As a brand-new biotechnology, Cyro-EM provides scientists an unprecedented scope on transiently vanished micro world, enabling them to look macromolecules’ interactions with their own eyes. Now, lets get on a trip with Mr, Zhou, and find out what Cyro-EM is!
Current Utility and Future Prospects of Cyro-EM Technology
Ruoyu Zhou
When the precision of biology was approaching molecular and atomic level, X-ray crystallography and MRI renders the precise study of complex biology macromolecules possible. However, unconquerable limitation exists within these two biotechnologies. X-ray crystallography is only enabled to study crystalized biomolecules, and it only observes the molecules’ basic phase, which means no processes transporting ions or forming complexes can be seen with this method. MRI, similarly, can only observe relatively small macromolecules dissolved in water. For the macromolecules that neither can crystalize or dissolve nor be in relatively small mass, for instance, the tau protein crucial in Alzheimer’s disease, the two methods become unsuitable. In contrast, Cryogenic Electron Microscopy (cyro-EM), is a reliable biotechnology that has broad utility and unprecedented universality. As a novel biotechnology, cyro-EM analyzes macromolecules with neither the rays nor the sound waves. Instead, it uses electron microscopes to fire electrons, and detect the silhouettes of frozen macromolecules in different angles.
According to Professor Hongwei Wang, the processes of cyro-EM analysis include specimen preparation, electron microscope observation, image processing, and structural analyses. When forming an image, cyro-EM technique accelerates electrons in magnetic field to sub-light speed, and fire them through the vacuum interior of the electron microscope, where electromagnetic lens focus them together and magnetize any detectable interactions between the electrons and specimen in liquid nitrogen temperature, forming an image that is enlarged by millions of times in record agents. Applying computer to analyze the image left in the record agents, scientists are able to acquire a precise and three-dimensional image of the macromolecule structure. With no prerequisites to the solubility or size of samples, the cyro-EM technique forms a three-dimensional image from a large number of two-dimensional ones with the use of computer, demonstrating unprecedented universality and preciseness. The method is especially crucial in the study of complex biology macromolecules, for it reveals structures in extremely high accuracy and can capture the transient moment when certain macromolecules interact with ions or make structural changes. Cyro-EM’s capability is unique, and is crucial for the progress in medics, contagion, and molecular biology.
We can say that the cyro-EM is “the God’s eye” in biology study in molecular perspective, for it is able to see the micro world in the accuracy of 3~50Å(1 Å is equal to 0.1 nanometer), and render human perspective on micro world more instructive and direct, decoding the mystery of lives. With cyro-EM technology, the accurate structure of transport proteins, channel proteins, and sub organelles could be revealed and examined, and the study of enzyme’s and membrane proteins’ mechanisms can be carried out more efficaciously. Through delicately analyzing and comparing the functional mode and mechanisms of high and low level life forms, scientists will be enabled to unveil the route of evolvement with higher precision. For instance, applying cyro-EM to accurately analyzing the structures and functionalities of life forms’ mitochondrion ribosomes, a cell organelle crucial for mitochondrion synthesizing specific proteins, biologists will be able to determine the evolving path of a given species. Furthermore, the scientists would be able to reveal unknown or demonstrate known evolve paths, giving the question of “where are we from” a plausible answer. In addition, cyro-EM detects the accurate structure of receptor proteins. Take a research in 2017 for example: biologists examined the incomplete structure of an immunity receptor—toll-like receptor — using cyro-EM, and reveals its close relationship with inflammation and infection resist, providing an insight for structure-based tumor or virus targeted drugs. It can be proclaimed that given its preciseness and reliability, cyro-EM has become increasingly potent as a biology research technique and has been participating more in human’s perceiving to the micro world. Potentially, cyro-EM has the capability to contribute in assisting pharmaceutical industry, saving the lives of millions of patients.
cyro-EM is valuable in virology research. Due to its extremely high image resolution, the technology can be directly used to study the exact structure of each part of the virus. For example, in COVID-19 epidemic, scientists used cyro-EM to analyze the spike structure of the virus, revealing the structural reasons for its extremely contagious nature. Another example, the team of Rao Zihe and academician of Tsinghua Medical College took the lead in successfully analyzing the cryo-EM structure of the new coronavirus’ “RdRp-nsp7-nsp8” replication machine in 2.9 Å accuracy and proposed a possible mechanism of how Redecive and other drugs’ effector molecules inhibit the polymerase RdRp.
In face of the analysis of infectious disease pathogens, time is life, biomacromolecule cyro-EM technology is an extremely reliable and effective method. It has bought precious time for controlling the epidemic and saving lives, and it also provides a new perspective for humans’ struggle against diseases.
Cyro-EM technology can also be used to analyze the pathogenic proteins of protein-related diseases (such as Alzheimer’s disease), and contribute to the development of targeted drugs for the elimination of such proteins. The technology can also provide supportive forces to the patients of fatal disease, curbing any further disease developments. Besides, cyro-EM can be used to explore the operation and synthesis process of an array of proteins in animals and plants, so that scientists are able to observe the results of precise biological experiments more intuitively, so to solve the world’s population and food crises.
Although it has so many advantages, cyro-EM technology still has its limitations. Firstly, precision comes with price: the high-precision cyro-EM equipment is extremely expensive, and the computer algorithms required for its imaging are also highly complex, sometimes even requiring the participation of supercomputers, which is a limiting factor for the popularization of this technology globally. Secondly, the specimen preparation process is comparative difficult. The sample must be cooled to the temperature of liquid nitrogen and must be transferred at low temperature to avoid damage to the thin ice layer on its surface, technically it requires professional equipment. For now, although many breathtaking results have been achieved, biomacromolecule cyro-EM technology is still not completely “on its own.” It can be said that the cyro-EM technology relates to the fields of computer and engineering. Only when there are major breakthroughs in these two fields can the technology be better developed and popularized.
It is undeniable that biomacromolecule cyro-EM technology is a historic achievement on the scientific road of mankind. On the long road of scientific exploration in the future, it will enable us to have a deeper and more detailed understanding of the molecular and atomic level of the microscopic world. Cryo-electron microscopy technology is to today’s human society, just as its predecessor optical microscope was of value to us in the eighteenth and nineteenth centuries, it opens a way for human society to have a deeper glimpse at life itself in the journey to the stars. Using this ability to accurately “see” the microscopic world, mankind has the potential to fight incurable diseases more efficiently, solve social problems, and explore the unknowns of life itself.
References：
1. Wang Hongwei “The status and prospects of cryo-electron microscopy in structural biology research”, Science China: Life Sciences
2. Tsinghua News Network Tsinghua Medical College Rao Zihe and the team of academicians collaborate to decipher the three-dimensional structure of key anti-coronavirus drug targets April 23, 2020 https://news.tsinghua.edu.cn/info/1416/78401.htm
3. Wang Hongwei, “Cryo-electron microscopy technology reveals the details of biomolecules”, “Science and Technology” column of “People’s Daily”, 17th edition, February 07, 2020
4. “Bio Valley” public account “The latest research progress in cryo-electron microscopy analysis of biomolecular structure”, Sohu web version, October 08, 2017
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