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.