编译 | 未玖
Science，24 JUN 2022，VOL 376，ISSUE 6600
《科学》2022年6月24日，第376卷，6600期
化学Chemistry
催化剂控制的二羧酸位点选择性亚甲基C-H内酯化
▲ 作者：HAU SUN SAM CHAN，JI-MIN YANG，AND JIN-QUAN YU.
▲ 链接：
▲ 摘要：
催化剂控制的自由羧酸的β-和γ-亚甲基碳氢（C-H）键的位点选择性活化是一个长期存在的挑战。
研究组表明，当一对钯催化剂与不同螯合环尺寸的喹啉-吡啶酮配体组装在一起时，可以与多种二羧酸进行高位点选择性的单内酯化反应，通过位点选择性β-或γ-亚甲基C-H活化，可生成结构多样且有高合成价值的γ-和δ-内酯。
剩余羧基是进一步合成应用的多功能关键，研究组在丰富的二羧酸中实现了两种天然产物（黄花蒿酮A和pedicellosine）的全合成，充分证明了这一点。
▲ Abstract：
Catalyst-controlled site-selective activation of β- and γ-methylene carbon-hydrogen (C–H) bonds of free carboxylic acids is a long-standing challenge. Here we show that，with a pair of palladium catalysts assembled with quinoline-pyridone ligands of different chelate ring sizes，it is possible to perform highly site-selective monolactonization reactions with a wide range of dicarboxylic acids，generating structurally diverse and synthetically useful γ- and δ-lactones via site-selective β- or γ-methylene C–H activation. The remaining carboxyl group serves as a versatile linchpin for further synthetic applications，as demonstrated by the total synthesis of two natural products，myrotheciumone A and pedicellosine，from abundant dicarboxylic acids.
地球科学Earth Science
Rapid changes to global river suspended sediment flux by humans
人类活动加剧全球河流悬浮沉积物通量的变化
▲ 作者：EVAN N. DETHIER，CARL E. RENSHAW，AND FRANCIS J. MAGILLIGAN.
▲ 链接：
▲ 摘要：
河流支持着不可或缺的生态功能、人类健康和基础设施。然而，有限的河流采样妨碍了人们对河流系统重大变化的理解。
基于卫星对414条主要河流悬浮沉积物浓度和通量的估算，研究组揭示了过去半个世纪人类活动直接导致的广泛全球变化。
北半球河流的大坝拦截导致全球沉积物通量下降至筑坝前的49%。最近，南半球水文土地利用的剧烈变化加剧了侵蚀，河流悬浮沉积物浓度与1980年代相比平均增加了41±7%。
这种南北差异迅速改变了全球海洋沉积物通量的模式，悬浮沉积物的主要来源从亚洲转移到南美。
▲ Abstract：
Rivers support indispensable ecological functions and human health and infrastructure. Yet limited river sampling hinders our understanding of consequential changes to river systems. Satellite-based estimates of suspended sediment concentration and flux for 414 major rivers reveal widespread global change that is directly attributable to human activity in the past half-century. Sediment trapping by dams in the global hydrologic north has contributed to global sediment flux declines to 49% of pre-dam conditions. Recently，intensive land-use change in the global hydrologic south has increased erosion，with river suspended sediment concentration on average 41±7% greater than in the 1980s. This north-south divergence has rapidly reconfigured global patterns in sediment flux to the oceans，with the dominant sources of suspended sediment shifting from Asia to South America.
Global ocean lipidomes show a universal relationship between temperature and lipid unsaturation
全球海洋脂质体揭示温度和脂质不饱和度之间的普遍关系
▲ 链接：
▲ 摘要：
利用“组学”技术对浮游生物群落进行的全球范围调查彻底改变了人们对海洋的理解。脂质组学已证明有潜力进一步深入了解海洋生态系统功能，但尚未在全球范围内应用。
研究组使用统一的高分辨率精确质谱分析流程分析了全球海洋中的930个脂质样品，揭示了此前未知的海洋浮游脂质体特征。针对10种不同分子的甘油脂类，他们确定了1151种不同的脂质体，发现脂肪酸的不饱和度（即碳-碳双键的数量）基本上受到温度的限制。
研究组预测，在下个世纪，必需脂肪酸二十碳五烯酸将大幅下降，这可能对经济上至关重要的渔业产生严重有害影响。
▲ Abstract：
Global-scale surveys of plankton communities using “omics” techniques have revolutionized our understanding of the ocean. Lipidomics has demonstrated the potential to add further essential insights on ocean ecosystem function but has yet to be applied on a global scale. We analyzed 930 lipid samples across the global ocean using a uniform high-resolution accurate-mass mass spectrometry analytical workflow，revealing previously unknown characteristics of ocean planktonic lipidomes. Focusing on 10 molecularly diverse glycerolipid classes，we identified 1151 distinct lipid species，finding that fatty acid unsaturation (i.e.，number of carbon-carbon double bonds) is fundamentally constrained by temperature. We predict substantial declines in the essential fatty acid eicosapentaenoic acid over the next century，which are likely to have serious deleterious effects on economically critical fisheries.
8000-year doubling of Midwestern forest biomass driven by population- and biome-scale processes
种群和生物群落规模进程推动美国中西部森林生物量8000年间翻倍
▲ 作者：A. M. RAIHO，C. J. PACIOREK，A. DAWSON，S. T. JACKSON，D. J. MLADENOFF，J. W. WILLIAMS，ET AL.
▲ 链接：
▲ 摘要：
木本植物生物量在几个世纪到几千年间的变化鲜为人知，因此在工业时代的干扰之前，陆地碳通量的规模尚不清楚。
研究组利用贝叶斯模型对工业化之前的森林生物量估计和花粉化石记录进行校准，对美国上中西部地区过去10000年的森林生物量变化进行了统计重建。在经历了冰期后的最初下降之后，木本植物生物量在过去8000年中几乎翻了一番，封存了1800太克的碳。
这种碳的稳定积累由两种不同的区域气候变化的生态反应所驱动：森林生物群落的扩展和森林中高生物量树种的种群扩张。然而，用数千年时间积累起来的碳汇仅用不到两个世纪的时间就被工业时代的伐木和农业所消除。
▲ Abstract：
Changes in woody biomass over centuries to millennia are poorly known，leaving unclear the magnitude of terrestrial carbon fluxes before industrial-era disturbance. Here，we statistically reconstructed changes in woody biomass across the upper Midwestern region of the United States over the past 10，000 years using a Bayesian model calibrated to preindustrial forest biomass estimates and fossil pollen records. After an initial postglacial decline，woody biomass nearly doubled during the past 8000 years，sequestering 1800 teragrams. This steady accumulation of carbon was driven by two separate ecological responses to regionally changing climate: the spread of forested biomes and the population expansion of high-biomass tree species within forests. What took millennia to accumulate took less than two centuries to remove: Industrial-era logging and agriculture have erased this carbon accumulation.
Current global efforts are insufficient to limit warming to 1.5℃
目前的全球努力不足以将升温控制在1.5℃
▲ 作者：H. DAMON MATTHEWS AND SETH WYNES
▲ 链接：
▲ 摘要：
实现1.5℃兼容路径的主要障碍不是地球物理因素，而是反映了我们政治和技术体系的惰性。要克服这种惰性，需要政治和企业的领导，以及提高社会对系统层面和个人生活方式改变需求的认识。
现有证据尚未表明，世界已认真致力于实现全球升温1.5℃的目标。
▲ Abstract：
Human activities have caused global temperatures to increase by 1.25℃，and the current emissions trajectory suggests that we will exceed 1.5℃ in less than 10 years. Though the growth rate of global carbon dioxide emissions has slowed and many countries have strengthened their emissions targets，current midcentury net zero goals are insufficient to limit global warming to 1.5℃ above preindustrial temperatures. The primary barriers to the achievement of a 1.5℃-compatible pathway are not geophysical but rather reflect inertia in our political and technological systems. Both political and corporate leadership are needed to overcome this inertia，supported by increased societal recognition of the need for system-level and individual lifestyle changes. The available evidence does not yet indicate that the world has seriously committed to achieving the 1.5℃ goal.
公共卫生Public Health
Twin peaks: The Omicron SARS-CoV-2 BA.1 and BA.2 epidemics in England
双峰：英国新冠病毒奥密克戎BA.1和BA.2大流行
▲ 作者：PAUL ELLIOTT，OLIVER EALES，NICHOLAS STEYN，DAVID TANG，BARBARA BODINIER，HAOWEI WANG，ET AL.
▲ 链接：
▲ 摘要：
新冠病毒奥密克戎变体的快速传播导致了全球各地创纪录的发病率。
“社区传播实时评估-1”（REACT-1）研究利用逆转录聚合酶链反应（RT-PCR）跟踪了英国SARS-CoV-2感染情况，从2020年5月至2022年3月，大约每月一次对随机选择的5岁及以上参与者采集咽拭子和鼻拭子。
2022年3月，REACT-1的加权患病率最高，为6.37%（共109181名参与者），其中奥密克戎BA.2变体的患病率最高，基本上取代了BA.1变体。
患病率总体来说呈上升趋势，其中65-74岁和75岁及以上的人群增幅最大。这与住院人数和死亡人数的增加有关，但在高水平疫苗接种的背景下，该数字远低于前几波疫情。
▲ Abstract：
Rapid transmission of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant has led to record-breaking incidence rates around the world. The Real-time Assessment of Community Transmission-1 (REACT-1) study has tracked SARS-CoV-2 infection in England using reverse transcription polymerase chain reaction (RT-PCR) results from self-administered throat and nose swabs from randomly selected participants aged 5 years and older approximately monthly from May 2020 to March 2022. Weighted prevalence in March 2022 was the highest recorded in REACT-1 at 6.37% (N = 109，181)，with the Omicron BA.2 variant largely replacing the BA.1 variant. Prevalence was increasing overall，with the greatest increase in those aged 65 to 74 years and 75 years and older. This was associated with increased hospitalizations and deaths，but at much lower levels than in previous waves against a backdrop of high levels of vaccination.
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