Diselenide Linkages Research Articles

Well-Defined Shell-Sheddable Core-Crosslinked Micelles with pH and Oxidation Dual-Response for On-Demand Drug Delivery.

Micellar-nanocarrier-based drug delivery systems possessing characteristics such as an excellent circulation stability, inhibited premature release and on-demand site-specific release are urgently needed for enhanced therapeutic efficacy. Therefore, a novel kind of shell-sheddable core-crosslinked polymeric micelles with pH and oxidation dual-triggered on-demand drug release behavior was facilely constructed. The multifunctional micelles were self-assembled from a carefully designed amphiphilic triblock PEGylated polyurethane (PEG-acetal-PUBr-acetal-PEG) employing an acid-labile acetal linker at the hydrophilic-hydrophobic interface and pendant reactive bromo-containing polyurethane (PU) as the hydrophobic block, followed by a post-crosslinking via oxidation-cleavable diselenide linkages. These well-defined micelles exhibited an enhanced structural stability against dilution, achieved through the incorporation of diselenide crosslinkers. As expected, they were found to possess dual pH- and oxidation-responsive dissociation behaviors when exposure to acid pH (~5.0) and 50 mM H2O2 conditions, as evidenced using dynamic light-scattering (DLS) and atomic force microscopy (AFM) analyses. An in vitro drug release investigation showed that the drug indomethacin (IND) could be efficiently encapsulated in the micelles, which demonstrated an inhibited premature release compared to the non-crosslinked ones. It is noteworthy that the resulting micelles could efficiently release entrapped drugs at a fast rate in response to either pH or oxidation stimuli. Moreover, the release could be significantly accelerated in the presence of both acid pH and oxidation conditions, relative to a single stimulus, owing to the synergetic degradation of micelles through pH-induced dePEGylation and oxidation-triggered decrosslinking processes. The proposed shell-sheddable core-crosslinked micelles with a pH and oxidation dual-response could be potential candidates as drug carriers for on-demand drug delivery.

Reactive Oxygen Species and Folate Receptor-Targeted Nanophotosensitizers Composed of Folic Acid-Conjugated and Poly(ethylene glycol)-Chlorin e6 Tetramer Having Diselenide Linkages for Targeted Photodynamic Treatment of Cancer Cells.

Folic acid-conjugated nanophotosensitizers composed of folic acid (FA), poly(ethylene glycol) (PEG) and chlorin e6 (Ce6) tetramer were synthesized using diselenide linkages for reactive oxygen species (ROS)- and folate receptor-specific delivery of photosensitizers. Ce6 was conjugated with 3-[3-(2-carboxyethoxy)-2,2-bis(2-carboxyethoxymethyl)propoxy]propanoic acid (tetra acid, or TA) to make Ce6 tetramer via selenocystamine linkages (TA-sese-Ce6 conjugates). In the carboxylic acid end group of the TA-sese-Ce6 conjugates, FA-PEG was attached again using selenocystamine linkages to make FA-PEG/TA-sese-Ce6 conjugates (abbreviated as FAPEGtaCe6 conjugates). Nanophotosensitizers were fabricated by a dialysis procedure. In the morphological observations, they showed spherical shapes with small diameters of less than 200 nm. Stability of the aqueous FAPEGtaCe6 nanophotosensitizer solution was maintained (i.e., their particle sizes were not significantly changed until 7 days later). When H2O2 was added to the nanophotosensitizer solution, the particle size distribution was changed from a monomodal pattern to a multimodal pattern. In addition, the fluorescence intensity and Ce6 release rate from the nanophotosensitizers were also increased by the addition of H2O2. These results indicated that the nanophotosensitizers had ROS-sensitive properties. In an in vitro cell culture study, an FAPEGtaCe6 nanophotosensitizer treatment against cancer cells increased the Ce6 uptake ratio, ROS generation and light-irradiated cytotoxicity (phototoxicity) compared with Ce6 alone against various cancer cells. When the folic acid was pretreated to block the folate receptors of the Y79 cells and KB cells (folate receptor-overexpressing cells), the intracellular Ce6 uptake, ROS generation and thereby phototoxicity were decreased, while the MCF-7 cells did not significantly respond to blocking of the folate receptors. These results indicated that they could be delivered by a folate receptor-mediated pathway. Furthermore, an in vivo pulmonary metastasis model using Y79 cells showed folate receptor-specific delivery of FAPEGtaCe6 nanophotosensitizers. When folic acid was pre-administered, the fluorescence intensity of the lungs was significantly decreased, indicating that the FAPEGtaCe6 nanophotosensitizers had folate receptor specificity in vitro and in vivo. We suggest that FAPEGtaCe6 nanophotosensitizers are promising candidates for a targeted photodynamic therapy (PDT) approach against cancer cells.

Reactive Oxygen Species-Sensitive Nanophotosensitizers of Methoxy Poly(ethylene glycol)-Chlorin e6/Phenyl Boronic Acid Pinacol Ester Conjugates Having Diselenide Linkages for Photodynamic Therapy of Cervical Cancer Cells.

The aim of this study is to fabricate nanophotosensitizers composed of methoxy poly(ethylene glycol) (mPEG), chlorin e6 (Ce6), and phenylboronic acid pinacol ester (PBAP) with diselenide linkages for reactive oxygen species (ROS)-sensitive photodynamic therapy (PDT) of cervical cancer cells. To fabricate nanophotosensitizers, Ce6 was conjugated with mPEG via selenocystamine linkage and then remaining carboxylic acid groups of Ce6 was attached to PBAP (mPEGseseCe6PBAP conjugates). Nanophotosensitizers of mPEGseseCe6PBAP conjugates were prepared by dialysis method. In transmission electron microscope (TEM) observation, nanophotosensitizers of mPEGseseCe6PBAP conjugates have spherical shapes and their diameters were less than 150 nm. The average diameter of mPEGseseCe6PBAP nanophotosensitizers was 92.7 ± 9.6 nm in particle size analysis. When H2O2 was added to the nanophotosensitizer solution, nanophotosensitizers were sensitively disintegrated according to the H2O2 concentration and then changed from monomodal distribution to multimodal distribution in particle size distribution. Furthermore, Ce6 release from nanophotosensitizers also increased according to the H2O2 concentration. When H2O2 was added to cell culture of HeLa human cervical cancer cells, intracellular Ce6 uptake of nanophotosensitizers were gradually increased according to the H2O2 concentration, indicating that nanophotosensitizers showed ROS-sensitive delivery of Ce6 against cancer cells.As well as free Ce6, nanophotosensitizers in the absence of light irradiation have low intrinsic cytotoxicity against RAW264.7 cells and HeLa cells. However, nanophotosensitizers induced cell death dose-dependently under light irradiation. Especially, nanophotosensitizers showed significantly higher ROS generation and phototoxicity against HeLa cells in vitro. When nanophotosensitizers were intravenously administered to animal tumor xenograft model of HeLa cells, tumor tissues revealed stronger fluorescence intensity than other tissues by light irradiation while absence of light irradiation induced relatively lower fluorescence intensity in tumor tissues, indicating that nanophotosensitizers have sensitivity against oxidative stress in tumor tissues. We suggest that nanophotosensitizers of mPEGseseCe6PBAP conjugates are promising vehicle for PDT of cervical cancer cells.

Redox-Sensitive and Folate-Receptor-Mediated Targeting of Cervical Cancer Cells for Photodynamic Therapy Using Nanophotosensitizers Composed of Chlorin e6-Conjugated β-Cyclodextrin via Diselenide Linkage.

The aim of this study was to fabricate a reactive oxygen species (ROS)-sensitive and folate-receptor-targeted nanophotosensitizer for the efficient photodynamic therapy (PDT) of cervical carcinoma cells. Chlorin e6 (Ce6) as a model photosensitizer was conjugated with succinyl β-cyclodextrin via selenocystamine linkages. Folic acid (FA)-poly(ethylene glycol) (PEG) (FA-PEG) conjugates were attached to these conjugates and then FA-PEG-succinyl β-cyclodextrin-selenocystamine-Ce6 (FAPEGbCDseseCe6) conjugates were synthesized. Nanophotosensitizers of FaPEGbCDseseCe6 conjugates were fabricated using dialysis membrane. Nanophotosensitizers showed spherical shapes with small particle sizes. They were disintegrated in the presence of hydrogen peroxide (H2O2) and particle size distribution changed from monomodal distribution pattern to multimodal pattern. The fluorescence intensity and Ce6 release rate also increased due to the increase in H2O2 concentration, indicating that the nanophotosensitizers displayed ROS sensitivity. The Ce6 uptake ratio, ROS generation and cell cytotoxicity of the nanophotosensitizers were significantly higher than those of the Ce6 itself against HeLa cells in vitro. Furthermore, the nanophotosensitizers showed folate-receptor-specific delivery capacity and phototoxicity. The intracellular delivery of nanophotosensitizers was inhibited by folate receptor blocking, indicating that they have folate-receptor specificity in vitro and in vivo. Nanophotosensitizers showed higher efficiency in inhibition of tumor growth of HeLa cells in vivo compared to Ce6 alone. These results show that nanophotosensitizers of FaPEGbCDseseCe6 conjugates are promising candidates as PDT of cervical cancer.

Mitochondria-targeted ROS- and GSH-responsive diselenide-crosslinked polymer dots for programmable paclitaxel release

Enhancing therapeutic efficacy of drugs from reactive oxygen species (ROS) and glutathione (GSH)-responsive matrix and minimizing toxic effects on normal cells remains a challenge in programmable anticancer drug delivery. Herein, ROS- and GSH-responsive paclitaxel (PTX)-loaded polymer dot (PD) with mitochondria-targeting capability was designed by constructing diselenide linkage and triphenylphosphonium (TPP) for tunable PTX release and fluorescence for cancer theranostics. PD-TPP nanocarrier could improve the PTX stability after loading (PD-TPP(PTX)), and the cleavage of diselenide bond in the presence of H2O2 and GSH triggered the controllable PTX release, providing higher fluorescence intensity. As the levels of H2O2 and GSH are higher in cancer cells compared to normal cells, PTX was selectively released from PD-TPP in cancer cells, reducing cell viability (∼25%) and causing enhanced apoptosis of cancer cells compared to normal cells. The PD-TPP(PTX) selectivity was also reflected by distinct fluorescence intensity in HeLa and PC-3 cells (cancer) compared to CHO-K1 cells (normal). Furthermore, conjugated TPP promoted the PD-TPP(PTX) accumulation in mitochondria due to specific targeting of TPP towards mitochondria, allowing PTX release in mitochondria of cancer cells. Hence, this approach could be a potential strategy to enhance therapeutic efficacy of cancer drugs and minimize the side effects on normal cells.

Design and Fabrication of Dual Redox Responsive Nanoparticles with Diselenide Linkage Combined Photodynamically to Effectively Enhance Gene Expression.

BackgroundPEI is currently the most used non-viral gene carrier and the transfection efficiency is closely related to the molecular weight; however, the prominent problem is that the cytotoxicity increased with the molecular weight.MethodsA novel redox responsive biodegradable diselenide cross-linked polymer (dPSP) was designed to enhance gene expression. ICG-pEGFP-TRAIL/dPSP nanoparticles with high drug loading are prepared, which have redox sensitivity and plasmid protection. The transfection efficiency of dPSP nanoparticle was evaluated in vitro.ResultsThe plasmid was compressed by 100% at the N/P ratio of 16, and the particle size was less than 100 nm. When explored onto high concentrations of GSH/H2O2, dPSP4 degraded into small molecular weight cationic substances with low cytotoxicity rapidly. Singlet oxygen (1O2) was produced when indocyanine green (ICG) was irradiated by near-infrared laser irradiation (NIR) to promote oxidative degradation of dPSP4 nanoparticles. Under the stimulation of NIR 808 and redox agent, the particle size and PDI of ICG-pDNA/dPSP nanoparticle increased significantly.ConclusionCompared with gene therapy alone, co-transportation of dPSP4 nanoparticle with ICG and pEGFP-TRAIL had better antitumor effect. Diselenide-crosslinked polyspermine had a promising prospect on gene delivery and preparation of multifunctional anti-tumor carrier.

Chemo-Photothermal Combination Cancer Therapy with ROS Scavenging, Extracellular Matrix Depletion, and Tumor Immune Activation by Telmisartan and Diselenide-Paclitaxel Prodrug Loaded Nanoparticles.

Extracellular matrix (ECM) accumulating in the tumor microenvironment (TME) is generated by tumor-associated fibroblasts. It can elevate interstitial fluid pressure and form dense barriers in tumor tissues. Consequently, nanocarriers are hindered from permeating into deeper tumor sites. Thus, the programmed drug-releasing nanoparticles, G(TM)PPSP, were developed for TME remodeling and breast cancer therapy. Gelatin nanoparticles were linked with platinum nanoparticles (PtNPs) to obtain G(TM)PPSP with a size of 214.0 ± 5.0 nm. Telmisartan (TM) was loaded in gelatin nanoparticles. Paclitaxel (PTX) was attached to PtNPs via a dual redox responsive diselenide bond. TM release was mediated by MMP-2 because of gelatin degradation in TME, and then intracellular PTX was released because of diselenide linkage fracture triggered by ROS or glutathione. ECM was depleted owing to TGF-β downregulation by TM and direct ablation by the photothermal effect of PtNPs. 4T1 tumor progression was inhibited by PTX chemotherapy, intracellular ROS scavenging of PtNPs, and photothermal therapy (PTT). The tumor spheroid penetration assay proved G(TM)PPSP could permeate into deep tumor regions when MMP-2 existed. In vivo antitumor experiments implied G(TM)PPSP with PTT could inhibit tumor growth effectively and remodel TME via ECM depletion and immunity activation, indicating the potential of G(TM)PPSP-based chemo-photothermal combination therapy for breast cancer treatment.

Structural reorganization and crack-healing properties of hydrogels based on dynamic diselenide linkages

ABSTRACT We report the dynamic behavior of diselenide-containing hydrophilic polyurethanes and hydrogels based on diselenide exchange reactions in an aqueous media. Diselenide-containing linear and cross-linked polyurethanes were synthesized via polyaddition reactions using diselenide-containing diol in combination with pyridinium diol that enhances the hydrophilicity of the polymer chains. The obtained linear polyurethanes underwent photo-induced diselenide exchange reactions with small diselenide compounds and degraded to smaller fragments, confirming the dynamicity of the obtained hydrophilic polyurethanes. The prepared hydrogels displayed characteristic large swelling behavior based on the structural reorganization through diselenide exchange either under photo-irradiation at 365 nm or even in the dark at room temperature. The diselenide-containing hydrogels also showed crack-healing behavior under the same exchanging conditions, presenting the utility of diselenide linkages as simple and useful units to offer high dynamicity to hydrogels.

Isolation and structure of an 18-membered macrocycle containing two diselenide linkages and its precursor.

The structures of the 18-membered diselenide-linked macrocycle 10,27-di-tert-butyl 11,28-dioxo-2,3,19,20-tetraselena-10,12,27,29-tetraazapentacyclo[28.4.0.04,9.013,18.021,26]tetratriaconta-1(30),4(9),5,7,13,15,17,21,23,25,31,33-dodecaene-10,27-dicarboxylate, C36H34N4O6Se4, and its precursor di-tert-butyl 2,2'-[diselane-1,2-diylbis(2,1-phenylene)]dicarbamate, C22H28N2O4Se2, are reported. The precusor to the macrocycle contains two tert-butyl phenylcarbamate arms connected to a diselenide group, with Se-C and Se-Se bond lengths of 1.914 (4) and 2.3408 (6) Å, respectively. The macrocycle resides on a crystallographic center of inversion in space group P-1 with one molecule in the unit cell (Z' = 1/2). It contains an 18-membered macrocyclic ring with two diselenide linkages. In this macrocycle, there are two free and two protected amino groups.

Redox- and pH-Responsive Nanoparticles Release Piperlongumine in a Stimuli-Sensitive Manner to Inhibit Pulmonary Metastasis of Colorectal Carcinoma Cells

Redox-responsive nanoparticles having a diselenide linkage were synthesized to target pulmonary metastasis of cancer cells. Methoxy poly(ethylene glycol)-grafted chitosan (ChitoPEG) was crosslinked using selenocystine-acetyl histidine (Ac-histidine) conjugates (ChitoPEGse) for stimuli-responsive delivery of piperlongumine (PL). ChitoPEGse nanoparticles swelled in an acidic environment and became partially disintegrated in the presence of H2O2, resulting in an increase of particle size and in a size distribution having multimodal pattern. PL release increased under acidic conditions and in the presence of H2O2. Uptake of ChitoPEGse nanoparticles by CT26 cells significantly increased in acidic and redox state. PL-incorporated ChitoPEGse nanoparticles (PL NPs) showed similar anticancer activity in vitro against A549 and CT26 cells compared to PL itself. PL NP showed superior anticancer and antimetastatic activity in an in vivo CT26 cell pulmonary metastasis mouse model. Furthermore, an immunofluorescence imaging study demonstrated that PL NP conjugates were specifically delivered to the tumor mass in the lung. Conclusively, ChitoPEGse nanoparticles were able to be delivered to cancer cells with an acidic- or redox state-sensitive manner and then efficiently targeted pulmonary metastasis of cancer cells since ChitoPEGse nanoparticles have dual pH- and redox-responsiveness.

Near-infrared AIEgen-functionalized and diselenide-linked oligo-ethylenimine with self-sufficing ROS to exert spatiotemporal responsibility for promoted gene delivery.

Reversible stabilities are required for therapeutic (e.g. DNA) delivery systems to afford adequate stability in the journey to therapeutic targets but make the systems susceptible to structural disassembly and the liberation of their therapeutic payloads. For this purpose, we attempted to synthesize an oligo-ethyleneimine (OEI)-crosslinked polycation, characterized with self-sufficing reactive oxygen species (ROS) by virtue of a functional aggregation-induced emissive (AIE) component (with good near-infrared imaging functions) and an ROS-labile diselenide linkage. The strategic AIE component was capable of exerting facile ROS production upon convenient daylight irradiation (unprecedented ROS-producing efficiency of 80.14%), consequently helping to activate an endosomal escape functionality and the fragmentation of the OEI-crosslinked polycation into low molecular weight OEI products. Consequently, the engineered capabilities enabled the spatiotemporal control of the stabilities of the electrostatic-based DNA self-assembled formation so that it was adequately stable in the gene transportation journey to the targets but could reverse the stabilities to liberate pDNA to execute the subsequent biological processes, evidenced by the disassociation of the near-infrared emission of AIEgen and Cy5-pDNA. Therefore, our devised strategies provided tempting design implications for utilizing daylight as an impetus for the intracellular delivery of functional molecules, and thus could be developed further to find broad utilities in the transportation of a variety of biological substances in therapeutic applications.

Advances in nanomicelles for sustained drug delivery

Abstract The efficient direct access of therapeutic molecules to the target tissues is still a major obstacle in developing useful therapeutic interventions. Over the past decades, polymeric micelles are interesting nanocarries for drug delivery systems due to small size (10–100 nm), low toxicity, capacity to solubilize lipophilic drugs in core and high drug loading. Here, the design of various nanomicelles such as amphiphilic dendrimer, boronate ester linked, X-shaped four-armed gemini-like, amphiphilic based vitamin E, styrene-maleic acid, diselenide linkages, oleic acid and natural polymeric inulin and vitamin E, siRNA and natural water soluble polysaccharides nanomicelles described and their efficacy discussed.

Dramatic substituent effects on the mechanisms of nucleophilic attack on Se-S bridges

The reactions of XSeSX, XSeSY, and YSeSX (X, Y = CH3, NH2, OH, F) with F(-) and CN(-) nucleophiles have been investigated by means of B3PW91/6-311+G(2df,p) and G4 calculations. In systems where the two substituents are not identical (XSeSY), the more stable of the two possible isomers corresponds to those in which the most electronegative substituent is attached to Se. Nucleophilic attack takes place at Se, independent of the nature of the nucleophile, with the only exception being XSeSF (X = CH3 , NH2 , OH), in which case the attack occurs at S. In agreement with recent results for disulfide and diselenide linkages, the mechanisms leading to Se-S bond cleavage are not always the more favorable ones because for highly electronegative substituents the most favorable process is fission of the chalcogen-substituent bond. These dissimilarities in the observed reactivity pattern as a function of the electronegativity of the substituents are due to the fact that the σ-type Se-S antibonding orbital, which for low-electronegative substituents is the lowest unnoccupied molecular orbital (LUMO), becomes strongly destabilized when the electronegativity of the substituent increases, and is replaced by an antibonding π-type Se-X (or S-X) orbital. In contrast, however, with what has been found for disulfide and diselenide derivatives, the observed reactivity does not change with the nature of the nucleophile. The activation strain model provides interesting insight into these processes, showing that in most cases the activation barriers are the consequence of subtle differences in the strain or in the interaction energies.

Revealing Unexpected Mechanisms for Nucleophilic Attack on SS and SeSe Bridges

The reactivity of disulfide and diselenide derivatives towards F(-) and CN(-) nucleophiles has been investigated by means of B3PW91/6-311+G(2df,p) calculations. This theoretical survey shows that these processes, in contrast with the generally accepted view of disulfide and diselenide linkages, do not always lead to SS or SeSe bond cleavage. In fact, SS or SeSe bond fission is the most favorable process only when the substituents attached to the S or the Se atoms are not very electronegative. Highly electronegative substituents (X) strongly favor SX bond fission. This significant difference in the observed reactivity patterns is directly related to the change in the nature of the LUMO orbital of the disulfide or diselenide derivative as the electronegativity of the substituents increases. For weakly electronegative substituents, the LUMO is a σ-type SS (or SeSe) antibonding orbital, but as the electronegativity of the substituents increases the π-type SX antibonding orbital stabilizes and becomes the LUMO. The observed reactivity also changes with the nature of the nucleophile and with the S or Se atom that undergoes the nucleophilic attack in asymmetric disulfides and diselenides. The activation strain model provides interesting insights into these processes. There are significant similarities between the reactivity of disulfides and diselenides, although some dissimilarities are also observed, usually related to the different interaction energies between the fragments produced in the fragmentation process.

One‐electron addition on short‐loop selenylsulfide and diselenide‐linked biomolecules: From diethyldichalcogens to Grx3‐like selenopeptides

AbstractOne‐electron uptake by thiaselenide or diselenide linkages of a series of short‐loop selenopeptides, is examined by means of hybrid QM:QM′ and QM:MM calculations. A special emphasis is given to the identification of key factors tuning adiabatic electron affinity, in comparison with established trends for disulfides. The conclusions are threefold: first, electron capture is intrinsically favored by 0.20 and 0.36 eV upon sulfur‐to‐selenium mono‐ or bi‐substitution. This order of reactivity, established on diethyldichalcogens, is globally transferable to linear dipeptides, with a dramatic increase of ∼1eV of adiabatic electron affinities. Cyclization impact is then quantified along a representative set of short‐loop peptides: conformational strain tends to reinforce dichalcogen propensity to act as an “electron buffer,” although this contribution is attenuated for seleno‐containing linkages because of their longer equilibrium distance. Collective electrostatic effects, such as the dipole created by a N‐terminal α‐helix, result in the same shifting, e.g., ∼1eV as a dodecalanine is grafted onto a given tetrapeptide. Structural features for neutral and radical anion species are also analyzed, in line with their spectroscopic aftermaths. This analysis delineates some useful trends for assisting design of seleno agents and artificial enzymes. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

77Se Solid-State NMR of Inorganic and Organoselenium Systems: A Combined Experimental and Computational Study

Experimental 77Se NMR parameters for 17 selenium-containing compounds have been determined by analysis of 77Se solid-state NMR spectra. These are compared to values obtained from first-principles gauge including projector augmented wave (or GIPAW) calculations performed on geometry-optimized crystal structures. Good agreement is observed between experimental and calculated values across a wide chemical shift range, enabling assignment of the experimental 77Se NMR spectra for compounds containing more than one crystallographically distinct selenium site. Calculations for isolated molecules extracted from the optimized structure reveal that intermolecular interactions have a relatively small effect on isotropic shifts in general, but larger effects on the chemical shift anisotropy are observed for some compounds. Further calculations for a model structure give insight into the effects of local bonding geometry on the 77Se chemical shift in a diselenide linkage. The 77Se chemical shift is found to be highly ...

Cs 4P 2Se 10: A new compound discovered with the application of solid-state and high temperature NMR

The new compound Cs 4P 2Se 10 was serendipitously produced in high purity during a high-temperature synthesis done in a nuclear magnetic resonance (NMR) spectrometer. 31P magic angle spinning (MAS) NMR of the products of the synthesis revealed that the dominant phosphorus-containing product had a chemical shift of −52.8 ppm that could not be assigned to any known compound. Deep reddish brown well-formed plate-like crystals were isolated from the NMR reaction ampoule and the structure was solved with X-ray diffraction. Cs 4P 2Se 10 has the triclinic space group P-1 with a=7.3587(11) Å, b=7.4546(11) Å, c=10.1420(15) Å, α=85.938(2)°, β=88.055(2)°, and γ=85.609(2)° and contains the [P 2Se 10] 4− anion. To our knowledge, this is the first compound containing this anion that is composed of two tetrahedral (PSe 4) units connected by a diselenide linkage. It was also possible to form a glass by quenching the melt in ice water, and Cs 4P 2Se 10 was recovered upon annealing. The static 31P NMR spectrum at 350 °C contained a single peak with a −35 ppm chemical shift and a ∼7 ppm peak width. This study highlights the potential of solid-state and high-temperature NMR for aiding discovery of new compounds and for probing the species that exist at high temperature.

Mass spectrometric determination of selenenylsulfide linkages in rat selenoprotein P

The reversible formation of a selenenylsulfide linkage in mammalian thioredoxin reductase was identified as having a key role in its activity. Identification of selenenylsulfide and/or diselenide linkages is therefore critical to the determination of the structure and function of selenoproteins. A selenopeptide, (298)SGSAITUQCAENLPSLCSUQGLFAEEK(324) (U=selenocysteine), was isolated from a tryptic digest of rat selenoprotein P. Its two cysteine residues and two selenocysteine (Sec) residues were determined to be present in oxidized form by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The selenopeptide was subjected to partial reduction by dithiothreitol with immediate alkylation by iodoacetamide. This process was monitored by MALDI-TOFMS to determine the number of alkylations that had taken place. The partially reduced and alkylated peptides were then analyzed by nano-electrospray ionization tandem mass spectrometry and the results indicated that selenenylsulfide linkages Sec304-Cys314 and Cys306-Sec316 were present. It is concluded that selenoprotein P contains these two selenenylsulfide bonds.

Novel Conjugated Polymer Containing Aromatic Ring and Selenium in Backbone. Side Reactions in the Addition Polymerization of Benzenediselenol to Diethynylbenzene

Irregular linkage in polymers obtained by the radical addition polymerization (so called polyaddition) of 1,4-benzenediselenol (BDSe) to 1,4-diethynylbenzene (DEB) was investigated. BDSe and DEB were polymerized by UV-irradiation in toluene at 60°C under nitrogen atmosphere to give a pale-yellowish polymer in 71% for 6 min. A diselenide linkage was found in the obtained polymer by Raman spectroscopy. A coupling reaction between seleno radicals may occur in the course of the polymerization. The extent of diselenide linkage (–Se–Se–) was estimated to be one unit against 82±5 repeating units (–CH = CH–⌬–CH = CH–Se–⌬–Se–) from the Raman intensities of the diselenide linkage at 271 cm−1 relative to 1,4-diselenophenylene group (–Se–⌬–Se–) at 1055 cm−1. The effects of the polymerization conditions were also investigated. The coupling reaction between seleno radicals occurred more frequently when excess BDSe was used in the monomer feed ratio. The polymerization temperature and concentration of added oxygen in the reaction vessel affected little the diselenide linkage. The electrical conductivity of the polymers was of the order of 10−10 S cm−1 without dopant and 10−7 S cm−1 on I2 doping regardless of the content of the diselenide linkage in the polymers. The diselenide linkage in the polymers did not reflect appreciably the electrical conductivity of the polymer.

Synthesis of novel polymer containing selenium by radical addition polymerization of 1,4‐benzenediselenol to 1,4‐divinylbenzene

AbstractA novel addition polymerization of 1,4‐benzenediselenol (BDSe) to 1,4‐divinylbenzene (DVB) was carried out with various azo radical initiators [dimethyl 2,2′‐azobisisobutyrate (DAIB), 1,1′‐azobis(1‐acetoxy‐1‐phenylethane) (AAPE), and AIBN] in toluene at 65 and 75°C under a nitrogen atmosphere. The polymerization proceded without an induction period, and pale‐yellowish powder polymers were obtained in 89% yields for 75 h (DAIB), 89% yields for 24 h (AAPE), and 60% yields for 8 h (AIBN). The molecular weight (Mw) of the insoluble polymers in toluene was about 4000 (IBN) to 14,000 (DAIB or AAPE) by GPC. The polymer had an alternating structure of BDSe to DVB units by 1H‐NMR, IR analyses, and selenium contents, but the polymer contained the diselenide linkage by Raman spectroscopy. By AIBN initiator, the yield of the polymers did not increase over 60% and higher molecular weight polymer was hardly obtained. According to the model addition reaction of benzeneselenol to styrene by AIBN, it was found that AIBN was consumed by the side reaction between dimethyl‐N‐(2‐cyano‐2‐propyl)ketenimine derivedAppl 11 from AIBN and benzeneselenol to give the adduct C, MH+ 295 by DCI MS. On the other hand, DAIB and AAPE initiators, which do not form a ketenimine intermediate, gave the polymers of higher molecular weight in a higher yield. The polymer film exhibited high refractive index (n25D = 1.81) and a reversible phase transition between a transparency and an opaque by thermal mode. © 1994 John Wiley & Sons, Inc.