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Issue 41, 2020
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NMR investigations on binding and dynamics of imidazolium-based ionic liquids with HEWL

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Abstract

Molecular level insights on protein–ionic liquid (P–IL) interactions are beneficial for assessing protein stability, binding and dynamics. In the present work, interactions of ILs, namely, 1-butyl 3-methylimidazolium methyl sulfate (IL1), 1-butyl 3-methylimidazolium octyl sulfate (IL2) and 1-butyl 3-methylimidazolium chloride (IL3) with hen egg white lysozyme (HEWL) protein were investigated using solution-state nuclear magnetic resonance (NMR) spectroscopy. To ascertain the binding and dynamics from the perspective of both protein and IL, various ligand based NMR approaches such as selective and non-selective nuclear spin-relaxation (R1SEL and R1NS), saturation transfer difference (STD), difference of inversion recovery rate with and without target irradiation (DIRECTION), 35Cl line-shape and spin-relaxation, and protein back bone amide chemical shift perturbations (CSPs) from 1H–15N HSQC were utilized. Among the ILs investigated, IL2 experiences significant interaction relative to those of IL1 and IL3, as revealed by the combined R1SEL and R1NS analysis, which is further supported by STD NMR. CSP analyses of 1H–15N HSQC spectra of aqueous P–IL mixtures enabled to identify the potential binding sites of ILs with HEWL. Whereas, 15N longitudinal (R1) and transverse (R2) spin-relaxation rates and 15N{1H} heteronuclear nuclear Overhauser effect (hetNOE) data subjected to the model free analysis for IL2 yielded the rotational correlation times and order parameters of various residues of HEWL. Furthermore, the results could discern the nature of interactions between studied ILs and HEWL in terms of specific and non-specific interactions.

Graphical abstract: NMR investigations on binding and dynamics of imidazolium-based ionic liquids with HEWL

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Supplementary files

Article information


Submitted
30 Aug 2020
Accepted
08 Oct 2020
First published
09 Oct 2020

Phys. Chem. Chem. Phys., 2020,22, 23824-23836
Article type
Paper

NMR investigations on binding and dynamics of imidazolium-based ionic liquids with HEWL

R. R. Reddy, J. G. Reddy and B. V. N. P. Kumar, Phys. Chem. Chem. Phys., 2020, 22, 23824
DOI: 10.1039/D0CP04584E

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