What Is Cryo-EM, And How Does It Work?

Cryo-EM is cryo-electron microscopy. Having been developed for more than two decades now, this technique involves getting the structures of macromolecules visualized. It is a type of electron microscopy where transmission is involved and where the samples can be studied while being placed in temperatures that are that on a cryogenic level. Through the Cryo-EM technology, various biological structures have been successfully defined in their respective atomic levels. This includes the mitochondria and ribosomes of various pathogens.

There is a need for a thorough understanding and visualization of biological structures as it is considered a critical step in developing new treatments and drugs. Thanks to the added advantage of the Cryo-EM technique, it has become quite a preferred tool that structural biologists are considerably relying on upon in recent days.

Using Cryo-Em for Visualizing Biological Structures

When utilizing the Cryo-EM technique, a biological material’s sample gets flash-frozen before it is observed. This is done by using thin sample films and dousing them in baths made of ethane, which are then cooled to -180C or the same temperature level of liquid nitrogen. The frozen state of the solution is retained and electrons are used to bombard the sample films. When the electrons pass through a lens, the effect is a magnified image that can be seen on the detector. This allows for the sample’s structure to be magnified thus, making it possible to get it duly analyzed.

Two types of Cryo-EM are available today. There is the Cryo-EM which analyzes single particles where 3D structures are created out of projections in 2D. The 2D images from the same biological object that are part of the structure that has been frozen are captured initially. They are then organized as structures in 3D through algorithms in image processing.

Another type is Cryo-Electron tomography. In this method, several images coming from the biological object that is being observed are captured. This is done by getting the object tilted and moved in various angles to ensure that the beams containing the electrons can successfully penetrate the structure. The resulting image is a three-dimensional representation of the structure.

Benefits in Structural Biology

In the past, techniques that are used in structural biology used to include crystallography of x-ray as well as the use of spectroscopy in magnetic resonance. Both these methods, however, only have very limited applications since both require a large array of samples for any relevant data to be gathered. Also, crystallography via x-ray requires specimens to be crystallized. This process can be quite difficult as this causes the environment to be transformed into a non-physiological setting.

Cryo-EM, on the other hand, does not require a large size of samples. It doesn’t require samples to go through crystallization too. This makes it highly ideal to allow the viewing of the biological structures at their near-atomic state. Specimens undergoing Cryo-Em observation do not need to be stained or chemically fixed too. This allows scientists to observe them in an environment that is native to their physiological properties.

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