A svedberg, symbol , is a non-SI unit of sedimentation coefficient, with . A sedimentation coefficient is a settling velocity divided by the applied acceleration, so its physical dimension is time. It is a transport property under specified conditions, rather than the time required for a particle to cross a sample.[ref]
For example, let a particle have sedimentation coefficient in a centrifugal acceleration . Its local settling speed is , or one micrometre per second. The acceleration in a rotating sample varies with radius, so this local calculation is not a whole-tube travel time.
Two joined particles do not generally have the sum of their separate sedimentation coefficients: joining changes both the net driving force and the resistance to motion. A label such as 16S ribosomal RNA therefore describes sedimentation behavior, not a molecular mass of16 units or a count of16 components.
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The Svedberg (symbol: S) is a unit of time used in the field of biochemistry and molecular biology to measure the sedimentation rate of particles in a centrifuge. It is named after the Swedish chemist Theodor Svedberg, who won the Nobel Prize in Chemistry in 1926 for his work on the ultracentrifuge and the behavior of colloids. One Svedberg unit is defined as \(10^{-13}\) seconds.