Manganese-catalyzed dehydrogenative synthesis of urea derivatives and polyureas

A.K. thanks the Leverhulme Trust for an early career fellowship (ECF-2019-161). M.B. wishes to thank the School of Chemistry and EaStCHEM for their support. A.E.O. gratefully acknowledges a fellowship from the Akwa Ibom State University (TETFund).Urea derivatives have significant applications in the synthesis of resin precursors, dyes, agrochemicals, and pharmaceutical drugs. Furthermore, polyureas are useful plastics with applications in coating, adhesive, and biomedical industries. However, the conventional methods for the synthesis of urea derivatives and polyureas involve toxic reagents such as (di)isocyanates, phosgene, CO, and azides. We present here the synthesis of (poly)ureas using much less toxic reagents─(di)amines and methanol─via a catalytic dehydrogenative coupling process. The reaction is catalyzed by a pincer complex of an earth-abundant metal, manganese, and liberates H2 gas, valuable by itself, as the only byproduct, making the overall process highly atom-economic. A broad variety of symmetrical and unsymmetrical urea derivatives and polyureas have been synthesized in moderate to quantitative yields using this catalytic protocol. Mechanistic insights have also been provided using experiments and DFT computation, suggesting that the reaction proceeds via an isocyanate intermediate.Publisher PDFPeer reviewe

An immunoglobulin Cκ-reactive single chain antibody fusion protein induces tolerance through receptor editing in a normal polyclonal immune system

Understanding immune tolerance mechanisms is a major goal of immunology research, but mechanistic studies have generally required the use of mouse models carrying untargeted or targeted antigen receptor transgenes, which distort lymphocyte development and therefore preclude analysis of a truly normal immune system. Here we demonstrate an advance in in vivo analysis of immune tolerance that overcomes these shortcomings. We show that custom superantigens generated by single chain antibody technology permit the study of tolerance in a normal, polyclonal immune system. In the present study we generated a membrane-tethered anti-Igκ–reactive single chain antibody chimeric gene and expressed it as a transgene in mice. B cell tolerance was directly characterized in the transgenic mice and in radiation bone marrow chimeras in which ligand-bearing mice served as recipients of nontransgenic cells. We find that the ubiquitously expressed, Igκ-reactive ligand induces efficient B cell tolerance primarily or exclusively by receptor editing. We also demonstrate the unique advantages of our model in the genetic and cellular analysis of immune tolerance

Enhanced photoluminescence and reduced dimensionality via vacancy ordering in a 10H halide perovskite

H.L. would like to thank the University of St. Andrews for financial support via a St. Leonard’s scholarship. The authors acknowledge facilities access made possible through support from the EPSRC Light Element Analysis facility Grant EP/T019298/1 and the EPSRC Strategic Equipment Resource Grant EP/R023751/1.Vacancy-ordered halide perovskites have received great interest in optoelectronic applications. In this work, we report the novel inorganic halide Cs10MnSb6Cl30 with a distinctive 10H (10-layer hexagonal) perovskite polytype structure with (hcccc)2 stacking. Cs10MnSb6Cl30 has 30% B-site vacancies ordered at both corner- and face-sharing sites, resulting in [MnSb6Cl30]10–n columns, i.e., a reduction of octahedral connectivity to 1D. This results in enhanced photoluminescence in comparison to the previously reported 25% vacancy-ordered 3C polytype Cs4MnSb2Cl12 with 2D connectivity. This demonstrates not only the existence of the 10H perovskite structure in halides but also demonstrates the degree of B-site deficiency and stacking sequence variation as a direction to tune the optical properties of perovskite polytypes via vacancy rearrangements.Publisher PDFPeer reviewe

Manganese catalysed dehydrogenative synthesis of polyureas from diformamide and diamines

Authors acknowledge the funding from UKRI Future Leaders Fellowship (MR/W007460/1). M.T. and J.C.T. thank the ERC Consolidator Grant (PROMOFS grant agreement 771575) for funding the research. ABN gratefully acknowledges funding from the EPSRC through grant numbers EP/L017008/1, EP/R023751/1 and EP/T019298/1.We report here the synthesis of polyureas from the dehydrogenative coupling of diamines and diformamides. The reaction is catalysed by a manganese pincer complex and releases H2 gas as the only by-product making the process atom-economic and sustainable. The reported method is greener in comparison to the current state-of-the-art production routes that involve diisocyanate and phosgene feedstock. We also report here the physical, morphological, and mechanical properties of synthesized polyureas. Based on our mechanistic studies, we suggest that the reaction proceeds via isocyanate intermediates formed by the manganese catalysed dehydrogenation of formamides.Publisher PDFPeer reviewe

Doing cold smarter

Cold has been much neglected in the energy debate. Governments are developing strategies and policies to green everything from electricity to transport to heat, but the energy and environmental impacts of cooling have so far been largely ignored. This is a serious oversight, since making things cold is energy intensive and can be highly polluting, and demand for cooling in all its forms is booming worldwide – especially in developing countries. According to one projection, by the end of this century global demand for air conditioning alone could consume the equivalent of half our worldwide electricity generation today – and most of the increase will come in developing markets. The ‘greening’ of cold is clearly an urgent global problem – but it may also offer Britain a massive business opportunity. Cold may have been ignored but is vitally important to many aspects of modern life. An effective cold chain, for example, is essential for tackling problems such as food waste, food security, water conservation and public health. Cooling is also critical for many less obvious but essential functions: data centres couldn’t operate without it, nor for example MRI scanners in medicine or superconductors in power electronics. Cooling also provides modern levels of comfort in hot countries – and can make the difference between some regions being habitable or not. At the same time, vast amounts of cold are wasted – for instance during the regasification of LNG – which could in principle be recycled to satisfy some of this demand and start to reduce the environmental damage caused by cooling. Such a system-level approach – which starts by asking what energy services we need, and what is the least damaging way to provide them, rather than accepting existing practices as a fait accompli – has recently been coined the ‘Cold Economy’. It is clear the Cold Economy could unleash a wide range of innovative clean cold technologies and provide energy resilience, economic growth and environmental benefits, but there is an urgent need to develop a system-level analysis of this problem and the potential solutions to inform both industry and policymakers. The Birmingham Policy Commission: Doing Cold Smarter was convened to start this work

Predicting plankton net community production in the Atlantic Ocean

We present, test and implement two contrasting models to predict euphotic zone net community production (NCP), which are based on 14C primary production (PO14CP) to NCP relationships over two latitudinal (ca. 30°S–45°N) transects traversing highly productive and oligotrophic provinces of the Atlantic Ocean (NADR, CNRY, BENG, NAST-E, ETRA and SATL, Longhurst et al., 1995 [An estimation of global primary production in the ocean from satellite radiometer data. Journal of Plankton Research 17, 1245–1271]). The two models include similar ranges of PO14CP and community structure, but differ in the relative influence of allochthonous organic matter in the oligotrophic provinces. Both models were used to predict NCP from PO14CP measurements obtained during 11 local and three seasonal studies in the Atlantic, Pacific and Indian Oceans, and from satellite-derived estimates of PO14CP. Comparison of these NCP predictions with concurrent in situ measurements and geochemical estimates of NCP showed that geographic and annual patterns of NCP can only be predicted when the relative trophic importance of local vs. distant processes is similar in both modeled and predicted ecosystems. The system-dependent ability of our models to predict NCP seasonality suggests that trophic-level dynamics are stronger than differences in hydrodynamic regime, taxonomic composition and phytoplankton growth. The regional differences in the predictive power of both models confirm the existence of biogeographic differences in the scale of trophic dynamics, which impede the use of a single generalized equation to estimate global marine plankton NCP. This paper shows the potential of a systematic empirical approach to predict plankton NCP from local and satellite-derived P estimates

Lesson from the Stoichiometry Determination of the Cohesin Complex: A Short Protease Mediated Elution Increases the Recovery from Cross-Linked Antibody-Conjugated Beads

Affinity purification of proteins using antibodies coupled to beads and subsequent mass spectrometric analysis has become a standard technique for the identification of protein complexes. With the recent transfer of the isotope dilution mass spectrometry principle (IDMS) to the field of proteomics, quantitative analysesssuch as the stoichiometry determination of protein complexesshave become achievable. Traditionally proteins were eluted from antibody-conjugated beads using glycine at low pH or using diluted acids such as HCl, TFA, or FA, but elution was often found to be incomplete. Using the cohesin complex and the anaphase promoting complex/cyclosome (APC/C) as examples, we show that a short 15-60 min predigestion with a protease such as LysC (modified on-bead digest termed protease elution) increases the elution efficiency 2- to 3-fold compared to standard acid elution protocols. While longer incubation periodssas performed in standard on-bead digestionsled to partial proteolysis of the cross-linked antibodies, no or only insignificant cleavage was observed after 15-60 min protease mediated elution. Using the protease elution method, we successfully determined the stoichiometry of the cohesin complex by absolute quantification of the four core subunits using LC-SRM analysis and 19 reference peptides generated with the EtEP strategy. Protease elution was 3-fold more efficient compared to HCl elution, but measurements using both elution techniques are in agreement with