Polypeptides can form a wide variety of aggregate states in solution depending on pH and salt concentrations. Repulsive electrostatic interactions as well as non-specific attractive interactions between polypeptides present serious challenges to discriminating aggregate states in solution.

This poster discusses the role of the buffer at a fixed pH and salt content on insulin's tendency to form associated states. In particular, the role in literature is that only acetate buffers can be utilized to assay insulin's transition from monomer to dimer (and higher association states).

This work evaluated citrate and formate buffers to see if the association occurs or not. Also, a comparison of the self-association tendency between natural human insulin (X) and a mutant version of the same (Y) was conducted. The association state was measured using a batch light scattering method. Nonlinear regression methods can provide a good estimate of both interactions as well as aggregation equilibrium provided data of sufficient resolution are available