One hundred years after the technique was recognized with the Nobel Prize in Chemistry, analytical ultracentrifugation (AUC) is still making waves in the scientific world. Theodor Svedberg developed the approach in the 1920s, using it to characterize tiny gold particles. Now, AUC helps researchers determine specific properties of individual molecules clustered together, such as those used in pharmaceuticals or industrial chemicals.
A team led by researchers at the University Akron recently published a review of the technology, cataloging use cases focused on how AUC can help solve challenges in characterizing molecular clusters. These clusters comprise clumps of proteins, sugars and other particles that scientists need to understand in deep detail to predict interactions, stability and more of the many diverse solutions encountered across a bevy of areas. They published their work on May 27 in Polyoxometalates .
"Analytic ultracentrifugation is a powerful and information-rich technique for characterizing the molecular weight, size, shape, dispersity and association behavior of species in their native solution environment," said corresponding author Tianbo Liu, professor in the Department of Polymer Science at the University of Akron. "With recent instrumentation and data analysis software, AUC enables more accurate and reliable characterization of diverse species in solution systems, including biomacromolecules, like proteins and carbohydrates; colloids, such as nanoparticle suspensions; surfactants assemblies such as micelle; and polymers, including synthetic polymers in solution and polymer-based nanoparticles in dispersion."
AUC works by spinning solution samples up to 60,000 rotations per minute, forcing the contents to sediment, or to disperse into concentrated gradients based on size and weight. The approach also integrates optical analytics to monitor and characterize the sedimentation of each molecule, taking AUC a step beyond traditional centrifugation, according to Liu.
"This overcomes a key limitation of techniques such as light and X-ray scattering, which typically measure the collective properties of solute mixtures," Liu said, explaining that the other techniques work by assessing how light or X-rays at a sample scatter.
He noted that AUC also lacks the need for stationary phases or calibration standards like other techniques, such as chromatography, enabling direct, absolute determination of molecular properties. Another benefit of AUC is that the measurements are performed in solution, meaning surface interactions and system perturbations — and the artifacts they may result in — are minimized.
To demonstrate the wide array of information AUC can glean, the researchers highlighted several examples.
The first pointed to how AUC reveals the more complicated nature of hydration shells, or the water encapsulating various molecules. Rather than a homogenous layer of oxygen and hydrogen atoms, the water shifts in physical properties and behaviors through the shell, which also varies in thickness.
The second example focused on determining the distance between components in molecular cluster solutions. According to the researchers, measuring intermolecular distances is key to understanding how charged macroions self-assemble in dilute solution and how changes in these distances correlate with transitions between different macroscopic phases.
The third example detailed the interactions of molecular clusters with amino acids — the compounds that make up proteins. Understanding how amino acids interact with the surfaces of molecular clusters can help inform understanding of how the clusters will interact with biomolecules. Liu noted that these structures are governed by weak, noncovalent interactions between molecules. Although these forces are difficult to measure directly, AUC can reveal their effects by detecting subtle changes in molecular size, weight and shape in solution.
"AUC is a powerful technique for investigating complex solution systems," Liu said. "Owing to their well-defined and uniform size, shape and mass, molecular clusters are particularly well suited for AUC
measurements. … AUC offers the distinct advantage of resolving different species prior to analysis, enabling direct determination of their individual concentrations."
According to the researchers, there is a drawback, however.
"The technique requires substantial expertise, experience and instrumentation resources," Liu said. "As a result, the barrier to entry for new users can be relatively high, with a need for extensive training covering both experimental operation and data analysis."
Other contributors include Ruixin Li, Xiaohan Xu, Kexing Xiao and Bahareh Afsari, all with the University Akron; and Lake N. Paul, with BioAnalysis, LLC.
The University of Akron supported this research.
DOI Link:
https://doi.org/10.26599/POM.2026.9140132
About Polyoxometalates
Polyoxometalates (ISSN 2957-9821) is a peer-reviewed (single-blind), open-access and interdisciplinary journal, sponsored by Tsinghua University. Polyoxometalates publishes original high-quality research papers and significant review articles that focus on cutting-edge advancements in Polyoxometalates, and clusters of metals, metal oxides and chalcogenides. Rapid review to ensure quick publication is a key feature of Polyoxometalates. The journal is indexed by ESCI (IF 2025 = 10.4, Top 3), Scopus (CiteScore 2025 = 17.6, Top 3), Ei Compendex, CAS, and DOAJ. For details about Polyoxometalates, please visit: https://www.sciopen.com/journal/2957-9821 .
