Efficient and selective capture of uranium by polyethyleneimine-modified chitosan composite microspheres from radioactive nuclear waste.

Uranium extraction from radioactive nuclear waste is vital for sustainable energy supply and ecological security. Herein, a polyethyleneimine-chitosan composite microspheres n-PEI/ECH-CTS (n = 0.1, 0.2, 0.3, 0.4, 0.5) were synthetized for efficient and selective uranium adsorption. The prepared chitosan microspheres with uniform size, uniform dispersion and good mechanical strength combine cost-effectiveness and environmental benefits. The 0.4-PEI/ECH-CTS exhibits the highest adsorption capacity of 380.65 mg g-1 within only 4 h due to high nitrogen content of 6.57 mol kg-1. The DFT calculations confirms that the optimal coordination mode of UO22+ and 0.4-PEI/ECH-CTS is one UO22+ chelated with two -NH2 from two adsorption units, respectively. Adsorption efficiency of U(VI) from simulated nuclear wastewater achieves to 100%, and the Kd value is up to 1.1 × 104 mL g-1, which is 1.7 × 104-6.1 × 104 times that of coexisting ions. The CU(VI) reduces in simulated wastewater from 10.98 mg L-1 to 1 µg L-1, which is well below the US Environmental Protection Agency uranium limits for drinking water (30 µg L-1). Besides, 0.4-PEI/ECH-CTS still maintains above 95% adsorption efficiency after seven cycles. In short, the 0.4-PEI/ECH-CTS microspheres integrate high performance, practicality and cost-effectiveness, which has great advantages in practical industrial applications.

Graphene dispersant-assisted in situ growth of Re-doped MoS2 nanosheets on carbon cloth and their performance for hydrogen evolution reaction.

Uniform distribution of electrochemically active transition metal compounds on carbon cloth can effective improve their hydrogen evolution reaction (HER) performance, however, harsh chemical treatment of carbon substrates is always unavoidable during this process. Herein, a hydrogen protonated polyamino perylene bisimide (HAPBI) was used as interface active agent for the in situ growth of rhenium (Re) doped MoS2 nanosheets on carbon cloth (Re-MoS2/CC). HAPBI contains a large conjugated core and multiple cationic groups and has been shown to be an effective graphene dispersant. It endowed the carbon cloth excellent hydrophilicity through simple noncovalent functionalization and, meanwhile, provided sufficient active sites to anchor MoO42- and ReO4- via electrostatic interaction. Uniform and stable Re-MoS2/CC composites were facilely obtained by immersing carbon cloth in HAPBI solution followed by hydrothermal treatment in the precursor solution. The doping of Re induced the formation of 1 T phase MoS2, which reached about 40% in the mixture with 2H phase MoS2. Electrochemical measurements showed an overpotential of 183 mV at a current density of 10 mA cm-2 in 0.5 mol L-1 H2SO4 when the molar ratio of Re to Mo is 1:100. This strategy can be further extended to construct other electrocatalysts that using graphene, carbon nanotubes, etc. as conductive additives.

CTAB assisted evaporation-induced self-assembly to construct imidazolium-based hierarchical porous covalent organic polymers for ReO4-/TcO4- removal.

Evaporation-induced self-assembly method (EISA) was a facile and reliable method to synthesize porous materials. Herein, we report a kind of hierarchical porous ionic liquid covalent organic polymers (HPnDNH2) under cetyltrimethylammonium bromide (CTAB) assisted by EISA for ReO4-/TcO4- removal. Unlike covalent organic frameworks (COFs), which usually needed to be prepared in a closed environment or with a long reaction time, HPnDNH2 in this study was prepared within 1 h in an open environment. It was worth noting that CTAB not only served as a soft template for forming pore, but also induced ordered structure, which was verified by SEM, TEM, and Gas sorption. Benefit from its hierarchical pore structure, HPnDNH2 exhibited higher adsorption capacity (690.0 mg g-1 for HP1DNH2 and 808.7 mg g-1 for HP1.5DNH2) and faster kinetics for ReO4-/TcO4- than 1DNH2 (without employing CTAB). Additionally, the material used to remove TcO4- from alkaline nuclear waste was seldom reported, because combining features of alkali resistance and high uptake selectivity was not easy to achieve. In this study, in the case of HP1DNH2, it displayed outstanding adsorption efficiency toward aqueous ReO4-/TcO4- in 1 mol L-1 NaOH solution (92%) and simulated Savannah River Site High-level waste (SRS HLW) melter recycle stream (98%), which could be a potentially excellent nuclear waste adsorbing material.

In situ anchor of Na2Ti3O7 in nitrogen-rich carbon hollow red blood cell-like structure as a 0D-3D hierarchical electrode material for efficient electrochemical desalination.

Reasonable design of the structure and complementary compounding of electrode materials is helpful to enhance capacitive deionization (CDI) performance. Herein, a novel 0D-3D hierarchical electrode material containing Na2Ti3O7 nanoparticles anchored at hollow red blood cell (HRBC)-like nitrogen-rich carbon (HRBC-NTO/N-C-60) was prepared via selective protection, pyrolysis, and alkalization. Specifically, a HRBC-like NH2-MIL-125-based material (HRBC-MOF-60) was first constructed by a selective protection approach of tannic acid (TN), which addresses the shortcomings of using sacrificial templates or corrosive agents. Afterwards, HRBC-NTO/N-C-60 was obtained in situ by annealing and alkalization of HRBC-MOF-60. The nitrogen-rich carbon with a HRBC-like structure has the ability to rapidly transport electrons, and its porous structure enables remarkable charge transfer. Benefiting from the grafted 3D N-doped porous carbon with a HRBC-like structure, well-dispersed 0D Na2Ti3O7 nanoparticles, and satisfactory bonding effects, HRBC-NTO/N-C-60 exhibited high specific capacitance and fast ionic and electronic diffusion kinetics. Moreover, HRBC-NTO/N-C-60 was well-suited for desalination by functioning as a cathode material for capacitive deionization (CDI), and delivering a high desalination capacity of 66.8 mg g-1 in 200 mg L-1 NaCl solution at 1.4 V. This work introduces an excellent high-performance candidate for electrochemical deionization as well as affording afflatus for accurately inventing OD-3D hierarchical materials with hollow structures.

Potassium promoted Gd0.06Co catalysts for highly efficient catalytic N2O decomposition in presence of impurity gases at low temperature.

In order to enhance the catalytic performance of the Gd-modified Co3O4 catalyst (Gd0.06Co) for the N2O decomposition, alkali metal K was introduced as the promoter by impregnating the Gd0.06Co powder with an aqueous solution of KNO3 (with K/Co ratios 0.01-0.05). With the doping of K, the catalytic activity over Gd0.06Co was significantly improved and the temperature of N2O complete decomposition was decreased from 350 °C to 300 °C. Combining the results of XPS and O2-TPD, the superior catalytic performance of the optimum catalyst K0.025Gd0.06Co was mainly owing to the synergistic effect of Gd and K, which weakened the Co-O bond and endowed the catalyst surface with much more amount of oxygen vacancies. Even under the coexist of the impurity gases, such as 5 vol% O2, 100 ppmv NO and 2 vol% H2O, the K0.025Gd0.06Co catalyst exhibited prominently better catalytic activity than Gd0.06Co and K0.025Co catalysts.

Immersion grinding and in-situ polymerization synthesis of poly(ionic liquid)s incorporation into MOF composites as radioactive TcO4- scavenger.

Imidazolium-based ionic liquids (ILs) are a promising candidate for efficient separation of radioactive pertechnetate (TcO4-) from nuclear waste. However, their effective fixation, availability of active sites and slow adsorption kinetics remain challenges. Here, we incorporated the bisimidazolium-based ILs into porous metal-organic frameworks (MOFs) via a combination of immersion grinding and in-situ polymerization. 3,3'-divinyl-1,1'(1,4-butanediyl) diimidazolium dichloride is tightly bound inside and outside the porous MOFs matrix by uniform immersion grinding, which facilitates the exposure of more adsorption sites and provides channels for the anions to travel through quickly. Solvent-free polymerization reduces environmental pollution and energy consumption. Notably, the composite P[C4(VIM)2]Cl2@MIL-101 possesses an admirable removal efficiency (673 mg g-1) compared with the pristine poly(ionic liquid)s (215 mg g-1). Meanwhile, it exhibits fast sorption kinetics (92% in 2 min), good ß and γ radiation-resistance, excellent regeneration and eminent removal efficiency in high alkaline conditions (83%). These superior traits endow that P[C4(VIM)2]Cl2@MIL-101 effectively separated TcO4- from simulated Hanford Low-activity Waste (LAW) Melter off-gas scrubber solution tested in this work. DFT density functional theory confirms that the strong electrostatic attraction and minimum Gibbs free energy (-6.2 kcal mol-1) achieve high selective adsorption for TcO4-. P[C4(VIM)2]Cl2@MIL-101 demonstrates the considerable potential to remove TcO4- from radioactive contaminants.

Altered protein secretion of Chlamydia trachomatis in persistently infected human endocervical epithelial cells.

Chlamydia trachomatis is the most common bacterial infection of the human reproductive tract globally; however, the mechanisms underlying the adaptation of the organism to its natural target cells, human endocervical epithelial cells, are not clearly understood. To secure its intracellular niche, C. trachomatis must modulate the host cellular machinery by secreting virulence factors into the host cytosol to facilitate bacterial growth and survival. Here we used primary human endocervical epithelial cells and HeLa cells infected with C. trachomatis to examine the secretion of bacterial proteins during productive growth and persistent growth induced by ampicillin. Specifically, we observed a decrease in secretable chlamydial protease-like activity factor (CPAF) in the cytosol of host epithelial cells exposed to ampicillin with no evident reduction of CPAF product by C. trachomatis. In contrast, the expression of CopN and Tarp was downregulated, suggesting that C. trachomatis responds to ampicillin exposure by selectively altering the expression of secretable proteins. In addition, we observed a greater accumulation of outer-membrane vesicles from C. trachomatis in persistently infected cells. Taken together, these results suggest that the regulation of both gene expression and the secretion of chlamydial virulence proteins is involved in the adaptation of the bacteria to a persistent infection state in human genital epithelial cells.

An advanced hollow bimetallic carbide/nitrogen-doped carbon nanotube for efficient catalysis of oxygen reduction and hydrogen evolution and oxygen evolution reaction.

Rational design and synthesis of multifunctional electrocatalysts with high-efficient activity and robust stability toward the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly desirable, but remain a challenging step. Herein, a novel hollow bimetallic carbide/nitrogen-doped carbon nanotube (Co6Mo6C2@NCNT) is successfully synthesized through the simple pyrolysis of polypyrrole (PPy)-supported metal-organic framework (MOF) composite. Remarkable characteristics of the large surface area, hollow and porous structure, rich active sites and synergistic effect between Co6Mo6C2 and NCNT arouse high catalytic efficiency. Notably, the Co6Mo6C2@NCNT presents excellent ORR catalytic activity (a high half-wave potential of 0.875 V vs. reversible hydrogen electrode (RHE) and diffusion-limited current density of 6.22 mA cm-2) via a four-electron pathway, together with outstanding stability and methanol tolerance over commercial Pt/C in 0.1 M KOH solution. The composite also exhibits superior HER performance, delivering a low overpotential of 122.14 mV at current density of 10 mA cm-2, as well as good catalytic performance for OER in 1.0 M KOH solution. This work may provide some insight in design multifunctional electrocatalysts derived from MOF with advanced performance for sustainable energy technologies.

Mutagenesis of region 4 of sigma 28 from Chlamydia trachomatis defines determinants for protein-protein and protein-DNA interactions.

Transcription factor sigma(28) in Chlamydia trachomatis (sigma(28)(Ct)) plays a role in the regulation of genes that are important for late-stage morphological differentiation. In vitro mutational and genetic screening in Salmonella enterica serovar Typhimurium was performed in order to identify mutants with mutations in region 4 of sigma(28)(Ct) that were defective in sigma(28)-specific transcription. Specially, the previously undefined but important interactions between sigma(28)(Ct) region 4 and the flap domain of the RNA polymerase beta subunit (beta-flap) or the -35 element of the chlamydial hctB promoter were examined. Our results indicate that amino acid residues E206, Y214, and E222 of sigma(28)(Ct) contribute to an interaction with the beta-flap when sigma(28)(Ct) associates with the core RNA polymerase. These residues function in contacts with the beta-flap similarly to their counterpart residues in Escherichia coli sigma(70). Conversely, residue Q236 of sigma(28)(Ct) directly binds the chlamydial hctB -35 element. The conserved counterpart residue in E. coli sigma(70) has not been reported to interact with the -35 element of the sigma(70) promoter. Observed functional disparity between sigma(28)(Ct) and sigma(70) region 4 is consistent with their divergent properties in promoter recognition. This work provides new insight into understanding the molecular basis of gene regulation controlled by sigma(28)(Ct) in C. trachomatis.

Bimetal-Organic Framework-Derived Porous Rodlike Cobalt/Nickel Nitride for All-pH Value Electrochemical Hydrogen Evolution.

Developing advanced hydrogen evolution reaction (HER) electrocatalysts is of great significance. Herein, we report porous rodlike cobalt-nickel bimetal nitrides (Co xNi yN) as high-efficiency HER electrocatalysts in a wide pH range through nitridation from a bimetal-organic framework (MOF-74) precursor. Thanks to collaborative superiorities of high surface areas, abundant mesoporous structure, perfect metal element dispersion, and electron modulation effect, the as-prepared Co xNi yN possess a superior catalytic ability toward HER at all pH values. In particular, the optimal Co2Ni1N requires overpotentials of 102.6 and 92.0 mV to afford a current density of 10 mA cm-2 in alkaline and acidic solution, respectively. In addition, it also presents favorable activity in neutral media and excellent stability under different pH conditions. The present study not only offers a strategy for the design and synthesis of porous bimetal nitrides derived from binuclear MOF but also brings up new avenues for the development of cost-effective and competent all-pH HER catalysts for renewable energy systems.

Comparative study of carbon fiber structure on the electrocatalytic performance of ZIF-67.

In this study, novel ZIF-67@carbon fiber composites were fabricated by a simple and facile approach. In order to explore the influence of carbon fiber structure on enhancing the electrocatalytic efficiency of the ZIF-67, different structural carbon fibers (hollow porous carbon fiber (PCF) and solid carbon fiber (SCF)) were used for preparing ZIF-67/carbon fiber catalysts. ZIF-67/carbon fiber composites were characterized via X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. Thanks to excellent hollow structural characteristic of PCF, ZIF-67/PCF possesses more exposed active sites, smaller particle size of ZIF-67, better conductivity, electrochemical stability, more mass transport channels as well as superior electrocatalytic abilities than ZIF-67/SCF. Furthermore, ZIF-67/PCF(1:1) sample-modified glassy carbon electrode presents a linear range to nitrobenzene that is composed by two line segments, i.e. from 0.3 to 50 µM with a sensitivity of 454.7 µA mM-1 and from 50 to 390 µM with a sensitivity of 132.0 µA mM-1, and a low detection limit of 0.16 µM. It also exhibits a wide linear response to l-cysteine in the range of 5-160 µM and 160-1580 µM with a rapidly response within 1.0 s as well as high catalytic rate constant, good stability and anti-interference ability. Our work provides useful information for searching and choosing carbon materials with excellent structure benefit to electrochemical applications.

Identification of surface-exposed components of MOMP of Chlamydia trachomatis serovar F.

The identification of surface-exposed components of the major outer membrane protein (MOMP) of Chlamydia is critical for modeling its three-dimensional structure, as well as for understanding the role of MOMP in the pathogenesis of Chlamydia-related diseases. MOMP contains four variable domains (VDs). In this study, VDII and VDIV of Chlamydia trachomatis serovar F were proven to be surface-located by immuno-dot blot assay using monoclonal antibodies (MAbs). Two proteases, trypsin and endoproteinase Glu-C, were applied to digest the intact elementary body of serovar F under native conditions to reveal the surface-located amino acids. The resulting peptides were separated by SDS-PAGE and probed with MAbs against these VDs. N-terminal amino acid sequencing revealed: (1) The Glu-C cleavage sites were located within VDI (at Glu61) and VDIII (at Glu225); (2) the trypsin cleavage sites were found at Lys79 in VDI and at Lys224 in VDIII. The tryptic peptides were then isolated by HPLC and analyzed with a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer and a quadrupole-orthogonal-TOF mass spectrometer coupled with a capillary liquid chromatograph. Masses and fragmentation patterns that correlated to the peptides cleaved from VDI and VDIII regions, and C-terminal peptides Ser333-Arg358 and Ser333-Lys350 were observed. This result demonstrated that these regions are surface-exposed. Data derived from comparison of nonreduced outer membrane complex proteolytic fragments with their reduced fractions revealed that Cys26, 29, 33, 116, 208, and 337 were involved in disulfide bonds, and Cys26 and 337, and 116 and 208 were paired. Based on these data, a new two-dimensional model is proposed.

Andrographolide inhibits intracellular Chlamydia trachomatis multiplication and reduces secretion of proinflammatory mediators produced by human epithelial cells.

Chlamydia trachomatis is the most common sexually transmitted bacterial disease worldwide. Untreated C. trachomatis infections may cause inflammation and ultimately damage tissues. Here, we evaluated the ability of Andrographolide (Andro), a natural diterpenoid lactone component of Andrographis paniculata, to inhibit C. trachomatis infection in cultured human cervical epithelial cells. We found that Andro exposure inhibited C. trachomatis growth in a dose- and time-dependent manner. The greatest inhibitory effect was observed when exponentially growing C. trachomatis was exposed to Andro. Electron micrographs demonstrated the accumulation of unusual, structurally deficient chlamydial organisms, correlated with a decrease in levels of OmcB expressed at the late stage of infection. Additionally, Andro significantly reduced the secretion of interleukin6, CXCL8 and interferon-γ-induced protein10 produced by host cells infected with C. trachomatis. These results indicate the efficacy of Andro to perturb C. trachomatis transition from the metabolically active reticulate body to the infectious elementary body and concurrently reduce the production of a proinflammatory mediator by epithelial cells in vitro. Further dissection of Andro's anti-Chlamydia action may provide identification of novel therapeutic targets.

Selective promoter recognition by chlamydial sigma28 holoenzyme.

The sigma transcription factor confers the promoter recognition specificity of RNA polymerase (RNAP) in eubacteria. Chlamydia trachomatis has three known sigma factors, sigma(66), sigma(54), and sigma(28). We developed two methods to facilitate the characterization of promoter sequences recognized by C. trachomatis sigma(28) (sigma(28)(Ct)). One involved the arabinose-induced expression of plasmid-encoded sigma(28)(Ct) in a strain of Escherichia coli defective in the sigma(28) structural gene, fliA. The second was an analysis of transcription in vitro with a hybrid holoenzyme reconstituted with E. coli RNAP core and recombinant sigma(28)(Ct). These approaches were used to investigate the interactions of sigma(28)(Ct) with the sigma(28)(Ct)-dependent hctB promoter and selected E. coli sigma(28) (sigma(28)(Ec))-dependent promoters, in parallel, compared with the promoter recognition properties of sigma(28)(EC). Our results indicate that RNAP containing sigma(28)(Ct) has at least three characteristics: (i) it is capable of recognizing some but not all sigma(28)(EC)-dependent promoters; (ii) it can distinguish different promoter structures, preferentially activating promoters with upstream AT-rich sequences; and (iii) it possesses a greater flexibility than sigma(28)(EC) in recognizing variants with different spacing lengths separating the -35 and -10 elements of the core promoter.