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Rice and Saka injuries 'don't look good' - Arteta

Arsenal manager Mikel Arteta says that injuries to Bukayo Saka and Declan Rice "don't look good" after they came off against Chelsea.




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Dozens detained after protesters defy ban in Amsterdam

Pro-Palestinian demonstrators gathered following violence against Israeli football fans earlier in the week.




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'Disappointed but proud' - Arteta on Chelsea draw

Arsenal boss Mikel Arteta praises his side's performance against Chelsea in the Premier League, but says that getting results is "what is missing" at the moment.




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Beta 2 of iOS 18.2, MacOS Sequoia 15.2, & iPadOS 18.2 Available for Testing

The second beta versions of iOS 18.2, MacOS Sequoia 15.2, and iPadOS 18.2 are now available for users participating in the beta testing programs for Apple system software. The new betas continue to focus on additional Apple Intelligence features, expanding beyond the writing tools, smart replies, and summary features what was initially introduced in iOS ... Read More




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Beta 3 of iOS 18.2, iPadOS 18.2, MacOS Sequoia 15.2, Available for Testing

The third betas of iOS 18.2, iPadOS 18.2, and MacOS Sequoia 15.2, are available for beta testers of Apple system software. The latest betas continue to emphasize on new Apple Intelligence features, including ChatGPT integration, Genmoji custom Emoji creation, Image Playground for AI image generation, and more. These new AI features are in addition to ... Read More




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The full list of major US companies slashing staff this year, including Goldman Sachs, Meta, and Chegg

Companies have continued to cut jobs in 2024 after a wave of layoffs last year. Meta, Goldman Sachs, Google, and Tesla are among those shedding staff.





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Breaking: Republicans Retain Control Over House of Representatives, Handing Trump the Keys to His Agenda

Republicans have solidified their control of Washington by retaining control of the House of Representatives. President-elect Donald Trump’s overwhelming victory in the presidential race, coupled with GOP control of the […]

The post Breaking: Republicans Retain Control Over House of Representatives, Handing Trump the Keys to His Agenda appeared first on The Western Journal.




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Trump Makes His Pick for Secretary of the Department of Homeland Security Secretary: Report

In a surprise move that broke in the early hours of Tuesday morning, President-elect Donald Trump has reportedly picked South Dakota Gov. Kristi Noem as his nominee to head the […]

The post Trump Makes His Pick for Secretary of the Department of Homeland Security Secretary: Report appeared first on The Western Journal.




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Report Shows New Front-Runner for Trump's Press Secretary Spot: The Media Should Be Terrified

President-elect Donald Trump is reportedly considering lawyer Alina Habba to be the White House press secretary. Habba often spoke to the media while she was on the legal team representing […]

The post Report Shows New Front-Runner for Trump's Press Secretary Spot: The Media Should Be Terrified appeared first on The Western Journal.




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The West, a New Haven for the ‘Muslim Brotherhood’s Planetary Nebula’?

By SADF – Nov. 30, 2022 Online conversation on The West, a New Haven for the ‘Muslim Brotherhood’s Planetary Nebula’? On November the 29th at 16H.00 (CET), SADF promoted an online conversation in the web platform StreamYard titled ‘The West, a New Haven for the ‘Muslim Brotherhood’s Planetary Nebula’?’ The conversation included the Member of the European Parliament (EPP, […]




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Newsroom: Carvana Now Among Top 10 US Retailers by Ecommerce Sales

Carvana is America’s fastest-growing e-tailer   February 23, 2022 (New York, NY) – Americans have taken to buying cars online, so much so that ecommerce car dealer Carvana is now […]




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Analysis of {beta}-lactone formation by clinically observed carbapenemases informs on a novel antibiotic resistance mechanism [Enzymology]

An important mechanism of resistance to β-lactam antibiotics is via their β-lactamase–catalyzed hydrolysis. Recent work has shown that, in addition to the established hydrolysis products, the reaction of the class D nucleophilic serine β-lactamases (SBLs) with carbapenems also produces β-lactones. We report studies on the factors determining β-lactone formation by class D SBLs. We show that variations in hydrophobic residues at the active site of class D SBLs (i.e. Trp105, Val120, and Leu158, using OXA-48 numbering) impact on the relative levels of β-lactones and hydrolysis products formed. Some variants, i.e. the OXA-48 V120L and OXA-23 V128L variants, catalyze increased β-lactone formation compared with the WT enzymes. The results of kinetic and product studies reveal that variations of residues other than those directly involved in catalysis, including those arising from clinically observed mutations, can alter the reaction outcome of class D SBL catalysis. NMR studies show that some class D SBL variants catalyze formation of β-lactones from all clinically relevant carbapenems regardless of the presence or absence of a 1β-methyl substituent. Analysis of reported crystal structures for carbapenem-derived acyl-enzyme complexes reveals preferred conformations for hydrolysis and β-lactone formation. The observation of increased β-lactone formation by class D SBL variants, including the clinically observed carbapenemase OXA-48 V120L, supports the proposal that class D SBL-catalyzed rearrangement of β-lactams to β-lactones is important as a resistance mechanism.




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Mutation of an atypical oxirane oxyanion hole improves regioselectivity of the {alpha}/{beta}-fold epoxide hydrolase Alp1U [Enzymology]

Epoxide hydrolases (EHs) have been characterized and engineered as biocatalysts that convert epoxides to valuable chiral vicinal diol precursors of drugs and bioactive compounds. Nonetheless, the regioselectivity control of the epoxide ring opening by EHs remains challenging. Alp1U is an α/β-fold EH that exhibits poor regioselectivity in the epoxide hydrolysis of fluostatin C (compound 1) and produces a pair of stereoisomers. Herein, we established the absolute configuration of the two stereoisomeric products and determined the crystal structure of Alp1U. A Trp-186/Trp-187/Tyr-247 oxirane oxygen hole was identified in Alp1U that replaced the canonical Tyr/Tyr pair in α/β-EHs. Mutation of residues in the atypical oxirane oxygen hole of Alp1U improved the regioselectivity for epoxide hydrolysis on 1. The single site Y247F mutation led to highly regioselective (98%) attack at C-3 of 1, whereas the double mutation W187F/Y247F resulted in regioselective (94%) nucleophilic attack at C-2. Furthermore, single-crystal X-ray structures of the two regioselective Alp1U variants in complex with 1 were determined. These findings allowed insights into the reaction details of Alp1U and provided a new approach for engineering regioselective epoxide hydrolases.




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Allosteric activation of proto-oncogene kinase Src by GPCR-beta-arrestin complexes [Enzymology]

G protein–coupled receptors (GPCRs) initiate signaling cascades via G-proteins and beta-arrestins (βarr). βarr-dependent actions begin with recruitment of βarr to the phosphorylated receptor tail and are followed by engagement with the receptor core. βarrs are known to act as adaptor proteins binding receptors and various effectors, but it is unclear whether in addition to the scaffolding role βarrs can allosterically activate their downstream targets. Here we demonstrate the direct allosteric activation of proto-oncogene kinase Src by GPCR–βarr complexes in vitro and establish the conformational basis of the activation. Whereas free βarr1 had no effect on Src activity, βarr1 in complex with M2 muscarinic or β2-adrenergic receptors reconstituted in lipid nanodiscs activate Src by reducing the lag phase in Src autophosphorylation. Interestingly, receptor–βarr1 complexes formed with a βarr1 mutant, in which the finger-loop, required to interact with the receptor core, has been deleted, fully retain the ability to activate Src. Similarly, βarr1 in complex with only a phosphorylated C-terminal tail of the vasopressin 2 receptor activates Src as efficiently as GPCR–βarr complexes. In contrast, βarr1 and chimeric M2 receptor with nonphosphorylated C-terminal tail failed to activate Src. Taken together, these data demonstrate that the phosphorylated GPCR tail interaction with βarr1 is necessary and sufficient to empower it to allosterically activate Src. Our findings may have implications for understanding more broadly the mechanisms of allosteric activation of downstream targets by βarrs.




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Extending the Limits of Quantitative Proteome Profiling with Data-Independent Acquisition and Application to Acetaminophen-Treated Three-Dimensional Liver Microtissues

Roland Bruderer
May 1, 2015; 14:1400-1410
Research




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Interpretation of Shotgun Proteomic Data: The Protein Inference Problem

Alexey I. Nesvizhskii
Oct 1, 2005; 4:1419-1440
Tutorial




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A drug-resistant {beta}-lactamase variant changes the conformation of its active-site proton shuttle to alter substrate specificity and inhibitor potency [Microbiology]

Lys234 is one of the residues present in class A β-lactamases that is under selective pressure due to antibiotic use. Located adjacent to proton shuttle residue Ser130, it is suggested to play a role in proton transfer during catalysis of the antibiotics. The mechanism underpinning how substitutions in this position modulate inhibitor efficiency and substrate specificity leading to drug resistance is unclear. The K234R substitution identified in several inhibitor-resistant β-lactamase variants is associated with decreased potency of the inhibitor clavulanic acid, which is used in combination with amoxicillin to overcome β-lactamase–mediated antibiotic resistance. Here we show that for CTX-M-14 β-lactamase, whereas Lys234 is required for hydrolysis of cephalosporins such as cefotaxime, either lysine or arginine is sufficient for hydrolysis of ampicillin. Further, by determining the acylation and deacylation rates for cefotaxime hydrolysis, we show that both rates are fast, and neither is rate-limiting. The K234R substitution causes a 1500-fold decrease in the cefotaxime acylation rate but a 5-fold increase in kcat for ampicillin, suggesting that the K234R enzyme is a good penicillinase but a poor cephalosporinase due to slow acylation. Structural results suggest that the slow acylation by the K234R enzyme is due to a conformational change in Ser130, and this change also leads to decreased inhibition potency of clavulanic acid. Because other inhibitor resistance mutations also act through changes at Ser130 and such changes drastically reduce cephalosporin but not penicillin hydrolysis, we suggest that clavulanic acid paired with an oxyimino-cephalosporin rather than penicillin would impede the evolution of resistance.




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High temperature promotes amyloid {beta}-protein production and {gamma}-secretase complex formation via Hsp90 [Neurobiology]

Alzheimer's disease (AD) is characterized by neuronal loss and accumulation of β-amyloid-protein (Aβ) in the brain parenchyma. Sleep impairment is associated with AD and affects about 25–40% of patients in the mild-to-moderate stages of the disease. Sleep deprivation leads to increased Aβ production; however, its mechanism remains largely unknown. We hypothesized that the increase in core body temperature induced by sleep deprivation may promote Aβ production. Here, we report temperature-dependent regulation of Aβ production. We found that an increase in temperature, from 37 °C to 39 °C, significantly increased Aβ production in amyloid precursor protein-overexpressing cells. We also found that high temperature (39 °C) significantly increased the expression levels of heat shock protein 90 (Hsp90) and the C-terminal fragment of presenilin 1 (PS1-CTF) and promoted γ-secretase complex formation. Interestingly, Hsp90 was associated with the components of the premature γ-secretase complex, anterior pharynx-defective-1 (APH-1), and nicastrin (NCT) but was not associated with PS1-CTF or presenilin enhancer-2. Hsp90 knockdown abolished the increased level of Aβ production and the increased formation of the γ-secretase complex at high temperature in culture. Furthermore, with in vivo experiments, we observed increases in the levels of Hsp90, PS1-CTF, NCT, and the γ-secretase complex in the cortex of mice housed at higher room temperature (30 °C) compared with those housed at standard room temperature (23 °C). Our results suggest that high temperature regulates Aβ production by modulating γ-secretase complex formation through the binding of Hsp90 to NCT/APH-1.




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In conversation with Julien Harneis, UN Assistant Secretary-General

In conversation with Julien Harneis, UN Assistant Secretary-General 18 November 2024 — 2:30PM TO 3:30PM Anonymous (not verified) Chatham House and Online

In this discussion, Julien Harneis will give critical insights into the UN’s humanitarian response in Yemen and the importance of maintaining independent humanitarian assistance.

According to the United Nations, Yemen has faced the world’s worst humanitarian crisis in the last decade, with over 20 million people in need of assistance. Years of ongoing conflict have devastated infrastructure, displaced millions, and caused widespread food insecurity and health emergencies. Access to essential services remains a daily struggle, and the escalating economic collapse has left vulnerable communities facing critical shortages in food, water, and medical supplies.

However, humanitarian actors are continually facing challenges in delivering aid to Yemen due to security threats and supply chain barriers, highlighting the urgent need for coordinated and sustainable international assistance.

UN Assistant Secretary-General and Humanitarian Coordinator for Yemen, Julien Harneis, will provide an account of the humanitarian mission and evolving strategies in Yemen, the impact of regional conflicts in the delivery of aid and discuss other key questions including:

  • What are the priorities and goals of the UN’s current aid plan for Yemen, and how is it designed to reach those most in need?
  • How are recent developments in the Red Sea affecting food security, trade routes, and humanitarian access in Yemen?
  • What strategies are in place to ensure the delivery of humanitarian aid remains independent and neutral?

This is a ‘register interest’ event. Confirmations to successful applicants for in-person attendance will be sent on Thursday at 16.00 GMT. Virtual attendees will be granted access to the event.

The institute occupies a position of respect and trust, and is committed to fostering inclusive dialogue at all events. Event attendees are expected to uphold this by adhering to our code of conduct.

 

 




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A Conversation With: Steven T Mnuchin, Secretary, US Treasury




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Undercurrents: Episode 55 - Benjamin Netanyahu's Trial, and the Identity Politics of Eurovision




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Fish oils and plasma lipid and lipoprotein metabolism in humans: a critical review

WS Harris
Jun 1, 1989; 30:785-807
Reviews




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The role of short-chain fatty acids in the interplay between diet, gut microbiota, and host energy metabolism

Gijs den Besten
Sep 1, 2013; 54:2325-2340
Reviews




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Thematic review series: Brain Lipids. Cholesterol metabolism in the central nervous system during early development and in the mature animal

John M. Dietschy
Aug 1, 2004; 45:1375-1397
Thematic Reviews




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High density lipoprotein metabolism

S Eisenberg
Oct 1, 1984; 25:1017-1058
Reviews




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Thematic review series: The Pathogenesis of Atherosclerosis. Effects of infection and inflammation on lipid and lipoprotein metabolism mechanisms and consequences to the host

Weerapan Khovidhunkit
Jul 1, 2004; 45:1169-1196
Thematic Reviews




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Remnant lipoprotein metabolism: key pathways involving cell-surface heparan sulfate proteoglycans and apolipoprotein E

Robert W. Mahley
Jan 1, 1999; 40:1-16
Reviews




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Preparation of fatty acid methyl esters and dimethylacetals from lipids with boron fluoride--methanol

William R. Morrison
Oct 1, 1964; 5:600-608
Articles




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Lipoprotein lipase and lipolysis: central roles in lipoprotein metabolism and atherogenesis

IJ Goldberg
Apr 1, 1996; 37:693-707
Reviews




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Hepatocyte nuclear factor 1{beta} suppresses canonical Wnt signaling through transcriptional repression of lymphoid enhancer-binding factor 1 [Molecular Bases of Disease]

Hepatocyte nuclear factor-1β (HNF-1β) is a tissue-specific transcription factor that is required for normal kidney development and renal epithelial differentiation. Mutations of HNF-1β produce congenital kidney abnormalities and inherited renal tubulopathies. Here, we show that ablation of HNF-1β in mIMCD3 renal epithelial cells results in activation of β-catenin and increased expression of lymphoid enhancer–binding factor 1 (LEF1), a downstream effector in the canonical Wnt signaling pathway. Increased expression and nuclear localization of LEF1 are also observed in cystic kidneys from Hnf1b mutant mice. Expression of dominant-negative mutant HNF-1β in mIMCD3 cells produces hyperresponsiveness to exogenous Wnt ligands, which is inhibited by siRNA-mediated knockdown of Lef1. WT HNF-1β binds to two evolutionarily conserved sites located 94 and 30 kb from the mouse Lef1 promoter. Ablation of HNF-1β decreases H3K27 trimethylation repressive marks and increases β-catenin occupancy at a site 4 kb upstream to Lef1. Mechanistically, WT HNF-1β recruits the polycomb-repressive complex 2 that catalyzes H3K27 trimethylation. Deletion of the β-catenin–binding domain of LEF1 in HNF-1β–deficient cells abolishes the increase in Lef1 transcription and decreases the expression of downstream Wnt target genes. The canonical Wnt target gene, Axin2, is also a direct transcriptional target of HNF-1β through binding to negative regulatory elements in the gene promoter. These findings demonstrate that HNF-1β regulates canonical Wnt target genes through long-range effects on histone methylation at Wnt enhancers and reveal a new mode of active transcriptional repression by HNF-1β.





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Minerals and Metals for a Low-Carbon Future: Implications for Developing Countries

Minerals and Metals for a Low-Carbon Future: Implications for Developing Countries 30 October 2017 — 5:00PM TO 8:00PM Anonymous (not verified) 13 October 2017 Chatham House, London

This roundtable will explore two sides of minerals and metals for a low-carbon future - the growing demand for metals required for low-carbon technology and the technological and policy innovations that will be required to manage the carbon footprint of the mining sector and its wider energy and industrial linkages. Based around a presentation and scenarios developed by the World Bank, this roundtable discussion will assess which strategic metals will likely rise in demand in order to deliver a low-carbon future, before exploring the possible implications for resource-rich developing countries. In particular, what does a growing demand of minerals for a clean energy future mean for governments and industry, and how might developing countries benefit from this trend? What impact might growth of the mining sector have on a sustainable and climate-smart development? Can renewable energy and other clean tech innovations in the mining industry help reduce the carbon footprint of the sector and related industries, and under what circumstances? And how fit-for-purpose are current donor approaches to the mining sector in an increasingly carbon-constrained world?

Attendance at this event is by invitation only.




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Mining and the Circular Economy: Implications for the Minerals and Metals Industries

Mining and the Circular Economy: Implications for the Minerals and Metals Industries 6 November 2017 — 4:00PM TO 5:30PM Anonymous (not verified) 31 October 2017 Chatham House, London

The concept of the circular economy has climbed up the international agenda, promoted by China, the EU, and other major metals and minerals producers and consumers. International policy processes including the G7 and G20 have reaffirmed these commitments and have increasingly issued policy guidance on resource efficiency. Many of the core elements of the circular economy are familiar – including enhanced resource efficiency, recycling and the development of ‘secondary markets’. Others require new thinking, from the development of smart designs and systems that ensure ‘circularity’, to the creation of new business models and partnerships that aim to preserve the long-term value of metals and minerals.
At this roundtable, Professor Paul Ekins will discuss the implications of the transition from a linear system of production-use-disposal, to a more circular economy. Looking at current trends, to what extent is a ‘decoupling’ of metal and mineral resources and economic growth underway in OECD and developing economies? Across the value chain, which actors are leading the way in resource efficiency and circular economy approaches? And what are the potential implications for primary demand and for the mining and metals industries and major mining economies?
Attendance at this event is by invitation only.




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Visualizing the Data: The Evolution of Trade Tensions in Metals and Minerals Markets

Visualizing the Data: The Evolution of Trade Tensions in Metals and Minerals Markets 18 January 2018 — 4:30PM TO 6:00PM Anonymous (not verified) 19 December 2017 Chatham House, London

Over the past decade, producer countries such as South Africa, Zambia, Indonesia, the DRC and, most recently, Tanzania have restricted exports of unprocessed precious metals, copper, nickel, cobalt and other minerals in an attempt to support, or create, downstream processing industries and jobs or increase revenues. These moves have invariably created tensions with trading partners. Research suggests that export restrictions are not the best way to achieve such policy objectives and can instead harm the producer country’s economy and undermine the functioning of international metals and minerals.

Drawing on OECD and Chatham House research on resource trade, the speaker will present analysis and data visualizations exploring the drivers of past export restrictions and their political and economic impacts. They will also consider how the drivers of ‘resource nationalist measures’ are changing, whether and where export restrictions might present strategic and economic risks in the current context, and the extent to which producer and consumer governments and international governance mechanisms are prepared to address them.

Attendance at this event is by invitation only.




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A New Era for China: Implications for the Global Mining and Metals Industries

A New Era for China: Implications for the Global Mining and Metals Industries 18 June 2018 — 9:00AM TO 10:30AM Anonymous (not verified) 8 June 2018 Chatham House, London

Since the turn of the century, China’s demand for resources has dominated global headlines. It’s rapid demand growth through the early 2000s sparked the beginning of the commodities ‘super cycle’, and encouraged a growing Chinese presence in international mining, and in global metals and minerals markets. More recently, its transition toward the ‘new normal’ of slower but higher quality growth has underpinned the sudden slowdown in global commodities demand.

Drawing on China’s domestic ambitions, as set out in the 19th party congress, and on its wider strategic ambitions through the Belt and Road Initiative, the speaker will set out his thoughts on China’s next era of growth, and its likely implications for international mining investment and global metals and minerals markets.




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Mining, Minerals and Metals Expert Roundtable: Forest-Smart Mining Report Launch

Mining, Minerals and Metals Expert Roundtable: Forest-Smart Mining Report Launch 10 May 2019 — 5:30PM TO 6:30PM Anonymous (not verified) 12 April 2019 Chatham House | 10 St James's Square | London | SW1Y 4LE

The impact of mining on forests has received relatively limited attention at the global level despite its implications for climate change, biodiversity and the wider Sustainable Development Goals. Three new studies – commissioned by the World Bank and the Program on Forests (PROFOR) and delivered by a consortium including Fauna and Flora International, Levin Sources, Fairfields Sustainability Consulting and Swedish Geological AB – shed new light on the impact of mining on deforestation, current practices to protect forests in mining areas and how ‘forest-smart’ mining policies, practices and partnerships can be scaled-up and accelerated.
The report authors will introduce the key findings of the reports, as they relate to large-scale mining (LSM), artisanal and small-scale mining (ASM) and the implementation of biodiversity offset schemes, with a focus on landscape-level efforts that avoid or minimize adverse impacts on forests – and ideally result in a net gain for forest outcomes. The speakers will then set out policy and practical recommendations designed to support ‘forest-smart’ mining, conserve biodiversity and ensure a ‘well below 2c’ future, before opening up the discussion to participants.




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Describing Dryland Vegetation Patterns

Math is often described as the science of patterns, which makes it a natural subject to help in the study of the underlying causes of patterns found in nature, for example, bands of vegetation that often occur on gently sloped terrains in certain near-desert ecosystems worldwide. We are starting to learn more about these bands' common properties by using mathematical models built on data, such as rainfall totals and the curvature of the terrain. Mary Silber talks about these mathematical models of vegetation bands.




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Corgi Toys - Corgi Whizzwheels - Porsche 917 - Miniature Diecast Metal 1/43 Scale Model Motor Vehicle

firehouse.ie posted a photo:




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Corgi Toys - Corgi Whizzwheels - Porsche 917 - Miniature Diecast Metal 1/43 Scale Model Motor Vehicle

firehouse.ie posted a photo:




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Corgi Toys - Corgi Whizzwheels - Porsche 917 - Miniature Diecast Metal 1/43 Scale Model Motor Vehicle

firehouse.ie posted a photo:




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Tekno - The Irish Collection - Ref. 258 - Scania Articulated Truck - Glynns, Galway - Miniature Diecast Metal Scale Model Heavy Goods Vehicle

firehouse.ie posted a photo:




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Tekno - The Irish Collection - Ref. 258 - Scania Articulated Truck - Glynns, Galway - Miniature Diecast Metal Scale Model Heavy Goods Vehicle

firehouse.ie posted a photo:




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Trump says he will nominate anti-'woke' Fox News host Pete Hegseth for defense secretary




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Carnosine synthase deficiency is compatible with normal skeletal muscle and olfactory function but causes reduced olfactory sensitivity in aging mice [Developmental Biology]

Carnosine (β-alanyl-l-histidine) and anserine (β-alanyl-3-methyl-l-histidine) are abundant peptides in the nervous system and skeletal muscle of many vertebrates. Many in vitro and in vivo studies demonstrated that exogenously added carnosine can improve muscle contraction, has antioxidant activity, and can quench various reactive aldehydes. Some of these functions likely contribute to the proposed anti-aging activity of carnosine. However, the physiological role of carnosine and related histidine-containing dipeptides (HCDs) is not clear. In this study, we generated a mouse line deficient in carnosine synthase (Carns1). HCDs were undetectable in the primary olfactory system and skeletal muscle of Carns1-deficient mice. Skeletal muscle contraction in these mice, however, was unaltered, and there was no evidence for reduced pH-buffering capacity in the skeletal muscle. Olfactory tests did not reveal any deterioration in 8-month-old mice lacking carnosine. In contrast, aging (18–24-month-old) Carns1-deficient mice exhibited olfactory sensitivity impairments that correlated with an age-dependent reduction in the number of olfactory receptor neurons. Whereas we found no evidence for elevated levels of lipoxidation and glycation end products in the primary olfactory system, protein carbonylation was increased in the olfactory bulb of aged Carns1-deficient mice. Taken together, these results suggest that carnosine in the olfactory system is not essential for information processing in the olfactory signaling pathway but does have a role in the long-term protection of olfactory receptor neurons, possibly through its antioxidant activity.




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Peptidoglycan analysis reveals that synergistic deacetylase activity in vegetative Clostridium difficile impacts the host response [Glycobiology and Extracellular Matrices]

Clostridium difficile is an anaerobic and spore-forming bacterium responsible for 15–25% of postantibiotic diarrhea and 95% of pseudomembranous colitis. Peptidoglycan is a crucial element of the bacterial cell wall that is exposed to the host, making it an important target for the innate immune system. The C. difficile peptidoglycan is largely N-deacetylated on its glucosamine (93% of muropeptides) through the activity of enzymes known as N-deacetylases, and this N-deacetylation modulates host–pathogen interactions, such as resistance to the bacteriolytic activity of lysozyme, virulence, and host innate immune responses. C. difficile genome analysis showed that 12 genes potentially encode N-deacetylases; however, which of these N-deacetylases are involved in peptidoglycan N-deacetylation remains unknown. Here, we report the enzymes responsible for peptidoglycan N-deacetylation and their respective regulation. Through peptidoglycan analysis of several mutants, we found that the N-deacetylases PdaV and PgdA act in synergy. Together they are responsible for the high level of peptidoglycan N-deacetylation in C. difficile and the consequent resistance to lysozyme. We also characterized a third enzyme, PgdB, as a glucosamine N-deacetylase. However, its impact on N-deacetylation and lysozyme resistance is limited, and its physiological role remains to be dissected. Finally, given the influence of peptidoglycan N-deacetylation on host defense against pathogens, we investigated the virulence and colonization ability of the mutants. Unlike what has been shown in other pathogenic bacteria, a lack of N-deacetylation in C. difficile is not linked to a decrease in virulence.




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The cation diffusion facilitator protein MamM's cytoplasmic domain exhibits metal-type dependent binding modes and discriminates against Mn2+ [Molecular Biophysics]

Cation diffusion facilitator (CDF) proteins are a conserved family of divalent transition metal cation transporters. CDF proteins are usually composed of two domains: the transmembrane domain, in which the metal cations are transported through, and a regulatory cytoplasmic C-terminal domain (CTD). Each CDF protein transports either one specific metal or multiple metals from the cytoplasm, and it is not known whether the CTD takes an active regulatory role in metal recognition and discrimination during cation transport. Here, the model CDF protein MamM, an iron transporter from magnetotactic bacteria, was used to probe the role of the CTD in metal recognition and selectivity. Using a combination of biophysical and structural approaches, the binding of different metals to MamM CTD was characterized. Results reveal that different metals bind distinctively to MamM CTD in terms of their binding sites, thermodynamics, and binding-dependent conformations, both in crystal form and in solution, which suggests a varying level of functional discrimination between CDF domains. Furthermore, these results provide the first direct evidence that CDF CTDs play a role in metal selectivity. We demonstrate that MamM's CTD can discriminate against Mn2+, supporting its postulated role in preventing magnetite formation poisoning in magnetotactic bacteria via Mn2+ incorporation.




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Unique active-site and subsite features in the arabinogalactan-degrading GH43 exo-{beta}-1,3-galactanase from Phanerochaete chrysosporium [Enzymology]

Arabinogalactan proteins (AGPs) are plant proteoglycans with functions in growth and development. However, these functions are largely unexplored, mainly because of the complexity of the sugar moieties. These carbohydrate sequences are generally analyzed with the aid of glycoside hydrolases. The exo-β-1,3-galactanase is a glycoside hydrolase from the basidiomycete Phanerochaete chrysosporium (Pc1,3Gal43A), which specifically cleaves AGPs. However, its structure is not known in relation to its mechanism bypassing side chains. In this study, we solved the apo and liganded structures of Pc1,3Gal43A, which reveal a glycoside hydrolase family 43 subfamily 24 (GH43_sub24) catalytic domain together with a carbohydrate-binding module family 35 (CBM35) binding domain. GH43_sub24 is known to lack the catalytic base Asp conserved among other GH43 subfamilies. Our structure in combination with kinetic analyses reveals that the tautomerized imidic acid group of Gln263 serves as the catalytic base residue instead. Pc1,3Gal43A has three subsites that continue from the bottom of the catalytic pocket to the solvent. Subsite −1 contains a space that can accommodate the C-6 methylol of Gal, enabling the enzyme to bypass the β-1,6–linked galactan side chains of AGPs. Furthermore, the galactan-binding domain in CBM35 has a different ligand interaction mechanism from other sugar-binding CBM35s, including those that bind galactomannan. Specifically, we noted a Gly → Trp substitution, which affects pyranose stacking, and an Asp → Asn substitution in the binding pocket, which recognizes β-linked rather than α-linked Gal residues. These findings should facilitate further structural analysis of AGPs and may also be helpful in engineering designer enzymes for efficient biomass utilization.




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Inhibition of mitochondrial oxidative metabolism attenuates EMCV replication and protects {beta}-cells from virally mediated lysis [Immunology]

Viral infection is one environmental factor that may contribute to the initiation of pancreatic β-cell destruction during the development of autoimmune diabetes. Picornaviruses, such as encephalomyocarditis virus (EMCV), induce a pro-inflammatory response in islets leading to local production of cytokines, such as IL-1, by resident islet leukocytes. Furthermore, IL-1 is known to stimulate β-cell expression of iNOS and production of the free radical nitric oxide. The purpose of this study was to determine whether nitric oxide contributes to the β-cell response to viral infection. We show that nitric oxide protects β-cells against virally mediated lysis by limiting EMCV replication. This protection requires low micromolar, or iNOS-derived, levels of nitric oxide. At these concentrations nitric oxide inhibits the Krebs enzyme aconitase and complex IV of the electron transport chain. Like nitric oxide, pharmacological inhibition of mitochondrial oxidative metabolism attenuates EMCV-mediated β-cell lysis by inhibiting viral replication. These findings provide novel evidence that cytokine signaling in β-cells functions to limit viral replication and subsequent β-cell lysis by attenuating mitochondrial oxidative metabolism in a nitric oxide–dependent manner.




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CDKN2A/p16INK4a suppresses hepatic fatty acid oxidation through the AMPK{alpha}2-SIRT1-PPAR{alpha} signaling pathway [Metabolism]

In addition to their well-known role in the control of cellular proliferation and cancer, cell cycle regulators are increasingly identified as important metabolic modulators. Several GWAS have identified SNPs near CDKN2A, the locus encoding for p16INK4a (p16), associated with elevated risk for cardiovascular diseases and type-2 diabetes development, two pathologies associated with impaired hepatic lipid metabolism. Although p16 was recently shown to control hepatic glucose homeostasis, it is unknown whether p16 also controls hepatic lipid metabolism. Using a combination of in vivo and in vitro approaches, we found that p16 modulates fasting-induced hepatic fatty acid oxidation (FAO) and lipid droplet accumulation. In primary hepatocytes, p16-deficiency was associated with elevated expression of genes involved in fatty acid catabolism. These transcriptional changes led to increased FAO and were associated with enhanced activation of PPARα through a mechanism requiring the catalytic AMPKα2 subunit and SIRT1, two known activators of PPARα. By contrast, p16 overexpression was associated with triglyceride accumulation and increased lipid droplet numbers in vitro, and decreased ketogenesis and hepatic mitochondrial activity in vivo. Finally, gene expression analysis of liver samples from obese patients revealed a negative correlation between CDKN2A expression and PPARA and its target genes. Our findings demonstrate that p16 represses hepatic lipid catabolism during fasting and may thus participate in the preservation of metabolic flexibility.