Cdc20 is an essential cell-cycle regulator required for the completion of mitosis in organisms from yeast to man and contains at its C terminus a WD40 repeat domain that mediates protein-protein ...interactions. In mitosis, Cdc20 binds to and activates the ubiquitin ligase activity of a large molecular machine called the anaphase-promoting complex/cyclosome (APC/C) and enables the ubiquitination and degradation of securin and cyclin B, thus promoting the onset of anaphase and mitotic exit. APC/C
Cdc20 is temporally and spatially regulated during the somatic and embryonic cell cycle by numerous mechanisms, including the spindle checkpoint and the cytostatic factor (CSF). Therefore, Cdc20 serves as an integrator of multiple intracellular signaling cascades that regulate progression through mitosis. This review summarizes recent progress toward the understanding of the functions of Cdc20, the mechanisms by which it activates APC/C, and its regulation by phosphorylation and by association with its binding proteins.
Photocatalytic production of H2O2 from the reduction of O2 by semiconductor photocatalysts (e.g., graphitic carbon nitride, C3N4) has been regarded as an alternative for small-scale decentralized ...H2O2 production. However, the efficiency of pristine C3N4 photocatalysts is still limited by the narrow light absorption range and rapid charge recombination. Here, we presented a facile approach to simultaneously enhance the light absorption and promote the charge separation by introducing alkali metal dopants and N vacancies on C3N4. The introduction of alkali metal dopants and N vacancies successfully broadened the light absorption range, reduced the band gap from 2.85 to 2.63 eV, and greatly inhibited the charge recombination. The synergistic effect of doping and defect resulted in the improvement of photocatalytic performance with a H2O2 production rate of 10.2 mmol/h/g, which is 89.5 times that of pristine C3N4. Thus, this work not only gives insights into the synergistic effect of doping and defect for simultaneously manipulating the light absorption and charge separation processes but also inspires further work to develop more efficient photocatalysts for H2O2 production.
Electrochemical reduction of CO2 is an attractive technique for reducing CO2 emission and converting it into useful chemicals, but it suffers from high overpotential, low efficiency or poor product ...selectivity. Here, N-doped nanodiamond/Si rod array (NDD/Si RA) was proposed as an efficient nonmetallic electrocatalyst for CO2 reduction. It preferentially and rapidly converted CO2 to acetate over formate with an onset potential of −0.36 V (vs RHE), overcoming the usual limitation of low selectivity for C2 products. Moreover, faradic efficiency of 91.2–91.8% has been achieved for CO2 reduction at −0.8 to −1.0 V. Its superior performance for CO2 reduction can be attributed to its high overpotential for hydrogen evolution and N doping, where N-sp3C species was highly active for CO2 reduction. Electrokinetic data and in situ infrared spectrum revealed the main pathway for CO2 reduction might be CO2 → CO2 •– → (COO)2 • → CH3COO–.
Cohesin is a chromosome-bound, multisubunit adenosine triphosphatase complex. After loading onto chromosomes, it generates loops to regulate chromosome functions. It has been suggested that cohesin ...organizes the genome through loop extrusion, but direct evidence is lacking. Here, we used single-molecule imaging to show that the recombinant human cohesin-NIPBL complex compacts both naked and nucleosome-bound DNA by extruding DNA loops. DNA compaction by cohesin requires adenosine triphosphate (ATP) hydrolysis and is force sensitive. This compaction is processive over tens of kilobases at an average rate of 0.5 kilobases per second. Compaction of double-tethered DNA suggests that a cohesin dimer extrudes DNA loops bidirectionally. Our results establish cohesin-NIPBL as an ATP-driven molecular machine capable of loop extrusion.
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•MIL-88B-Fe exhibited high catalytic activity and stability in Fenton-like processes.•Coordinatively unsaturated irons were the active sites of MIL-88B-Fe.•Contact of H2O2 with the ...active sites was necessary for the Fenton-like reaction.•Enhanced Fe(III)/Fe(II) redox cycle of MIL-88B-Fe contributed to its high catalytic activity.
The Fenton reaction is an efficient technology for degrading refractory organic pollutants in water. Heterogeneous Fenton-like catalysts have been demonstrated to be promising alternatives to homogeneous catalysts because of their reusability and lack of sludge production. These catalysts, however, generally show low activity for generating OH due to their limited exposed active sites and difficulty in the reduction of Fe(III) to Fe(II). Here, enhanced catalytic performance was achieved by using an iron-based metal organic framework (MIL-88B-Fe) as a heterogeneous Fenton-like catalyst over a wide pH range (4–6). The catalytic activity of MIL-88B-Fe was about 1–3 orders of magnitude higher than that of three other conventional catalysts (Fe2O3, α-FeOOH, and Fe3O4) and two other iron-based MOFs (MIL-53-Fe and MIL-101-Fe). The superior activity of MIL-88B-Fe could originate from the abundance of active sites, the flexible structure, and facilitated reduction of Fe(III) to Fe(II). Hydroxyl radicals generated from reaction between MIL-88B-Fe and H2O2 were the main reactive oxidative species for phenol degradation.
During mitosis, the spindle checkpoint senses kinetochores not properly attached to spindle microtubules and prevents precocious sister-chromatid separation and aneuploidy. The constitutive ...centromere-associated network (CCAN) at inner kinetochores anchors the KMN network consisting of Knl1, the Mis12 complex (Mis12C), and the Ndc80 complex (Ndc80C) at outer kinetochores. KMN is a critical kinetochore receptor for both microtubules and checkpoint proteins. Here, we show that nearly complete inactivation of KMN in human cells through multiple strategies produced strong checkpoint defects even when all kinetochores lacked microtubule attachment. These KMN-inactivating strategies reveal multiple KMN assembly mechanisms at human mitotic kinetochores. In one mechanism, the centromeric kinase Aurora B phosphorylates Mis12C and strengthens its binding to the CCAN subunit CENP-C. In another, CENP-T contributes to KMN attachment in a CENP-H-I-K-dependent manner. Our study provides insights into the mechanisms of mitosis-specific assembly of the checkpoint platform KMN at human kinetochores.
Electrochemical reduction of CO2 to chemical feedstocks is an attractive solution that prevents CO2 accumulation in the atmosphere, but it remains a great challenge to develop the cost-effective ...catalysts. Herein, we synthesized oxide-derived Cu/carbon (OD Cu/C) catalysts by a facile carbonization of Cu-based MOF (HKUST-1). The resulting materials exhibited highly selective CO2 reduction to alcohol compounds with total faradic efficiencies of 45.2–71.2% at −0.1 to −0.7 V versus reversible hydrogen electrode (RHE). High-yield methanol and ethanol has been achieved on OD Cu/C-1000 with the production rates of 5.1–12.4 and 3.7–13.4 mg L–1 h–1, respectively. Notably, the onset potential for C2H5OH formation is near −0.1 V (versus RHE), corresponding to ∼190 mV of overpotential, which is among the lowest overpotentials reported to date for the reduction of CO2 to C2H5OH. The improvements in activity and selectivity of the oxide-derived Cu/carbon might be attributed to the synergistic effect between the highly dispersed copper and the matrix of porous carbon. These findings provide a new insight into design of practical catalysts for decreasing atmospheric CO2 levels and synthesizing liquid fuels.
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•LaCo1-xMxO3 (M = Cu, Fe and Mn) perovskites were prepared via the sol-gel method.•Effects of different B-site substituted metal and metal content were studied.•LaCo0.4Cu0.6O3 showed ...highly efficient catalytic performance for PMS activation.•The cycle CoII/CoIII, CuI/CuII and O2−/O2 are responsible for PMS activation.
Recently cobalt-based heterogeneous catalysts have been widely investigated for peroxymonosulfate (PMS) activation in sulfate radical-based advanced oxidation processes. However, the improvement of the catalytic performance for PMS activation remains to be a challenge. As the limiting step, the rapid transformation of CoII/CoIII redox pairs is crucial for PMS activation. Perovskites attract increasing attention due to their controllable oxidation state of B-site metal and formation of oxygen vacancies, which accelerates the cycle of redox pairs. LaCo1-xMxO3 (M = Cu, Fe and Mn) perovskites as heterogeneous catalysts of PMS were synthesized for the degradation of phenol. The results showed that LaCo0.4Cu0.6O3 exhibited the highest catalytic activity. The pseudo first-order kinetic constant of phenol degradation on LaCo0.4Cu0.6O3 is 0.302 min−1, being about 5 times as high as Co2+ with same molar concentration of cobalt in LaCo0.4Cu0.6O3. XPS analysis confirmed that substitution of copper could promote the cycle of CoII/CoIII, thus enhance the catalytic efficiency for PMS activation. The facilitated cycle of CoII/CoIII played a crucial role in the generation of sulfate radicals, hydroxyl radicals and singlet oxygen. And sulfate radical was the primary radical responsible for pollutants degradation. The results provide insights into constructing novel perovskite catalysts for the removal of organic pollutants in water.
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•The F-doped hierarchically porous carbon (FPC) was synthesized by a facile method.•The F content and species was tuned to enhance H2O2 selectivity.•A high-yield electrosynthesis of ...H2O2 could be achieved on FPC.•Incorporation of covalent CF2, 3 into carbon materials was crucial to H2O2 synthesis.
Electrochemical synthesis of hydrogen peroxide (H2O2) via two-electron pathway of oxygen reduction reaction is a promising alternative to the current anthraquinone process. The H2O2 production from O2 is a competing reaction with four-electron O2 reduction to H2O, and the selectivity is related to the adsorption energy of the OOH intermediate on electrocatalysts surface. Generally, the properties for binding of OOH intermediate on catalysts can be controlled by changing its electronic structure. Herein, the electronic structure of porous carbon materials was tuned by doping different types and contents of fluorine species. The yield of H2O2 generation depended on the F content and the best catalytic activity toward H2O2 electrosynthesis was obtained with F content of 3.41 at.%. The resultant F-doped porous carbon (FPC) catalysts exhibited good H2O2 selectivity of 97.5–83.0% and the H2O2 production rate could reach 112.6–792.6 mmol h−1 g−1 over the potential range of 0.2 V to −0.3 vs. RHE (pH 1). The density functional theory (DFT) calculations and experiments revealed that the incorporation of CF2, 3 into carbon plane promotes the activation of O2 molecule and facilitates desorption of OOH intermediate, which was crucial to H2O2 synthesis.
As a ring-shaped adenosine triphosphatase (ATPase) machine, cohesin organizes the eukaryotic genome by extruding DNA loops and mediates sister chromatid cohesion by topologically entrapping DNA. How ...cohesin executes these fundamental DNA transactions is not understood. Using cryo-electron microscopy (cryo-EM), we determined the structure of human cohesin bound to its loader NIPBL and DNA at medium resolution. Cohesin and NIPBL interact extensively and together form a central tunnel to entrap a 72-base pair DNA. NIPBL and DNA promote the engagement of cohesin's ATPase head domains and ATP binding. The hinge domains of cohesin adopt an "open washer" conformation and dock onto the STAG1 subunit. Our structure explains the synergistic activation of cohesin by NIPBL and DNA and provides insight into DNA entrapment by cohesin.
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