the sedimentation coefficient is measured in Svedberg units named after the scientist Theodore Svedberg. the shape of the particle being measured in the ultracentrifuge is one of the factors that determines the sedimentation coefficient. the values are usually not additive as the sedimentation coefficient is based on the rate at which a particle sediments in an ultracentrifuge and not on the size. for example, the sedimentation coefficient of eukaryotic ribosome is 80S but is made up of the 60S large subunit and the 40S small subunit.
