Biochemical Techniques and Instrumentation

4.2.1.2.1.Kinds of experiments

The two kinds of experiments commonly performed by ultracentrifuges are sedimentation velocity and sedimentation equilibrium.

1. Sedimentation velocity

This experiment reports on the shape and molar mass of the dissolved macromolecules as well as their size distribution. Their size resolution depends on the particle radii and rotor speed and ranges from 100 Da to 10 GDa. They are used to study reversible chemical equilibria between macromolecular species.

2. Sedimentation equilibrium

These experiments are concerned only with the final steady-state and gives time-independent concentration profile. The sedimentation equilibrium distribution in the centrifugal field are characterized by Boltzmann distribution. This experiment is insensitive to the shape of the macromolecule, and reports on the molar mass of the molecule and chemical equlibrium constants of the reaction mixtures.