Misplaced Pages

Buoyant density centrifugation

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
(Redirected from Density gradient centrifugation)
This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.
Find sources: "Buoyant density centrifugation" – news · newspapers · books · scholar · JSTOR (January 2012) (Learn how and when to remove this message)
Electron microscope image of canine parvovirus isolated using buoyant density centrifugation

Buoyant density centrifugation (also isopycnic centrifugation or equilibrium density-gradient centrifugation) uses the concept of buoyancy to separate molecules in solution by their differences in density.

Implementation

Historically a cesium chloride (CsCl) solution was often used, but more commonly used density gradients are sucrose or Percoll. This application requires a solution with high density and yet relatively low viscosity, and CsCl suits it because of its high solubility in water, high density owing to the large mass of Cs, as well as low viscosity and high stability of CsCl solutions.

The sample is put on top of the solution, and then the tube is spun at a very high speed for an extended time, at times lasting days. The CsCl molecules become densely packed toward the bottom, so a continuous gradient of layers of different densities (and CsCl concentrations) form. Since the original solution was approximately the same density, they go to a level where their density and the CsCl density are the same, to which they form a sharp, distinctive band.

Caesium chloride (CsCl) solution and two morphological types of rotavirus. Following centrifugation at 100g a density gradient forms in the CsCl solution and the virus particle separate according to their densities.

Isotope separation

This method very sharply separates molecules, and is so sharp that it can even separate different molecular isotopes from one another. It has been utilized in the Meselson-Stahl experiment.

DNA separation

Buoyant density of the majority of DNA is 1.7g/cm which is equal to the density of 6M CsCl solution. Buoyant density of DNA changes with its GC content. The term "satellite DNA" refers to small bands of repetitive DNA sequences with distinct base composition floating above (A+T rich) or below (G+C rich) the main component DNA.

See also

References

  1. Burt, Richard O. (2000-12-04). "Cesium and Cesium Compounds". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.0305190902211820.a01. ISBN 978-0-471-48494-3.
  2. Dumont, Marc G.; Murrell, J. Colin (June 2005). "Stable isotope probing — linking microbial identity to function". Nature Reviews Microbiology. 3 (6): 499–504. doi:10.1038/nrmicro1162. ISSN 1740-1534. PMID 15886694. S2CID 24051877.
  3. Arrighi, Frances E.; Mandel, Manley; Bergendahl, Janet; Hsu, T. C. (June 1970). "Buoyant densities of DNA of mammals". Biochemical Genetics. 4 (3): 367–376. doi:10.1007/BF00485753. PMID 4991030.

Further reading


Stub icon

This article about analytical chemistry is a stub. You can help Misplaced Pages by expanding it.

Categories: