Editing Ultracentrifuge

{{Short description|Centrifuge for spinning a rotor at very high speeds}}
[[File:Beckman-Coulter ultracentrifuge XL-100K -01.jpg|thumb|A standard ultracentrifuge by manufacturer [[Beckman Coulter]]]]
An '''ultracentrifuge''' is a [[centrifuge]] optimized for spinning a rotor at very high speeds, capable of generating acceleration as high as {{nowrap|1&thinsp;000&thinsp;000 [[G-force|g]]}} (approx. {{nowrap|9&thinsp;800 km/s²}}).<ref>{{cite web |url= https://www.beckmancoulter.com/wsrportal/wsr/research-and-discovery/products-and-services/centrifugation/optima-max-xp/index.htm|title=Optima MAX-XP | access-date =2016-02-20}}</ref> There are two kinds of ultracentrifuges, the preparative and the [[analytical ultracentrifuge]]. Both classes of instruments find important uses in [[molecular biology]], [[biochemistry]], and [[polymer]] science.<ref name=Bioanalytical>Susan R. Mikkelsen & Eduardo Cortón. Bioanalytical Chemistry, Ch. 13. Centrifugation Methods. John Wiley & Sons, Mar 4, 2004, pp. 247-267.</ref>

==History==
In 1924 [[Theodor Svedberg]] built a centrifuge capable of generating 7,000 g (at 12,000 rpm), and called it the ultracentrifuge, to juxtapose it with the [[Ultramicroscope]] that had been developed previously. In 1925-1926 Svedberg constructed a new ultracentrifuge that permitted fields up to 100,000 g (42,000 rpm).<ref name="Svedberg Lecture">{{cite web |url= https://www.nobelprize.org/prizes/chemistry/1926/svedberg/lecture/ |title= Svedberg Lecture |access-date=2019-02-18 }}</ref> Modern ultracentrifuges are typically classified as allowing greater than 100,000 g.<ref>{{cite web |url= https://www.beckman.com/centrifuges |title= Beckman Centrifuges |access-date=2019-02-18 }}</ref> Svedberg won the [[Nobel Prize in Chemistry]] in 1926 for his research on colloids and proteins using the ultracentrifuge.<ref>{{cite web |url= http://www.rsc.org/chemsoc/timeline//pages/1925.html |title= Svedberg |access-date=2010-06-23 }}</ref><ref name="RosenGothard2009">Joe Rosen; Lisa Quinn Gothard. ''[https://books.google.com/books?id=avyQ64LIJa0C Encyclopedia of Physical Science]''. Infobase Publishing; 2009. {{ISBN|978-0-8160-7011-4}}. p. 77.</ref><ref name="Svedberg Lecture"/>

In early 1930s, [[Émile Henriot (chemist)|Émile Henriot]] found that suitably placed jets of compressed air can spin a bearingless top to very high speeds and developed an ultracentrifuge on that principle. [[Jesse Beams]] from the Physics Department at the [[University of Virginia]] first adapted that principle to a [[high-speed camera]], and then started improving Henriot's ultracentrifuge, but his rotors consistently overheated.<ref>{{cite web | url=https://www.beckman.com/resources/technologies/analytical-ultracentrifugation/history/light-beams | title=Light Beams }}</ref>

Beam's student [[Edward Greydon Pickels]] solved the problem in 1935 by [[vacuum]]izing the system, which allowed a reduction in [[friction]] generated at high speeds.  Vacuum systems also enabled the maintenance of constant [[temperature]] across the sample, eliminating [[convection current]]s that interfered with the interpretation of sedimentation results.<ref name=Elzen>Elzen B. ''Vacuum ultracentrifuge.'' In:  Encyclopedia of 20th-Century Technology, Colin Hempstead & William Worthington, eds. Routledge, 2005. p. 868.</ref>

[[File:Beckman model e hm50tr96s.tiff|thumb|right|Comparing Serial Numbers 1 and 1000 of Spinco's Model E Analytical Ultracentrifuge, 1965]]
In 1946, Pickels cofounded [[Spinco]] (Specialized Instruments Corp.) to market analytical and preparative ultracentrifuges based on his design. Pickels considered his design to be too complicated for commercial use and developed a more easily operated, “foolproof” version. But even with the enhanced design, sales of analytical centrifuges remained low, and Spinco almost went bankrupt. The company survived by concentrating on sales of preparative ultracentrifuge models, which were becoming popular as workhorses in biomedical laboratories.<ref name=Elzen/> In 1949, Spinco introduced the Model L, the first preparative ultracentrifuge to reach a maximum speed of 40,000 [[Revolutions per minute|rpm]]. In 1954, [[Beckman Instruments]] (later [[Beckman Coulter]]) purchased the company, forming the basis of its Spinco centrifuge division.<ref>Arnold O. Beckman: One Hundred Years of Excellence. By Arnold Thackray and Minor Myers, Jr. Philadelphia: Chemical Heritage Foundation, 2000.</ref>

==Instrumentation==
Ultracentrifuges are available with a wide variety of rotors suitable for a great range of experiments.  Most rotors are designed to hold tubes that contain the samples.  ''Swinging bucket rotors'' allow the tubes to hang on hinges so the tubes reorient to the horizontal as the rotor initially accelerate.<ref>{{Cite web|title=Swinging-Bucket Centrifuge Rotors - Beckman Coulter|url=https://www.beckman.com/centrifuges/rotors/swinging-bucket|access-date=2021-10-13|website=www.beckman.com}}</ref>  ''Fixed angle rotors'' are made of a single block of material and hold the tubes in cavities bored at a predetermined angle.  ''Zonal rotors'' are designed to contain a large volume of sample in a single central cavity rather than in tubes.  Some zonal rotors are capable of dynamic loading and unloading of samples while the rotor is spinning at high speed.

Preparative rotors are used in biology for pelleting of fine particulate fractions, such as cellular organelles ([[Mitochondrion|mitochondria]], [[microsome]]s, [[ribosome]]s) and [[virus]]es.  They can also be used for [[gradient]] separations, in which the tubes are filled from top to bottom with an increasing concentration of a dense substance in solution.  [[Sucrose]] gradients are typically used for separation of cellular organelles.  Gradients of [[caesium]] salts are used for separation of nucleic acids.  After the sample has spun at high speed for sufficient time to produce the separation, the rotor is allowed to come to a smooth stop and the gradient is gently pumped out of each tube to isolate the separated components.

==Hazards==
The tremendous rotational [[kinetic energy]] of the rotor in an operating ultracentrifuge makes the [[catastrophic failure]] of a spinning rotor a serious concern, as it can explode spectacularly. Rotors conventionally have been made from high strength-to-weight metals such as aluminum or titanium.  The stresses of routine use and harsh chemical solutions eventually cause rotors to deteriorate.  Proper use of the instrument and rotors within recommended limits and careful maintenance of rotors to prevent corrosion and to detect deterioration is necessary to mitigate this risk.<ref>Beckman Instruments, Spinco Division. [http://www.chem.purdue.edu/chemsafety/newsandstories/beckmanletter.pdf Urgent corrective action notice: Reclassification to Minimize Ultracentrifuge Chemical Explosion Hazard.] June 22, 1984.</ref><ref>Goodman, T. [http://www.americanlaboratory.com/914-Application-Notes/1326-Centrifuge-Safety-and-Security/ ''Centrifuge Safety and Security.''] American Laboratory, February 01, 2007</ref>

More recently some rotors have been made of lightweight carbon fiber composite material, which are up to 60% lighter, resulting in faster acceleration/deceleration rates. Carbon fiber composite rotors also are corrosion-resistant, eliminating a major cause of rotor failure.<ref>Piramoon, Sheila. "Carbon fibers boost centrifuge flexibility: advancements in centrifuge rotors over the years have led to improved lab productivity." Laboratory Equipment Mar. 2011: 12+. General Reference Center GOLD. Web. 15 Feb. 2015.</ref>

==See also==
*[[Analytical ultracentrifugation]]
*[[Gas centrifuge]]
*[[Theodor Svedberg]]
*[[Differential centrifugation]]
*[[Buoyant density ultracentrifugation]]
*[[Zippe-type centrifuge]]

==References==
{{Reflist}}

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==External links==
* [https://onlinelibrary.wiley.com/doi/full/10.1110/ps.0207702 Modern analytical ultracentrifugation in protein science: A tutorial review]
* [http://www.pnas.org/cgi/content/full/102/1/81 Studying multiprotein complexes by multisignal sedimentation velocity analytical ultracentrifugation]
* [https://web.archive.org/web/20021031093703/http://www.ehrs.upenn.edu/programs/labsafety/ultra_explosion.html Report on an ultracentrifuge explosion]

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[[Category:Centrifuges]]