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Lipidico Injection Protocol for Serial Crystallography Measurements at the Australian Synchrotron
Published on: September 23, 2020
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Lysozyme conformational changes with ionic liquids: Spectroscopic, small angle x-ray scattering and crystallographic
Qi Han1, Kate M Smith2, Connie Darmanin3
1School of Science, College of Science, Engineering and Health, RMIT University, 124 La Trobe Street, Melbourne, VIC 3000, Australia.
Journal of Colloid and Interface Science
|October 28, 2020
Summary
Ionic liquids (ILs) maintain lysozyme secondary structure but alter its Tryptophan environment and tertiary structure. Specific binding sites and IL-sensitive regions were identified, offering insights into protein-solvent interactions.
Area of Science:
- Biochemistry and structural biology
- Protein-solvent interactions
- Biophysical chemistry
Background:
- Protein functionality relies on suitable solvents for biochemical applications.
- Development of novel solvents is crucial for advancing biochemical research.
- Understanding how solvents affect protein structure is essential for protein engineering and drug design.
Purpose of the Study:
- To investigate the conformational changes of lysozyme in the presence of various ionic liquids (ILs).
- To elucidate the impact of IL concentration and type on protein structure and stability.
- To identify specific interactions between ILs and protein residues.
Main Methods:
- Fourier-transform infrared (FTIR) and fluorescence spectroscopies to assess secondary structure and Tryptophan environment.
- Small-angle X-ray scattering (SAXS) to determine changes in the radius of gyration and overall protein conformation.
- X-ray crystallography to resolve high-resolution structural details and identify binding sites.
Main Results:
- Lysozyme's secondary structure was preserved at low IL concentrations (1 and 5 mol%).
- Nitrate-based ILs significantly altered the Tryptophan environment.
- SAXS revealed concentration-dependent changes in the radius of gyration, with an initial increase followed by a decrease.
- Tertiary structure, especially loop regions, showed alterations dependent on IL type and concentration.
- X-ray crystallography confirmed loop extension and identified three nitrate ion binding sites in ethylammonium nitrate.
Conclusions:
- Ionic liquids can maintain lysozyme secondary structure while inducing significant changes in its tertiary structure and Tryptophan microenvironment.
- The conformational response of lysozyme is dependent on both the concentration and chemical nature of the ionic liquid.
- Specific binding interactions between nitrate ions and positively charged protein regions were identified, highlighting IL-sensitive areas.
- This study provides a comprehensive understanding of protein-IL interactions, with implications for designing functional proteins in IL-based systems.
