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7 pages, 461 KiB

Open AccessArticle

Modes of Neighbouring Group Participation by the Methyl Selenyl Substituent in β-Methylselenylmethyl-substituted 1-Phenylethyl Carbenium Ions

by Benjamin L. Harris and Jonathan M. White

Molecules 2013, 18(10), 11705-11711; https://doi.org/10.3390/molecules181011705 - 25 Sep 2013

Cited by 4 | Viewed by 5186

Abstract

Selenium substituents which are disposed β to an electron deficient centre, such as a carbocation p-orbital, or the π* orbital of an electron deficient p-system, interact in a stabilising way by a combination of C-Se hyperconjugation (σ_Se-C–π* interaction), [...] Read more.

Selenium substituents which are disposed β to an electron deficient centre, such as a carbocation p-orbital, or the π* orbital of an electron deficient p-system, interact in a stabilising way by a combination of C-Se hyperconjugation (σ_Se-C–π* interaction), and a through-space homoconjugative n_Se–π* interaction. The relative importance of these two modes of interaction is dependant on the electron demand of the cation, with hyperconjugation predominating for low electron demand systems, and the n_Se–π* interaction predominating for high electron demand cations. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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14 pages, 655 KiB

Open AccessArticle

Synthesis and Biological Activity of 6-Selenocaffeine: Potential Modulator of Chemotherapeutic Drugs in Breast Cancer Cells

by Inês L. Martins, Joana P. Miranda, Nuno G. Oliveira, Ana S. Fernandes, Sandrina Gonçalves and Alexandra M. M. Antunes

Molecules 2013, 18(5), 5251-5264; https://doi.org/10.3390/molecules18055251 - 8 May 2013

Cited by 29 | Viewed by 7991

Abstract

We report the development of a new microwave-based synthetic methodology mediated by Woollins’ reagent that allowed an efficient conversion of caffeine into 6-selenocaffeine. A preliminary evaluation on the modulation of antioxidant activity upon selenation of caffeine, using the DPPH assay, indicated a mild [...] Read more.

We report the development of a new microwave-based synthetic methodology mediated by Woollins’ reagent that allowed an efficient conversion of caffeine into 6-selenocaffeine. A preliminary evaluation on the modulation of antioxidant activity upon selenation of caffeine, using the DPPH assay, indicated a mild antioxidant activity for 6-selenocaffeine, contrasting with caffeine, that exhibited no antioxidant activity under the same experimental conditions. Interestingly, whereas 6-selenocaffeine has revealed to have a low cytotoxic potential in both MCF10A and MCF-7 breast cells (24 h, up to 100 µM, MTT assay), a differential effect was observed when used in combination with the anticancer agents doxorubicin and oxaliplatin in MCF-7 breast cancer cells. The co-treatment of doxorubicin (1 µM) and 6-selenocaffeine (100 µM) resulted in a slight decrease in cellular viability when compared to doxorubicin (1 µM) alone. Conversely, the seleno-caffeine derivative at the same concentration markedly increased the viability of oxaliplatin (100 µM)-treated cells (p < 0.01). Overall, this work highlights an emerging methodology to synthesize organoselenium compounds and points out the differential roles of 6-selenocaffeine in the modulation of the cytotoxicity of anticancer agents. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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14 pages, 510 KiB

Open AccessArticle

Changes in SeMSC, Glucosinolates and Sulforaphane Levels, and in Proteome Profile in Broccoli (Brassica oleracea var. Italica) Fertilized with Sodium Selenate

by Ignacio Sepúlveda, Herna Barrientos, Andrea Mahn and Alejandra Moenne

Molecules 2013, 18(5), 5221-5234; https://doi.org/10.3390/molecules18055221 - 7 May 2013

Cited by 20 | Viewed by 7063

Abstract

The aim of this work was to analyze the effect of sodium selenate fortification on the content of selenomethyl selenocysteine (SeMSC), total glucosinolates and sulforaphane, as well as the changes in protein profile of the inflorescences of broccoli (Brassica oleracea var. Italica [...] Read more.

The aim of this work was to analyze the effect of sodium selenate fortification on the content of selenomethyl selenocysteine (SeMSC), total glucosinolates and sulforaphane, as well as the changes in protein profile of the inflorescences of broccoli (Brassica oleracea var. Italica). Two experimental groups were considered: plants treated with 100 mmol/L sodium selenate (final concentration in the pot) and control plants treated with water. Fortification began 2 weeks after transplantation and was repeated once a week during 10 weeks. Broccoli florets were harvested when they reached appropriate size. SeMSC content in broccoli florets increased significantly with sodium selenate fortification; but total glucosinolates and sulforaphane content as well as myrosinase activity were not affected. The protein profile of broccoli florets changed due to fortification with sodium selenate. Some proteins involved in general stress-responses were up-regulated, whereas down-regulated proteins were identified as proteins involved in protection against pathogens. This is the first attempt to evaluate the physiological effect of fortification with sodium selenate on broccoli at protein level. The results of this work will contribute to better understanding the metabolic processes related with selenium uptake and accumulation in broccoli. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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10 pages, 214 KiB

Open AccessArticle

A Selenium-Based Ionic Liquid as a Recyclable Solvent for the Catalyst-Free Synthesis of 3-Selenylindoles

by Everton G. Zimmermann, Samuel Thurow, Camilo S. Freitas, Samuel R. Mendes, Gelson Perin, Diego Alves, Raquel G. Jacob and Eder J. Lenardão

Molecules 2013, 18(4), 4081-4090; https://doi.org/10.3390/molecules18044081 - 5 Apr 2013

Cited by 42 | Viewed by 6997

Abstract

The ionic liquid 1-butyl-3-methylimidazolium methylselenite, [bmim][SeO₂(OCH₃)], was successfully used as solvent in the catalyst-free preparation of 3-arylselenylindoles by the reaction of indole with ArSeCl at room temperature. The products were obtained selectively in good yields without the need of [...] Read more.

The ionic liquid 1-butyl-3-methylimidazolium methylselenite, [bmim][SeO₂(OCH₃)], was successfully used as solvent in the catalyst-free preparation of 3-arylselenylindoles by the reaction of indole with ArSeCl at room temperature. The products were obtained selectively in good yields without the need of any additive and the solvent was easily reused for several cycles with good results. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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8 pages, 211 KiB

Open AccessArticle

The Protection of Selenium against Cadmium-Induced Cytotoxicity via the Heat Shock Protein Pathway in Chicken Splenic Lymphocytes

by Xi Chen, Yi-Hao Zhu, Xin-Yue Cheng, Zi-Wei Zhang and Shi-Wen Xu

Molecules 2012, 17(12), 14565-14572; https://doi.org/10.3390/molecules171214565 - 7 Dec 2012

Cited by 63 | Viewed by 6059

Abstract

Cadmium (Cd) is a heavy metal that poses a hazard to animal health due to its toxicity. Selenium (Se) is an important nutritional trace element. However, the potential protective effects of Se against Cd-induced toxicity remain to be elucidated. To investigate the cytotoxicity [...] Read more.

Cadmium (Cd) is a heavy metal that poses a hazard to animal health due to its toxicity. Selenium (Se) is an important nutritional trace element. However, the potential protective effects of Se against Cd-induced toxicity remain to be elucidated. To investigate the cytotoxicity of Cd on bird immunocytes in vitro and the protective effects of Se against exposure to Cd, chicken splenic lymphocytes received Cd (10⁻⁶ mol/L), Se (10⁻⁷ mol/L), and the mixture of 10⁻⁷ mol/L Se and 10⁻⁶ mol/L Cd and were incubated for 12 h, 24 h, 36 h, 48 h, respectively. The transcription of heat shock protein (HSP) 27, HSP40, HSP60, HSP70 and HSP90 mRNA was tested by fluorescence quantitative PCR. The results showed that the mRNA expression of HSPs exposed to 10⁻⁶ mol/L Cd showed a sustained decrease at 12–48 h exposure. A statistically significant increase in the mRNA expression of HSPs in the case of Se group was observed, as compared to the control group of chicken splenic lymphocytes. Concomitantly, treatment of chicken splenic lymphocytes with Se in combination with Cd enhanced the mRNA expression of HSPs which were reduced by Cd treatment. This indicated that the protective effect of Se against the toxicity of Cd might, at least partially, be attributed to stimulation of the level of HSPs. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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17 pages, 613 KiB

Open AccessArticle

Excitation and Circular Dichroism Spectra of (+)-(S,S)-bis(2-Methylbutyl)chalcogenides

by Yasushi Honda, Atsushi Kurihara, Yusuke Kenmochi and Masahiko Hada

Molecules 2010, 15(4), 2357-2373; https://doi.org/10.3390/molecules15042357 - 31 Mar 2010

Cited by 4 | Viewed by 10823

Abstract

Theoretical electronic spectra and natural circular dichroism (CD) spectra of (+)-(S,S)-bis(2-methylbutyl)chalcogenides, Ch[CH₂CH(CH₃)C₂H₅]₂ (Ch = S, Se, and Te), were calculated by the symmetry adapted cluster (SAC) and SAC-configuration interaction (SAC-CI) [...] Read more.

Theoretical electronic spectra and natural circular dichroism (CD) spectra of (+)-(S,S)-bis(2-methylbutyl)chalcogenides, Ch[CH₂CH(CH₃)C₂H₅]₂ (Ch = S, Se, and Te), were calculated by the symmetry adapted cluster (SAC) and SAC-configuration interaction (SAC-CI) methods. Whereas the calculated CD spectrum for each stable conformation itself did not reproduce the corresponding experimental one, their Boltzmann-averaged spectra showed good agreement with the experimental results. We provided the assignment for each spectral band according to our calculation results. For the telluride compound, temperature dependence of the CD spectra was experimentally observed due to variation in the Boltzmann factor, and our calculations reproduced it qualitatively. The spectral features that we could not reproduce can be attributed to triplet transitions through the spin-orbit interaction effects as well as accuracy incompleteness on the calculation conditions. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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14 pages, 275 KiB

Open AccessArticle

The Effect of Long-Running Severe Selenium-Deficiency on the Amount of Iron and Zinc in the Organs of Rats

by Ken-ichiro Matsumoto, Sachiyo Terada, Marie Ariyoshi, Aya Okajo, Atsushi Hisamatsu, Iori Ui and Kazutoyo Endo

Molecules 2009, 14(11), 4440-4453; https://doi.org/10.3390/molecules14114440 - 5 Nov 2009

Cited by 7 | Viewed by 8818

Abstract

The amounts of selenium (Se), iron (Fe), and zinc (Zn) in the liver, kidney, and spleen as a function of age of rats measured using instrumental neutron activation analysis were compared between Se-deficient (SeD) rats and normal rats. The SeD model rats can [...] Read more.

The amounts of selenium (Se), iron (Fe), and zinc (Zn) in the liver, kidney, and spleen as a function of age of rats measured using instrumental neutron activation analysis were compared between Se-deficient (SeD) rats and normal rats. The SeD model rats can live for more than 50 weeks. The effect of Se-deficinecy in rats might be weak, compared to the marked malfunction of GSH-Px. The SeD rats can be considered as a model of nonlethal chronic oxidative stress. Fluctuations of Fe and Zn in the liver of Se-deficient rats were observed. The amount of redox-relating minerals, such as Fe and Zn, in SeD rat organs is changeable depending on the age. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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9 pages, 247 KiB

Open AccessCommunication

Cesium Carbonate-Catalyzed α-Phenylchalcogenation of Carbonyl Compounds with Diphenyl Dichalcogenide

by Yutaka Nishiyama, Yuya Koguma, Toshimasa Tanaka and Rui Umeda

Molecules 2009, 14(9), 3367-3375; https://doi.org/10.3390/molecules14093367 - 2 Sep 2009

Cited by 13 | Viewed by 10269

Abstract

It was found that cesium carbonate has a unique catalytic ability on the reaction of carbonyl compounds with diphenyl diselenide to give the corresponding α-phenylseleno carbonyl compounds in moderate to good yields. Similarly, the α-phenylthiolation of carbonyl compounds with diphenyl disulfide was promoted [...] Read more.

It was found that cesium carbonate has a unique catalytic ability on the reaction of carbonyl compounds with diphenyl diselenide to give the corresponding α-phenylseleno carbonyl compounds in moderate to good yields. Similarly, the α-phenylthiolation of carbonyl compounds with diphenyl disulfide was promoted by the cesium carbonate catalyst. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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26 pages, 825 KiB

Open AccessArticle

Synthesis and Pharmacological Screening of Several Aroyl and Heteroaroyl Selenylacetic Acid Derivatives as Cytotoxic and Antiproliferative Agents

by Carmen Sanmartín, Daniel Plano, Enrique Domínguez, María Font, Alfonso Calvo, Celia Prior, Ignacio Encío and Juan Antonio Palop

Molecules 2009, 14(9), 3313-3338; https://doi.org/10.3390/molecules14093313 - 1 Sep 2009

Cited by 52 | Viewed by 13145

Abstract

The synthesis and cytotoxic activity of a series of twenty six aroyl and heteroaroyl selenylacetic acid derivatives of general formula Ar-CO-Se-CH₂-COOH or Heterar-CO-Se-CH₂-COOH are reported. The synthesis was carried out by reaction of acyl chlorides with sodium hydrogen selenide, [...] Read more.

The synthesis and cytotoxic activity of a series of twenty six aroyl and heteroaroyl selenylacetic acid derivatives of general formula Ar-CO-Se-CH₂-COOH or Heterar-CO-Se-CH₂-COOH are reported. The synthesis was carried out by reaction of acyl chlorides with sodium hydrogen selenide, prepared in situ, and this led to the formation of sodium aroylselenides that subsequently reacted with α-bromoacetic acid to produce the corresponding selenylacetic acid derivatives. All of the compounds were tested against a prostate cancer cell line (PC-3) and some of the more active compounds were assessed against a panel of four human cancer cell lines (CCRF-CEM, HTB-54, HT-29, MCF-7) and one mammary gland-derived non-malignant cell line (184B5). Some of the compounds exhibited remarkable cytotoxic and antiproliferative activities against MCF-7 and PC-3 that were higher than those of the reference compounds doxorubicin and etoposide, respectively. For example, in MCF-7 when Ar = phenyl, 3,5-dimethoxyphenyl or benzyl the TGI values were 3.69, 4.18 and 6.19 μM. On the other hand, in PC-3 these compounds showed values of 6.8, 4.0 and 2.9 μM. Furthermore, benzoylselenylacetic acid did not provoke apoptosis nor did it perturb the cell cycle in MCF-7. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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8 pages, 214 KiB

Open AccessArticle

Theoretical Studies of [2,3]-Sigmatropic Rearrangements of Allylic Selenoxides and Selenimides

by Craig A. Bayse and Sonia Antony

Molecules 2009, 14(9), 3229-3236; https://doi.org/10.3390/molecules14093229 - 28 Aug 2009

Cited by 3 | Viewed by 10856

Abstract

Density-functional theory is used to model the endo and exo transition states for [2,3]-sigmatropic rearrangement of allylic aryl-selenoxides and -selenimides. The endo transition state is generally preferred for selenoxides if there is no substitution at the 2 position of the allyl group. Based [...] Read more.

Density-functional theory is used to model the endo and exo transition states for [2,3]-sigmatropic rearrangement of allylic aryl-selenoxides and -selenimides. The endo transition state is generally preferred for selenoxides if there is no substitution at the 2 position of the allyl group. Based upon the relative energies of the endo and exo transition states, enantioselectivity of rearrangements is expected to be greatest for molecules with substitutions at the 1- or (E)-3- position of the allyl group. Ortho substitution of a nitro group on the ancillary selenoxide phenyl ring reduces the activation barriers, increases the difference between the endo and exo activation barriers and shifts the equilibrium toward products. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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18 pages, 580 KiB

Open AccessArticle

Diaroyl Tellurides: Synthesis, Structure and NBO Analysis of (2-MeOC₆H₄CO)₂Te – Comparison with Its Sulfur and Selenium Isologues. The First Observation of [MgBr][R(C=Te)O] Salts

by Osamu Niyomura, Shoho Nakaiida, Ryo Yamada, Shinzi Kato, Masaru Ishida, Masahiro Ebihara, Fumio Ando and Jugo Koketsu

Molecules 2009, 14(7), 2555-2572; https://doi.org/10.3390/molecules14072555 - 13 Jul 2009

Cited by 4 | Viewed by 14217

Abstract

A series of aromatic diacyl tellurides were prepared in moderate to good yields by the reactions of sodium orpotassium arenecarbotelluroates with acyl chlorides in acetonitrile. X-ray structure analyses and theoretical calculations of 2-methoxybenzoic anhydride and bis(2-methoxybenzoyl) sulfide, selenide and telluride were carried out. [...] Read more.

A series of aromatic diacyl tellurides were prepared in moderate to good yields by the reactions of sodium orpotassium arenecarbotelluroates with acyl chlorides in acetonitrile. X-ray structure analyses and theoretical calculations of 2-methoxybenzoic anhydride and bis(2-methoxybenzoyl) sulfide, selenide and telluride were carried out. The two 2-MeOC₆H₄CO moieties of bis(2-methoxybenzoyl) telluride are nearly planar and the two methoxy oxygen atoms intramolecularly coordinate to the central tellurium atom from both side of C(11)-Te(11)-C(22) plane. In contrast, the oxygen and sulfur isologues (2-MeOC₆H₄CO)₂E (E = O, S), show that one of the two methoxy oxygen atoms contacts with the oxygen atom of the carbonyl group connected to the same benzene ring. The structure of di(2-methoxybenzoyl) selenide which was obtained by MO calculation resembles that of tellurium isologues rather than the corresponding oxygen and sulfur isologues. The reactions of di(aroyl) tellurides with Grignard reagents lead to the formation of tellurocarboxylato magnesium complexes [MgBr][R(C=Te)O]. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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13 pages, 283 KiB

Open AccessArticle

Association Mechanism of S-Dinitrophenyl Glutathione with Two Glutathione Peroxidase Mimics: 2, 2¢-Ditelluro- and 2, 2¢-Diseleno-bridged b-cyclodextrins

by Ya-Qiong Hao, Xing-Chen Liu, Jun-Qiu Liu and Yu-Qing Wu

Molecules 2009, 14(3), 904-916; https://doi.org/10.3390/molecules14030904 - 25 Feb 2009

Cited by 5 | Viewed by 12475

Abstract

Complex formation of the glutathione peroxidase mimics 2,2¢-ditelluro-bridged b-cyclodextrin (1) and 2,2¢-diseleno-bridged b-cyclodextrin (2), with S-substituted dinitrophenyl glutathione (3) were determined by ultraviolet-visible (UV-Vis) absorption spectroscopy in phosphate buffer (pH 7.4) and ¹H-NMR spectroscopy. Molecular mechanics (MM2) modeling calculations were used [...] Read more.

Complex formation of the glutathione peroxidase mimics 2,2¢-ditelluro-bridged b-cyclodextrin (1) and 2,2¢-diseleno-bridged b-cyclodextrin (2), with S-substituted dinitrophenyl glutathione (3) were determined by ultraviolet-visible (UV-Vis) absorption spectroscopy in phosphate buffer (pH 7.4) and ¹H-NMR spectroscopy. Molecular mechanics (MM2) modeling calculations were used to deduce a three-dimensional model for each complex. The dinitrophenyl (DNP) group of 3 appears to penetrate the cavity of b-cyclodextrin (b-CD) or 1, but it is located between the two secondary rims of 2. The complexes’ stability constants (K_s) from 19 to 37 °C, Gibbs free energy changes (DG° ), DH° and TDS° for 1:1 complexes of b-CD, 1 and 2 with ligand 3 as obtained from UV-Vis spectra were compared. The binding of 3 by the three cyclodextrin hosts generally decreased in the order of 1>2>b-CD. The binding ability of 3 by b-CD, 1 and 2 was discussed with regard to the size/shape-fit concept, the induced-fit interaction, and the cooperative interaction of the dual hydrophobic cavities. The binding ability of 1>2indicated that the length of linkage between two cyclodextrin units plays a crucial role in the interaction with 3. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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9 pages, 399 KiB

Open AccessArticle

The X-Ray Crystal Structures of Primary Aryl Substituted Selenoamides

by Yang Li, Guo-Xiong Hua, Alexandra M. Z. Slawin and J. Derek Woollins

Molecules 2009, 14(2), 884-892; https://doi.org/10.3390/molecules14020884 - 23 Feb 2009

Cited by 18 | Viewed by 9645

Abstract

The X-ray structures of 12 primary selenoamides are reported. Metric parameters are provided, together with an illustration of the range of hydrogen bonding motifs. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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19 pages, 393 KiB

Open AccessArticle

Selenium Status and Cardiovascular Risk Profile in Healthy Adult Saudi Males

by Eman M. Alissa, Waqar H. Ahmed, Nabeel Al-ama and Gordon A. A. Ferns

Molecules 2009, 14(1), 141-159; https://doi.org/10.3390/molecules14010141 - 31 Dec 2008

Cited by 13 | Viewed by 15867

Abstract

The purpose of this research was to investigate the relationship between selenium levels, thyroid function and other coronary risk factors in 140 Saudi subjects without overt coronary heart disease stratified by age. Demographic data and serum fasting lipid profile, glucose, thyroid function tests, [...] Read more.

The purpose of this research was to investigate the relationship between selenium levels, thyroid function and other coronary risk factors in 140 Saudi subjects without overt coronary heart disease stratified by age. Demographic data and serum fasting lipid profile, glucose, thyroid function tests, selenium status and dietary intake was assessed. The relationships between selenium status, thyroid function and cardiovascular risk factors were assessed by univariate and multivariate analysis. The results showed that thyroid hormone levels did not differ with age. Erythrocyte glutathione peroxidase (GPx) levels were significantly higher in the youngest vs. oldest tertile (p<0.0001). Selenium and iodine intake did not differ significantly with age tertile, but the average intake for the population sample was below the estimated average requirements for both elements. Serum lipoprotein (a) concentrations correlated with selenium (r = 0.417, p<0.0001) and TSH (r = 0.172, p<0.05). After adjustment for confounding variables; serum fT₄ and erythrocytes GPx remained significant determinants of serum TSH levels, whilst serum selenium and TSH were determinants of serum fT₄ levels. Serum Lp(a), a coronary risk factor, was strongly related to measures of selenium status. A significant relationship between measures of selenium status and thyroid function was found. Serum Lp(a) a known risk factor for cardiovascular disease was also related to selenium status in our population. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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Review

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20 pages, 235 KiB

Open AccessReview

Selenium in the Environment, Metabolism and Involvement in Body Functions

by Youcef Mehdi, Jean-Luc Hornick, Louis Istasse and Isabelle Dufrasne

Molecules 2013, 18(3), 3292-3311; https://doi.org/10.3390/molecules18033292 - 13 Mar 2013

Cited by 575 | Viewed by 30886

Abstract

Selenium (Se34 79) is a metalloid which is close to sulfur (S) in terms of properties. The Se concentration in soil varies with type, texture and organic matter content of the soil and with rainfall. Its assimilation by plants is influenced [...] Read more.

Selenium (Se34 79) is a metalloid which is close to sulfur (S) in terms of properties. The Se concentration in soil varies with type, texture and organic matter content of the soil and with rainfall. Its assimilation by plants is influenced by the physico-chemical properties of the soil (redox status, pH and microbial activity). The presence of Se in the atmosphere is linked to natural and anthropogenic activities. Selenoproteins, in which selenium is present as selenocysteine, present an important role in many body functions, such as antioxidant defense and the formation of thyroid hormones. Some selenoprotein metabolites play a role in cancer prevention. In the immune system, selenium stimulates antibody formation and activity of helper T cells, cytotoxic T cells and Natural Killer (NK) cells. The mechanisms of intestinal absorption of selenium differ depending on the chemical form of the element. Selenium is mainly absorbed in the duodenum and caecum by active transport through a sodium pump. The recommended daily intake of selenium varies from 60 μg/day for women, to 70 μg/day for men. In growing ruminants the requirements are estimated at 100 μg/kg dry matter and 200 μg/Kg for pregnant or lactating females. A deficiency can cause reproductive disorders in humans and animals. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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12 pages, 335 KiB

Open AccessReview

Selenium Utilization Strategy by Microalgae

by Hiroya Araie and Yoshihiro Shiraiwa

Molecules 2009, 14(12), 4880-4891; https://doi.org/10.3390/molecules14124880 - 30 Nov 2009

Cited by 81 | Viewed by 13965

Abstract

The diversity of selenoproteins raises the question of why so many life forms require selenium. Selenoproteins are found in bacteria, archaea, and many eukaryotes. In photosynthetic microorganisms, the essential requirement for selenium has been reported in 33 species belonging to six phyla, although [...] Read more.

The diversity of selenoproteins raises the question of why so many life forms require selenium. Selenoproteins are found in bacteria, archaea, and many eukaryotes. In photosynthetic microorganisms, the essential requirement for selenium has been reported in 33 species belonging to six phyla, although its biochemical significance is still unclear. According to genome databases, 20 species are defined as selenoprotein-producing organisms, including five photosynthetic organisms. In a marine coccolithophorid, Emiliania huxleyi (Haptophyta), we recently found unique characteristics of selenium utilization and novel selenoproteins using ⁷⁵Se-tracer experiments. In E. huxleyi, selenite, not selenate, is the main substrate used and its uptake is driven by an ATP-dependent highaffinity, active transport system. Selenite is immediately metabolized to low-molecular mass compounds and partly converted to at least six selenoproteins, named EhSEP1–6. The most (EhSEP2) and second-most abundant selenoproteins (EhSEP1) are disulfide isomerase (PDI) homologous protein and thioredoxin reductase (TR) 1, respectively. Involvement of selenium in PDI is unique in this organism, while TR1 is also found in other organisms. In this review, we summarize physiological, biochemical, and molecular aspects of selenium utilization by microalgae and discuss their strategy of selenium utilization. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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14 pages, 440 KiB

Open AccessReview

Forming Glasses from Se and Te

by Bruno Bureau, Catherine Boussard-Pledel, Pierre Lucas, Xianghua Zhang and Jacques Lucas

Molecules 2009, 14(11), 4337-4350; https://doi.org/10.3390/molecules14114337 - 26 Oct 2009

Cited by 120 | Viewed by 16589

Abstract

Despite being close neighbors on the Periodic Table, selenium and tellurium present a totally different abilities to form glasses. Se is a very good glass former, and gives rise to numerous glass compositions which are popular for their transparency in the infrared range [...] Read more.

Despite being close neighbors on the Periodic Table, selenium and tellurium present a totally different abilities to form glasses. Se is a very good glass former, and gives rise to numerous glass compositions which are popular for their transparency in the infrared range and their stability against crystallization. These glasses can be shaped into sophisticated optical devices such as optical fibers, planar guides or lenses. Nevertheless, their transparencies are limited at about 12 μm (depending on the thickness of the optical systems) due to the relatively small mass of the Se element. On the other hand, tellurium is heavier and its use in substitution for Se permits to shift the IR cutoff beyond 20 μm. However, the semimetallic nature of Te limits its glass formation ability and this glass family is known to be unstable and consequently has found application as phase change material in the Digital Versatile Disk (DVD) technology. In this paper, after a review of selenide glasses and their applications, it will be shown how, in a recent past, it has been possible to stabilize tellurium glasses by introducing new elements like Ga or I in their compositions. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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14 pages, 150 KiB

Open AccessReview

Selenium in Oncology: From Chemistry to Clinics

by Oliver Micke, Lutz Schomburg, Jens Buentzel, Klaus Kisters and Ralph Muecke

Molecules 2009, 14(10), 3975-3988; https://doi.org/10.3390/molecules14103975 - 12 Oct 2009

Cited by 83 | Viewed by 20215

Abstract

The essential trace element selenium, which is a crucial cofactor in the most important endogenous antioxidative systems of the human body, is attracting more and more the attention of both laypersons and expert groups. The interest of oncologists mainly focuses in the following [...] Read more.

The essential trace element selenium, which is a crucial cofactor in the most important endogenous antioxidative systems of the human body, is attracting more and more the attention of both laypersons and expert groups. The interest of oncologists mainly focuses in the following clinical aspects: radioprotection of normal tissues, radiosensitizing in malignant tumors, antiedematous effect, prognostic impact of selenium, and effects in primary and secondary cancer prevention. Selenium is a constituent of the small group of selenocysteine-containing selenoproteins and elicits important structural and enzymatic functions. Selenium deficiency has been linked to increased infection risk and adverse mood states. It has been shown to possess cancer-preventive and cytoprotective activities in both animal models and humans. It is well established that Se has a key role in redox regulation and antioxidant function, and hence in membrane integrity, energy metabolism and protection against DNA damage. Recent clinical trials have shown the importance of selenium in clinical oncology. Our own clinical study involving 48 patients suggest that selenium has a positive effect on radiation-associated secondary lymphedema in patients with limb edemas, as well as in the head and neck region, including endolaryngeal edema. Another randomized phase III study of our group was performed to examine the cytoprotective properties of selenium in radiation oncology. The aim was to evaluate whether sodium selenite is able to compensate a preexisting selenium deficiency and to prevent radiation induced diarrhea in adjuvant radiotherapy for pelvic gynecologic malignancies. Through this study, the significant benefits of sodium selenite supplementation with regards to selenium deficiency and radiotherapy induced diarrhea in patients with cervical and uterine cancer has been shown for the first time in a prospective randomized trial. Survival data imply that supplementation with selenium does not interfere with the positive biological effects of radiation treatment and might constitute a valuable adjuvant therapy option especially in marginally supplied individuals. More recently there were emerging concerns coming up from two large clinical prevention trials (NPC, SELECT), that selenium increases the possible risk of developing diabetes type II. Despite obvious flaws of both studies and good counterarguments, a controversial debate remains on the possible advantage and risks of selenium in cancer prevention. However, in the light of the recent clinical trials the potential benefits of selenium supplementation in tumor patients are undeniable, even if further research is needed. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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22 pages, 856 KiB

Open AccessReview

Chemistry of the M (M=Fe, Ca, Ba)-Se-H₂O Systems at 25 °C

by Tadahisa Nishimura, Ryosuke Hata and Fumihiko Hasegawa

Molecules 2009, 14(9), 3567-3588; https://doi.org/10.3390/molecules14093567 - 14 Sep 2009

Cited by 13 | Viewed by 11881

Abstract

The chemistry of the M (M=Fe, Ca, Ba)-Se-H₂O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H₂O, Ca-Se(IV,VI)-H₂O and Ba-Se(IV,VI)-H₂O systems at 25 °C [...] Read more.

The chemistry of the M (M=Fe, Ca, Ba)-Se-H₂O systems at 25 °C is reviewed based on our previous papers. In this paper, the phase equilibria in the Fe(III)-Se(IV)-H₂O, Ca-Se(IV,VI)-H₂O and Ba-Se(IV,VI)-H₂O systems at 25 °C are discussed. Then, the three-stage process for removal of selenium from industrial waste water [Se(IV,VI) < 1,500 mg/L] containing sulfuric acid was introduced. This seems to be a promising process for selenium removal from acidic sulfate waste water containing high concentration levels of selenium to below 0.1 mg/L. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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19 pages, 328 KiB

Open AccessReview

Mouse Models Targeting Selenocysteine tRNA Expression for Elucidating the Role of Selenoproteins in Health and Development

by Bradley A. Carlson, Min-Hyuk Yoo, Petra A. Tsuji, Vadim N. Gladyshev and Dolph L. Hatfield

Molecules 2009, 14(9), 3509-3527; https://doi.org/10.3390/molecules14093509 - 10 Sep 2009

Cited by 43 | Viewed by 14287

Abstract

Selenium (Se) deficiency has been known for many years to be associated with disease, impaired growth and a variety of other metabolic disorders in mammals. Only recently has the major role that Se-containing proteins, designated selenoproteins, play in many aspects of health and [...] Read more.

Selenium (Se) deficiency has been known for many years to be associated with disease, impaired growth and a variety of other metabolic disorders in mammals. Only recently has the major role that Se-containing proteins, designated selenoproteins, play in many aspects of health and development begun to emerge. Se is incorporated into protein by way of the Se-containing amino acid, selenocysteine (Sec). The synthesis of selenoproteins is dependent on Sec tRNA for insertion of Sec, the 21^st amino acid in the genetic code, into protein. We have taken advantage of this dependency to modulate the expression of Sec tRNA that in turn modulates the expression of selenoproteins by generating transgenic, conditional knockout, transgenic/standard knockout and transgenic/conditional knockout mouse models, all of which involve the Sec tRNA gene, to elucidate the intracellular roles of this protein class. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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17 pages, 1091 KiB

Open AccessReview

Solid State Polyselenides and Polytellurides: A Large Variety of Se–Se and Te–Te Interactions

by Christian Graf, Abdeljalil Assoud, Oottil Mayasree and Holger Kleinke

Molecules 2009, 14(9), 3115-3131; https://doi.org/10.3390/molecules14093115 - 24 Aug 2009

Cited by 65 | Viewed by 13621

Abstract

A large variety of different interactions between the chalcogen atoms, Q, occur in the solid state structures of polyselenides and polytellurides, including both molecular and infinite units. The simplest motifs are classical Q₂^2– dumbbells and nonlinear Q_n^2– chains [...] Read more.

A large variety of different interactions between the chalcogen atoms, Q, occur in the solid state structures of polyselenides and polytellurides, including both molecular and infinite units. The simplest motifs are classical Q₂^2– dumbbells and nonlinear Q_n^2– chains (n = 3, 4, 5, ..), e.g. found in alkali metal polychalcogenides. In addition, nonclassical so-called hypervalent motifs exist in the form of linear Q₃^4– units or within larger units such as Q₄^4– and Q₅^4–. Infinitely extended Q units include zigzag, cis/trans and linear chains, as well as planar and slightly puckered layers. Several of those are susceptible to Peierls distortions, leading to the formation of both commensurate and incommensurate superstructures and anomalies in transport properties, including metal-nonmetal transitions. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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8 pages, 54 KiB

Open AccessReview

Selenium and the Methionine Sulfoxide Reductase System

by Derek B. Oien and Jackob Moskovitz

Molecules 2009, 14(7), 2337-2344; https://doi.org/10.3390/molecules14072337 - 1 Jul 2009

Cited by 14 | Viewed by 13876

Abstract

Selenium is a chemical element participating in the synthesis of selenocysteine residues that play a pivotal role in the enzymatic activity efficiency of selenoproteines. The methionine sulfoxide reductase (Msr) system that reduces methionine sulfoxide (MetO) to methionine comprises the selenoprotein MsrB (MsrB1) and [...] Read more.

Selenium is a chemical element participating in the synthesis of selenocysteine residues that play a pivotal role in the enzymatic activity efficiency of selenoproteines. The methionine sulfoxide reductase (Msr) system that reduces methionine sulfoxide (MetO) to methionine comprises the selenoprotein MsrB (MsrB1) and the non-selenoprotein MsrA, which reduce the R- and the S- forms of MetO, respectively. The effects of a selenium deficient (SD) diet, which was administrated to wild type (WT) and MsrA knockout mice (MsrA^-/^-), on the expression and function of Msr-related proteins are examined and discussed. Additionally, new data about the levels of selenium in brain, liver, and kidneys of WT and MsrA^-/^- mice are presented and discussed. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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16 pages, 205 KiB

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Selenium as an Essential Micronutrient: Roles in Cell Cycle and Apoptosis

by Huawei Zeng

Molecules 2009, 14(3), 1263-1278; https://doi.org/10.3390/molecules14031263 - 23 Mar 2009

Cited by 178 | Viewed by 19296

Abstract

Selenium is an essential trace element for humans and animals, and selenium deficiency is associated with several disease conditions such as immune impairment. In addition, selenium intakes that are greater than the recommended daily allowance (RDA) appear to protect against certain types of [...] Read more.

Selenium is an essential trace element for humans and animals, and selenium deficiency is associated with several disease conditions such as immune impairment. In addition, selenium intakes that are greater than the recommended daily allowance (RDA) appear to protect against certain types of cancers. In humans and animals, cell proliferation and death must be regulated to maintain tissue homeostasis, and it has been well documented that numerous human diseases are directly related to the control of cell cycle progression and apoptosis. Thus, the elucidation of the mechanisms by which selenium regulates the cell cycle and apoptosis can lead to a better understanding of the nature of selenium’s essentiality and its role in disease prevention. This article reviews the status of knowledge concerning the effect of selenium on cell cycle and apoptosis Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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15 pages, 153 KiB

Open AccessReview

Laser Photolysis and Thermolysis of Organic Selenides and Tellurides for Chemical Gas-phase Deposition of Nanostructured Materials

by Josef Pola and Akihiko Ouchi

Molecules 2009, 14(3), 1111-1125; https://doi.org/10.3390/molecules14031111 - 12 Mar 2009

Cited by 6 | Viewed by 13540

Abstract

Laser radiation-induced decomposition of gaseous organic selenides and tellurides resulting in chemical deposition of nanostructured materials on cold surfaces is reviewed with regard to the mechanism of the gas-phase decomposition and properties of the deposited materials. The laser photolysis and laser thermolysis of [...] Read more.

Laser radiation-induced decomposition of gaseous organic selenides and tellurides resulting in chemical deposition of nanostructured materials on cold surfaces is reviewed with regard to the mechanism of the gas-phase decomposition and properties of the deposited materials. The laser photolysis and laser thermolysis of the Se and Te precursors leading to chalcogen deposition can also serve as a useful approach to nanostructured chalcogen composites and IVA group (Si, Ge, Sn) element chalcogenides provided that it is carried out simultaneously with laser photolysis or thermolysis of polymer and IVA group element precursor. Full article

(This article belongs to the Special Issue Selenium and Tellurium Chemistry)

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