新烟碱类杀虫剂(如吡虫啉)选择性毒杀昆虫而对哺乳动物毒性较低,这种选择性的分子基础是什么?
Neonicotinoid insecticides such as imidacloprid kill insects selectively with relatively low mammalian toxicity. What is the molecular basis of this selectivity?
新烟碱作用于昆虫中枢神经的烟碱型乙酰胆碱受体(nAChR),其硝基亚氨基/氰基等吸电基团使其与昆虫受体亚基的结合亲和力比对哺乳动物受体高数百至上千倍。哺乳动物nAChR对该类化合物的结合位点构象不同且亲和力弱,加之血脑屏障阻挡,故在治疗剂量下难以中毒。这种受体水平的差异构成了新烟碱选择性的核心机制,但也带来传粉昆虫暴露的生态风险争议。
Neonicotinoids target nicotinic acetylcholine receptors in the insect central nervous system; their electron-withdrawing nitroimine or cyano groups give binding affinities for insect receptor subunits hundreds to thousands of times higher than for mammalian ones. Mammalian nAChRs differ in binding-site conformation and bind these compounds weakly, and the blood–brain barrier further limits exposure, explaining the favorable acute-toxicity profile. This receptor-level selectivity is the core mechanism, though it remains debated because of risks to pollinating insects.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Tomizawa 与 Casida,《NEONICOTINOID INSECTICIDE TOXICOLOGY: Mechanisms of Selective Action》,Annual Review of Pharmacology and Toxicology 45, 247,2005 (DOI: 10.1146/annurev.pharmtox.45.120403.095930)
Tomizawa and Casida, 'NEONICOTINOID INSECTICIDE TOXICOLOGY: Mechanisms of Selective Action', Annual Review of Pharmacology and Toxicology 45, 247, 2005, DOI: 10.1146/annurev.pharmtox.45.120403.095930
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1146/annurev.pharmtox.45.120403.095930
#烟碱型受体 #杀虫剂选择性
缓释肥料包衣层(如硫磺或聚合物包覆尿素)是如何控制氮素释放速率的?其释放动力学受哪些因素影响?
How do coated controlled-release fertilizers (e.g. sulfur- or polymer-coated urea) regulate nitrogen release, and what factors govern the release kinetics?
水蒸气透过包衣微孔渗入核心溶解尿素,形成的内压使养分通过扩散或膜破裂逐步释放,因此释放速率主要由包衣厚度、孔隙率和聚合物的亲水/疏水比决定。土壤温度显著影响膜渗透系数与尿素溶解度,通常符合 Arrhenius 型温度依赖;土壤湿度和微生物降解也会改变包衣完整性。合理设计可使氮素释放曲线与作物需肥规律同步,减少淋失。
Water vapor permeates micropores of the coating, dissolves the urea core, and the resulting internal pressure releases nutrients gradually by diffusion or film rupture; hence release rate is governed mainly by coating thickness, porosity, and the hydrophilic/hydrophobic balance of the polymer. Soil temperature strongly affects membrane permeability and urea solubility, often following Arrhenius-type dependence, while moisture and microbial degradation alter coating integrity. Proper design synchronizes nitrogen release with crop demand and reduces leaching losses.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Trenkel, Controlled-Release and Stabilized Fertilizers in Agriculture, IFA, Paris, 1997
M. E. Trenkel, Controlled-Release and Stabilized Fertilizers in Agriculture, International Fertilizer Industry Association, Paris, 1997
#农业化学 #控释肥料机理
硝酸铵为什么既能当化肥又很危险？
Why is ammonium nitrate both a fertilizer and a hazard?
它同时含铵根和硝酸根，是高效氮肥；但在强热或受冲击时分解产气极快，可能爆炸，因此储运需严格管理。
It carries both ammonium and nitrate, making a potent fertilizer; but under strong heat or shock it decomposes explosively fast, so storage is tightly regulated.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#硝酸铵 #化肥 #爆炸
过磷酸钙是怎么做的，为什么能当磷肥？
How is superphosphate made, and why does it work as phosphate fertilizer?
用硫酸处理不溶的磷酸钙矿石，生成可溶于水的磷酸一钙，植物能直接吸收，于是成了常用的磷肥。
Treating insoluble calcium phosphate rock with sulfuric acid yields water-soluble monocalcium phosphate, which plants can take up directly.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#磷肥 #过磷酸钙 #硫酸
化肥包装上的N-P-K数字是什么意思？
What do the N–P–K numbers on fertilizer bags mean?
它们分别表示氮、磷、钾三种主要养分的质量百分比，数字越大代表该养分含量越高，按作物需要选配。
They are the mass percentages of the three main nutrients—nitrogen, phosphorus, potassium—with larger numbers meaning more of that nutrient.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#化肥 #NPK #养分
为什么尿素是当今最主要的氮肥？
Why is urea the dominant nitrogen fertilizer today?
尿素含氮量高(约46%)、易运输、对土壤酸性小，施入土壤后被脲酶慢慢分解成铵态氮供作物吸收。
Urea is ~46% nitrogen, easy to ship, and barely acidifies soil; soil urease slowly converts it to ammonium that crops can absorb.
难度 入门 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#尿素 #氮肥 #农业
哈伯-博施法对世界有什么意义？
Why is the Haber-Bosch process important to the world?
在高温高压下用铁催化剂把 N₂ 与 H₂ 合成氨，支撑化肥与粮食产量，却也极为耗能。
It uses iron catalysts at high T and P to make ammonia from N₂ and H₂, enabling fertilizers and food but consuming huge energy.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#合成氨 #催化 #化肥
为什么青香蕉和苹果放一起熟得更快？
Why do green bananas ripen faster next to apples?
苹果会释放乙烯气体，乙烯是植物催熟激素，促进香蕉淀粉转糖、叶绿素分解，加快变黄变软。
Apples release ethylene gas, a ripening hormone that speeds bananas' starch-to-sugar conversion and chlorophyll loss, accelerating yellowing.
难度 入门 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#乙烯 #催熟 #香蕉