Crown ethers are small, cyclic polyethers that have found wide-spread use in phase-transfer catalysis and, to a certain degree, in protein chemistry. Crown ethers readily bind metallic and organic cations, including positively charged amino acid side chains. We elucidated the crystal structures of several protein-crown ether co-crystals grown in the presence of 18-crown-6. We then employed biophysical methods and molecular dynamics simulations to compare these complexes with the corresponding apoproteins and with similar complexes with ring-shaped low-molecular-weight polyethylene glycols. Our studies show that crown ethers can modify protein surface behavior dramatically by stabilizing either intra- or intermolecular interactions. Consequently, we propose that crown ethers can be used to modulate a wide variety of protein surface behaviors, such as oligomerization, domain-domain interactions, stabilization in organic solvents, and crystallization.
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Lee, C. C., Maestre-Reyna, M., Hsu, K. C., Wang, H. C., Liu, C. I., Jeng, W. Y., Lin, L. L., Wood, R., Chou, C. C., Yang, J. M., & Wang, A. H. J. (2014). Crowning proteins: Modulating the protein surface properties using crown ethers. Angewandte Chemie - International Edition, 53(48), 13054-13058. https://doi.org/10.1002/anie.201405664