Fortification of thermal and structural stability of hemoglobin using choline chloride-based deep eutectic solvents

Of late, DESs have occupied the centre stage due to their eco-friendly and resource-efficient nature and their low toxicity. In this work, we have investigated the structural and thermal stability of hemoglobin (Hb) in two choline chloride ([Ch]Cl)-based DESs namely urea [Ch]Cl-urea (DES1) and [Ch]Cl-glycerol (Gly); (DES 2). Different biophysical techniques reveal that the presence of DESs facilitates the stability of Hb in a concentration-dependent manner and the extent of stability is more pronounced in [Ch]Cl-Gly as compared to [Ch]Cl-urea. Additionally, for a better understanding of the role of DESs in modulating the thermal and structural stability of Hb, studies have been performed on Hb in the presence of individual constituents of DESs, i.e., [Ch]Cl, urea, and Gly. Altogether, it was observed that the effect on the stability of Hb was by the presence of the DESs rather than their individual constituents. For instance, urea itself is a destabilizing co-solvent for biomolecules. However, the harmful effects of urea were surpassed when a DES is formed in the presence of [Ch]Cl. Therefore, overall, it can be concluded that both DESs can be described as potential non-harmful, green, and promising solvents for enhancing the structural and thermal stability of Hb.