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)(3)NH][H-2 PO4] (TEAP), trimethylammonium acetate [(CH3)(3)NH](CH3COO] (TMAA), trimethylammonium dihydrogen phosphate [(CH3)(3)NH][H2PO4] (TMAP) and trimethylammonium hydrogen sulfate [(CH3)(3)NH][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. (c) 2012 Elsevier B.V. All rights reserved.