CentrifugeBeckman XL-I Analytical Ultracentrifuge

Analytical ultracentrifugation is a classical method of biochemistry and molecular biology. Because analytical ultracentrifugation relies on the principal property of mass and the fundamental laws of gravitation, it has broad applicability. It is a primary technique requiring no standards for comparison. Sedimentation can be used to analyze the solution behavior of nearly any molecule over a wide range of solute concentrations and in a wide variety of solvents. Thus, while low concentration regimes are of interest for analyzing tight associations, the ability to characterize the thermodynamic behavior of a macromolecule at high concentrations makes ultracentrifugation a good adjunct for drug formulation studies, NMR, or crystallography. Add to these merits the fact that sedimentation is nondestructive, rapid, and simple, and it is easy to see why it has endured for more than 70 years.

 Analytical ultracentrifugation provides two complementary views of solution behavior. Although the same instrument is used, different experimental protocols are employed. Sedimentation velocity provides first-principle, hydrodynamic information about the size and shape of a molecule, whereas sedimentation equilibrium provides first-principle, thermodynamic information about the solution molar mass, association constants, stoichiometries, and solution nonideality. For many questions, there is no substitute method of analysis.

 (T. M. Laue and W. F. Stafford III (1999) Annu. Rev. Biophys. Biomol. Struct. 28:75-100.)