Transmission electron cryomicroscopy

CryoTEM image of GroEL suspended in amorphous ice at 50000× magnification
Structure of Alcohol oxidase from Pichia pastoris by CryoTEM

Transmission electron cryomicroscopy (CryoTEM), commonly known as cryo-EM, is a form of cryogenic electron microscopy, more specifically a type of transmission electron microscopy (TEM) where the sample is studied at cryogenic temperatures (generally liquid-nitrogen temperatures).[1] Cryo-EM, specifically 3-dimensional electron microscopy (3DEM), is gaining popularity in structural biology.[2]

The utility of transmission electron cryomicroscopy stems from the fact that it allows the observation of specimens that have not been stained or fixed in any way, showing them in their native environment. This is in contrast to X-ray crystallography, which requires crystallizing the specimen, which can be difficult, and placing them in non-physiological environments, which can occasionally lead to functionally irrelevant conformational changes.

Advances in electron detector technology, particularly DED (Direct Electron Detectors) as well as more powerful software imaging algorithms have allowed for the determination of macromolecular structures at near-atomic resolution.[3] Imaged macromolecules include viruses, ribosomes, mitochondria, ion channels, and enzyme complexes. Starting in 2018, cryo-EM could applied to structures as small as hemoglobin (64 kDa)[4] and with resolutions up to 1.8 Å.[5] In 2019, cryo-EM structures represented 2.5% of structures deposited in the Protein Data Bank,[6] and this number continues to grow.[7] An application of cryo-EM is cryo-electron tomography (cryo-ET), where a 3D reconstruction of the sample is created from tilted 2D images.

  1. ^ Kühlbrandt W (August 2014). "Cryo-EM enters a new era". eLife. 3: e03678. doi:10.7554/elife.03678. PMC 4131193. PMID 25122623.
  2. ^ Callaway E (September 2015). "The revolution will not be crystallized: a new method sweeps through structural biology". Nature. 525 (7568): 172–4. Bibcode:2015Natur.525..172C. doi:10.1038/525172a. PMID 26354465.
  3. ^ Murata K, Wolf M (Feb 2018). "Cryo-electron microscopy for structural analysis of dynamic biological macromolecules". Biochimica et Biophysica Acta (BBA) - General Subjects. 1862 (2): 324–334. doi:10.1016/j.bbagen.2017.07.020. PMID 28756276.
  4. ^ Khoshouei M, Radjainia M, Baumeister W, Danev R (June 2017). "Cryo-EM structure of haemoglobin at 3.2 Å determined with the Volta phase plate". Nature Communications. 8: 16099. Bibcode:2017NatCo...816099K. doi:10.1038/ncomms16099. PMC 5497076. PMID 28665412.
  5. ^ Merk A, Bartesaghi A, Banerjee S, Falconieri V, Rao P, Davis MI, Pragani R, Boxer MB, Earl LA, Milne JL, Subramaniam S (June 2016). "Breaking Cryo-EM Resolution Barriers to Facilitate Drug Discovery". Cell. 165 (7): 1698–1707. doi:10.1016/j.cell.2016.05.040. PMC 4931924. PMID 27238019.
  6. ^ "PDB Data Distribution by Experimental Method and Molecular Type". www.rcsb.org. Retrieved 2019-12-03.
  7. ^ "PDB Statistics: Growth of Structures from 3DEM Experiments Released per Year". www.rcsb.org. Retrieved 2018-12-22.