Abstract
Recent developments in the UltraScan-III software make it possible to model multi-speed analytical ultracentrifugation sedimentation velocity experiments using finite-element solutions of the Lamm equation. Using simulated data, we demonstrate here how these innovations can be used to enhance the resolution of sedimentation velocity experiments when compared to single-speed experiments. Using heterogeneous systems covering as much as five orders of magnitude in molar mass and fivefold in anisotropy, we compare results from runs performed at multiple speeds to those obtained from single-speed experiments, fitted individually and analyzed globally over multiple speeds, and quantify resolution for sample heterogeneous in size and anisotropy. We also provide guidance on the design of multi-speed experiments and offer a program that can be used to deduce optimal spacing of rotor speeds and speed step durations when a few parameters from the experiment can be estimated. These include the meniscus position, the sedimentation coefficient of the largest species in a mixture, and a solute distribution. Our results show that errors observed in the determination of hydrodynamic parameters for system with great heterogeneity are markedly reduced when multi-speed analysis is employed.
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Acknowledgements
This work was supported by NIH Grant GM120600 and NSF Grant NSF-ACI-1339649 (to BD). Supercomputer calculations were performed on Comet at the San Diego Supercomputing Center (support through NSF/XSEDE Grant TG-MCB070039N to BD) and on Lonestar-5 at the Texas Advanced Computing Center (supported through UT Grant TG457201 to BD).
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Special Issue: 23rd International AUC Workshop and Symposium.
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Williams, T.L., Gorbet, G.E. & Demeler, B. Multi-speed sedimentation velocity simulations with UltraScan-III. Eur Biophys J 47, 815–823 (2018). https://doi.org/10.1007/s00249-018-1308-0
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DOI: https://doi.org/10.1007/s00249-018-1308-0