Structural Basis and IP6 Requirement for Pds5-Dependent Cohesin Dynamics.

The ring-shaped cohesin complex regulates transcription, DNA repair, and chromosome segregation by dynamically entrapping chromosomes to promote chromosome compaction and sister-chromatid cohesion. The cohesin ring needs to open and close to allow its loading to and release from chromosomes. Cohesin dynamics are controlled by the releasing factors Pds5 and Wapl and the cohesin stabilizer Sororin. Here, we report the crystal structure of human Pds5B bound to a conserved peptide motif found in both Wapl and Sororin. Our structure establishes the basis for how Wapl and Sororin antagonistically influence cohesin dynamics. The structure further reveals that Pds5 can bind inositol hexakisphosphate (IP6). The IP6-binding segment of Pds5B is shaped like the jaw of a plier lever and inhibits the binding of Scc1 to Smc3. We propose that Pds5 stabilizes a transient, open state of cohesin to promote its release from chromosomes.

Electrokinetic Enhancement of Water Flux and Ion Rejection through Graphene Oxide/Carbon Nanotube Membrane.

Graphene oxide (GO) is promising for constructing next-generation high-performance membranes for water treatment and desalination. However, GO-based membranes are still subjected to low ion rejection or limited water flux. Herein, the electrokinetic effect is employed as a new strategy for the coenhancement of water flux and ion rejection through an ethylenediamine-polystyrenesulfonate intercalated graphene oxide/carbon nanotube (GO&EDA-PSS/CNT) asymmetric membrane. Benefiting from the external voltage applied across the GO&EDA-PSS layer, the electrokinetically driven water transport velocity is significantly increased from 0 to 23.7 µm s-1 with increasing the voltage from 0 to 3.0 V. As a result, the water flux is improved from 9.1 to 17.4 L m-2 h-1 under a transmembrane pressure of 1 bar. Simultaneously, the rejection rate for NaCl is increased from 52.4% to 78.3%. Numerical analysis reveals that the increased rejection rate is attributed to the electrokinetic enhancements of water transport through the membrane and ion partitioning between the membrane and bulk solution. These results indicate that the assistance of the electrokinetic effect is an effective means to improve membrane filtration performance, which provides a new perspective on the design of advanced membranes for achieving high water flux and rejection efficiency.

In vitro lung and gastrointestinal bioaccessibility of potentially toxic metals in Pb-contaminated alkaline urban soil: The role of particle size fractions.

Potentially toxic metals (PTMs), associated with different size particles in soil, may play an important role in adverse health effect and risk for human. The objective is to evaluate the lung and gastrointestinal bioaccessibility and risk of PTMs in Pb-contaminated alkaline urban soil depending on the particle size fractions. The size fractions of 50-250 µm, 5-50 µm, 1-5 µm, <1 µm in Pb-contaminated alkaline urban soil from Baoji Heavy Industrial Base City, NW China, were screened by Sequential Wet Sieving Separation Procedure (SWSSP) based on Stokes' Law. The concentrations of 9 potentially toxic metals (As, Ba, Co, Cr, Cu, Mn, Ni, Pb and Zn) in each particle size fractions were characterized by ICP-OES and ICP-MS, and the in vitro bioaccessibility dependent of size fractions were evaluated by the simulation fluids of Artificial Lysosomal Fluid (ALF) and Gamble for lung, PBET, SBET, IVG, SBRC, UBM for gastric and intestinal, respectively. Health risks were assessed considering simulated external exposure using intestinal and lung bioaccessibility. The lung and gastrointestinal bioaccessibility and exposure risks of PTMs in fine particle size (i.e. <1 µm) was higher than larger particle size fractions (i.e. 50-250 µm, 5-50 µm, 1-5 µm), however, some different variations of bioaccessibility observed the simulation fluids and time dependent. In case of single PTMs, the lung bioaccessibilities of PTMs in ALF were higher than those in Gamble fluids, most prominent in Co, Cu, Mn and Zn, while the gastrointestinal [G + I] bioaccessibility of PTMs was less than those in gastric [G], like Cu, Mn, Pb and Zn mostly. The non-carcinogenic risks of these PTMs to children via inhalation were acceptable and higher than those of adults, but reverse for carcinogenic risk. Comparatively, the non-carcinogenic and carcinogenic risks of PTMs via ingestion pathway were both higher than those for adults. Although the risks from ingestion were in acceptable range, the total carcinogenic risks for children were more than 10-4, which would bring carcinogenic risks and should be paid attention to. It was noted that the toxic metal, Co in all size fractions was the most important contributor for noncarcinogenic risks and Cr mostly for carcinogenic risks via inhalation pathway for adults and children in local areas. However, Pb was the most important contributor for noncarcinogenic risk both for adults and children via ingestion pathway relative to Co and Cr for carcinogenic risks through hand-to-mouth ingestion. Those observations demonstrated the important role that the smaller particle fractionations in Pb-contaminated alkaline soil played in both bioaccessibility and the refinement of human health-risk assessments for the inhalation and ingestion pathway.

Improving Ion Rejection of Conductive Nanofiltration Membrane through Electrically Enhanced Surface Charge Density.

Nanofiltration (NF) is considered a promising candidate for brackish and seawater desalination. NF exhibits high multivalent ion rejection, but the rejection rate for monovalent ions is relatively low. Besides, great challenges remain for conventional NF membranes to achieve high ion rejection without sacrificing water flux. This work presents an effective strategy for improving the ion rejection of conductive NF membrane without decreasing the permeability through electrically assisted enhancement of surface charge density. When external voltage is increased from 0 to 2.5 V, the surface charge density of the membrane increases from 11.9 to 73.0 mC m-2, which is 6.1× higher than that without external voltage. Correspondingly, the rejection rate for Na2SO4 increases from 81.6 to 93.0% and that for NaCl improves from 53.9 to 82.4%; meanwhile, the membrane retains high permeabilities of 14.0 L m-2 h-1 bar-1 for Na2SO4 filtration and 14.5 L m-2 h-1 bar-1 for NaCl filtration. The Donnan steric pore model analysis suggests that the Donnan potential difference between the membrane and bulk solution is increased under electrical assistance, leading to increased ion transfer resistance for improved ion rejection. This work provides new insight into the development of advanced NF technologies for desalination and water treatment.

Combined Effects of Surface Charge and Pore Size on Co-Enhanced Permeability and Ion Selectivity through RGO-OCNT Nanofiltration Membranes.

Nanofiltration (NF) has received much attention for wastewater treatment and desalination. However, NF membranes generally suffer from the trade-off between permeability and selectivity. In this work, the coenhancement of permeability and ion selectivity was achieved through tuning the surface charge and pore size of oxidized carbon nanotube (OCNT) intercalated reduced graphene oxide (RGO) membranes. With the increase of OCNT content from 0 to 83%, the surface charge and the pore size were increased. The permeability increased to 10.6 L m-2 h-1 bar-1 and rejection rate reached 78.1% for Na2SO4 filtration at a transmembrane pressure of 2 bar, which were 11.8 and 1.3 times higher than those of pristine RGO membrane. The composite membrane also showed 11.1 times higher permeability (11.1 L m-2 h-1 bar-1) and 2.9 times higher rejection rate (35.3%) for NaCl filtration. The analyses based on Donnan steric pore model suggest that the increased permeability is attributed to the combined effects of enlarged pore size and increased surface charge, while the enhanced ion selectivity is mainly dependent on the electrostatic interaction between the membrane and target ions. This finding provides a new insight for the development of high-performance NF membranes in water treatment and desalination.

A Redox-Dependent Electrochromic Material: Tetri-EDOT Substituted Thieno[3,2-b]thiophene.

Organic electrochromic materials change color rapidly under applied potential. A butterfly-shaped compound, 5,5',-5″,-5'″-(thieno[3,2-b]thiophene-2,3,5,6-tetrayl) tetrakis-(2,3-dihydrothieno[3,4-b][1,4]dioxine) (t-EDOT-TT) is synthesized for the first time and polymerized at different potentials via electropolymerization technique. By applying different polymerization potentials, the optical and electrochromic properties of this newly synthesized polymer can be tuned. Owing to the dependence of functional group position in the polymer structure on the redox potential, this polymer can be utilized in very interesting organic optoelectronic applications.

A controlled wet-spinning and dip-coating process for preparation of high-permeable TiO2 hollow fiber membranes.

In order to improve the permeate flux of photocatalytic membranes, we present an approach for coupling TiO2 with ceramic hollow fiber membranes. The ceramic hollow fiber membranes with high permeate flux were fabricated by a controlled wet-spinning process using polyethersulfone (PESf) and ceramic powder as precursors and 1-methyl-2-pyrrolidinone as solvent, and the subsequent TiO2 coating was performed by a dip-coating process using tetra-n-butyl titanate as precursor. It has been found that the PESf/ceramic powder ratio could influence the structure of the membranes. Here the as-prepared TiO2 hollow fiber membranes had a pure water flux of 4,450 L/(m(2)·h). The performance of the TiO2 hollow fiber membrane was evaluated using humic acid (HA) as a test substance. The results demonstrated that this membrane exhibited a higher permeate flux under UV irradiation than in the dark and the HA removal efficiency was enhanced. The approach described here provides an operable route to the development of high-permeable photocatalytic membranes for water treatment.

Enhanced permeability, selectivity, and antifouling ability of CNTs/Al2O3 membrane under electrochemical assistance.

Membrane filtration provides effective solutions for removing contaminants, but achieving high permeability, good selectivity, and antifouling ability remains a great challenge for existing membrane filtration technologies. In this work, membrane filtration coupled with electrochemistry has been developed to enhance the filtration performance of a CNTs/Al2O3 membrane. The as-prepared CNTs/Al2O3 membrane, obtained by coating interconnected CNTs on an Al2O3 substrate, presented good pore-size tunability, mechanical stability, and electroconductivity. For the removal of a target (silica spheres as a probe) with a size comparable to the membrane pore size, the removal efficiency and flux at +1.5 V were 1.1 and 1.5 times higher, respectively, than those without electrochemical assistance. Moreover, the membrane also exhibited a greatly enhanced removal efficiency for contaminants smaller than the membrane pores, providing enhancements of 4 orders of magnitude and a factor of 5.7 for latex particles and phenol, respectively. These results indicated that both the permeability and the selectivity of CNTs/Al2O3 membranes can be significantly improved by electrochemical assistance, which was further confirmed by the removal of natural organic matter (NOM). The permeate flux and NOM removal efficiency at +1.5 V were about 1.6 and 3.0 times higher, respectively, than those without electrochemical assistance. In addition, the lost flux of the fouled membrane was almost completely recovered by an electrochemically assisted backwashing process.

Constructing all carbon nanotube hollow fiber membranes with improved performance in separation and antifouling for water treatment.

Manipulating carbon nanotubes (CNTs) through engineering into advanced membranes with superior performance for disinfection and decontamination of water shows great promise but is challenging. In this paper, a facile assembly of CNTs into novel hollow fiber membranes with tunable inner/outer diameters and structures is developed for the first time. These free-standing membranes composed entirely of CNTs feature a porosity of 86±5% and a permeation flux of about 460±50 L m(-2) h(-1) at a pressure differential of 0.04 MPa across the membrane. The randomly oriented interwoven structure of CNTs endows the membranes considerable resistance to pore blockage. Moreover, the adsorption capability of the CNT hollow fiber membranes, which is crucial in the efficient removal of small and trace contaminant molecules, is about 2 orders of magnitude higher than that of commercial polyvinylidene fluoride hollow fiber membranes. The unique advantage of the CNT hollow fiber membranes over other commercial membranes is that they can be in situ electrochemically regenerated after adsorption saturation.

Integrating plasmonic nanoparticles with TiO2 photonic crystal for enhancement of visible-light-driven photocatalysis.

Aimed at enhancing photocatalysis through intensifying light harvesting, a new photocatalyst was fabricated by infiltrating Au nanoparticles into TiO(2) photonic crystals (TiO(2) PC/Au NPs). Scanning electron microscopy (SEM) and transmission electron microscope (TEM) images showed that the Au NPs with average diameter around 15 nm were dispersed uniformly into the porous TiO(2) material. The results of the transmittance spectra demonstrated that the light absorption by Au NPs was amplified after they were infiltrated into TiO(2) 240, which was fabricated from 240 nm polystyrene spheres. In the photocatalytic experiments of 2,4-dichlorophenol degradation under visible light (λ > 420 nm) irradiation, the kinetic constant using TiO(2) 240/Au NPs was 2.3 fold larger than that using TiO(2) nanocrystalline/Au NPs (TiO(2) NC/Au NPs). The excellent photocatalysis benefited from the cooperatively enhanced light harvesting owing to the localized surface plasmon resonance of Au NPs, which extended the light response spectra and the photonic effect of the TiO(2) 240 which intensified the plasmonic absorption by Au NPs. The hydroxyl radicals originated from the electroreduction of dissolved oxygen with photogenerated electrons via chain reactions were the main reactive oxygen species responsible for the pollutant degradation.

Prolonged activation of innate immune pathways by a polyvalent STING agonist.

The stimulator of interferon genes (STING) is an endoplasmic reticulum transmembrane protein that is a target of therapeutics for infectious diseases and cancer. However, early-phase clinical trials of small-molecule STING agonists have shown limited antitumour efficacy and dose-limiting toxicity. Here, we show that a polyvalent STING agonist-a pH-sensitive polymer bearing a seven-membered ring with a tertiary amine (PC7A)-activates innate-immunity pathways through the polymer-induced formation of STING-PC7A condensates. In contrast to the natural STING ligand 2',3'-cyclic-GMP-AMP (cGAMP), PC7A stimulates the prolonged production of pro-inflammatory cytokines by binding to a non-competitive STING surface site that is distinct from the cGAMP binding pocket. PC7A induces antitumour responses that are dependent on STING expression and CD8+ T-cell activity, and the combination of PC7A and cGAMP led to synergistic therapeutic outcomes (including the activation of cGAMP-resistant STING variants) in mice bearing subcutaneous tumours and in resected human tumours and lymph nodes. The activation of the STING pathway through polymer-induced STING condensation may offer new therapeutic opportunities.

Enhanced adsorption of ionizable antibiotics on activated carbon fiber under electrochemical assistance in continuous-flow modes.

Ionizable antibiotics have attracted serious concerns because of their variable dissociation forms and thereby rendering unique toxicity and microorganism resistance. Developing an efficient and environmentally friendly method for removing these micropollutants from environmental media remains very challenging. Here, electro-assisted adsorption onto activated carbon fiber in continuous-flow mode was used to remove three ionizable antibiotics, sulfadimethoxine (SDM), ciprofloxacin (CIP), and clarithromycin (CLA), from water. Benefiting from strengthened electrostatic interactions, the adsorption capacities for the target antibiotics (10 mg/L) in flow mode (70.9-202.2 mg/g) increased by ∼5 times under a potential of 1.0 V (SDM) or -1.0 V (CIP and CLA) relative to those of open circuit (OC) adsorption. Meanwhile, effluent concentration decreased from >100 µg/L to 9.6 µg/L with removal efficiency increasing from 99.0% to 99.9%. Moreover, high recovery efficiency of ACF up to 96.35 ±â€¯0.65% was achieved by imposing a reverse potential (-1.0 V) relative to that used for SDM adsorption. In addition, trace levels of antibiotics (364-580 ng/L) in surface water could be removed effectively to achieve low effluent concentration (0.4-1.2 ng/L) and high removal efficiency (99.9%) upon treating up to ∼1560 bed volumes (BVs), demonstrating the potential of electro-assisted adsorption for practical application in water treatment.

An unusual photoconductive property of polyiodide and enhancement by catenating with 3-thiophenemethylamine salt.

During our investigation of perovskite solar cell materials, we serendipitously discovered an unusual photoconductive property of polyiodide, which can be enhanced greatly through the interaction of in situ-formed polyiodide and 3-thiophenemethylamine salt. This communication examined the photoconductive properties of polyiodide with and without adding different aromatic methylamine compounds. MATPI2 exhibits a high photoconductivity and short response time. The enhanced photoelectric conversion efficiencies are attributed to the strong interaction of polyiodide and the 3-thiophenemethylamine salt.

Voltage-Gated Transport of Nanoparticles across Free-Standing All-Carbon-Nanotube-Based Hollow-Fiber Membranes.

Understanding the mechanism underlying controllable transmembrane transport observed in biological membranes benefits the development of next-generation separation membranes for a variety of important applications. In this work, on the basis of common structural features of cell membranes, a very simple biomimetic membrane system exhibiting gated transmembrane performance has been constructed using all-carbon-nanotube (CNT)-based hollow-fiber membranes. The conductive CNT membranes with hydrophobic pore channels can be positively or negatively charged and are consequently capable of regulating the transport of nanoparticles across their pore channels by their "opening" or "closing". The switch between penetration and rejection of nanoparticles through/by CNT membranes is of high efficiency and especially allows dynamic control. The underlying mechanism is that CNT pore channels with different polarities can prompt or prevent the formation of their noncovalent interactions with charged nanoparticles, resulting in their rejection or penetration by/through the CNT membranes. The theory about noncovalent interactions and charged pore channels may provide new insight into understanding the complicated ionically and bimolecularly gated transport across cell membranes and can contribute to many other important applications beyond the water purification and resource recovery demonstrated in this study.

Transcriptional profiling of biomass degradation-related genes during Trichoderma reesei growth on different carbon sources.

To identify all the gene products involved in cellulosic biomass degradation, we employed RNA sequencing technology to perform a genome-wide comparison of gene expression during growth of Trichoderma reesei QM9414 on cellulose or glucose. Due to their important role in lignocellulose decomposition, we focused on CAZymes and other secreted proteins. In total, 122 CAZymes showed at least a two-fold change in mRNA abundance, and 97 of those were highly induced by cellulose. Compared to the well-characterized cellulases and hemicellulases, a majority of the other upregulated CAZymes showed lower transcriptional levels. In addition, 64 secreted proteins, including oxidoreductases, exhibited at least two-fold upregulation on cellulose medium. To better understand the potential roles of low-abundance CAZymes in cellulose breakdown, we compared the expression patterns of 25 glycoside hydrolase genes under different conditions via real-time PCR. Substantial differences for the 25 genes were observed for individual strains grown on different carbon sources, and between QM9414 and RUTC30 when grown on the same carbon source. Moreover, we identified 3 genes that are coregulated with known cellulases. Collectively, this study highlights a comprehensive transcriptional profile for biomass degradation-related proteins and provides a first step toward the identification of candidates to construct optimized enzyme cocktails.

Signal amplification via cation exchange reaction: an example in the ratiometric fluorescence probe for ultrasensitive and selective sensing of Cu(II).

Cation-exchange reaction was applied to transform internal chemical input between luminescent CdTe nanorods and metal-bound organic dyes Calcein Blue into fluorescence signal output with amplified response, which provided ultrasensitive and highly selective detection of Cu(II) ions.

Barrier height of free energy on confined polymer translocation through a short nano-channel.

The translocation of a confined polymer chain through a nano-channel has been simulated by using two-dimensional bond fluctuation model (BFM) with Monte Carlo dynamics. It is found that the trapping time for the polymer chain to overcome the free energy barrier during the translocation, tautrap, depends exponentially on the chain length N and the channel length M, respectively. The results suggest that the barrier height of free energy depends linearly on N and M, which is different from that predicted for the Gaussian chain.