Analytical ultracentrifugation is a classical technique that
has played a critical role in laying the foundations for
modern molecular biology. Among its achievements is the
demonstration that proteins are macromolecules rather than
complexes of smaller units, and direct support for the semiconservative
replication mechanism of DNA as proposed
by Watson and Crick. Unlike techniques such as SDS PAGE
or gel permeation chromatography, analytical ultracentrifugation
can be used to determine absolute molecular weights
without the use of molecular weight standards or interference
from the sieving matrix used for separation.