Analytical ultracentrifugation (AUC) technique for studying molecular cluster solutions

Analytical ultracentrifugation (AUC) is a powerful and information-rich technique for characterizing molecular weight, size, shape, dispersity, and association behavior of species directly in their native solution environment, covering a broad molecular weight range of 100 – 100M Daltons. Unlike many orthogonal methods, AUC does not require immobilization, labeling, or assumptions about sample homogeneity. With recent advances in both instrumentation and data analysis software, AUC now provides more accurate and reliable measurements on various solutions systems such as biomacromolecules, colloids, surfactants and polymers. Molecular clusters with their uniform and well-defined molecular weights, sizes and shapes, possess unique advantages as candidates for AUC studies. Here we demonstrate some applications of AUC technique on studying molecular cluster solutions to highlight the considerable potential of AUC technique. Even simple AUC experiments can reveal important and accurate features in molecular cluster solutions, such as the thickness of hydration shell of clusters, intermolecular distance between their dimers and the surface adsorption of organic ligands (amino acids).