Implication of Threonine‐Based Ionic Liquids on the Structural Stability, Binding and Activity of Cytochrome c

Abstract

Ionic liquids (ILs) are useful in pharmaceutical industries and biotechnology as alternative solvents or sources for protein extraction and purification, preservation of biomolecules and for regulating the catalytic activity of enzymes. However, the binding mechanism, the non-covalent forces responsible for protein-IL interactions and dynamics of proteins in IL need to be investigated in depth for the effective use of ILs as alternatives. Herein, we disclose the molecular level understanding of the structural intactness and reactivity of a model protein cytochrome c (Cyt c) in biocompatible threonine-based ILs with the help of experimental techniques such as isothermal titration calorimetry (ITC), fluorescence spectroscopy, transmission electron microscopy (TEM) as well as molecular docking. Hydrophobic and electrostatic forces are responsible for the structural and conformational integrity of Cyt c in IL. The ITC experiments revealed the Cyt c-IL binding free energies are in the range of 10-14 kJ/mol and the molecular docking studies demonstrated that ILs interact at the surfaces of Cyt c. The results look promising as the ILs used here are non-toxic and biocompatible, and thus may find potential applications in structural biology and biotechnology.

Structural Dynamics of RNA in the Presence of Choline Amino Acid Based Ionic Liquid: A Spectroscopic and Computational Outlook

“… 19 − 23 They can act as green alternatives to organic solvents for drug delivery and biochemistry applications. 18 , 24 − 27 Furthermore, they are suitable for long-term storage and extraction of macromolecules. 15 , 28 − 30 The suitability of ILs for storing proteins and DNA is widely practiced since these macromolecules can retain their functionalities.…”

“…On the other hand, ionic liquids (ILs) have recently gained interest, particularly for their role as efficient solvents to store biopolymers, proteins, and enzymes. − ILs are molten salts with low volatility, high ionic conductivity, and nontoxicity-like unique properties. − They can act as green alternatives to organic solvents for drug delivery and biochemistry applications. ,− Furthermore, they are suitable for long-term storage and extraction of macromolecules. ,− The suitability of ILs for storing proteins and DNA is widely practiced since these macromolecules can retain their functionalities. − However, in the case of RNA, their high vulnerability to degradation with external factors like temperature, pH, and enzymes pose a difficult task to store them for an extended period . The advancement in finding a nontoxic and biocompatible solvent for RNA also demonstrates that ILs could be adequate and effective substitutes.…”

Noncovalent interactions in proteins and nucleic acids: beyond hydrogen bonding and π-stacking

“…It is responsible for more than 1000 fold selectivity against inhibitors. 82 Following this, a systematic investigation of X-bond tuned protein–ligand interaction was reported by Hardegger et al 83 The binding location of the inhibitor of human Cathepsin L (hCatL) protein where the X-bond was observed between the backbone CO group of Gly 61 in the S3 pocket and the chlorophenyl group of the inhibitor (Fig. 5B).…”

“…49,57,58 In addition to the techniques mentioned above, isothermal calorimetric titration (ITC) is also employed to determine the equilibrium constant and other thermodynamic parameters such as Gibbs free energy, entropy and enthalpy. [59][60][61][62] The techniques mentioned above are helpful in identifying the presence of various NCIs and their strength in the solid and solution phases. However, the interpretation often becomes more difficult due to the involvement of solvent molecules and other neighbouring interactions.…”

“…49,57,58 In addition to the techniques mentioned above, isothermal calorimetric titration (ITC) is also employed to determine the equilibrium constant and other thermodynamic parameters such as Gibbs free energy, entropy and enthalpy. 59–62…”