Spinosyn A and Its Derivative Inhibit Colorectal Cancer Cell Growth via the EGFR Pathway.

Spinosyn A (SPA), derived from a soil microorganism, Saccharopolyspora spinosa, and its derivative, LM2I, has potential inhibitory effects on a variety of cancer cells. However, the effects of SPA and LM2I in inhibiting the growth of human colorectal cancer cells and the molecular mechanisms underlying these effects are not fully understood. Cell viability was tested by using a 3-(4,5-dimethylthiazol-2-yl-)-2,5-diphenyltetrazolium bromide (MTT) assay and a colony formation assay. On the basis of the IC50 values of SPA and LM2I in seven colorectal cancer (CRC) cell lines, sensitive (HT29 and SW480) and insensitive (SW620 and RKO) cell lines were screened. The GSE2509 and GSE10843 data sets were used to identify 69 differentially expressed genes (DEGs) between sensitive and insensitive cell lines. Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and protein-protein interactions (PPI) were performed to elucidate the molecular mechanisms of the DEGs. The hub gene of the DEGs was detected by Western blot analysis and verified using the CRISPR/Cas9 system. Our data indicate that SPA and its derivative LM2I have significant antiproliferative activity in seven colorectal cancer cell lines and colorectal xenograft tumors. On the basis of bioinformatics analysis, it was demonstrated that epidermal growth factor receptor (EGFR) was the hub gene of the DEGs and was associated with the inhibitory effects of SPA and LM2I in CRC cell lines. The study also revealed that SPA and LM2I inhibited the EGFR pathway in vitro and in vivo.

ZLM-7 Blocks Breast Cancer Progression by Inhibiting MDM2 via Upregulation of 14-3-3 Sigma.

Breast cancer is one of the most prevalent malignancies with poor prognosis. Inhibition of angiogenesis is becoming a valid and evident therapeutic strategy to treat cancer. Recent studies uncovered the antiangiogenic activity of ZLM-7 (a combretastain A-4 derivative), but the regulatory mechanism is unclear. ZLM-7 treatment was applied in estrogen receptor-positive cell MCF-7, triple-negative breast cancer cell MDA-MB-231 and xenograft models. Transfections were conducted to overexpress or knockdown targeted genes. The gene and protein expressions were measured by qPCR and Western blotting assay, respectively. Cell proliferation and apoptosis were evaluated using the CCK8 method, clone formation assay and flow cytometry. We found that ZLM-7 upregulated 14-3-3 sigma expression but downregulated MDM2 expression in breast cancer cells. ZLM-7 delayed cell proliferation, promoted apoptosis and blocked cell-cycle progression in human breast cancer cells in vitro, while those effects were abolished by 14-3-3 sigma knockdown; overexpression of 14-3-3 sigma reproduced the actions of ZLM-7 on the cell cycle, which could be reversed by MDM2 overexpression. In xenograft models, ZLM-7 treatment significantly inhibited tumor growth while the inhibition was attenuated when 14-3-3 sigma was silenced. Collectively, ZLM-7 could inhibit MDM2 via upregulating 14-3-3 sigma expression, thereby blocking the breast cancer progression.

Ginsenoside Rh2 inhibits breast cancer cell growth via ERß-TNFα pathway.

Ginsenoside Rh2 is one of rare panaxidiols extracted from Panax ginseng and a potential estrogen receptor ligand that exhibits moderate estrogenic activity. However, the effect of Rh2 on growth inhibition and its underlying molecular mechanism in human breast cells are not fully understood. In this study, we tested cell viability by MTT and colony formation assays. Cell growth and cell cycle were determined to investigate the effect of ginsenoside Rh2 by flow cytometry. The expressions of estrogen receptors (ERs), TNFα, and apoptosis-related proteins were detected by qPCR and western blot analysis. The mechanisms of ERα and ERß action were determined using transfection and inhibitors. Antitumor effect of ginsenoside Rh2 against MCF-7 cells was investigated in xenograft mice. Our results showed that ginsenoside Rh2 induced apoptosis and G1/S phase arrest in MCF-7 cells. Treatment of cells with ginsenoside Rh2 down-regulated protein levels of ERα, and up-regulated mRNA and protein levels of ERß and TNFα. We also found that ginsenoside Rh2-induced TNFα over-expression is through up-regulation of ERß initiated by ginsenoside Rh2. Furthermore, ginsenoside Rh2 induced MCF-7 cell apoptosis via estrogen receptor ß-TNFα pathway in vivo. These results demonstrate that ginsenoside Rh2 promotes TNFα-induced apoptosis and G1/S phase arrest via regulation of ERß.

The Interaction of Mandarin Fish DDX41 with STING Evokes type I Interferon Responses Inhibiting Ranavirus Replication.

DDX41 is an intracellular DNA sensor that evokes type I interferon (IFN-I) production via the adaptor stimulator of interferon gene (STING), triggering innate immune responses against viral infection. However, the regulatory mechanism of the DDX41-STING pathway in teleost fish remains unclear. The mandarin fish (Siniperca chuatsi) is a cultured freshwater fish species that is popular in China because of its high market value. With the development of a high-density cultural mode in mandarin fish, viral diseases have increased and seriously restricted the development of aquaculture, such as ranavirus and rhabdovirus. Herein, the role of mandarin fish DDX41 (scDDX41) and its DEAD and HELIC domains in the antiviral innate immune response were investigated. The level of scDDX41 expression was up-regulated following treatment with poly(dA:dT) or Mandarin fish ranavirus (MRV), suggesting that scDDX41 might be involved in fish innate immunity. The overexpression of scDDX41 significantly increased the expression levels of IFN-I, ISGs, and pro-inflammatory cytokine genes. Co-immunoprecipitation and pull-down assays showed that the DEAD domain of scDDX41 recognized the IFN stimulatory DNA and interacted with STING to activate IFN-I signaling pathway. Interestingly, the HELIC domain of scDDX41 could directly interact with the N-terminal of STING to induce the expression levels of IFN-I and ISGs genes. Furthermore, the scDDX41 could enhance the scSTING-induced IFN-I immune response and significantly inhibit MRV replication. Our work would be beneficial to understand the roles of teleost fish DDX41 in the antiviral innate immune response.

Metal Oxy-Hydroxides with a Hierarchical and Hollow Structure for Highly Efficient Solar-Thermal Water Evaporation.

Solar-thermal water evaporation is a promising technology for pure water production. However, the design of low-cost systems for efficient antifouling solar-thermal water evaporation remains a challenge. Herein, an evaporator based on metal oxy-hydroxides with a hierarchical and hollow structure is rationally designed through material selection and structural engineering. The obtained evaporator possesses good light absorption performance, excellent antifouling property against oil, and enhanced heat localization ability. Consequently, the water evaporation rate reaches as high as 1.65 kg m-2 h-1 with a solar-thermal conversion efficiency up to 82.3% under 1 sun illumination. More importantly, the evaporator exhibits almost identical evaporation performance in oily wastewater and natural seawater due to its superhydrophilicity and underwater superoleophobicity. This work provides a worth-adopted approach to prepare solar-thermal evaporators with high efficiency and anti-oil-fouling property, highlighting the new application of metal oxy-hydroxide-based materials and the importance of a hierarchical and hollow structure for efficient solar-thermal water evaporation.

Two Key Amino Acids Variant of α-l-arabinofuranosidase from Bacillus subtilis Str. 168 with Altered Activity for Selective Conversion Ginsenoside Rc to Rd.

α-l-arabinofuranosidase is a subfamily of glycosidases involved in the hydrolysis of l-arabinofuranosidic bonds, especially in those of the terminal non-reducing arabinofuranosyl residues of glycosides, from which efficient glycoside hydrolases can be screened for the transformation of ginsenosides. In this study, the ginsenoside Rc-hydrolyzing α-l-arabinofuranosidase gene, BsAbfA, was cloned from Bacilus subtilis, and its codons were optimized for efficient expression in E. coli BL21 (DE3). The recombinant protein BsAbfA fused with an N-terminal His-tag was overexpressed and purified, and then subjected to enzymatic characterization. Site-directed mutagenesis of BsAbfA was performed to verify the catalytic site, and the molecular mechanism of BsAbfA catalyzing ginsenoside Rc was analyzed by molecular docking, using the homology model of sequence alignment with other ß-glycosidases. The results show that the purified BsAbfA had a specific activity of 32.6 U/mg. Under optimal conditions (pH 5, 40 °C), the kinetic parameters Km of BsAbfA for pNP-α-Araf and ginsenoside Rc were 0.6 mM and 0.4 mM, while the Kcat/Km were 181.5 s-1 mM-1 and 197.8 s-1 mM-1, respectively. More than 90% of ginsenoside Rc could be transformed by 12 U/mL purified BsAbfA at 40 °C and pH 5 in 24 h. The results of molecular docking and site-directed mutagenesis suggested that the E173 and E292 variants for BsAbfA are important in recognizing ginsenoside Rc effectively, and to make it enter the active pocket to hydrolyze the outer arabinofuranosyl moieties at C20 position. These remarkable properties and the catalytic mechanism of BsAbfA provide a good alternative for the effective biotransformation of the major ginsenoside Rc into Rd.

ZLM-7 inhibits the occurrence and angiogenesis of breast cancer through miR-212-3p/Sp1/VEGFA signal axis.

BACKGROUND: Breast cancer (BC) is a common malignant tumor with poor prognosis. Angiogenesis is related to the growth and progression of solid tumors and associated with prognosis. ZLM-7, SP1, VEGFA and miR-212-3p were associated with BC angiogenesis and proliferation, however the detailed mechanism was not clear. This study aimed to reveal the regulatory mechanism of angiogenesis of BC. METHODS: BC cell lines were treated with 10 nM ZLM-7 for 8 h. We detected protein expression level by western blot and RNA expression level by qRT-PCR. Overexpression or inhibition of miR-212-3p is performed using miR-212-3p mimics or miR-212-3p inhibitor, Sp1 overexpression using pcDNA3.1 vector. Angiogenesis was analyzed by co-culturing BC cell lines and HUVEC cells. To evaluate regulatory relationship between miR-212-3p and Sp1, dual luciferase assay was performed. Besides, the direct interaction between Sp1 and VEGFA was analyzed by ChIP. Migration and invasion were analyzed by transwell assay and proliferation was detected by clone formation assay. In mice xenograft model developed using BC cells, we also detected angiogenesis marker CD31 through immunohistochemistry. RESULTS: ZLM-7 up-regulated miR-212-3p and inhibited invasion, migration, proliferation and angiogenesis of BC, while miR-212-3p inhibitor antagonized such effects. Binding sequence was revealed between miR-212-3p and Sp1, and expression of Sp1 was inhibited by miR-212-3p on both protein and mRNA level. Sp1 could interact with VEGFA and promoted its expression. Overexpression of miR-212-3p inhibited migration, invasion, proliferation and angiogenesis of BC cell lines, while Sp1 overexpression showed the opposite effect and could antagonize these effects of miR-212-3p overexpression. ZLM-7 decreased VEGFA expression, which was rescued by co-transfection with miR-212-3p inhibitor. Similar, ZLM-7 could inhibit tumor growth and angiogenesis through the miR-212-3p/Sp1/VEGFA axis in vivo. CONCLUSIONS: ZLM-7 could directly up-regulate miR-212-3p in BC. MiR-212-3p could inhibit VEGFA expression through Sp1, thereby inhibiting angiogenesis and progression of BC.

Synthesis and biological evaluation of novel isothiazoloquinoline quinone analogues.

Natural quinones and their analogues have attracted growing attention because of their novel anticancer activities. A series of novel isothiazoloquinoline quinone analogues were synthesized and evaluated for antitumor activities against four different kind of cancer cells. Among them, isothiazoloquinolinoquinones inhibited cancer cells proliferation effectively with IC50 values in the nanomolar range, and isothiazoloquinolinoquinone 13a induced the cell apoptosis. Further exploration of possible mechanism of action indicates that 13a not only activates ROS production through NQO1-directed redox cycling but also inhibits the phosphorylation of STAT3. These findings indicate that 13a has potential use for the development of new skeleton drug candidate as an efficient substrate of NQO1 and STAT3 inhibitor.

The roles of mandarin fish STING in innate immune defense against Infectious spleen and kidney necrosis virus infections.

The mandarin fish Siniperca chuatsi is a cultured freshwater fish species that is popular in China because of its high market value. With the development of high-density cultural mode in mandarin fish, viral diseases such as Infectious spleen and kidney necrosis virus (ISKNV) are becoming increasingly serious. Stimulator of interferon genes (STING) is a central component in the innate immune response to cytosolic DNA and RNA derived from different pathogens. However, the roles of STING in innate immune response of mandarin fish remain unknown. In the present study, S. chuatsi STING (scSTING)-mediated host immune response against ISKNV infection was investigated. ScSTING transcription level increased remarkably in response to ISKNV infection, LPS, PMA, or poly (I:C) stimulation in mandarin fish fry (MFF-1) cells. Immunofluorescence results showed that scSTING localized majorly in the endoplasmic reticulum. scSTING overexpression remarkably increased the expression levels of scIFN-h, scMx, scISG15, scPKR, scViperin, scIL-1ß, scIL-18, and scTNF-α genes. IFN-ß-luciferase report assay results showed that the relative expressions of luciferin were remarkably increased in MFF-1 cells. Site mutation of serine (S) on C-terminus of scSTING showed that both S388 and S396 were important for mediated signaling. Furthermore, scSTING overexpression inhibited ISKNV infection, and knockdown of scSTING promoted ISKNV infection, indicating that scSTING could suppress ISKNV infection in MFF-1 cells. These observations suggested that the scSTING played an important role in innate immune against ISKNV infection. Our work would help elucidate the roles of teleost fish STING in innate immunity.

Synthesis and anti-OXPHOS, antitumor activities of DLC modified spinosyn derivatives.

A series of DLC (delocalized lipophilic cation) modified spinosyn derivatives were synthesized and evaluated for antitumor efficacies both in vitro and in vivo. Cancer cell based antiproliferative assays indicated that the more lipophilic derivatives had stronger inhibitory effects on the tested cancer cell lines. Compound 7b and 8b exhibited strong anti-OXPHOS and apoptosis inducing ability. Notable antitumor efficacies of 7b (5 mg/kg) and 8b (2.5 mg/kg) were observed in the in vivo tumor xenograft experiments, however, lethal toxicities were observed on higher dosages. Our findings indicated that DLC modification is a viable strategy to enhance the anti-OXPHOS and antitumor efficacies of spinosyn derivatives.

Cauliflower-like Nickel with Polar Ni(OH)2/NiO x F y Shell To Decorate Copper Meshes for Efficient Oil/Water Separation.

In recent years, superhydrophilic and underwater superoleophobic membranes have shown promising results in advanced oil/water separation. However, these membranes still have some drawbacks, like tedious preparation process and instability, which hinder their application in oil/water separation. Accordingly, the development of a facile approach to prepare superhydrophilic membranes with excellent oil/water separation performance is still coveted. Here, a copper mesh decorated with cauliflower-like nickel (Cu mesh@CF-Ni) is synthesized via a facile one-step electrodeposition method. Due to the surface polar -OH and -O-Ni-F groups of the Ni(OH)2/NiO x F y shell of the cauliflower-like nickel (CF-Ni), this Cu mesh@CF-Ni displays superhydrophilic and underwater superoleophobic wettability. The results show that the Cu mesh@CF-Ni has excellent oil/water separation efficiency (higher than 99.2%) and ultrahigh water flux (around 20 L h-1 cm-2). Moreover, it also displays good stability in a 10 wt % NaCl solution and 1 M NaOH solution for oil/water separation. By introducing the CF-Ni with polar Ni(OH)2/NiO x F y components onto the surface of the materials via a simple electrodeposition method, the materials will acquire the capability to not only achieve oil/water separation but also realize many other applications, like self-cleaning, underwater bubble manipulation, and fog harvesting.

Deletion of the Infectious spleen and kidney necrosis virus ORF069L reduces virulence to mandarin fish Siniperca chuatsi.

Mandarin fish (Siniperca chuatsi) is a significant cultured species with high added value in China. With the expansion of farming, diseases of mandarin fish such as Infectious spleen and kidney necrosis virus (ISKNV) diseases are becoming more and more serious. Human endogenous retrovirus subfamily H long terminal repeat associating protein 2 (HHLA2) is a type 1 transmembrane molecule with three extracellular Ig domains (IgV-IgC-IgV) and plays important roles in the T cell proliferation and tumorigenesis. The HHLA2-homologues have not been found in virus. In this study, a viral HHLA2 protein encoded by ISKNV ORF069L was identified and the virulence of the deleted ORF069L reconstruction ISKNV strain (ΔORF069L) was investigated. ISKNV ORF069L gene was predicted to encode a 222-amino acids peptide. The bioinformation analysis revealed that ISKNV ORF069L contained an Ig HHLA2 domain and was homologous to vertebrate B7-CD28 family proteins. The recombinant virus strain of ΔORF069L was constructed by homologous recombination technology. The virus titer and growth curves between ISKNV wild type (WT) and ΔORF069L on cellular level showed no significant differences indicating that the ORF069L did not influence the ISKNV replication. The expression levels of immune-related genes (Mx1, IL-1ß, IL-8, TNF-a and IgM) were increased in fish infected with ΔORF069L, compared to those in fish infected with ISKNV WT. Furthermore, the lethality caused by ΔORF069L declined by 40% compared with ISKNV WT, indicating that ORF069L was a virulence gene of ISKNV. Most importantly, the protection rate was nearly 100% for fish immunized with ΔORF069L strain. Those results suggested that ΔORF069L could be developed as a potential attenuated vaccine against ISKNV. Our work will be beneficial to promote the development of gene deletion attenuated vaccines for ISKNV disease.

Highly Selective Production of Compound K from Ginsenoside Rd by Hydrolyzing Glucose at C-3 Glycoside Using ß-Glucosidase of Bifidobacterium breve ATCC 15700.

To investigate a novel ß-glucosidase from Bifidobacterium breve ATCC 15700 (BbBgl) to produce compound K (CK) via ginsenoside F2 by highly selective and efficient hydrolysis of the C-3 glycoside from ginsenoside Rd, the BbBgl gene was cloned and expressed in E. coli BL21. The recombinant BbBgl was purified by Ni-NTA magnetic beads to obtain an enzyme with specific activity of 37 U/mg protein using pNP-Glc as substrate. The enzyme activity was optimized at pH 5.0, 35°C, 2 or 6 U/ml, and its activity was enhanced by Mn2+ significantly. Under the optimal conditions, the half-life of the BbBgl is 180 h, much longer than the characterized ß-glycosidases, and the Km and Vmax values are 2.7 mM and 39.8 µmol/mg/min for ginsenoside Rd. Moreover, the enzyme exhibits strong tolerance against high substrate concentration (up to 40 g/l ginsenoside Rd) with a molar biotransformation rate of 96% within 12 h. The good enzymatic properties and gram-scale conversion capacity of BbBgl provide an attractive method for large-scale production of rare ginsenoside CK using a single enzyme or a combination of enzymes.

Synthesis and antiproliferative activities of novel quartenary ammonium spinosyn derivatives.

In order to enhance the mitochondria-targeting ability of spinosad. A series of quartenary ammonium spinosyn derivatives was designed and synthesized. Some of the derivatives displayed greatly enhanced antiproliferative ability towards tested human cancer cell lines. The structure activity relationship study indicated that lipophilicity has a great influence on the antiproliferative effects of these derivatives. The most active compound 11d exhibited remarkably enhanced OXPHS inhibition and apoptosis inducing ability than spinosyn A.

7-O-aminoalkyl-2,3-dehydrosilibinins: Synthesis and in vitro Anti-cancer Efficacy.

BACKGROUND: The heptaprotective flavonolignan silibinin and dehydrosilibinin have exhibited moderate antiproliferative activities toward many cancer cell lines. Considering of the nontoxic profile of these natural products, chemical modification to enhance the anticancer potentials is promising. METHOD: A series of 7-O-aminoalkyl-2,3-dehydrosilibinin derivatives were synthesized and evaluated for their antiproliferative activities against several cancer cell lines. RESULTS: A number of the synthesized dehydrosilibinin derivatives exhibited greatly enhanced potency with 50% growth inhibition at low micromolar concentrations. Structure activity study indicated that the distance between N and 7-O on the side chain has a limited influence on the antiproliferative activity, while the presence of a morpholino group decreases the antiproliferative activities dramatically. Flow cytometry based assays on human colon cancer HCT116 cells revealed that 6a and 6c, two of the most potent derivatives, effectively arrested the cell cycle in the G2 phase and stimulated cell apoptosis. CONCLUSION: Our findings suggest that attaching an appropriate tertiary amino alkyl side chain through 7-Oalkylation on 2,3-dehydrosilibinin, would be a viable strategy for the development of silibinin derivatives as anticancer agents.

[Effects of different fertilization regimes on nitrogen and phosphorus balance and eco-economic benefits in red paddy field.] / 不同施肥措施对红壤稻田氮磷平衡及生态经济效益的影响.

The nitrogen (N) and phosphorus (P) balance was studied and the eco-economic benefits of N and P were evaluated for the paddy field in a red soil area, under the fertilization treatments of no fertilization (CK), chemical fertilizer (NPK), organic fertilizer (M), and chemical fertilizers combined with organic fertilizers (NPKM, NPM, NKM), based on the long-term experiment started in 1982, to optimize fertilizer application and reduce N and P losses. The results indicated that the slight N surplus (27.10 kg·hm-2) and P deficit (-6.85 kg·hm-2) were obtained in CK, while the N and P surplus respectively with 110.94-243.98 kg·hm-2 and 19.06-67.49 kg·hm-2 in other treatments were obtained. The treatments NPK and M had no effects on the N and P balance. Under the same fertilization rates, the N surplus in treatment NPKM was lower than that in treatments NPM and NKM by 6.3% and 12.9%, while the P surplus was lower by 3.7% and 13.8%, respectively. The total-N, total-P, alkali-hydrolyzable N, and available P contents in the 0-20 cm soil layer increased under the treatments of NPKM. Comparatively, the available P contents were relatively higher in the 20-40 cm soil layer under the treatments of high P application rates. Furthermore, the NPKM treatment had the highest eco-economic benefit value of 0.762, which indicated the optimized fertilizer application for the paddy fields in the red soil area. The treatment CK had the lowest eco-economic benefit values with 0.560. Based on the observations, the N and P (in P2O5) fertilization respectively at the rates of 157.71 kg·hm-2 and 112.18 kg·hm-2 could well maintain the N and P balance for the paddy field in the red soil area.

Anti-RhoC siRNAs inhibit the proliferation and invasiveness of breast cancer cells via modulating the KAI1, MMP9, and CXCR4 expression.

Overexpression of RhoC in breast cancer cells indicates poor prognosis. In the present study, we aim to investigate the possible antitumor effects of anti-RhoC small-interfering RNA (siRNA) in inflammatory breast cancer cells. In this study, a specific anti-RhoC siRNA was used to inhibit RhoC synthesis. Transfection of anti-RhoC siRNA into two IBC cells SUM149 and SUM190 induced extensive degradation of target mRNA and led to significant decrease in the synthesis of protein. Anti-RhoC siRNA inhibited cell proliferation and invasion, increased cell apoptosis, and induced cell cycle arrest in vitro. Moreover, the transfection of siRNA increased the expression of KAI1 and decreased the expression of MMP9 and CXCR4 in both mRNA and protein levels. Furthermore, transplantation tumor experiments in BALB/c-nu mice showed that intratumoral injection of anti-RhoC siRNA inhibited tumor growth and increased survival rate. Our results suggested that RhoC gene silencing with specific anti-RhoC siRNA would be a potential therapeutic method for metastatic breast cancer.

Theoretical design of a new family of two-dimensional topological insulators.

A new family of two-dimensional topological insulator, hydrogenated monolayer Pb2XY (X = Ga/In, Y = Sb/Bi), has been predicted using first-principles density functional theory. The electronic bulk band gap of the proposed systems can be induced in the presence of a spin-orbit coupling effect and its highest value (0.25 eV) was observed in the hydrogenated monolayer Pb2GaBi, which is suitable for practical application. Our simulation study points out that the nanoribbons derived from this new family harbor gapless edge channels. The non-trivial topological nature was further confirmed by calculating the Z2 topological invariant. These novel systems provide a new platform for topological phenomena observation and spintronic applications.

WSe2 nanoribbons: new high-performance thermoelectric materials.

In this work, for the first time, we systematically investigate the ballistic transport properties of WSe2 nanoribbons using first-principles methods. Armchair nanoribbons with narrow ribbon width are mostly semiconductive but the zigzag nanoribbons are metallic. Surprisingly, an enhancement in thermoelectric performance is discovered moving from monolayers to nanoribbons, especially armchair ones. The maximum room-temperature thermoelectric figure of merit of 2.2 for an armchair nanoribbon is discovered. This may be contributed to by the effects of the disordered edges, owing to the existence of dangling bonds at the ribbon edge. H-passivation has turned out to be an effective way to stabilize the edge atoms, which enhances the thermodynamic stability of the nanoribbons. In addition, after H-passivation, all of the armchair nanoribbons exhibit semiconductive properties with similar band gaps (∼1.3 eV). Our work provides instructional theoretical evidence for the application of armchair WSe2 nanoribbons as promising thermoelectric materials. The enhancement mechanism of the disordered edge effect can also encourage further exploration to achieve outstanding thermoelectric materials.

[Study on the Catalytic Kinetic Spectrophotometric Determination of Trace Amounts of Iron(â ¢) and Its Reaction Mechanism].

A catalytic kinetic spectrophotometric method, which is based on the catalytic effect of Fe(Ⅲ) on the fading reaction between potassium persulfate(K2S2O8) and methyl red(MR) in the solution of 0.30 mol·L-1 hydrochloric acid, for the determination of trace amounts of Fe(Ⅲ) has been investigated. A novel detection system, Fe(Ⅲ)-HCl-K2S2O8-MR, has been developed. The optimum experimental conditions for the determination of trace amounts of Fe(Ⅲ) were found on the basis of orthogonal test. The kinetics parameters and equation of this fading reaction of MR were studied. Its reaction mechanism was discussed. The results show that there is a good linear relationship between the variation of MR absorbance at the maximum absorption wavelength of 518 nm and the concentration of Fe(Ⅲ) under the optimum experimental conditions: ln(A0/A)=1.334 1+0.001 0, the correlation coefficient is 0.999 1. The kinetic research shows that the reaction order with respect to Fe(Ⅲ) is 1 and the overall fading reaction is a pseudo-first order reaction. The apparent activation energy of the fading reaction of MR is 69.88 kJ·mol-1. Furthermore, the catalytic effects of Fe(Ⅲ) on this fading reaction is confirmed by its reaction mechanism. This novel method for the determination of trace Fe(Ⅲ) has never previously been published so far. Trace amounts of Fe(Ⅲ) can be selectively determined by this catalytic kinetic spectrophotometric method with high precision and accuracy. This method is simple and its reagents used are cheap and available. Its sensitivity is higher than that of conventional spectrophtometry with detection limit of 0.005 mg·L-1. This detection system is stable. This proposed method has been applied to the determination of trace amounts of Fe(Ⅲ) in food and water samples with satisfactory results. Relative standard deviation of the detection results is 1.18%～2.11%. Average recovery rate of the detection results is 98.0%～104.0%.