What is Cryo-Electron Microscopy [CryoEM]?

Cryo-Electron Microscopy is a structural-biology technique that can locate individual atoms within a protein. It is an increasingly popular technique used to elucidate complex macromolecular structures. It is a kind of Transmission Electron Microscope (TEM) in which the sample is studied at cryogenic temperature. It freezes the specimen rapidly to turn the water molecules into transparent ice crystals.

This ice crystal transforms the biomolecules into a rigid state to aid in acquiring a high-resolution image. Numerous images are from the frozen specimen placed on a grid which is then digitally processed to develop a high-resolution image. The best part of Cryo-EM is that the specimen is examined in its actual intact state without being subjected to any artificial treatment such as fixing, dehydration, or staining. Cryo-Electron Microscopy has evolved as the mainstream technique or tool for determining the structure of molecular complexes at atomic resolution.

Cryo-Electron Microscopy - The Technique Used

• Cryo-Electron Microscopy concludes by involving flash-freezing solutions of proteins and then bombarding them with electrons that help produce microscope images of individual molecules. These are then utilized to reconstruct the 3D structure or shape of the molecules. These 3D structures can then be used to identify and uncover how proteins work, how they malfunction in disease, and how to use drugs to target them. And the good part is that with continued improvements in hardware and software, the structural molecule determination by this technique is becoming more detailed.
• Cryo-Electron Microscopy Usage Across Research Fields
• Though originally Cryo ET was primarily used in structural biological, due to recent technological advancements, it is an important tool used across a wide range of research areas, such as microbiology, immunology, neurobiology, and cell, molecular biology, and developmental biology.
• In microbiology, researchers use Cryo-Electron Microscopy to visualize viral infection in bacteria.
• In neurobiology, this popular technique is used to visualize protein aggregation that leads to various neurodegenerative disorders.
• In immunology, researchers can study the structure of HIV-1 particles bound to HeLa cells, telling about their interaction.
• In cell biology, Cryo ET is employed because it is helpful to understand the connection between different intracellular membrane systems by membrane contact sites.
• By using Cryo ET, recent research in molecular biology could uncover structural details of purified Cas9.

Problems with Cryo-Electron Microscopy

1. The process may encounter a problem if the sample is unstable, degraded, or aggregated. Some ligands, which have less molecular weight, may not be visible in the density map.
2. The presence of organic substances such as sugar or glycerine or DMSO may decrease the contrast and resolution of the sample.
3. Even though the purity of the sample is good, it may have poor homogeneity that will affect the resolution.
4. Samples may get destroyed during freezing.
5. There are other parameters to be optimized other than the sample itself: sample concentration, block time, grid specification, temperature, etc.

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Thus, for the complete success of the Cryo-Electron Microscopy Technique, rich experience and sufficient machine time is crucial. And the good experimental results are dependent on the right time and place.

FAQs on Cryo-Electron Microscopy

Q.1. Which three scientists received the Noble Prize in 2017 for their contribution to Cryo-Electron Microscopy?

Ans. Three scientists who received the Noble Prize in Chemistry in 2017 for developing "Cryo-Electron Microscopy for the high-resolution determination structure of biomolecules in solution are Jacques Dubochet, Joachim Frank, and Richard Henderson.

Q.2. Which technique was used before the popularity of the Cryo-Electron Microscopy method?

Ans. Scientists were using X-ray crystallography to visualize protein before the Cryo-Electron Microscopy method.

Q.3. Why is Cryo-Electron Microscopy gaining in popularity?

Ans. Cryo-Electron Microscopy is growing in popularity over traditional X‐ray crystallography since it does not require crystals, is suitable for proteins and their large molecular weight complexes, reduces radiation damage, and can retain the samples' native condition.

Q.4. Is Cryo-Electron Microscopy the same as Cryo-EM?

Ans. Cryo-EM is the abbreviated version of Cryo-Electron Microscopy and refers to the same technique or method.