Editing Virology (section)

===Electron microscopy===
[[File:Gastroenteritis viruses.jpg|right|thumb|Electron micrographs of viruses. A, rotavirus; B, adenovirus; C, norovirus; and D, astrovirus.]]
Viruses were seen for the first time in the 1930s when electron microscopes were invented. These microscopes use beams of [[electron]]s instead of light, which have a much shorter wavelength and can detect objects that cannot be seen using light microscopes. The highest magnification obtainable by electron microscopes is up to 10,000,000 times<ref name =Payne>Payne S. Methods to Study Viruses. Viruses. 2017;37-52. doi:10.1016/B978-0-12-803109-4.00004-0</ref> whereas for light microscopes it is around 1,500 times.<ref>{{cite web|title=Magnification - Microscopy, size and magnification (CCEA) - GCSE Biology (Single Science) Revision - CCEA|url=https://www.bbc.co.uk/bitesize/guides/z3vypbk/revision/3|access-date=2023-01-02|website=BBC Bitesize|language=en-GB}}</ref>

Virologists often use [[negative staining#Transmission electron microscopy|negative staining]] to help visualise viruses. In this procedure, the viruses are suspended in a solution of metal salts such as uranium acetate. The atoms of metal are opaque to electrons and the viruses are seen as suspended in a dark background of metal atoms.<ref name =Payne/> This technique has been in use since the 1950s.<ref name="pmid13804200">{{cite journal |vauthors=Brenner S, Horne RW |title=A negative staining method for high resolution electron microscopy of viruses |journal=Biochimica et Biophysica Acta |volume=34 |issue= |pages=103–10 |date=July 1959 |pmid=13804200 |doi=10.1016/0006-3002(59)90237-9}}</ref> Many viruses were discovered using this technique and negative staining electron microscopy is still a valuable weapon in a virologist's arsenal.<ref name="pmid19822888">{{cite journal |vauthors=Goldsmith CS, Miller SE |title=Modern uses of electron microscopy for detection of viruses |journal=Clinical Microbiology Reviews |volume=22 |issue=4 |pages=552–63 |date=October 2009 |pmid=19822888 |pmc=2772359 |doi=10.1128/CMR.00027-09}}</ref>

Traditional electron microscopy has disadvantages in that viruses are damaged by drying in the high vacuum inside the electron microscope and the electron beam itself is destructive.<ref name=Payne/> In [[cryogenic electron microscopy]] the structure of viruses is preserved by embedding them in an environment of [[vitreous water]].<ref>{{cite journal|last1=Tivol|first1=William F.|last2=Briegel|first2=Ariane|last3=Jensen|first3=Grant J.|date=October 2008|title=An Improved Cryogen for Plunge Freezing|journal=Microscopy and Microanalysis|language=en|volume=14|issue=5|pages=375–379|doi=10.1017/S1431927608080781|issn=1431-9276|pmc=3058946|pmid=18793481|bibcode=2008MiMic..14..375T}}</ref> This allows the determination of biomolecular structures at near-atomic resolution,<ref>{{cite journal | vauthors = Cheng Y, Grigorieff N, Penczek PA, Walz T | title = A primer to single-particle cryo-electron microscopy | journal = Cell | volume = 161 | issue = 3 | pages = 438–449 | date = April 2015 | pmid = 25910204 | pmc = 4409659 | doi = 10.1016/j.cell.2015.03.050 }}</ref> and has attracted wide attention to the approach as an alternative to [[X-ray crystallography]] or [[NMR spectroscopy]] for the determination of the structure of viruses.<ref name="Stoddart">{{cite journal |last1=Stoddart |first1=Charlotte |title=Structural biology: How proteins got their close-up |journal=Knowable Magazine |date=1 March 2022 |doi=10.1146/knowable-022822-1|doi-access=free |url=https://knowablemagazine.org/article/living-world/2022/structural-biology-how-proteins-got-their-closeup |access-date=25 March 2022}}</ref>
[[File:Rotavirus Reconstruction.jpg|right|thumb|Cryoelectron micrograph of a rotavirus]]