Radical coupling of aryl halides to arenes facilitated by Ni(COD)(DQ) and other nickel sources

The air-stable complex Ni(COD)(DQ) (COD = 1,5-cyclooctadiene, DQ = duroquinone) promotes the coupling of aryl halides to arenes in the presence of KOtBu. This complex has recently been shown to perform coupling reactions based on organonickel intermediates, but in this case the coupling reactions proceed via aryl radicals as shown by our newly developed assay for aryl radicals. Coupling with this nickel source is more efficient than with Ni(COD)2, Ni(PPh3)4 and Ni(acac)2, all of which we also show to operate through aryl radical pathways

Barley Nodulin 26-like Intrinsic Protein permeates water, metalloids, saccharides, and ion pairs due to structural plasticity and diversification

OnlinePublAquaporins can facilitate the passive movement of water, small polar molecules and some ions. Here, we examined solute selectivity for the barley Nodulin 26-like Intrinsic Protein (HvNIP2;1) embedded in liposomes and examined through stopped-flow light scattering spectrophotometry and Xenopus laevis oocyte swelling assays. We found that HvNIP2;1 permeates water, boric and germanic acids, sucrose, and lactose but not d-glucose or d-fructose. Other saccharides, such as neutral (d-mannose, d-galactose, d-xylose, d-mannoheptaose) and charged (N-acetyl d-glucosamine, d-glucosamine, d-glucuronic acid) aldoses, disaccharides (cellobiose, gentiobiose, trehalose), trisaccharide raffinose, and urea, glycerol, and acyclic polyols were permeated to a much lower extent. We observed apparent permeation of hydrated KCl and MgSO4 ions, while CH3COONa and NaNO3 permeated at significantly lower rates. Our experiments with boric acid and sucrose revealed no apparent interaction between solutes when permeated together, and AgNO3 or H[AuCl4] blocked the permeation of all solutes. Docking of sucrose in HvNIP2;1 and spinach water-selective SoPIP2;1 aquaporins revealed the structural basis for sucrose permeation in HvNIP2;1 but not in SoPIP2;1, and defined key residues interacting with this permeant. In a biological context, sucrose transport could constitute a novel element of plant saccharide-transporting machinery. Phylogenomic analyses of 164 Viridiplantae and 2,993 Archaean, bacterial, fungal, and Metazoan aquaporins rationalized solute poly-selectivity in NIP3 sub-clade entries and suggested that they diversified from other sub-clades to acquire a unique specificity of saccharide transporters. Solute specificity definition in NIP aquaporins could inspire developing plants for food production.Akshayaa Venkataraghavan, Julian G. Schwerdt, Stephen D. Tyerman, Maria Hrmov

Potassium in the grape (Vitis vinifera L.) berry: transport and function

K⁺ is the most abundant cation in the grape berry. Here we focus on the most recent information in the long distance transport and partitioning of K⁺ within the grapevine and postulate on the potential role of K⁺ in berry sugar accumulation, berry water relations, cellular growth, disease resistance, abiotic stress tolerance and mitigating senescence. By integrating information from several different plant systems we have been able to generate new hypotheses on the integral functions of this predominant cation and to improve our understanding of how these functions contribute to grape berry growth and ripening. Valuable contributions to the study of K⁺ in membrane stabilization, turgor maintenance and phloem transport have allowed us to propose a mechanistic model for the role of this cation in grape berry development.Suzy Y. Rogiers, Zelmari A. Coetzee, Rob R. Walker, Alain Deloire and Stephen D. Tyerma

Facilitating return to work through early specialist health-based interventions (FRESH): protocol for a feasibility randomised controlled trial

Background Over one million people sustain traumatic brain injury each year in the UK and more than 10 % of these are moderate or severe injuries, resulting in cognitive and psychological problems that affect the ability to work. Returning to work is a primary rehabilitation goal but fewer than half of traumatic brain injury survivors achieve this. Work is a recognised health service outcome, yet UK service provision varies widely and there is little robust evidence to inform rehabilitation practice. A single-centre cohort comparison suggested better work outcomes may be achieved through early occupational therapy targeted at job retention. This study aims to determine whether this intervention can be delivered in three new trauma centres and to conduct a feasibility, randomised controlled trial to determine whether its effects and cost effectiveness can be measured to inform a definitive trial. Methods/design Mixed methods study, including feasibility randomised controlled trial, embedded qualitative studies and feasibility economic evaluation will recruit 102 people with traumatic brain injury and their nominated carers from three English UK National Health Service (NHS) trauma centres. Participants will be randomised to receive either usual NHS rehabilitation or usual rehabilitation plus early specialist traumatic brain injury vocational rehabilitation delivered by an occupational therapist. The primary objective is to assess the feasibility of conducting a definitive trial; secondary objectives include measurement of protocol integrity (inclusion/exclusion criteria, intervention adherence, reasons for non-adherence) recruitment rate, the proportion of eligible patients recruited, reasons for non-recruitment, spectrum of TBI severity, proportion of and reasons for loss to follow-up, completeness of data collection, gains in face-to-face Vs postal data collection and the most appropriate methods of measuring primary outcomes (return to work, retention) to determine the sample size for a larger trial. Discussion To our knowledge, this is the first feasibility randomised controlled trial of a vocational rehabilitation health intervention specific to traumatic brain injury. The results will inform the design of a definitive trial

Roles of Aquaporins in Setaria viridis Stem Development and Sugar Storage

Setaria viridis is a C4 grass used as a model for bioenergy feedstocks. The elongating internodes in developing S. viridis stems grow from an intercalary meristem at the base, and progress acropetally toward fully expanded cells that store sugar. During stem development and maturation, water flow is a driver of cell expansion and sugar delivery. As aquaporin proteins are implicated in regulating water flow, we analyzed elongating and mature internode transcriptomes to identify putative aquaporin encoding genes that had particularly high transcript levels during the distinct stages of internode cell expansion and maturation. We observed that SvPIP2;1 was highly expressed in internode regions undergoing cell expansion, and SvNIP2;2 was highly expressed in mature sugar accumulating regions. Gene co-expression analysis revealed SvNIP2;2 expression was highly correlated with the expression of five putative sugar transporters expressed in the S. viridis internode. To explore the function of the proteins encoded by SvPIP2;1 and SvNIP2;2, we expressed them in Xenopus laevis oocytes and tested their permeability to water. SvPIP2;1 and SvNIP2;2 functioned as water channels in X. laevis oocytes and their permeability was gated by pH. Our results indicate that SvPIP2;1 may function as a water channel in developing stems undergoing cell expansion and SvNIP2;2 is a candidate for retrieving water and possibly a yet to be determined solute from mature internodes. Future research will investigate whether changing the function of these proteins influences stem growth and sugar yield in S. viridis

GABA signalling modulates plant growth by directly regulating the activity of plant-specific anion transporters

The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.Australian Research Council; Waite Research Institute grants: (FT130100709, DP130104205, CE140100008); Fundação para a Ciência e Tecnologia grant: (PTDC/BEX-BCM/0376/2012); University of Maryland.info:eu-repo/semantics/publishedVersio

Picrotoxin Delineates Different Transport Configurations for Malate and gamma Aminobutyric Acid through TaALMT1

Plant-derived pharmacological agents have been used extensively to dissect the structure– function relationships of mammalian GABA receptors and ion channels. Picrotoxin is a noncompetitive antagonist of mammalian GABAA receptors. Here, we report that picrotoxin inhibits the anion (malate) efflux mediated by wheat (Triticum aestivum) ALMT1 but has no effect on GABA transport. The EC50 for inhibition was 0.14 nM and 0.18 nM when the ALMTs were expressed in tobacco BY2 cells and in Xenopus oocytes, respectively. Patch clamping of the oocyte plasma membrane expressing wheat ALMT1 showed that picrotoxin inhibited malate currents from both sides of the membrane. These results demonstrate that picrotoxin inhibits anion efflux effectively and can be used as a new inhibitor to study the ion fluxes mediated by ALMT proteins that allow either GABA or anion transport.Sunita A. Ramesh, Yu Long, Abolfazl Dashtbani-Roozbehani, Matthew Gilliham, Melissa H. Brown, and Stephen D. Tyerma

Arabidopsis plasma membrane intrinsic protein (AtPIP2;1) is implicated in a salinity conditional influence on seed germination

Published Online 6/6/2023 OnlinePublDynamic changes in aquaporin gene expression occur during seed germination. One example is the ~30-fold increase in Arabidopsis thaliana PIP2;1 transcripts within 24 h of seed imbibition. To investigate whether AtPIP2;1 can influence seed germination wild-type Columbia-0, single (Atpip2;1) and double (Atpip2;1-Atpip2;2) loss-of-function mutants, along with transgenic 2x35S::AtPIP2;1 over-expressing (OE) lines and null-segregant controls, were examined. The various genotypes were germinated in control and saline (75 mM NaCl treatment) conditions and tested for germination efficiency, imbibed seed maximum cross sectional (MCS) area, imbibed seed mass, and seed Na+ and K+ content. Seed lacking functional AtPIP2;1 and/or AtPIP2;2 proteins or constitutively over-expressing AtPIP2;1, had delayed germination in saline conditions relative to wild-type and null-segregant seed, respectively. Exposure to saline germination conditions resulted in Atpip2;1 mutants having greater imbibed seed mass and less accumulated Na+ than wild-type, whereas lines over-expressing AtPIP2;1 had reduced imbibed seed mass and greater seed K+ content than null-segregant control seed. The results imply a role for AtPIP2;1 in seed germination processes, whether directly through its capacity for water and ion transport or H2O2 signalling, or indirectly through potentially triggering dynamic differential regulation of other aquaporins expressed during germination. Future research will aid in dissecting the aquaporin functions influencing germination and may lead to novel solutions for optimising germination in sub-optimal conditions, such as saline soils.Phan Thi Thanh Hoai, Jiaen Qiu, Michael Groszmann, Annamaria De Rosa, Stephen D. Tyerman and Caitlin S. Byr

An assay for aryl radicals using BHAS coupling

Aryl radicals are intermediates in many reactions, but determining their presence unambiguously is often challenging. As we recently reported, reaction of 2-iodo-1,3-dimethylbenzene (7) in benzene with KOtBu and a suitable organic additive, leads to a base-induced homolytic aromatic substitution (BHAS) coupling reaction giving 2,6-dimethylbiphenyl (12) and biphenyl (3) as coupled products, together with xylene (13). In this case, biphenyl arises from a radical translocation and is the major coupling product. This paper now quantitatively investigates that reaction, which shows a very similar ratio for 3 : 12 [ca. 4 : 1] when using different sources of radical initiation. Deuterium isotope studies provide detailed mechanistic support for the proposed mechanism; when carried out in C6D6 vs. C6H6, the reaction is characterised by a strong isotope effect for formation of 3-d10 vs. 3, but not for formation of 12-d5 vs. 12. These distinctive properties mean that the transformation can act as an assay for aryl radicals. An advantage of such a BHAS process is its sensitivity, since it involves a chain reaction that can amplify radical activity

UK experience of ofatumumab in recurrence of focal segmental glomerulosclerosis post-kidney transplant

Background: Steroid-resistant nephrotic syndrome (SRNS), commonly caused by focal segmental glomerulosclerosis (FSGS), is associated with progression to stage 5 chronic kidney disease, requirement for kidney replacement therapy and a risk of disease recurrence post-kidney transplantation. Ofatumumab (OFA) is a fully humanised monoclonal antibody to CD20, with similar mechanisms of action to rituximab (RTX). Methods: We report a case series of seven UK patients (five paediatric, two adult), all of whom developed FSGS recurrence after kidney transplantation and received OFA as part of their therapeutic intervention. All also received concomitant plasmapheresis. The 2-year outcome of these seven patients is reported, describing clinical course, kidney function and proteinuria. Results: Four patients (all paediatric) achieved complete urinary remission with minimal proteinuria 12 months post-treatment. Three of those four also had normal graft function. Two patients showed partial remission—brief improvement to non-nephrotic proteinuria (197 mg/mmol) in one patient, maintained improvement in kidney function (estimated glomerular filtration rate 76 ml/min/1.73 m2) in the other. One patient did not demonstrate any response. Conclusions: OFA may represent a useful addition to therapeutic options in the management of FSGS recurrence post-transplantation, including where RTX has shown no benefit. Concomitant plasmapheresis in all patients prevents any definitive conclusion that OFA was the beneficial intervention