Systematic Investigation of Lanthanoid Transition Heavy Metal Acetates as Electron Staining Reagents for Protein Molecules in Biological Transmission Electron Microscopy
Systematic Investigation of Lanthanoid Transition Heavy Metal Acetates as Electron Staining Reagents for Protein Molecules in Biological Transmission Electron Microscopy
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DOI：
10.1017/s1431927622000411
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发表时间：
2022-04-01
影响因子：
2.8
通讯作者：
Ishii, Noriyuki
中科院分区：
文献类型：
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作者：
Ishii, Noriyuki
低温电子显微镜被广泛用于高分辨率蛋白质结构测定，不需要染色。然而，自20世纪50年代以来，由于其在室温下与普通电子显微镜的图像对比能力，使用醋酸铀酰等重金属盐进行负染一直是需求的焦点。然而，铀化合物是核燃料材料，在全球范围内受到严格控制。在相同的浓度(2%(w/v))下，制备了不同稀土元素的醋酸酯，并以马脾铁蛋白为模型进行了电子显微镜分析，系统地评价了它们作为蛋白质电子染色试剂的有效性。分析表明，三乙酸酯中的Sm和Eu，其次是Gd和Er，然后是La和Nd，可以作为电子显色剂。三醋酸钍沉淀出薄片状晶体，可用于选择较好的成像区域。在所研究的14种稀土三乙酸酯中，约有一半是作为铁蛋白电子着色剂的醋酸铀酰的可行替代品，而且有希望的稀土元素的离子大小存在一个最佳范围。这是首次从稀土元素收缩的角度，用电子显微镜密度分布直方图作为与醋酸铀酰比较的指标，对稀土过渡重金属三乙酸酯进行了系统的研究。
Cryo-electron microscopy, widely used for high-resolution protein structure determination, does not require staining. Yet negative staining with heavy metal salts such as uranyl acetate has been in persistent demand since the 1950s due to its image contrasting capabilities at room temperature with a common electron microscope. However, uranium compounds are nuclear fuel materials and are tightly controlled worldwide. Acetates of each lanthanoid series elements except promethium are prepared at the same concentration (2%(w/v)) and used as a model on horse spleen ferritin for electron microscopic analysis to systematically evaluate their effectiveness as electron staining reagents for the protein. Analysis shows that the triacetates of samarium and europium, followed by gadolinium and erbium, and then lanthanum and neodymium could function as electron staining reagents. Thulium-triacetate precipitates thin plate-like crystals and may be used for selecting better imaging fields. Of the 14 lanthanoid-triacetates examined, about half are viable alternatives to uranyl acetate as an electron staining reagent for ferritin, and there appears an optimal range in ionic sizes for promising lanthanoids. This is the first systematic investigation of lanthanoid transition heavy metal triacetates from the viewpoint of lanthanoid contraction, using density distribution histograms of electron micrographs as an indicator for comparison with uranyl acetate.