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Analytical Ultracentrifugation (AUC)

Beckman Coulter XL-I

An analytical ultracentrifuge is similar to a high-speed preparative centrifuge, except that the particles (proteins) in the sample being spun are monitored in real time by an integrated optical detection system. These optical systems (UV-Vis absorbance and Rayleigh interference) enable precise observation of the solution behavior of proteins as they undergo sedimentation. Using state-of-the-art software (SEDNTERP), data can be used for a comprehensive analysis of many biophysical characteristics of the protein(s) in the sample being studied:

  • Shape: How spherical is my protein?
  • Diameter: What’s the size of my particle?
  • Mass: What’s the molecular weight of my protein or complex in solution?
  • Stoichiometry: How many subunits comprise my protein?
  • Purity: Are there other particles in my sample?
  • Formulation: How does my protein behave in this buffer?
  • Heterogeneity: Is my protein bound to other molecules, and what’s the configuration of the complex?
  • Aggregation: Is my protein still in a usable form? Should I expect an immune response with my drug formulation?
  • Association: Does my protein associate and/or dissociate with other proteins?
  • Conformation:  Does the conformation of my protein change upon binding to a ligand?

For more information on these features of AUC, please consult the following resource:

The Beckman Coulter XL-I gives researchers two complementary views of protein behavior in solution. Sedimentation velocity provides hydrodynamic information about the size and shape of molecules. Sedimentation equilibrium provides the same type of information about the molar masses, stoichiometries, association constants and solution nonideality of proteins in solution.






Sedimentation Equilibrium (independent use)


Sedimentation Velocity (independent use)


Instrument use


*Cost of instrument time + $50/hr Facility Manager time



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Botterell Hall, Room 667



If you have any questions please contact Dr. Xiaohu Yan at