A Glimpse into the Inception of the Cryo-Electron Microscope

The 1960s witnessed a limitation in the use of Transmission Electron Microscopy for detailed analysis due to the radiation damage caused by high energy electron beams. Scientists theorized that examining specimens at low temperatures would mitigate beam-induced radiation damage. Both liquid helium and liquid nitrogen were explored as potential cryogens. However, the results of the experiment were not conclusive.

The first successful implementation of cryoEM was reported in 1981 by Alasdair McDowall and Jacques Dubochet, scientists at the European Molecular Biology Laboratory. They vitrified pure water in a thin film by spraying it onto a hydrophilic carbon film that was quickly plunged into cryogen (liquid propane or liquid ethane cooled to 100 K). The thin layer of amorphous ice was less than 1 µm thick and an electron diffraction pattern confirmed the presence of amorphous/vitreous ice.

The Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry – 2017 to Richard Henderson, Jacques Dubochet, and Joachim Frank. They were recognized for their contributions to the development of cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution. In 1990, Richard Henderson successfully used the electron microscope to generate a 3D image of a protein at atomic resolution. Joachim Frank made this technology widely accessible. Jacques Dubochet contributed to Cryo-electron microscopy by vitrifying water, ensuring that the biological sample retained its shape even when frozen or in a vacuum.

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The Working Principles of Cryo-Electron Microscopy

Cryo-electron microscopy is a distinct form of electron microscopy that constructs a 3D image by collecting and combining thousands of projections of bio-molecules. This technology allows researchers to visualize processes that have never been seen before by freezing the mid-movement of bio-molecules. Cryo-electron microscopy enables the freezing of bio-molecules at cryogenic temperatures, i.e., at -150°C, thereby preserving their natural shape. This reveals the structure of molecules in extraordinary detail. It is of great importance for the better understanding of basic Chemistry and for the development of pharmaceuticals as it simplifies and improves the imaging of bio-molecules.

It aids in the study of intricate viruses , protein complexes, and cellular structures at a molecular resolution. It provides scientists with an opportunity to examine the machinery of life in a 3D form. Previous forms of electron microscopes made it impossible to study bio-molecules in 3D form as the powerful beams often destroyed the biological matter. The resolution has now improved from shapeless blobs to imaging proteins at atomic resolution. Cryo-Electron Microscopy has overcome several limitations, ushering biochemistry into a new era.

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