Influence of protic ionic liquids on the structure and stability of succinylated Con A

We report the synthesis of a series of ionic liquids (ILs) from various ions having different kosmotropicity including dihydrogen phosphate (H₂PO₄^-), hydrogen sulfate (HSO₄^-) and acetate (CH₃COO^-) as anions and chaotropic cation such as trialkylammonium cation. To characterize the biomolecular interactions of ILs with protein, we have explored the stability of succinylated Con A (S Con A) in the presence of these aqueous ILs, which are varied combinations of kosmotropic anion with chaotropic cation such as triethylammonium dihydrogen phosphate [(CH₃CH₂)₃NH][H₂PO₄] (TEAP), trimethylammonium acetate [(CH₃)₃NH][CH₃COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH₃)₃NH][H₂PO₄] (TMAP) and trimethylammonium hydrogen sulfate [(CH₃)₃NH][HSO₄] (TMAS). Circular dichroism (CD) and fluorescence experiments have been used to characterize the stability of S Con A by ILs. Our data distinctly demonstrate that the long alkyl chain IL TEAP is a strong stabilizer for S Con A. Further, our experimental results reveal that TEAP is an effective refolding enhancer for S Con A from a thermally denatured protein structure.