A biophysical strategy to examine the impact of newly synthesized polymerizable ammonium-based ionic liquids on the structural stability and proteolytic activity of stem bromelain

Abstract

The present manuscript reports the synthesis and characterization of polymerizable ammonium-based ionic liquids (ILs) and explores their influence on structural stability of stem bromelain (BMN) by using various biophysical techniques. Thermal fluorescence results showed that N-ethyl-2-(methylacryloyloxy)-N,N-dimethylethan-1-ammonium bromide (IL2C) (at lower concentration (0.1 mg/mL)) is found to be increasing the thermal stability of BMN which can be evident from the transition temperature (Tm) for BMN in IL2C (68.51 °C) is higher than BMN in buffer (66.24 °C). Whereas, N-(2-(methacryloyloxy)ethyl)-N,N-dimethylpropan-1-ammonium bromide (IL3C) and N-(2-(methacryloyloxy)ethyl)-N,N-dimethylpentan-1-ammonium bromide (IL5C) are maintaining the Tm values very near to Tm of pure BMN. Though, N-(2-(methacryloyloxy)ethyl)-N,N-dimethylhexan-1-ammonium bromide (IL6C) is found to be destabilizing IL as it significantly decreased the Tm value of BMN at all concentrations. Additionally, consequence of ILs on the proteolytic activity of BMN has also performed for IL2C up to 5 mg/mL while IL3C and IL5C at 0.1 mg/mL and 0.5 mg/mL are enhancing the proteolytic activity of BMN. Later, molecular docking studies are also performed with AutoDock vina and results showed that all ILs have different binding sites on BMN however IL6C is observed to be binding to the catalytic site of the BMN, it turns out to be the most destabilizing IL.