Developing high activity and low price catalysts for the oxygen reduction reaction (ORR) is of critical importance for the commercial application of polymer electrolyte membrane fuel cells. On the basis of density functional theory, the catalytic activity of π-conjugated metal bis­(dithiolene) complex nanosheets (MC4S4, where M denotes Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt) for the ORR has been investigated systematically. It is found that the ORR activity of MC4S4 is sensitive to the selection of the central metal atom. The adsorption energies of ORR intermediates on MC4S4 decrease as the central atom varies from group 8 to group 10. The free energy change of the rate-determining step in the ORR increases in the order of IrC4S4 < CoC4S4 ≈ RhC4S4 < FeC4S4 < PdC4S4 ≈ PtC4S4 < NiC4S4 < RuC4S4 < OsC4S4. Due to the optimal adsorption properties, the IrC4S4 nanosheet shows the best ORR catalytic activity among the nine studied MC4S4 nanosheets. The free energy change of the rate-determining step in the ORR at high electrode potential follows an inverted volcano curve as a function of the adsorption strength of OH. This work may open new avenues for the development of high-performance ORR catalysts.

Background Polyadenylation plays a key role in producing mature mRNAs in eukaryotes. It is widely believed that the poly(A)-binding proteins (PABs) uniformly bind to poly(A)-tailed mRNAs, regulating their stability and translational efficiency. Results We observe that the homozygous triple mutant of broadly expressed Arabidopsis thaliana PABs, AtPAB2, AtPAB4, and AtPAB8, is embryonic lethal. To understand the molecular basis, we characterize the RNA-binding landscape of these PABs. The AtPAB-binding efficiency varies over one order of magnitude among genes. To identify the sequences accounting for the variation, we perform poly(A)-seq that directly sequences the full-length poly(A) tails. More than 10% of poly(A) tails contain at least one guanosine (G); among them, the G-content varies from 0.8 to 28%. These guanosines frequently divide poly(A) tails into interspersed A-tracts and therefore cause the variation in the AtPAB-binding efficiency among genes. Ribo-seq and genome-wide RNA stability assays show that AtPAB-binding efficiency of a gene is positively correlated with translational efficiency rather than mRNA stability. Consistently, genes with stronger AtPAB binding exhibit a greater reduction in translational efficiency when AtPAB is depleted. Conclusions Our study provides a new mechanism that translational efficiency of a gene can be regulated through the G-content-dependent PAB binding, paving the way for a better understanding of poly(A) tail-associated regulation of gene expression. Electronic supplementary material The online version of this article (10.1186/s13059-019-1799-8) contains supplementary material, which is available to authorized users.

The large-scale practical application of fuel cells cannot come true if the high-priced Pt-based electrocatalysts for oxygen reduction reaction (ORR) cannot be replaced by other efficient, low-cost, and stable electrodes. Here, based on density functional theory (DFT), we exploited the potentials of layered SiC sheets as a novel catalyst for ORR. From our DFT results, it can be predicted that layered SiC sheets exhibit excellent ORR catalytic activity without CO poisoning, while the CO poisoning is the major drawback in conventional Pt-based catalysts. Furthermore, the layered SiC sheets in alkaline media has better catalytic activity than Pt(111) surface and have potential as a metal-free catalyst for ORR in fuel cells.

For the goal of practical industrial development of fuel cells, inexpensive, sustainable, and highly efficient electrocatalysts for oxygen reduction reactions (ORR) are highly desirable alternatives to platinum (Pt) and other rare metals. In this work, based on density functional theory, silicon (Si)-doped carbon nanotubes (CNTs) and graphene as metal-free, low cost, and high-performance electrocatalysts for ORR are studied systematically. It is found that the curvature effect plays an important role in the adsorption and reduction of oxygen. The adsorption of O2 becomes weaker as the curvature varies from positive values (outside CNTs) to negative values (inside CNTs). The free energy change of the rate-determining step of ORR on the concave inner surface of Si-doped CNTs is smaller than that on the counterpart of Si-doped graphene, while that on the convex outer surface of Si-doped CNTs is larger than that on Si-doped graphene. Uncovering this new ORR mechanism on silicon-doped carbon electrodes is significant as the same principle could be applied to the development of various other metal-free efficient ORR catalysts for fuel cell applications.

The catalytic activity of the conversion of CH4 and CO2 on zinc modified H-ZSM-5 is strongly dependent on the structure of the active sites.

PADI4 post-translationally converts peptidylarginine to citrulline. PADI4 can disrupt the apoptotic process via the citrullination of histone H3 in the promoter of p53-target genes. The current study focused on PADI4 expression in various subtypes of oesophageal carcinoma (EC) by immunohistochemistry, western blotting and real time PCR. The study also investigated the effect of bile acid deoxycholate (DCA) on PADI4 expression in Eca-109 cells that originated from EC. Apoptosis and DCA-induced toxicity were analyzed by TUNEL, MTT assay and flow cytometry. Additionally, the present study investigated the correlation between single nucleotide polymorphism (SNP) in PADI4 gene and EC risk in Chinese population using Illumina GoldenGate assay. Compared with paraneoplastic tissues, the transcriptional and translational levels of PADI4 were significantly elevated in oesophageal squamous cell carcinoma (ESCC, n=9) and oesophageal adenocarcinoma (EAC, n=5) tissues. Immunolabeling detected expression of PADI4 in ESCC tissues (98.56%, n=139), EAC samples (87.5%, n=16) and oesophageal small cell undifferentiated carcinoma (91.7%, n=12) but not in normal tissues (0%, n=16). Furthermore, PADI4 levels is positively correlated with the pathological classification of ESCC (p=0.009). PADI4 expression levels were consistent with the number of apoptotic cells in the induced Eca-109 cells. rs10437048 [OR= 0.012831; 95% CI, 0.001746~0.094278; p=1.556×10-12] were significantly associated with decreased risk of EC, whereas rs41265997 [OR=12.7; 95% CI, 0.857077~33.207214; p=3.896×10-8] were significantly associated with increased risk of EC. rs41265997 in exon 3 of PADI4 gene is non-synonymous and converts ACG to ATG resulting in a threonine /methionine conversion at position 274 of the protein. Haplotypes GC that carries the variant alleles for rs2501796 and rs2477134 was significantly associated with increased risk of EC (frequency=0.085, p=0.0256, OR=2.7). The results suggest that PADI4 expression is related to the tumorigenic process of EC and the DCA-induced apoptosis. The PADI4 gene may be a valid EC susceptibility gene.

10 nm thick yttrium doped HfO2 (Y:HfO2) thin films are prepared on Si (100) substrates by the chemical solution deposition method using all‐inorganic aqueous salt precursors. The influence of the annealing process, consisting of annealing temperature, holding time, and heating rate, on the crystalline structure and ferroelectric properties of thin films is investigated. Results show that the crystalline structure and ferroelectric properties of films exhibit a strong annealing process dependence. The monoclinic phase and asymmetric orthorhombic phase coexist in the films. The annealing process of the best ferroelectric behavior is obtained by using annealing temperature at 700 °C for 30 s with a heating rate of 30 °C s−1 in N2 atmosphere. The film exhibits lowest m‐phase fraction of 17.9%, accompanied with the highest remanent polarization of 21.4 µC cm−2.

The adsorption strength of ORR intermediates, the reaction free energy of rate-determining step, and the overpotential increase with the increase of the size of N-doped graphene quantum dots.