium composite nanofibers with superior electrochemical performance for Li–Se/Na–Se batteries

A facile strategy is developed to synthesis selenium/carbon composites (Se@CNFs-CNT) by co-heating Se powder and electrospun Polyacrylonitrile (PAN)-CNT nanofibers at 600°Cin a sealed vessel. The Se molecules are chemically bonded and physical encapsulated by carbonized PAN-CNT composite (CNFs-CNT), which leads to prevent the dissolution of polyselenide intermediates in carbonate based electrolyte. When directly used as flexible free-standing cathode material for Li–Se batteries in low cost carbonate-based electrolyte, the Se@CNFs-CNT electrode exhibits improved cyclability (517 mAh g−1 after 500 cycles at 0.5 A g−1) and rate capability (485 mAh g−1 at 1 A g−1). Moreover, when tested as sodium batteries, it maintains a reversible capacity of 410 mAh g−1 after 240 cycles at 0.5 A g−1. The superior electrochemical performance (especially at high rates) of Se@CNFs-CNT is attributed to synergistic effect of the additive of CNT, the well confine of Se in the CNFs-CNT matrix through chemical bonding and the 3D interconnected carbon nanofibers (CNFs). This simple yet efficient process thus provides a promising route towards fabrication of a variety of high performance flexible Li–Se and Na–Se batteries.

A novel type of one-dimensional organic selenium-containing fiber with superior performance for lithium–selenium and sodium–selenium batteries

A novel type of organic selenide fiber composed of carbonized polyacrylonitrile/selenium (CPAN/Se) has been synthesized by heating polyacrylonitrile–selenium (PAN–Se) fibers via the electrospinning technique at 600 °C. The Se molecules are confined by N-containing carbon ring structures in the form of energy-storing selenium side chains in the carbonized PAN matrix. This unique stable chemical structure with a conductive carbon skeleton connected to the selenium side chains and excellent mechanical stability can allow CPAN/Se composite cathodes to be charged and discharged in a low-cost carbonate-based electrolyte with excellent long cycle stability and quite good rate performance. The superior electrochemical performance of CPAN/Se electrodes is demonstrated in both lithium-ion and sodium-ion batteries, where they have delivered a high capacity of nearly 600 mA h g−1 for 500 cycles in lithium–selenium (Li–Se) batteries and 410 mA h g−1 for 300 cycles in sodium–selenium (Na–Se) batteries at 0.3 C, respectively.

Predicting the stability of surface phases of molybdenum selenides

The selenization of molybdenum might become an important step in the production of nanostructures based on the layered compound MoSe2. It is already technologically relevant for the production of thin film chalcopyrite solar cells. However, the control of the process is still very poor, due to the lack of basic knowledge of the surface thermodynamics of the system. Here, we present a theoretical study on the stability of surface adlayers of Se on the Mo(110) surface, predicting surface patterns and their stability range in terms of temperature and selenium partial pressure. Our results, based on density functional theory, show that the attainable Se coverages range from 1/4 to 3/4 of a monolayer for systems in equilibrium with a gas formed of Se molecules. We provide simulated scanning tunneling microscopy images to help the experimental characterization of adsorbed surface patterns.

Pseudo Jahn-Teller coupling in trioxides XO3(0,1,−1) with 22 and 23 valence electrons

D3h and C2v geometries and energies, vertical excitation energies, as well as minimal energy paths as function of the O(1)(z)-X-O(2) angle α were obtained for XO3((0,1,-1)) (X = B, Al, Ga; C, Si, Ge; N, P, As; S, Se) molecules and ions with 22 and 23 valence electrons (VE), using density functional theory (DFT), coupled cluster with single and double substitutions with noniterative triple excitations (CCSD(T)), equation of motion (EOM)-CCSD, time-dependent DFT, and multi-reference configuration interaction methods. It is shown that pseudo Jahn-Teller (PJT) coupling increases as the central atom X becomes heavier, due to decreases in excitation energies. As is well known for CO3, the excited (1)E' states of the 22 VE systems SiO3, GeO3; NO3(+), PO3(+), AsO3(+); BO3(-), AlO3(-), GaO3(-) have strong vibronic coupling with the (1)A1' ground state via the e' vibrational modes, leading to a C2v minimum around α = 145°. For first and second row X atoms, there is an additional D3h minimum (α = 120°). Interacting excited states have minima around 135°. In the 23 VE systems CO3(-), SiO3(-); NO3, PO3; SO3(+), coupling of the excited (2)E' with the (2)A2' ground state via the e' mode does not generate a C2v state. Minima of interacting excited states are close to 120°. However, due to very strong PJT coupling, a double-well potential is predicted for GeO3(-), AsO3, and SeO3(+), with a saddle point at D3h symmetry. Interaction of the b2 highest occupied molecular orbital with the b2 lowest unoccupied molecular orbital, both oxygen lone pair molecular orbitals, is seen as the reason for the C2v stabilization of 22 VE molecules.

Positron-attachment to nonpolar or small dipole CXY (X, Y = O, S, and Se) molecules: vibrational enhancement of positron affinities with configuration interaction level of multi-component molecular orbital approach

To theoretically demonstrate the binding of a positron to a nonpolar or small dipole molecule, we have calculated the vibrational averaged positron affinity (PA) values along the harmonic asymmetric stretching vibrational coordinate with the configuration interaction level of multi-component molecular orbital method for CXY (X, Y = O, S, and Se) molecules. For CSe2 and CSSe molecules, a positron can even be attached at the equilibrium structures, due to the effect of the induced dipole moment with large polarizability values. For a CS2 molecule, the positive PA value is obtained at the lowest vibrational excited state in our scheme. Although there is no direct experimental evidence for the positron-binding to CO2, COS, and COSe molecules, we have predicted positron-binding for these molecules at higher vibrational excited states.

Reactive Sputtering Process for CuIn<sub>1-x</sub>Ga<sub>x</sub>Se<sub>2</sub> Thin Film Solar Cells

CuIn1-xGaxSe2 (CIGS) thin films are grown on Mo/soda lime glass using a reactive sputtering process in which a Se cracker is used to deliver reactive Se molecules. The Cu and (In0.7Ga0.3)2Se3 targets are simultaneously sputtered under the delivery of reactive Se. The effects of Se flux on film composition are investigated. The Cu/(In+Ga) composition ratio increases as the Se flux increases at a plasma power of less than 30 W for the Cu target. The (112) crystal orientation becomes dominant, and crystal grain size is larger with Se flux. The power conversion efficiency of a solar cell fabricated using an 800-nm CIGS film is 8.5%.