Interaction of Lysozyme with Monocationic and Dicationic Ionic Liquids: Toward Finding a Suitable Medium for Biomacromolecules

Abstract

With an objective to understand the differences in the behavior of monocationic and dicationic ionic liquids (ILs) in their interaction with protein, we have investigated the binding interaction of lysozyme enzyme with two monocation ionic liquids (MILs), [C 3 MIm][Br], [C 6 MIm][Br], and one dicationic ionic liquid (DIL), [C 6 (MIm) 2 ][Br] 2 , by exploiting various experimental methods. These ILs are purposefully chosen so that the effect of both hydrophobicity and structural arrangements of the cationic moiety of ionic liquids (ILs), if any, on the interaction event is understood. Both average ensemble and single molecule pathways have been adopted to obtain a comprehensive picture. For ensemble averaged measurements, the interaction events have been investigated by steady-state and time-resolved fluorescence spectroscopy, whereas for single molecule measurements, fluorescence correlation spectroscopy (FCS) has been utilized. Additionally, the behavior of protein in the absence and presence of ILs has also been investigated through circular dichroism (CD) measurements. The investigations have revealed that MILs and DIL interact differently with the protein. In particular, as compared to MILs, the influence of DIL toward protein is observed to be significantly less in terms of change in the structure and dynamics of protein. The outcome of the present work has demonstrated that imidazolium-based DIL can be a better choice over MILs for retaining native structure of protein in aqueous medium.

Structural Compactness in Hen Egg White Lysozyme Induced by Bisphenol S: A Spectroscopic and Molecular Dynamics Simulation Approach

“…With increasing concentrations of BPS, these two negative ellipticity values increased. This augmentation is a direct consequence of the enhancement in helicity and thus results in a more compact state of Lyz [15] . The rise in α ‐helical content of Lyz with an increase in the concentration of BPS is evident from Table S3.…”

“…However, there are very few reports on the interaction between proteins with its analogue, BPS [1,27] . Over the time, hen egg white lysozyme (Lyz) has become an emerging model protein for studying the interaction with many ligands, small molecules, drugs as well as EDCs [2,15–17,19,20,23] . To the best of our knowledge, we report for the first time the interaction of BPS with Lyz by several spectroscopic and molecular modelling methods.…”

“…Lysozyme (Lyz), also termed as N‐acetylmuramide glycanhydrolase, is a small globular monomeric protein containing 129 amino acid residues, with a molecular weight 14.3 kDa. It has six tryptophan, three tyrosine residues and four disulfide linkages (Scheme 1b) [15–18] . Out of six tryptophan (W) residues, W62 and W108 are responsible for exhibiting the intrinsic fluorescence properties of Lyz [15,19,20] .…”

“…It has six tryptophan, three tyrosine residues and four disulfide linkages (Scheme 1b) [15–18] . Out of six tryptophan (W) residues, W62 and W108 are responsible for exhibiting the intrinsic fluorescence properties of Lyz [15,19,20] . It is synthesized by macrophages and shows anti‐bacterial, anti‐viral, anti‐histaminic properties [21,22] .…”

“…Lyz is mainly present in human tears, milk, saliva, serum and cerebrospinal fluid and can also be found in cytoplasmic granules of the macrophages and the Poly Morphonuclear Neutrophils (PMNs) [22] . Research related to the interaction of several drugs and polyphenols with this carrier protein has become a topic of emerging interest [15–23] . Hen egg white lysozyme shows ∼60 % similarity to its human variant and has been widely used as a model system for biophysical research to understand the associated dynamics and functional properties [19] .…”