Xu Z, Lin D, Yin H
… +16 more, Feng Q, Foglia F, Zhen Y, Morris A, Berrod Q, Pang M, Huang L, Liu J, Tian J, Wang X, Yang C, Tang X, Zhang X, Wang B, Wang H, Liu K
Nanoporous anion-conducting membranes have gained considerable interest for their potential to reduce resistance in electrochemical devices. Current pore-forming methods, such as backbone engineering through polymers of...Nanoporous anion-conducting membranes have gained considerable interest for their potential to reduce resistance in electrochemical devices. Current pore-forming methods, such as backbone engineering through polymers of intrinsic microporosity or covalent organic and metal-organic frameworks, however, suffer from limited structural control, mechanical fragility or demanding synthesis. Here we establish a supramolecular strategy that overcomes these limitations by constructing uniform, dynamic nanopores. Co-assembly of the rigid macrocyclic host cucurbit[7]uril with the cationic polymer guest quaternized poly(piperidinium-terphenyl) yields a robust network of nanometre-scale channels while simultaneously enhancing mechanical and chemical stability. The dynamic host-guest interactions allow the pore structure to fluctuate on picosecond and angstrom scales. This transient environment supports low-friction hydroxide migration through a Grotthuss mechanism, producing a marked enhancement in ionic conductivity. This bottom-up design principle provides a versatile new tool for molecularly engineering transport pathways and promises to advance electrochemical reactors with respect to energy efficiency, operational stability and the production of high-purity products.
In an iconic experiment in 1924, Hilde Mangold and Hans Spemann established that the dorsal blastopore lip of amphibian embryos functions as an organizer and induces a secondary body axis when transplanted into a host em...In an iconic experiment in 1924, Hilde Mangold and Hans Spemann established that the dorsal blastopore lip of amphibian embryos functions as an organizer and induces a secondary body axis when transplanted into a host embryo. This discovery demonstrated that specific embryonic regions can regulate embryonic patterning and lead to the establishment of an entire body axis. Subsequent studies have revealed that cnidarians, the sister group to Bilateria, also possess a blastoporal embryonic organizer. However, the evolutionary origin of the organizer remains unclear. Here we report that the blastopore lip of the ctenophore Mnemiopsis leidyi, a member of the evolutionary sister group to all other metazoans, exhibits organizer activity. We show that transplanted fragments of blastopore lip tissue from M. leidyi gastrula induce secondary pharynx and mouth formation. Moreover, transphyletic transplantation experiments show that the blastopore lip of M. leidyi leads to the generation of a secondary body axis in embryos of the cnidarian Nematostella vectensis. Organizer function in M. leidyi requires both β-catenin and TGFβ signalling, and the TGFβ-family ligands probably provide this inductive capacity. These findings reveal the deep homology of the blastoporal organizer in ctenophores, cnidarians and vertebrates, implying the ancestral organizer role of the blastopore lip. We propose that the emergence of the organizer was an essential innovation that facilitated the change from the temporal cell differentiation of unicellular relatives to the spatial cell differentiation of the first multicellular embryo.
Bugai A, Hohmann U, Lorenzo A
… +13 more, Graf M, Fin L, Rouvière JO, Tirian L, Dou Y, Le Rest M, Polák P, Johnsen D, Jakobsen L, Andersen JS, Brennecke J, Plaschka C, Jensen TH
Eukaryotic genomes generate a plethora of polyadenylated (pA) RNAs, which are packaged into ribonucleoprotein particles (RNPs). To ensure faithful gene expression, functional pA RNPs, including protein-coding RNPs, are e...Eukaryotic genomes generate a plethora of polyadenylated (pA) RNAs, which are packaged into ribonucleoprotein particles (RNPs). To ensure faithful gene expression, functional pA RNPs, including protein-coding RNPs, are exported to the cytoplasm, whereas transcripts within non-functional pA RNPs are degraded in the nucleus. How cells distinguish these opposing fates remains unknown. The DExD-box ATPase UAP56 (also known as DDX39B) is a central component of functional pA RNPs, and promotes their docking to the nuclear pore complex-anchored TREX-2, which triggers transcript release from UAP56 to facilitate export. Here we reveal that the poly(A) tail exosome targeting (PAXT) connection binds a TREX-2-like module, which releases pA RNAs from UAP56 for decay by the nuclear exosome. The core of this module consists of a LENG8-PCID2-SEM1 trimer, which we show is structurally and biochemically equivalent to the central GANP-PCID2-SEM1 trimer of TREX-2. Mutagenesis and transcriptomic data demonstrate that the nuclear fate of pA RNPs is governed by the contending actions of nucleoplasmic PAXT and nuclear pore complex-associated TREX-2, which interpret RNA-bound UAP56 as a signal for RNA decay or export, respectively. As RNA targets of PAXT are generally short and intron-poor, we propose an overall model for pA RNP fate determination whereby the distinct sub-nuclear localizations of PAXT and TREX-2 govern the degradation of short non-functional pA RNAs while allowing export of their longer and functional counterparts.
Despite large uncertainties associated with future mass loss from the Antarctic Ice Sheet, ice-sheet models show that the rate of sea-level rise from Antarctic ice loss in 2025 is strongly predictive of the rate for the...Despite large uncertainties associated with future mass loss from the Antarctic Ice Sheet, ice-sheet models show that the rate of sea-level rise from Antarctic ice loss in 2025 is strongly predictive of the rate for the next several decades, regardless of emission pathway or model complexity. This finding is robust across all models that were considered in the Intergovernmental Panel on Climate Change Sixth Assessment Report global mean sea-level projections, including the low-likelihood, high-impact scenarios of sea-level rise. Given this strong near-term decadal predictability, ice-sheet models that can accurately reproduce present-day ice-mass loss provide a reliable basis for near-term sea-level planning and adaptation through to mid-century. The predictability breaks down by the end of the twenty-first century as feedbacks, such as those related to marine ice-sheet retreat, begin to emerge, leading to accelerating ice loss. Drawing on these results, we identify key feedback mechanisms that can account for the transition between near-term decadal predictability and the longer-term, feedback-driven evolution, and suggest priorities for ice-sheet model development aimed at resolving long-term sea-level rise uncertainty.