The Minnesota Nano Center recently acquired a powerful new analytical tool for those working with nanoparticles and macromolecules. The Beckman Optima analytical ultracentrifuge (AUC) is a state-of-the-art platform for characterizing proteins, polymers, nucleic acids, and other macromolecules, as well as measuring nanoparticle size, shape, and surface structure. The Optima AUC is the only instrument of its kind at the University of Minnesota, and was obtained with major funding from the National Institutes of Health.
What is AUC? Analytical ultracentrifugation is a technique that monitors the behavior of nanoscale materials as they sediment under the large settling force developed in a specialized high speed centrifuge. Sample vials are loaded in the AUC’s instrumented rotor, which has windows through which the sedimentation of suspended particles in the sample can be recorded. The rotor is spun at up to 60,000 rpm, developing a force on suspended particles equal to 250,000 times normal gravity. This huge force causes macromolecules and nanometer-scale particles to sediment (or rise, if their density is lower than that of the suspending liquid).
The sedimentation velocity measured by the AUC provides information on the size, shape, and molecular weight of macromolecules, as well as the interactions between them. This method is a direct measurement of molecular weight, and does not rely on calibration or assumptions about molecule shape. It can also reveal changes in molecular weight when molecules associate to form more complex structures, common in many biological systems.
Those working with inorganic or organic nanoparticles will also find the AUC useful, especially as an adjunct to other methods like dynamic light scattering and nanoparticle tracking analysis. Ultracentrifugation can determine size distributions of mixtures of multiple components, and no knowledge of particle optical properties is required.
We expect to complete testing on the Optima AUC soon. The Nano Center will be offering a series of webinars to introduce the AUC to the research community—check these web pages for updates.