Article
Thermodynamic destabilization of azurin by four different tetramethylguanidinium amino acid ionic liquids.
International Journal of Biological Macromolecules
(2021)
Abstract
The thermal unfolding of the copper redox protein azurin was studied in the presence of four different amino acid-based ionic liquids (ILs), all of which have tetramethylguanidium as cation. The anionic amino acid includes two with alcohol side chains, serine and threonine, and two with carboxylic acids, aspartate and glutamate. Control experiments showed that amino acids alone do not significantly change protein stability and pH changes anticipated by the amino acid nature have only minor effects on the protein. With the ILs, the protein is destabilized and the melting temperature is decreased. The two ILs with alcohol side chains strongly destabilize the protein while the two ILs with acid side chains have weaker effects. Unfolding enthalpy (ΔHunf°) and entropy (ΔSunf°) values, derived from fits of the unfolding data, show that some ILs increase ΔHunf°while others do not significantly change this value. All ILs, however, increase ΔSunf°. MD simulations of both the folded and unfolded protein conformations in the presence of the ILs provide insight into the different IL-protein interactions and how they affect the ΔHunf° values. The simulations also confirm that the ILs increase the unfolded state entropies which can explain the increased ΔSunf° values.
Disciplines
Publication Date
June 1, 2021
DOI
10.1016/J.IJBIOMAC.2021.03.090
Citation Information
Isabella DeStefano, Gabriella DeStefano, Nicholas J. Paradis, Roshani Patel, et al.. "Thermodynamic destabilization of azurin by four different tetramethylguanidinium amino acid ionic liquids." International Journal of Biological Macromolecules Vol. 180 (2021) p. 355 - 364 Available at: http://works.bepress.com/timothy-vaden/18/