Cooling Induced Surface Reconstruction during Synthesis of High‐Ni Layered Oxides

Transition metal layered oxides have been the dominant cathodes in lithium‐ion batteries, and among them, high‐Ni ones (LiNi_xMn_yCo_zO₂; x ≥ 0.7) with greatly boosted capacity and reduced cost are of particular interest for large‐scale applications. The high Ni loading, on the other hand, raises the critical issues of surface instability and poor rate performance. The rational design of synthesis leading to layered LiNi_0.7Mn_0.15Co_0.15O₂ with greatly enhanced rate capability is demonstrated, by implementing a quenching process alternative to the general slow cooling. In situ synchrotron X‐ray diffraction, coupled with surface analysis, is applied to studies of the synthesis process, revealing cooling‐induced surface reconstruction involving Li₂CO₃ accumulation, formation of a Li‐deficient layer and Ni reduction at the particle surface. The reconstruction process occurs predominantly at high temperatures (above 350 °C) and is highly cooling‐rate dependent, implying that surface reconstruction can be suppressed through synthetic control, i.e., quenching to improve the surface stability and rate performance of the synthesized materials. These findings may provide guidance to rational synthesis of high‐Ni cathode materials.     

PPARgamma activation primes human monocytes into alternative M2 macrophages with anti-inflammatory properties

Th1 cytokines promote monocyte differentiation into proatherogenic M1 macrophages, while Th2 cytokines lead to an "alternative" anti-inflammatory M2 macrophage phenotype. Here we show that in human atherosclerotic lesions, the expression of M2 markers and PPARgamma, a nuclear receptor controlling macrophage inflammation, correlate positively. Moreover, PPARgamma activation primes primary human monocytes into M2 differentiation, resulting in a more pronounced anti-inflammatory activity in M1 macrophages. However, PPARgamma activation does not influence M2 marker expression in resting or M1 macrophages, nor does PPARgamma agonist treatment influence the expression of M2 markers in atherosclerotic lesions, indicating that only native monocytes can be primed by PPARgamma activation to an enhanced M2 phenotype. Furthermore, PPARgamma activation significantly increases expression of the M2 marker MR in circulating peripheral blood mononuclear cells. These data demonstrate that PPARgamma activation skews human monocytes toward an anti-inflammatory M2 phenotype.     

Yeast Lsm1p-7p/Pat1p deadenylation-dependent mRNA-decapping factors are required for brome mosaic virus genomic RNA translation

Previously, we used the ability of the higher eukaryotic positive-strand RNA virus brome mosaic virus (BMV) to replicate in yeast to show that the yeast LSM1 gene is required for recruiting BMV RNA from translation to replication. Here we extend this observation to show that Lsm1p and other components of the Lsm1p-Lsm7p/Pat1p deadenylation-dependent mRNA decapping complex were also required for translating BMV RNAs. Inhibition of BMV RNA translation was selective, with no effect on general cellular translation. We show that viral genomic RNAs suitable for RNA replication were already distinguished from nonreplication templates at translation, well before RNA recruitment to replication. Among mRNA turnover pathways, only factors specific for deadenylated mRNA decapping were required for BMV RNA translation. Dependence on these factors was not only a consequence of the nonpolyadenylated nature of BMV RNAs but also involved the combined effects of the viral 5' and 3' noncoding regions and 2a polymerase open reading frame. High-resolution sucrose density gradient analysis showed that, while mutating factors in the Lsm1p-7p/Pat1p complex completely inhibited viral RNA translation, the levels of viral RNA associated with ribosomes were only slightly reduced in mutant yeast. This polysome association was further verified by using a conditional allele of essential translation initiation factor PRT1, which markedly decreased polysome association of viral genomic RNA in the presence or absence of an LSM7 mutation. Together, these results show that a defective Lsm1p-7p/Pat1p complex inhibits BMV RNA translation primarily by stalling or slowing the elongation of ribosomes along the viral open reading frame. Thus, factors in the Lsm1p-7p/Pat1p complex function not only in mRNA decapping but also in translation, and both translation and recruitment of BMV RNAs to viral RNA replication are regulated by a cell pathway that transfers mRNAs from translation to degradation.     

The DEAD-box RNA helicase Ded1p affects and accumulates in Saccharomyces cerevisiae P-bodies

Recent results suggest that cytoplasmic mRNAs can form translationally repressed messenger ribonucleoprotein particles (mRNPs) capable of decapping and degradation, or accumulation into cytoplasmic processing bodies (P-bodies), which can function as sites of mRNA storage. The proteins that function in transitions between the translationally repressed mRNPs that accumulate in P-bodies and mRNPs engaged in translation are largely unknown. Herein, we demonstrate that the yeast translation initiation factor Ded1p can localize to P-bodies. Moreover, depletion of Ded1p leads to defects in P-body formation. Overexpression of Ded1p results in increased size and number of P-bodies and inhibition of growth in a manner partially suppressed by loss of Pat1p, Dhh1p, or Lsm1p. Mutations that inactivate the ATPase activity of Ded1p increase the overexpression growth inhibition of Ded1p and prevent Ded1p from localizing in P-bodies. Combined with earlier work showing Ded1p can have a positive effect on translation, these results suggest that Ded1p is a bifunctional protein that can affect both translation initiation and P-body formation.     

Scale-up of the adenovirus expression system for the production of recombinant protein in human 293S cells

Human 293S cells, a cell line adapted to suspension culture, were grown to 5×10⁶ cells/mL in batch with calcium-free DMEM. These cells, infected with new constructions of adenovirus vectors, yielded as much as 10 to 20% recombinant protein with respect to the total cellular protein content. Until recently, high specific productivity of recombinant protein was limited to low cell density infected cultures of no more than 5×10⁵ cells/mL. In this paper, we show with a model protein, Protein Tyrosine Phosphatase 1C how high product yield can be maintained at high cell densities of 2×10⁶ cells/mL by a medium replacement strategy. This allows the production of as much as 90 mg/L of active recombinant protein per culture volume. Analysis of key limiting/inhibiting medium components showed that glucose addition along with pH control can yield the same productivity as a medium replacement strategy at high cell density in calcium-free DMEM. Finally, the above results were reproduced in 3L bioreactor suspension culture thereby establishing the scalability of this expression system. The process we developed is used routinely with the same success for the production of various recombinant proteins and viruses.Abbreviations CFDMEM calcium-free DMEM - CS bovine calf serum - hpi hours post-infection - J+ enriched Joklik medium - MLP major late promoter - MOI multiplicity of infection (# of infectious viral particle/cell) - q specific consumption rate (mole/cell.h) - pfu plaque forming unit (# of infectious viral particle) - Y yield (g/E6 cells or mole/cell)     

Induction of acetoacetate decarboxylase in Clostridium acetobutylicum

Abstract Factors that may initiate the biosynthesis of acetoacetate decarboxylase were investigated in resting cells of Clostridium acetobutylicum . Linear acids from C₁ to C₄ were inducers, whereas branched acids and linear acids from C₅ to C₇ were not inducers of acetoacetate decarboxylase biosynthesis. Induction of acetoacetate decarboxylase was maximal at pH 4.8 in the presence of acid concentrations comparable with those found during fermentation. In growth conditions repression of acetoacetate decarboxylase biosynthesis was found. This fact explains that acetone production by Clostridium acetobutylicum occurs when growth slows down.     

Biosynthesis of very-long-chain polyunsaturated fatty acids in transgenic oilseeds: constraints on their accumulation

Omega6- and omega3-polyunsaturated C20 fatty acids represent important components of the human diet. A more regular consumption and an accordingly sustainable source of these compounds are highly desirable. In contrast with the very high levels to which industrial fatty acids have to be enriched in plant oils for competitive use as chemical feedstocks, much lower percentages of very-long-chain polyunsaturated fatty acids (VLCPUFA) in edible plant oils would satisfy nutritional requirements. Seed-specific expression in transgenic tobacco (Nicotiana tabacum) and linseed (Linum usitatissimum) of cDNAs encoding fatty acyl-desaturases and elongases, absent from all agronomically important plants, resulted in the very high accumulation of Delta6-desaturated C18 fatty acids and up to 5% of C20 polyunsaturated fatty acids, including arachidonic and eicosapentaenoic acid. Detailed lipid analyses of developing seeds from transgenic plants were interpretated as indicating that, after desaturation on phosphatidylcholine, Delta6-desaturated products are immediately channeled to the triacylglycerols and effectively bypass the acyl-CoA pool. Thus, the lack of available Delta6-desaturated acyl-CoA substrates in the acyl-CoA pool limits the synthesis of elongated C20 fatty acids and disrupts the alternating sequence of lipid-linked desaturations and acyl-CoA dependent elongations. As well as the successful production of VLCPUFA in transgenic oilseeds and the identification of constraints on their accumulation, our results indicate alternative strategies to circumvent this bottleneck.     

Boosting Superior Lithium Storage Performance of Alloy‐Based Anode Materials via Ultraconformal Sb Coating–Derived Favorable Solid‐Electrolyte Interphase

Alloy materials such as Si and Ge are attractive as high‐capacity anodes for rechargeable batteries, but such anodes undergo severe capacity degradation during discharge–charge processes. Compared to the over‐emphasized efforts on the electrode structure design to mitigate the volume changes, understanding and engineering of the solid‐electrolyte interphase (SEI) are significantly lacking. This work demonstrates that modifying the surface of alloy‐based anode materials by building an ultraconformal layer of Sb can significantly enhance their structural and interfacial stability during cycling. Combined experimental and theoretical studies consistently reveal that the ultraconformal Sb layer is dynamically converted to Li₃Sb during cycling, which can selectively adsorb and catalytically decompose electrolyte additives to form a robust, thin, and dense LiF‐dominated SEI, and simultaneously restrain the decomposition of electrolyte solvents. Hence, the Sb‐coated porous Ge electrode delivers much higher initial Coulombic efficiency of 85% and higher reversible capacity of 1046 mAh g^?1 after 200 cycles at 500 mA g^?1, compared to only 72% and 170 mAh g^?1 for bare porous Ge. The present finding has indicated that tailoring surface structures of electrode materials is an appealing approach to construct a robust SEI and achieve long‐term cycling stability for alloy‐based anode materials.