Pub Date : 2026-02-10Epub Date: 2026-02-02DOI: 10.1073/pnas.2536185123
George Butler, Joanna Baker, Sarah R Amend, Kenneth J Pienta, Chris Venditti
{"title":"Reply to Compton et al.: Another paradoxical misunderstanding.","authors":"George Butler, Joanna Baker, Sarah R Amend, Kenneth J Pienta, Chris Venditti","doi":"10.1073/pnas.2536185123","DOIUrl":"10.1073/pnas.2536185123","url":null,"abstract":"","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"123 6","pages":"e2536185123"},"PeriodicalIF":9.1,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12890917/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146107095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-10Epub Date: 2026-02-03DOI: 10.1073/pnas.2534141123
Romane Cecchi, Stefano Palminteri
{"title":"Genuine learning biases persist after accounting for temporally decreasing learning rates: Insight from fitting six datasets.","authors":"Romane Cecchi, Stefano Palminteri","doi":"10.1073/pnas.2534141123","DOIUrl":"10.1073/pnas.2534141123","url":null,"abstract":"","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"123 6","pages":"e2534141123"},"PeriodicalIF":9.1,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12890888/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146113978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-10Epub Date: 2026-02-03DOI: 10.1073/pnas.2535857123
Prakhar Godara
{"title":"Reply to Cecchi and Palminteri: On the need to model temporal variation in learning rates.","authors":"Prakhar Godara","doi":"10.1073/pnas.2535857123","DOIUrl":"10.1073/pnas.2535857123","url":null,"abstract":"","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"123 6","pages":"e2535857123"},"PeriodicalIF":9.1,"publicationDate":"2026-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12890890/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146113989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Feng Chen, Xiaoen Zhao, Weipeng Yue, Shijie Wang, Yong Zhang, Youping Chen, Mao Hu, Jan Esper, Ulf Büntgen, Fredrik Charpentier Ljungqvist, Amy E. Hessl, Max C. A. Torbenson, Yujiang Yuan, Martín A. Hadad, Fidel A. Roig, Honghua Cao, Heli Zhang, Yaqun Liang, Fahu Chen
Although it is generally accepted today that climate and other environmental factors affected past human societies at different spatiotemporal scales, direct linkages are difficult to determine, and correlation should not be confused with causation. Here, we use a tree-ring width network of multimillennial chronologies from inner Eurasia to reconstruct annual changes in Net Primary Productivity (NPP) back to 200 BCE. Our findings reveal that episodes of reduced NPP around the 70s–100s, 360s–380s, and 470s–560s CE likely contributed to the westward and southward migration of nomadic people from their homelands in northwestern China and Mongolia. Although prolonged multidecadal periods of climate-induced low NPP served as tipping points for agricultural and pastoral subsistence systems, the inherent mobility of nomadic communities not only enabled them to adapt to adverse environmental conditions but also facilitated a widespread dispersal of ethnic groups.
{"title":"Climate-driven reduction in biomass production of the Eurasian steppe coincides with nomadic migration during the first millennium CE","authors":"Feng Chen, Xiaoen Zhao, Weipeng Yue, Shijie Wang, Yong Zhang, Youping Chen, Mao Hu, Jan Esper, Ulf Büntgen, Fredrik Charpentier Ljungqvist, Amy E. Hessl, Max C. A. Torbenson, Yujiang Yuan, Martín A. Hadad, Fidel A. Roig, Honghua Cao, Heli Zhang, Yaqun Liang, Fahu Chen","doi":"10.1073/pnas.2513573123","DOIUrl":"https://doi.org/10.1073/pnas.2513573123","url":null,"abstract":"Although it is generally accepted today that climate and other environmental factors affected past human societies at different spatiotemporal scales, direct linkages are difficult to determine, and correlation should not be confused with causation. Here, we use a tree-ring width network of multimillennial chronologies from inner Eurasia to reconstruct annual changes in Net Primary Productivity (NPP) back to 200 BCE. Our findings reveal that episodes of reduced NPP around the 70s–100s, 360s–380s, and 470s–560s CE likely contributed to the westward and southward migration of nomadic people from their homelands in northwestern China and Mongolia. Although prolonged multidecadal periods of climate-induced low NPP served as tipping points for agricultural and pastoral subsistence systems, the inherent mobility of nomadic communities not only enabled them to adapt to adverse environmental conditions but also facilitated a widespread dispersal of ethnic groups.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"88 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Leonard F. Lebender, Alexander Seidinger, Michaela Matthey, Birte Dyck, Christian Schlamm, Abdullah Kaddoura, Maximilian Hausherr, Britta Eggers, Katrin Marcus, Evi Kostenis, Volkmar Gieselmann, Michael Adamzik, Anna Klinke, Björn Koos, Bernd K. Fleischmann, Daniela Wenzel
Pulmonary arterial hypertension (PAH) is a serious disorder, in which increased vascular tone is one of the critical hallmarks. Since beta arrestins (bArrs) have been shown to regulate smooth muscle tone in the airways, we investigated the function of bArr1 in the pulmonary vasculature. Here, we report that bArr1 is essential for maintaining normal pulmonary arterial tone. Specifically, pulmonary arteries from bArr1−/− mice exhibited reduced NO-dependent vasorelaxation due to impaired soluble guanylyl cyclase (sGC) activity, which was restored by the heme-independent sGC activator BAY58-2667. We identified bArr1 as a binding partner of sGC and the sGC heme reductase cytochrome b5 reductase (Cyb5r3), indicating that bArr1 is vital for sensitizing sGC to NO. Finally, mice with either ubiquitous or smooth muscle-specific bArr1 deficiency developed pulmonary hypertension (PH). These findings highlight the important role of bArr1 in regulating pulmonary vascular tone and propose it as a potential therapeutic target for the treatment of PH.
{"title":"Beta arrestin 1 is a key regulator of pulmonary vascular tone","authors":"Leonard F. Lebender, Alexander Seidinger, Michaela Matthey, Birte Dyck, Christian Schlamm, Abdullah Kaddoura, Maximilian Hausherr, Britta Eggers, Katrin Marcus, Evi Kostenis, Volkmar Gieselmann, Michael Adamzik, Anna Klinke, Björn Koos, Bernd K. Fleischmann, Daniela Wenzel","doi":"10.1073/pnas.2512602123","DOIUrl":"https://doi.org/10.1073/pnas.2512602123","url":null,"abstract":"Pulmonary arterial hypertension (PAH) is a serious disorder, in which increased vascular tone is one of the critical hallmarks. Since beta arrestins (bArrs) have been shown to regulate smooth muscle tone in the airways, we investigated the function of bArr1 in the pulmonary vasculature. Here, we report that bArr1 is essential for maintaining normal pulmonary arterial tone. Specifically, pulmonary arteries from bArr1−/− mice exhibited reduced NO-dependent vasorelaxation due to impaired soluble guanylyl cyclase (sGC) activity, which was restored by the heme-independent sGC activator BAY58-2667. We identified bArr1 as a binding partner of sGC and the sGC heme reductase cytochrome b5 reductase (Cyb5r3), indicating that bArr1 is vital for sensitizing sGC to NO. Finally, mice with either ubiquitous or smooth muscle-specific bArr1 deficiency developed pulmonary hypertension (PH). These findings highlight the important role of bArr1 in regulating pulmonary vascular tone and propose it as a potential therapeutic target for the treatment of PH.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"3 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mosquito-disease vectors, such as Aedes aegypti , use their sense of taste before deciding whether to consume a blood meal, or fly away. However, the molecular mechanisms controlling gustatory decisions in mosquitoes are largely unknown. The transient receptor potential (TRP) channel, Painless1 (Pain1), is an intriguing candidate for participating in Ae. aegypti taste since pain1 transcripts are detected in gustatory receptor neurons (GRNs). The Drosophila homolog, painless ( pain ) is also expressed in GRNs, where it is required for sensing allyl-isothiocyanate. Here, to identify additional gustatory roles for pain homologs, we first focused on Drosophila pain , which is widely expressed in multiple GRN classes. We demonstrated that pain mutations eliminated gustatory attraction to low fatty acids levels, repulsion to high levels, and fatty acid-induced action potentials. The attraction and repulsion depended on pain expression in different GRN classes. In contrast to Drosophila , when Aedes contacts fatty acids, they induce gustatory rejection only. Aedes pain1 is expressed in taste organs, and is required for gustatory avoidance of fatty acids, and for fatty acid-induced action potentials. Given that Pain homologs are found in insects but not vertebrates, Pain1 represents an intriguing target for developing repellents to diminish biting, and transmission of infectious agents by mosquito disease vectors.
{"title":"Gustatory avoidance of fatty acids by Aedes aegypti depends on an arthropod-specific TRP channel","authors":"Subash Dhakal, Angela E. Bontempo, Ramandeep Singh, Pratik Dhavan, Craig Montell","doi":"10.1073/pnas.2522818123","DOIUrl":"https://doi.org/10.1073/pnas.2522818123","url":null,"abstract":"Mosquito-disease vectors, such as <jats:italic toggle=\"yes\">Aedes aegypti</jats:italic> , use their sense of taste before deciding whether to consume a blood meal, or fly away. However, the molecular mechanisms controlling gustatory decisions in mosquitoes are largely unknown. The transient receptor potential (TRP) channel, Painless1 (Pain1), is an intriguing candidate for participating in <jats:italic toggle=\"yes\">Ae. aegypti</jats:italic> taste since <jats:italic toggle=\"yes\">pain1</jats:italic> transcripts are detected in gustatory receptor neurons (GRNs). The <jats:italic toggle=\"yes\">Drosophila</jats:italic> homolog, <jats:italic toggle=\"yes\">painless</jats:italic> ( <jats:italic toggle=\"yes\">pain</jats:italic> ) is also expressed in GRNs, where it is required for sensing allyl-isothiocyanate. Here, to identify additional gustatory roles for <jats:italic toggle=\"yes\">pain</jats:italic> homologs, we first focused on <jats:italic toggle=\"yes\">Drosophila pain</jats:italic> , which is widely expressed in multiple GRN classes. We demonstrated that <jats:italic toggle=\"yes\">pain</jats:italic> mutations eliminated gustatory attraction to low fatty acids levels, repulsion to high levels, and fatty acid-induced action potentials. The attraction and repulsion depended on <jats:italic toggle=\"yes\">pain</jats:italic> expression in different GRN classes. In contrast to <jats:italic toggle=\"yes\">Drosophila</jats:italic> , when <jats:italic toggle=\"yes\">Aedes</jats:italic> contacts fatty acids, they induce gustatory rejection only. <jats:italic toggle=\"yes\">Aedes pain1</jats:italic> is expressed in taste organs, and is required for gustatory avoidance of fatty acids, and for fatty acid-induced action potentials. Given that Pain homologs are found in insects but not vertebrates, Pain1 represents an intriguing target for developing repellents to diminish biting, and transmission of infectious agents by mosquito disease vectors.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"22 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146108","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaolu Wang, Xu Jing, Ziheng Guo, Siwen Long, Xiaoting Sun, Sofia Appelberg, Gerald M. McInerney, Mikael Adner, Yihai Cao
COVID-19 has been associated with high prevalences of retinal diseases in humans. However, cellular and molecular mechanisms that underlie the COVID-19-associated retinopathy remains unknown. Here, we deployed a mouse COVID-19 model to investigate the causative link between SARS-CoV-2 infection and retinopathy development. Our data showed that COVID-19-induced pulmonary hypoxia triggered systemic hypoxia and markedly augmented VEGF expression levels in the retina and plasma. High VEGF levels altered vascular structures and functions in the retina, resulting in neovascularization, vascular disorganization, and increased leakiness. We deployed a terminology of coviretinopathy to accurately describe these COVID-19-induced pathological changes in the retina. Consequently, blocking VEGF by a specific neutralizing antibody (VEGF blockade) completely ablated the COVID-19-associated vascular changes in the retina. Together, these findings provide mechanistic insights into the COVID-19-associated retinopathy and propose a therapeutic paradigm for effective treatment of coviretinopathy.
{"title":"Coviretinopathy: COVID-19-induced VEGF-dependent retinopathy","authors":"Xiaolu Wang, Xu Jing, Ziheng Guo, Siwen Long, Xiaoting Sun, Sofia Appelberg, Gerald M. McInerney, Mikael Adner, Yihai Cao","doi":"10.1073/pnas.2516405123","DOIUrl":"https://doi.org/10.1073/pnas.2516405123","url":null,"abstract":"COVID-19 has been associated with high prevalences of retinal diseases in humans. However, cellular and molecular mechanisms that underlie the COVID-19-associated retinopathy remains unknown. Here, we deployed a mouse COVID-19 model to investigate the causative link between SARS-CoV-2 infection and retinopathy development. Our data showed that COVID-19-induced pulmonary hypoxia triggered systemic hypoxia and markedly augmented VEGF expression levels in the retina and plasma. High VEGF levels altered vascular structures and functions in the retina, resulting in neovascularization, vascular disorganization, and increased leakiness. We deployed a terminology of coviretinopathy to accurately describe these COVID-19-induced pathological changes in the retina. Consequently, blocking VEGF by a specific neutralizing antibody (VEGF blockade) completely ablated the COVID-19-associated vascular changes in the retina. Together, these findings provide mechanistic insights into the COVID-19-associated retinopathy and propose a therapeutic paradigm for effective treatment of coviretinopathy.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"6 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Laura G. Elsler, Jessica A. Gephart, Jessica Zamborain-Mason, Tim Cashion, Max Troell, Rosamond L. Naylor, Rahul Agrawal Bejarano, Christopher D. Golden
Aquaculture, the single fastest growing food sector, is central to achieving key Sustainable Development Goals (e.g., SDG 2: Zero Hunger). Linking the nutrient composition of >2,800 aquatic species with >2 million fishmeal and farmed fish transactions in international aquatic food trade between 2015 and 2019, we examined aquaculture’s nutritional flows and distributional equity. We found that aquaculture provided adequate intakes for nearly a quarter of a million individuals, on average, across 14 key nutrients, and for up to 2.7 billion individuals for several nutrients, such as Vitamin B 12 . The vast majority of these nutrients (76.8%) were domestically retained, contributing to the nutritional security of producer countries. With most internationally traded nutrients originating from nutritionally vulnerable countries (57.7% for fishmeal and 66.3% for farmed aquatic foods), rethinking existing distribution policies with nutrition as the primary objective may help unlock the full potential of aquaculture to eliminate hunger and malnutrition.
{"title":"Global nutritional equity of fishmeal and aquaculture trade flows","authors":"Laura G. Elsler, Jessica A. Gephart, Jessica Zamborain-Mason, Tim Cashion, Max Troell, Rosamond L. Naylor, Rahul Agrawal Bejarano, Christopher D. Golden","doi":"10.1073/pnas.2506699123","DOIUrl":"https://doi.org/10.1073/pnas.2506699123","url":null,"abstract":"Aquaculture, the single fastest growing food sector, is central to achieving key Sustainable Development Goals (e.g., SDG 2: Zero Hunger). Linking the nutrient composition of >2,800 aquatic species with >2 million fishmeal and farmed fish transactions in international aquatic food trade between 2015 and 2019, we examined aquaculture’s nutritional flows and distributional equity. We found that aquaculture provided adequate intakes for nearly a quarter of a million individuals, on average, across 14 key nutrients, and for up to 2.7 billion individuals for several nutrients, such as Vitamin B <jats:sub>12</jats:sub> . The vast majority of these nutrients (76.8%) were domestically retained, contributing to the nutritional security of producer countries. With most internationally traded nutrients originating from nutritionally vulnerable countries (57.7% for fishmeal and 66.3% for farmed aquatic foods), rethinking existing distribution policies with nutrition as the primary objective may help unlock the full potential of aquaculture to eliminate hunger and malnutrition.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"72 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Allison A. Baczynski, Ophélie M. Mcintosh, Danielle N. Simkus, Hannah L. McLain, Jason P. Dworkin, Daniel P. Glavin, Jamie E. Elsila, Mila Matney, Christopher H. House, Katherine H. Freeman, Harold C. Connolly, Dante S. Lauretta
Samples collected from the carbonaceous near-Earth asteroid Bennu and delivered to Earth by NASA’s OSIRIS-REx mission contain organic molecules relevant to prebiotic chemistry. Stable isotopic measurements of extraterrestrial soluble organic matter provide critical insights into the formation pathways and alteration histories of such molecules, which hold significance for understanding the origins of life. We leverage state-of-the-art techniques for picomolar-scale isotopic analyses of amino acids in samples of Bennu and, for comparison, the carbonaceous meteorite Murchison. We report intramolecular δ 13 C values for glycine, which have not previously been measured in extraterrestrial materials; molecular-averaged δ 13 C values for amino acids, aldehydes, and ketones; and δ 15 N values for glycine, β-alanine, and D/L-glutamic acid. Intramolecular carbon isotope patterns of glycine in Bennu contrast with those in Murchison, suggesting distinct formation pathways. We explore several formation mechanisms and hypothesize that the observed glycine in Murchison formed dominantly by a Strecker-like synthesis under aqueous conditions, whereas the glycine currently found in Bennu may have formed mainly by modified radical–radical reactions in primordial ices at the cold, outer reaches of the early Solar System and retained its isotopic values throughout accretion and multiple episodes of aqueous alteration. This hypothesis is supported by the highly 15 N-enriched δ 15 N values in Bennu amino acids (+170 to 277‰). Differences in the δ 15 N values of D- and L-glutamic acid (Δ = 87‰) in Bennu affirm published reports of enantiomeric differences in meteoritic amino acids and challenge the assumption of isotopic uniformity between amino acid chiral pairs.
{"title":"Multiple formation pathways for amino acids in the early Solar System based on carbon and nitrogen isotopes in asteroid Bennu samples","authors":"Allison A. Baczynski, Ophélie M. Mcintosh, Danielle N. Simkus, Hannah L. McLain, Jason P. Dworkin, Daniel P. Glavin, Jamie E. Elsila, Mila Matney, Christopher H. House, Katherine H. Freeman, Harold C. Connolly, Dante S. Lauretta","doi":"10.1073/pnas.2517723123","DOIUrl":"https://doi.org/10.1073/pnas.2517723123","url":null,"abstract":"Samples collected from the carbonaceous near-Earth asteroid Bennu and delivered to Earth by NASA’s OSIRIS-REx mission contain organic molecules relevant to prebiotic chemistry. Stable isotopic measurements of extraterrestrial soluble organic matter provide critical insights into the formation pathways and alteration histories of such molecules, which hold significance for understanding the origins of life. We leverage state-of-the-art techniques for picomolar-scale isotopic analyses of amino acids in samples of Bennu and, for comparison, the carbonaceous meteorite Murchison. We report intramolecular δ <jats:sup>13</jats:sup> C values for glycine, which have not previously been measured in extraterrestrial materials; molecular-averaged δ <jats:sup>13</jats:sup> C values for amino acids, aldehydes, and ketones; and δ <jats:sup>15</jats:sup> N values for glycine, β-alanine, and D/L-glutamic acid. Intramolecular carbon isotope patterns of glycine in Bennu contrast with those in Murchison, suggesting distinct formation pathways. We explore several formation mechanisms and hypothesize that the observed glycine in Murchison formed dominantly by a Strecker-like synthesis under aqueous conditions, whereas the glycine currently found in Bennu may have formed mainly by modified radical–radical reactions in primordial ices at the cold, outer reaches of the early Solar System and retained its isotopic values throughout accretion and multiple episodes of aqueous alteration. This hypothesis is supported by the highly <jats:sup>15</jats:sup> N-enriched δ <jats:sup>15</jats:sup> N values in Bennu amino acids (+170 to 277‰). Differences in the δ <jats:sup>15</jats:sup> N values of D- and L-glutamic acid (Δ = 87‰) in Bennu affirm published reports of enantiomeric differences in meteoritic amino acids and challenge the assumption of isotopic uniformity between amino acid chiral pairs.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"88 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Stratospheric CH 4 oxidation represents both an important sink in the global CH 4 budget and a major source of stratospheric water vapor and hydrogen radicals, exerting strong influences on global climate and ozone chemistry. Yet, the magnitude of stratospheric CH 4 chemical loss remains highly uncertain, with previous estimates largely relying on chemistry-climate models (CCMs). Here, we present an observationally based estimate of stratospheric CH 4 loss ( L STR ), derived from the CH 4 diabatic flux across the isentropic surface fitted to the tropical tropopause, using satellite measurements of CH 4 concentration, temperature, and radiative heating rates for 2007–2010. We obtain an L STR of 49.8 ± 7.8 Tg/y, compared with 38.1 Tg/y estimated from reanalysis, and 25.7 Tg/y (range: 19.6 to 35.9 Tg/y) derived from CCMs, indicating that both reanalysis and CCMs systematically underestimate stratospheric CH 4 loss. We show that discrepancies in global CH 4 diabatic fluxes from the reanalysis and CCMs, when compared with observations, are mainly driven by biases in CH 4 concentrations and further enhanced by errors in temperature and radiative heating. Substituting our observational estimate for the model-based stratospheric loss in the bottom-up global CH 4 budget reduces the reported imbalance for the 2000s from 23 to 3 Tg/y, bringing it into close agreement with the 5 Tg/y (range: −4 to 13 Tg/y) imbalance inferred from top-down estimates. These findings highlight the critical role of observational constraints on L STR in reconciling the global CH 4 budget. They also carry important implications for understanding stratospheric water vapor and ozone chemistry.
{"title":"Global stratospheric methane loss from satellite observations","authors":"Qiang Fu, Cong Dong","doi":"10.1073/pnas.2529774123","DOIUrl":"https://doi.org/10.1073/pnas.2529774123","url":null,"abstract":"Stratospheric CH <jats:sub>4</jats:sub> oxidation represents both an important sink in the global CH <jats:sub>4</jats:sub> budget and a major source of stratospheric water vapor and hydrogen radicals, exerting strong influences on global climate and ozone chemistry. Yet, the magnitude of stratospheric CH <jats:sub>4</jats:sub> chemical loss remains highly uncertain, with previous estimates largely relying on chemistry-climate models (CCMs). Here, we present an observationally based estimate of stratospheric CH <jats:sub>4</jats:sub> loss ( <jats:italic toggle=\"yes\"> L <jats:sub>STR</jats:sub> </jats:italic> ), derived from the CH <jats:sub>4</jats:sub> diabatic flux across the isentropic surface fitted to the tropical tropopause, using satellite measurements of CH <jats:sub>4</jats:sub> concentration, temperature, and radiative heating rates for 2007–2010. We obtain an <jats:italic toggle=\"yes\"> L <jats:sub>STR</jats:sub> </jats:italic> of 49.8 ± 7.8 Tg/y, compared with 38.1 Tg/y estimated from reanalysis, and 25.7 Tg/y (range: 19.6 to 35.9 Tg/y) derived from CCMs, indicating that both reanalysis and CCMs systematically underestimate stratospheric CH <jats:sub>4</jats:sub> loss. We show that discrepancies in global CH <jats:sub>4</jats:sub> diabatic fluxes from the reanalysis and CCMs, when compared with observations, are mainly driven by biases in CH <jats:sub>4</jats:sub> concentrations and further enhanced by errors in temperature and radiative heating. Substituting our observational estimate for the model-based stratospheric loss in the bottom-up global CH <jats:sub>4</jats:sub> budget reduces the reported imbalance for the 2000s from 23 to 3 Tg/y, bringing it into close agreement with the 5 Tg/y (range: −4 to 13 Tg/y) imbalance inferred from top-down estimates. These findings highlight the critical role of observational constraints on <jats:italic toggle=\"yes\"> L <jats:sub>STR</jats:sub> </jats:italic> in reconciling the global CH <jats:sub>4</jats:sub> budget. They also carry important implications for understanding stratospheric water vapor and ozone chemistry.","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":"314 1","pages":""},"PeriodicalIF":11.1,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146137","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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