Everything about Svedberg totally explained
A
svedberg (symbol
S, sometimes
Sv, not to be confused with Sv for the
SI unit
sievert as well as the non-SI
sverdrup) is a non-
SI physical unit used to characterize the behaviour of a particle type in
ultracentrifugation. Bigger particles have higher svedberg values. It is a unit of time amounting to 10
-13 s or 100
fs.
It is named after the
Swedish chemist Theodor Svedberg (
1884-
1971), winner of the
Nobel prize in
chemistry in
1926 for his work in the chemistry of
colloids and his invention of the
ultracentrifuge.
The sedimentation rate or coefficient of a particle or
macromolecule is computed through dividing the constant
speed of sedimentation (in
ms−1) by the
acceleration applied (in
ms−2). The speed is constant because the force applied by the ultracentrifuge (measuring typically in multiples of hundreds of thousands of
gravities) is canceled by the viscous resistance of the medium (normally
water) through which the particle is moving. The result has the
dimensions of a unit of
time and is expressed in svedbergs. One svedberg is defined as exactly 10
−13 s.
Bigger particles have higher svedberg values. The svedberg is
not additive, since the sedimentation rate is associated with the size of the particle, when two particles bind together there's inevitably a loss of surface area. Thus when measured separately that'll have svedberg values that don't add up to that of the particle formed when they bind together.
This is particularly the case with the
ribosome. The most important measure used to distinguish ribosomes, which indicates their source organism, is the svedberg. A 70 S ribosome comes from
eubacteria, but is composed of a 50 S subunit and a 30 S subunit.
Further Information
Get more info on 'Svedberg'.
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