What is sedimentation factor? in ribosome?

Question

What is sedimentation factor? in ribosome?

Answer 1

this is one way to describe protien -particularly used for rna

pieces of the rna are put into a tube and spun... then you can look at the different levels in the tube where the pices lined up - the sedementation

it's called the svedberg, that's where the s comes from when you are talking about 16s ribosomal rna or whatever size s

it's also not addative (50s +30s does not equal 80s)

Answer 2

The sedimentation factor is the rate at which the ribosomes will be sedimented out during the separation of ribosomes of different sizes by using ultracentrifugation. It is measured in S (Svedberg units).

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 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.

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.

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.