Non-ideal tracer sedimentation equilibrium: a powerful tool for the characterization of macromolecular interactions in crowded solutions.

Non-ideal tracer sedimentation equilibrium is a technique devised to quantify the effect of high concentrations of unrelated macromolecules on the self- or hetero-associations of dilute macromolecules. Principles and experimental techniques are reviewed, and previous experimental work summarized. A new analysis of experimental data is presented that requires no a priori assumptions regarding the nature of weak repulsive interactions between solute species and the concentrated (crowding) species.