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Variable Field Analytical Ultracentrifugation: II. Gravitational Sweep Sedimentation Velocity



Jia Ma, Huaying Zhao, Julia Sandmaier, James Alexander Liddle, Peter Schuck


Sedimentation velocity (SV) analytical ultracentrifugation is a classical biophysical technique for the determination of the size-distribution of macromolecules, macromolecular complexes, and nanoparticles. SV has traditionally been carried out at a constant rotor speed, which limits the range of sedimentation coefficients that can be detected in a single experiment. Recently we have introduced tools to implement experiments with variable rotor speeds, in combination with variable field solutions to the Lamm equation, with the application to expedite the approach to sedimentation equilibrium. Here, we describe the use of variable-field sedimentation analysis to increase the size-range of SV experiments by approximately 100-fold through the use of a quasi-continuous increase of rotor speed during the experiment. Such ‘gravitational sweep' sedimentation approaches has previously been shown to be very effective in the study of nanoparticles with large size ranges. However, previously diffusion processes were not accounted for, therefore posing a lower limit of particle sizes and limiting the accuracy of the distribution. In the present work, we combine variable field solutions to the Lamm equation with diffusion-deconvoluted sedimentation coefficient distributions c(s), which further extends the macromolecular size-range that can be observed in a single SV experiment while maintaining accuracy and resolution. In this way, approximately five orders of magnitudes of sedimentation coefficients, or eight orders of magnitude of particle mass, can be probed in a single experiment. This can be useful, for example, in the study of proteins forming large assemblies, for example, as in fibrillation process or capsid self-assembly, in studies of the interaction between very dissimilar sized macromolecular species, in the study of broadly distributed nanoparticles.
Biophysical Journal


analytical ultracentrifugation, sedimentation velocity, particle size-distribution, nanoparticles


Ma, J. , Zhao, H. , Sandmaier, J. , Liddle, J. and Schuck, P. (2016), Variable Field Analytical Ultracentrifugation: II. Gravitational Sweep Sedimentation Velocity, Biophysical Journal, [online],, (Accessed June 21, 2024)


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Created January 4, 2016, Updated October 12, 2021