A svedberg (symbol S, sometimes Sv, not to be confused with Sv for the
SIunit sievertas well as the non-SI sverdrup) is a non- SIphysical unit used for sedimentation coefficients. It characterizes the behaviour of a particle type in sedimentationprocesses, notably centrifugation. The svedberg is technically a measure of time, and is defined as exactly 10-13 seconds (100 fs).
The unit is named after the Swedish
chemist Theodor Svedberg( 1884- 1971), winner of the Nobel prizein chemistryin 1926for his work in the chemistry of colloids and his invention of the ultracentrifuge.
Bigger particles generally sediment faster, and therefore have higher svedberg values. The svedberg is however not additive. Since the sedimentation rate is associated with the size of the particle, when two particles bind together there is inevitably a loss of surface area. Thus when measured separately they will have svedberg values that do not add up to that of the particle formed when they bind together.
The svedberg is the most important measure used to distinguish ribosomes.
* [http://nobelprize.org/educational_games/medicine/dna/a/translation/svedberg_unit.html Svedberg unit] - Nobelprize.org
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