The University of Massachusetts Amherst

Beckman ProteomeLab XL-I Analytical Ultracentrifuge

Beckman ProteomeLab XL-I Analytical Ultracentrifuge with fluorescence detection system

The ProteomeLab XL-A/XL-I is used for in-solution characterization of proteins, oligomers, aggregates, particles, colloids, and small structures. The column-free separation technique of the ProteomeLab XL-A/XL-I measures the relative change in the distribution of molecular weights, providing an efficient way to measure heterogeneity, stoichiometry and self-associating systems. The measurements are based on the first principles of thermodynamics and hydrodynamics, so no standards or calibrations are required.

Sensitive absorbance optics enable analysis of most samples. Interference optics can be used for low concentrations or samples without chromophores. Both systems can be implemented simultaneously, to maximize data acquisition in a single run. There are two different rotor configurations, and a variety of cell types, to enable multiple experimental designs. The wide range of rotational velocities also allow investigators to probe protein size, oligomerization, and binding constants.

As mentioned, the analytical ultracentrifuge can be used for several types of experiments, but the two most widely used are sedimentation velocity and sedimentation equilibrium.

Sedimentation velocity experiments are utilized to determine protein molecular weight and identify degree of oligomerization. In a sedimentation velocity experiment, high rotor speeds are used to completely sediment all particles in solution. Protein oligomers sediment at a different rate than single protein molecules owing to their higher weight, and since the analytical ultracentrifuge measures protein formulations in their native state, the degree of oligomerization can be assessed to highly accurate levels.

Sedimentation equilibrium experiments use lower velocity, and assess the concentration distribution as a function of g-force applied. By measuring the concentration curve at several different g-forces, equilibrium binding constants can be measured.