The general theories of sedimentation equilibrium (SE) and static light scattering (SLS) have been recently extended to be applicable to mixtures of interacting solutes at arbitrary concentration. We have developed experimental procedures for the acquisition of SE and SLS data in concentrated solutions suitable for analysis, and provided examples of the use of these measurements to characterize protein associations.

The method of non-ideal tracer sedimentation equilibrium (NITSE) is described. We used NITSE to detect and quantitatively characterize intermolecular interactions in mixtures of dilute tracer species and concentrated proteins or polymers.

An experimental technique for rapid measurement of the light scattering of a protein solution over a broad range of concentration, and the theoretical treatment of static light scattering of highly nonideal solutions of multiple scattering species are outlined. We use this technique to measure solutions of non-associating globular proteins, binary mixtures of non-associating proteins and a self-associating protein, chymotrypsin A, at three different pH values.

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