Incorporation of animal-based foods into early hominin diets has been hypothesized to be a major catalyst of many important evolutionary events, including brain expansion. However, direct evidence of the onset and evolution of animal resource consumption in hominins remains elusive. The nitrogen-15 to nitrogen-14 ratio of collagen provides trophic information about individuals in modern and geologically recent ecosystems (<200,000 years ago), but diagenetic loss of this organic matter precludes studies of greater age.
View Article and Find Full Text PDFIdiopathic pulmonary fibrosis (IPF) remains a challenging disease with no drugs available to change the trajectory. It is a condition associated with excessive and highly progressive scarring of the lungs with remodelling and extracellular matrix deposition. It is a highly "destructive" disease of the lungs.
View Article and Find Full Text PDFThe ability of stony corals to thrive in the oligotrophic (low-nutrient, low-productivity) surface waters of the tropical ocean is commonly attributed to their symbiotic relationship with photosynthetic dinoflagellates. The evolutionary history of this symbiosis might clarify its organismal and environmental roles, but its prevalence through time, and across taxa, morphologies and oceanic settings, is currently unclear. Here we report measurements of the nitrogen isotope (N/N) ratio of coral-bound organic matter (CB-δN) in samples from Mid-Devonian reefs (Givetian, around 385 million years ago), which represent a constraint on the evolution of coral photosymbiosis.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
Organoboron compounds are widely utilized in organic synthesis for their diverse reactivity, modular preparation, and stability compared to other classes of organometallic reagents. While organoboron species are commonly employed as nucleophiles in cross-coupling reactions, their potential as racemic building blocks in enantioconvergent transformations remains largely untapped. Herein, we demonstrate the direct utilization of alkylboronic pinacol esters in intermolecular enantioconvergent transformations.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
August 2024
The nitrogen isotopes of the organic matter preserved in fossil fish otoliths (ear stones) are a promising tool for reconstructing past environmental changes. We analyzed the N/N ratio (δN) of fossil otolith-bound organic matter in Late Cretaceous fish otoliths (of , and sp.) from three deposits along the US east coast, with two of Campanian (83.
View Article and Find Full Text PDFMg/Ca is an independent proxy in paleoceanography to reconstruct past seawater temperature. Femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry (fs-LA-ICP-MS) was employed to determine the Mg/Ca composition of tests (shells) of the planktic foraminifer species Globigerinoides ruber albus (white chromotype) and G. ruber ruber (red/pink chromotype) sampled alive from the temperate to subtropical eastern North Atlantic with the research sailing yacht Eugen Seibold.
View Article and Find Full Text PDFChemodivergent construction of structurally distinct heterocycles from the same precursors by adjusting specific reaction parameters is an emergent area of organic synthesis; yet, understanding of the processes that underpin the reaction divergence is lacking, preventing the development of new synthetic methods by systematically harnessing key mechanistic effects. We describe herein cesium carbonate-promoted oxadiaza excision cross-coupling reactions of β-ketoesters with 1,2,3-triazine 1-oxides that form pyridones in good to high yields, instead of the sole formation of pyridines when the same reaction is performed in the presence of other alkali metal carbonates or organic bases. The reaction can be further extended to the construction of synthetically challenging pyridylpyridones.
View Article and Find Full Text PDFTricomponent cobalt(salen)-catalyzed carbofunctionalization of unsaturated substrates by radical-polar crossover has the potential to streamline access to broad classes of heteroatom-functionalized synthetic targets, yet the reaction platform has remained elusive, despite the well-developed analogous hydrofunctionalizations mediated by high-valent alkylcobalt intermediates. We report herein the development of a cobalt(salen) catalytic system that enables carbofunctionalization. The reaction entails a tricomponent decarboxylative 1,4-carboamination of dienes and provides a direct route to aromatic allylic amines by obviating preformed allylation reagents and protection of oxidation-sensitive aromatic amines.
View Article and Find Full Text PDFThe global ocean's oxygen inventory is declining in response to global warming, but the future of the low-oxygen tropics is uncertain. We report new evidence for tropical oxygenation during the Paleocene-Eocene Thermal Maximum (PETM), a warming event that serves as a geologic analog to anthropogenic warming. Foraminifera-bound nitrogen isotopes indicate that the tropical North Pacific oxygen-deficient zone contracted during the PETM.
View Article and Find Full Text PDFHolometabolan larvae are a major part of the animal biomass and an important food source for many animals. Many larvae evolved anti-predator strategies and some of these can even be recognized in fossils. A Lagerstätte known for well-preserved holometabolan larvae is the approximately 100-million-year-old Kachin amber from Myanmar.
View Article and Find Full Text PDFNevrorthidae, the group of dragon lacewings, has often been considered a relic group. Today, dragon lacewings show a scattered distribution, with some species occurring in southern Europe, Japan, Australia, and one in China. The idea that this distribution is only a remnant of an originally larger distribution is further supported by fossils of the group preserved in ambers from the Baltic region (Eocene, ca.
View Article and Find Full Text PDFBackground: Although asthma and chronic obstructive pulmonary disease (COPD) are two distinct chronic airway inflammatory diseases, they often co-exist in a patient and the condition is referred to as asthma-COPD overlap (ACO). Lack of evidence regarding the inflammatory cells in ACO airways has led to their poor prognosis and treatment. The objective of this endobronchial biopsy (EBB) study was to enumerate inflammatory cellular changes in the airway wall of ACO compared with asthma, COPD current smokers (CS) and ex-smokers (ES), normal lung function smokers (NLFS), and non-smoker controls (HC).
View Article and Find Full Text PDFThere is limited understanding of temperature and atmospheric circulation changes that accompany an Atlantic Meridional Overturning Circulation (AMOC) slowdown beyond the North Atlantic realm. A Peqi'in Cave (Israel) speleothem dated to the last interglacial period (LIG), 129-116 thousand years ago (ka), together with a large modern rainfall monitoring dataset, serve as the base for investigating past AMOC slowdown effects on the Eastern Mediterranean. Here, we reconstruct LIG temperatures and rainfall source using organic proxies (TEX) and fluid inclusion water d-excess.
View Article and Find Full Text PDFAnthropogenic climate change is predicted to severely impact the global hydrological cycle, particularly in tropical regions where agriculture-based economies depend on monsoon rainfall. In the Horn of Africa, more frequent drought conditions in recent decades contrast with climate models projecting precipitation to increase with rising temperature. Here we use organic geochemical climate-proxy data from the sediment record of Lake Chala (Kenya and Tanzania) to probe the stability of the link between hydroclimate and temperature over approximately the past 75,000 years, hence encompassing a sufficiently wide range of temperatures to test the 'dry gets drier, wet gets wetter' paradigm of anthropogenic climate change in the time domain.
View Article and Find Full Text PDFStereoselective construction of conjugated dienes and polyenes has remained an enduring synthetic problem, due to the central roles they play in natural product synthesis, methodology, and medicine. This review focuses on the recent developments in dienylation as an emerging strategy for the direct installation of unsaturated four carbon atom units of conjugated π-systems, outlining the regio- and stereoselectivity, as well as the synthetic scope of reactions with various dienylating reagents and the mechanistic implications of the catalytic cross-coupling processes that are used to enable dienylation.
View Article and Find Full Text PDFBackground: COPD is a common disease characterized by respiratory airflow obstruction. TGF-β1 and SMAD pathway is believed to play a role in COPD pathogenesis by driving epithelial mesenchymal transition (EMT).
Methods: We investigated TGF-β1 signalling and pSmad2/3 and Smad7 activity in resected small airway tissue from patients with; normal lung function and a smoking history (NLFS), current smokers and ex-smokers with COPD GOLD stage 1 and 2 (COPD-CS and COPD-ES) and compared these with normal non-smoking controls (NC).
One of the most important reactions of 1,2,3-triazines with a dienophile is inverse electron demand Diels-Alder (IEDDA) cycloaddition, which occurs through nucleophilic addition to the triazine followed by N loss and cyclization to generate a heterocycle. The site of addition is either at the 4- or 6-position of the symmetrically substituted triazine core. Although specific examples of the addition of nucleophiles to triazines are known, a comprehensive understanding has not been reported, and the preferred site for nucleophilic addition is unknown and unexplored.
View Article and Find Full Text PDFBackground: We have previously reported arterial remodelling in patients with idiopathic pulmonary fibrosis (IPF) and suggested that endothelial-to-mesenchymal transition (EndMT) might be central to these changes. This study aims to provide evidence for active EndMT in IPF patients.
Methods: Lung resections from 13 patients with IPF and 15 normal controls (NCs) were immunostained for EndMT biomarkers: vascular endothelial cadherin (VE-cadherin), neural cadherin (N-cadherin), S100A4 and vimentin.
Triazoles have major roles in chemistry, medicine, and materials science, as centrally important heterocyclic motifs and bioisosteric replacements for amides, carboxylic acids, and other carbonyl groups, as well as some of the most widely used linkers in click chemistry. Yet, the chemical space and molecular diversity of triazoles remains limited by the accessibility of synthetically challenging organoazides, thereby requiring preinstallation of the azide precursors and restricting triazole applications. We report herein a photocatalytic, tricomponent decarboxylative triazolation reaction that for the first time enables direct conversion of carboxylic acids to triazoles in a single-step, triple catalytic coupling with alkynes and a simple azide reagent.
View Article and Find Full Text PDFPermethylation of the phenylene linker in a cationic ferrocenyl-phenylthioxanthylium dyad increases the amount of the diradical ferrocenium thioxanthyl radical valence tautomer and aids in supressing dimerization of the latter and of the one-electron reduced neutral radical.
View Article and Find Full Text PDFLacewings have been suggested to be a relict group. This means that the group of lacewings, Neuroptera, should have been more diverse in the past, which also applies to many ingroups of Neuroptera. Psychopsidae, the group of silky lacewings, is one of the ingroups of Neuroptera which is relatively species-poor in the modern fauna.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
January 2023
The cyclic growth and decay of continental ice sheets can be reconstructed from the history of global sea level. Sea level is relatively well constrained for the Last Glacial Maximum (LGM, 26,500 to 19,000 y ago, 26.5 to 19 ka) and the ensuing deglaciation.
View Article and Find Full Text PDFWe report a fossil aphidlion-like larva preserved with its egg case in 100 million year old Kachin amber, Myanmar. It appears to have been enclosed very shortly after hatching, especially when comparing it with extant aphidlions during hatching. Although hatching aphidlion-like larvae are known from amber from other localities, this is the first case from Myanmar amber, despite the comparably high number of lacewing larvae known from the latter.
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