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Incorporation of monatomic 2p ligands into the core of iron-sulfur clusters has been researched since the discovery of interstitial carbide in the FeMo cofactor of Mo-dependent nitrogenase, but has proven to be a synthetic challenge. Herein, two distinct synthetic pathways are rationalized to install nitride ligands into targeted positions of W-Fe-S clusters, generating unprecedented nitride-ligated iron-sulfur clusters, namely [(Tp*)2 W2 Fe6 (μ4 -N)2 S6 L4 ]2- (Tp*=tris(3,5-dimethyl-1-pyrazolyl)hydroborate(1-), L=Cl- or Br- ). 57 Fe Mossbauer study discloses metal oxidation states of WIV 2 FeII 4 FeIII 2 with localized electron distribution, which is analogous to the mid-valent iron centres of FeMo cofactor at resting state. Good agreement of Mossbauer data with the empirical linear relationship for Fe-S clusters indicates similar ligand behaviour of nitride and sulfide in such clusters, providing useful reference for reduced nitrogen in a nitrogenase-like environment.

A highly efficient, green and sustainable protocol for rhodium(III)-catalyzed C-H alkylation of heterocycles with allylic alcohols has been achieved, which affords a series of β-aryl ketones in high yields. The reaction proceeds smoothly in water under air, and works well with heterocycles such as indoles, indolines, pyrroles and carbazoles. Notably, the expensive rhodium catalyst in water could be easily separated from the organic products, and reused for at least five times without loss of its catalytic activity and selectivity, which is a promising, green and sustainable pathway for the synthesis of β-aryl ketones. To the best of our knowledge, this is the first example for the reuse of expensive rhodium catalyst in water.

Structural mimicking of the nitrogenase FeMo cofactor has long been a challenge in synthetic inorganic chemistry and bioinorganic chemistry. This already very tough task had become even harder after the discovery of an interstitial light atom, which was later evidenced to be carbide. From a synthetic point of view, to introduce such a 2p atom into the core of a Fe–S cluster would have to overcome the coordination competition from overwhelming sulfide ligands. Recently, we have reported a controlled synthetic strategy named redox metathesis based on template-assisted structure design, and have successfully synthesized a couple of nitride-incorporated edge-bridged double cubane (N-EBDC) W–Fe–S clusters. In this work, we have systematically studied the terminal ligand substitutions of heteroleptic N-EBDC clusters, utilizing ethanethiolate, thiophenolate, p-thiocresolate, azide, and methoxide to replace the terminally bound chloride ligands. Structural analysis of this family of N-EBDC clusters reveals that different terminal ligands affect the fine structures of the cluster cores at different levels. Further studies by cyclic voltammetry indicate that these N-EBDC clusters with distinct terminal ligands exhibit different redox behaviors, furnishing in-depth information on the electronic structure of these clusters potentially related to their reactivity. This study provided useful information for the investigation of nitrogenase related Fe–S clusters toward structural and functional mimicking of the nitrogenase FeMo cofactor.

Development of the drug with high therapeutic efficacy and low toxicity is crucial to cancer ablation. In this study, we have demonstrated a red light-responsive prodrug BDP-TK-CPT by connecting the chemotherapeutic agent camptothecin with a boron dipyrromethene (BDP)-based photosensitizer via a reactive oxygen species (ROS)-labile thioketal chain. Since camptothecin is modified by a BDP-based macrocycle at the active site, the formed prodrug displays an extremely low toxicity in dark. However, upon illumination by red light, it can efficiently generate ROS leading to cell death by photodynamic therapy. Meanwhile, the ROS generated can destroy thioketal group to release free camptothecin which further results in local cell death by chemotherapy. The combined antitumor effects of the prodrug have been verified in HepG2, EC109, and HeLa cancer cells and mice bearing H22 tumors. This study may provide an alternative strategy for stimuli-responsive combination treatment of tumors by conjugation of ROS-activatable prodrugs with photosensitizing agents.

Here, we have synthesized and characterized a novel activatable photosensitizer (PS) 8a in which two well-designed boron dipyrromethene (BODIPY) derivatives are utilized as the photosensitizing fluorophore and quencher respectively, which are connected by a disulfide linker via two successive Cu (І) catalyzed click reactions. The fluorescence emission and singlet oxygen production of 8a are suppressed via intramolecular fluorescence resonance energy transfer (FRET) from the excited BODIPY-based PS part to quencher unit, but both of them can be simultaneously switched on by cancer-related biothiol glutathione (GSH) in phosphate buffered saline (PBS) solution with 0.05% Tween 80 as a result of cleavage of disulfide. Also, 8a exhibits a bright fluorescence image and a substantial ROS production in A549 human lung adenocarcinoma, HeLa human cervical carcinoma and H22 mouse hepatoma cells having a relatively high concentration of GSH, thereby leading to a significant photocytotoxicity, with IC50 values as low as 0.44 μM, 0.67 μM and 0.48 μM, respectively. In addition, the photosensitizer can be effectively activated and imaged in H22 transplanted hepatoma tumors of mice and shows a strong inhibition on tumor growth. All these results suggest that such a GSH-responsive photosensitizer based on FRET mechanism may provide a new strategy for tumor-targeted and fluorescence imaging-guided cancer therapy.

Molybdenum-dependent nitrogenases catalyze the transformation of dinitrogen into ammonia under ambient conditions. The active site (FeMo cofactor) is the structurally and electronically complex weak-field metal cluster [MoFe 7 S 9 C] built of Fe 4 S 3 and MoFe 3 S 3 C portions connected by three sulfur bridges and containing an interstitial carbon atom centered in an Fe 6 trigonal prism. Chemical synthesis of this cluster is a major challenge in biomimetic inorganic chemistry. One synthetic approach of core ligand metathesis has been developed based on the design and synthesis of unprecedented incomplete ([(Tp*)WFe 2 S 3 Q 3 ] − ) and complete ([(Tp*)WFe 3 S 3 Q 4 ] 2− ) cubane-type clusters containing bridging halide (Q = halide). These clusters are achieved by template-assisted assembly in the presence of sodium benzophenone ketyl reductant; products are controlled by reaction stoichiometry. Incomplete cubane clusters are subject to a variety of metathesis reactions resulting in substitution of a μ 2 -bridging ligand with other bridges such as N 3 − , MeO − , and EtS − . Reactions of complete cubanes with Me 3 SiN 3 and S 8 undergo a redox metathesis process and lead to core ligand displacement and formation of [(Tp*)WFe 3 S 3 ( μ 3 -Q)Cl 3 ] − (Q = Me 3 SiN 2− , S 2− ). This work affords entry to a wide variety of heteroleptic clusters derivable from incomplete and complete cubanes; examples are provided. Among these is the cluster [(Tp*)WFe 3 S 3 ( μ 3 -NSiMe 3 )Cl 3 ] − , one of the very few instances of a synthetic Fe–S cluster containing a light atom (C, N, O) in the core, which constitutes a close mimic of the [MoFe 3 S 3 C] fragment in FeMo cofactor. Superposition of them and comparison of metric information disclose a clear structural relationship [Tp* = tris(3,5-dimethyl-1-pyrazolyl)hydroborate(1−)].

The functionalized ligand 9,10-anthraquinone-1,4-dicarboxylate acid (H2AQDC) was designed and synthesized in order to develop metal-organic coordination polymers as heterogeneous catalysts with a photosensitizing feature. Two major considerations of the ligand design are anthraquinone moieties for photosensitizing to harvest light and carboxylate groups for polymeric coordination toward less solubility. A series of transition metal complexes based on this ligand were synthesized subsequently, namely {Co(AQDC)(H2O)3·2H2O}n (Co-AQDC), {Ni(AQDC)(H2O)3·2H2O}n (Ni-AQDC), {[Cu(AQDC)(H2O)3][Cu(AQDC)(H2O)2(DMF)]·(H2O)4}n (Cu-AQDC), {Zn1.5(AQDC)(OH)(H2O)2·H2O}n (Zn-AQDC), {Ag2(AQDC)(CH3OH)}n (Ag-AQDC). Both the ligand and its transition metal complexes are able to catalyze the visible-light driven oxidation reactions of alkynes into 1,2-diketones in air under mild conditions, in which compound Ni-AQDC demonstrates the best activity. This catalyst can be easily isolated from the reaction mixture by filtration with a trace amount of loss in solution and is ready for recycled use after simple washing and drying without any need for regeneration. Remarkably, the catalyst shows no loss of activity after five catalytic cycles and X-ray powder diffraction proves no change in the structure after five runs. This designed metal-organic coordination polymer represents an environmentally friendly, economical and recyclable photocatalyst, constituting a good candidate for photocatalytic organic syntheses in terms of green chemistry.

Osteoarthritis disease can easily lead to articular cartilage degeneration and subchondral bone damage, so the demand for suitable articular substitutes is gradually increasing. In order to simulate the complex environment of different layers in natural joint, we fabricate the continuous one-phase gradient scaffold. In the study, CS (chitosan) was modified with SH (sodium hyaluronate) and GO (graphene oxide) to form the whole scaffold. nHAP (Nano-hydroxyapatite) was in situ generated with gradient distribution in the scaffold. Continuous interface can better imitate the combination style of cartilage and subchondral bone at joint. The diverseness of scaffold’s different layer in water absorption/retention rate and mechanical property is similar to the difference of articular cartilage and subchondral bone. Meanwhile, the cell experiments demonstrated that the bionic scaffold can well promote the proliferation of bone marrow mesenchymal stem cell. Articular defect model further confirmed that the scaffold can better induce articular regeneration. Herein, the prepared scaffold might be an excellent candidate for endogenous articular repair.

The objective of this paper is to analyze the relationship between the carbon emission, GDP and its growth rate, energy consumption, and unemployment rate in case of the United States and moreover, we also aim to explore where US and the fifty states now lie on the Kuznets curve. By using the panel data to investigate five different districts from 2000 to 2015 and the US as a whole, the empirical results indicate a long-run equilibrium relationship between variables and the positions the United States and its different states now lie on the curve. These findings suggest that the United States should adopt other low-carbon supporting policies and technologies to real-ize the movement from the left side of the curve to the right side of it, with the major goal to abstain from negatively affecting economic development by decreasing vitality utilization.

The time-of-flight method was used to calibrate an optical fiber length standard and its uncertainty of measurement was evaluated theoretically and experimentally according to the Evaluation of measurement data - Guide to the expression of uncertainty in measurement (GUM), JCGM 100:2008. The major uncertainty components in the measurement of transit time difference were identified and analyzed. The uncertainty due to temperature instability was investigated experimentally in the temperature range from 20 °C to 25 °C using a temperature chamber with precise temperature control. The temperature coefficient of the fiber length standard was derived by linear regression of the measurement data. The experimental results showed that the temperature control is critical for the calibration of optical fiber length standard. When the temperature instability was improved from ± 2 °C to ± 0.1 °C, the expanded measurement uncertainties for the optical fiber length standard (optical length : ~11780 m) were significantly reduced from 0.16 m to 0.014 m at wavelength of 1310 nm and from 0.19 m to 0.015 m at wavelength of 1550 nm.

Fertilin beta may play an important role in sperm-egg plasma membrane adhesion and fusion. To explore the effects of fertilin beta, the sperm membrane protein subunit, in the sheep fertilization process, we used RACE technique for cloning the full length cDNA of the coding region (CDS) of fertilin beta. The coding region was 2, 217 bp, which consists of 738 amino acids. The fertilin beta in the sperm membrane of sheep shares 79.4%, 66.7%, and 58.1% sequence identity with that in bovine, pig and human, respectively. The phylogenetic analysis of the fertilin beta gene family indicated the fertilin beta was clustered with bovine, and is closest to the one of bovine. This result is consistent with the result of the traditional classification. The protein structure analysis showed the disintegrin domain of sheep fertilin beta contains a TDE. Besides the above tripeptide sequence, the family member of ADAM (A Disintegrin and A Metalloprotease) follow the conserved sequence of ECD of X-D/E-E, and formed the conserved sequence of X-D/E-ECD. The pentapeptide sequence of the sheep fertilin beta is TDECE.