Cryo-electron microscopy (cryo-EM) has become the method of choice in the field of structural biology, owing to its unique ability to deduce structures of vitreous ice-embedded, hydrated biomolecules over a wide range of structural resolutions. As cryo-transmission electron microscopes (cryo-TEM) become increasingly specialised for high, near-atomic resolution studies, operational complexity and associated costs serve as significant barriers to widespread usability and adoptability. To facilitate the expansion and accessibility of the cryo-EM method, an efficient, user-friendly means of imaging vitreous ice-embedded biomolecules has been called for. In this study, we present a solution to this issue by integrating cryo-EM capabilities into a commercial scanning electron microscope (SEM). Utilising the principle of low-energy in-line electron holography, our newly developed hybrid microscope permits low-to-moderate resolution imaging of vitreous ice-embedded biomolecules without the need for any form of sample staining or chemical fixation. Operating at 20 kV, the microscope takes advantage of the ease-of-use of SEM-based imaging and phase contrast imaging of low-energy electron holography. This study represents the first reported successful application of low-energy in-line electron holographic imaging to vitreous ice-embedded small biomolecules, the effectiveness of which is demonstrated here with three morphologically distinct specimens.

中文翻译：

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使用改进的扫描电子显微镜对玻璃体冰嵌入的小生物分子进行低能在线电子全息成像

冷冻电子显微镜 (cryo-EM) 已成为结构生物学领域的首选方法，因为它具有在广泛的结构分辨率范围内推断玻璃体冰嵌入的水合生物分子结构的独特能力。随着低温透射电子显微镜 (cryo-TEM) 越来越专用于高、近原子分辨率的研究，操作复杂性和相关成本成为广泛使用和采用的重大障碍。为了促进冷冻电镜方法的扩展和可及性，需要一种高效、用户友好的玻璃体冰嵌入生物分子成像手段。在这项研究中，我们通过将冷冻电镜功能集成到商用扫描电子显微镜 (SEM) 中来提出解决方案。利用低能量在线电子全息的原理，我们新开发的混合显微镜可以对玻璃体冰嵌入的生物分子进行中低分辨率成像，而无需任何形式的样品染色或化学固定。该显微镜在 20 kV 下运行，利用了基于 SEM 的成像和低能电子全息相衬成像的易用性。这项研究代表了首次报道的低能量在线电子全息成像成功应用于玻璃体冰嵌入的小生物分子，这里用三个形态不同的标本证明了其有效性。该显微镜在 20 kV 下运行，利用了基于 SEM 的成像和低能电子全息相衬成像的易用性。这项研究代表了首次报道的低能量在线电子全息成像成功应用于玻璃体冰嵌入的小生物分子，这里用三个形态不同的标本证明了其有效性。该显微镜在 20 kV 下运行，利用了基于 SEM 的成像和低能电子全息相衬成像的易用性。这项研究代表了首次报道的低能量在线电子全息成像成功应用于玻璃体冰嵌入的小生物分子，这里用三个形态不同的标本证明了其有效性。