Transmission electron microscopy (TEM) has revolutionized our understanding of protein structures by enabling atomic-resolution visualization without the need for crystallography, thanks to advancements in cryo-TEM and single particle analysis methods. However, conventional electron microscopy remains relevant for studying stained samples, as it allows the practical determination of optimal conditions through extensive experimentation. TEM also facilitates the examination of supramolecular complexes encompassing proteins, lipids, and nucleic acids. In this study, we investigated the applicability of lanthanoid reagents as electron-staining alternatives to uranyl acetate, which is globally regulated as a nuclear fuel material. We focus on a model biomembrane vesicle system, the chromatophores from the purple photosynthetic eubacterium Rhodospirillum rubrum, which integrate proteins and lipids. Through density distribution analysis of electron micrographs, we evaluated the efficacy of various lanthanoid acetates and found that triacetates of neodymium, samarium, and gadolinium exhibited similar staining effectiveness to uranyl acetate. Additionally, triacetates of praseodymium, erbium, and lutetium, followed by europium show promising results as secondary candidates. Our findings suggest that lanthanoid transition heavy metal acetates could serve as viable alternatives for electron staining in TEM, offering potential advantages over uranyl acetate.

中文翻译：

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镧系重金属乙酸盐作为生物膜囊泡电子染色试剂的功效研究。

得益于冷冻 TEM 和单颗粒分析方法的进步，透射电子显微镜 (TEM) 无需晶体学即可实现原子分辨率可视化，彻底改变了我们对蛋白质结构的理解。然而，传统电子显微镜仍然适用于研究染色样品，因为它允许通过大量实验实际确定最佳条件。TEM 还有助于检查包含蛋白质、脂质和核酸的超分子复合物。在这项研究中，我们研究了镧系试剂作为醋酸双氧铀电子染色替代品的适用性，醋酸双氧铀在全球范围内作为核燃料材料受到监管。我们重点研究模型生物膜囊泡系统，即来自紫色光合真细菌红色红螺菌的色素细胞，它整合了蛋白质和脂质。通过电子显微照片的密度分布分析，我们评估了各种镧系元素乙酸盐的功效，发现钕、钐和钆的三乙酸盐表现出与乙酸铀酰相似的染色效果。此外，镨、铒和镥的三乙酸盐，以及铕，作为次要候选者显示出有希望的结果。我们的研究结果表明，镧系过渡重金属乙酸盐可以作为 TEM 电子染色的可行替代品，比乙酸双氧铀具有潜在优势。