Comparative Effects of Mono‐ and Dicationic Imidazolium Ionic Liquids on CRABP I Structure and Stability

In the present study, the effects of three structurally distinct imidazolium-based ionic liquids on the model protein CRABP I were investigated using a combination of spectroscopic and computational approaches. The spectroscopic results reveal that the ionic liquids interact primarily with surface-exposed regions of CRABP I, leading to concentration-dependent fluorescence quenching and minor perturbations in the local environment of tryptophan residues while largely preserving the β-sheet-dominated secondary structure of the protein. Spectroscopic observations suggest that the quenching process involves contributions from both ground-state association and excited-state interactions, indicating a mixed quenching mechanism. Circular dichroism measurements further confirm that the global secondary structure of CRABP I remains largely intact in the presence of the ionic liquids. To complement the experimental observations, molecular docking and molecular dynamics simulations were carried out. The combined results demonstrate that variations in ionic liquid cation architecture influence the strength and mode of interaction with CRABP I, with each system showing distinct interaction patterns and stabilization effects. This study provides insight into how structural differences in ionic liquids govern their interactions with proteins and highlights the importance of ionic liquid design in developing biocompatible media for protein stabilization and related biotechnological applications.