Zwitterions fine-tune interactions in electrolyte solutions

Hallett, J. E. ORCID: https://orcid.org/0000-0002-9747-9980, Agg, K. J. and Perkin, S. (2023) Zwitterions fine-tune interactions in electrolyte solutions. Proceedings of the National Academy of Sciences, 120 (8). e2215585120. ISSN 1091-6490 doi: 10.1073/pnas.2215585120

Abstract/Summary

Cellular organisms regulate electrolyte composition in the cytosol to optimize intracellular molecular interactions at the same time as balancing external osmotic pressure. While osmotic pressure can be tuned using multiple ionic, zwitterionic, and nonionic solutes, interactions between proteins and other macromolecules are sensitive to the precise composition of the medium. Nonetheless, the roles of individual ions and nonionic solutes in mediating cellular interactions remain relatively unexplored, and standard buffer solutions used in laboratory studies often contain only a few simple salts. Here, we report on model experiments investigating the combined effect of ionic and zwitterionic solutes on interaction forces across electrolytes, revealing a clear role for zwitterions in modifying interactions compared to simple salt solutions. First, we find that zwitterions act to disrupt water layering at interfaces, leading to smoothed interaction potentials. Second, we find that zwitterions strengthen electrostatic repulsions by enhancing effective surface charge. Third, zwitterions enhance the effective dielectric permittivity of the solution, and this “dielectricizer” effect extends the range of electrostatic repulsions compared to solutions without zwitterion present. The latter two effects are likely important in stabilizing proteins and other macromolecules when external osmotic and mechanical pressure are very high and simple ionic solutes alone would lead to collapse.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/111206
Identification Number/DOI	10.1073/pnas.2215585120
Refereed	Yes
Divisions	Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
Publisher	National Academy of Sciences
Download/View statistics	View download statistics for this item