Enzyme aggregation in ionic liquids studied by dynamic light scattering and small angle neutron scattering

Abstract

Candida antarctica Lipase B (CALB) formed a seemingly homogeneous solution in water, 1-ethyl-3-methylimidazolium dicyanamide ([C 2 mim][N(CN) 2 ]) or dimethyl sulfoxide (DMSO). However, dynamic light scattering (DLS) and small angle neutron scattering (SANS) demonstrated that the enzyme formed aggregates in the non-aqueous solvents. In aqueous solution, SANS measurements revealed that CALB formed cylindrical nano-structures with a diameter of 5 nm and a length of 4 nm, equivalent to the dimensions of a single CALB molecule. The enzyme also formed cylindrical structures in DMSO but the diameter was 4 nm and the length was 12 nm, indicating that the enzyme had aggregated to form dimers or trimers. In [C 2 mim][N(CN) 2 ], discshaped aggregates were formed, with an average diameter of 49 nm and a length of 3.8 nm, equivalent to the volume of 150 CALB molecules. In all cases, the hydrodynamic diameters measured by DLS matched the long axial lengths of the aggregates determined by SANS, indicating a good consistency between the two techniques. DLS measurements showed that CALB aggregates in. In all cases, the aggregation observed in the solvents was associated with loss of enzymatic activity.

Comparison of Three Ionic Liquid-Tolerant Cellulases by Molecular Dynamics

“…These studies usually focus on low or high concentrations of IL in water, and they skip over the important intermediate region where denaturation and aggregation effects have been observed previously. Still, in certain neat ILs, aggregation of other enzymes, like lipase, are observed (67). There are many factors that play a role in protein stability and aggregation in ILs, including IL species, protein structure, and temperature.…”

How ionic liquids can help to stabilize native proteins

“…Very likely, in most of these studies the enzymes were in finely dispersed states rather than being dissolved at the molecular level, as suggested by small-angle neutron and light scattering of CALB in [C 2 mim][dca], which reveals aggregates of mesoscopic size. 82 As an important consequence, the observed preservation of the enzymatic activities of some proteins in hydrophobic ILs at high temperatures seems to be founded in heterogeneous rather than homogeneous biocatalysis.…”

“…34 Results for lipases, which are often tolerant to non-aqueous solvents, confirm the picture deduced from molecular solvents. For example, candida antarctica lipase B (CALB) maintained its activity in [C 4 82 We have attempted to characterize the effect of a hydrophobic IL on the melting temperature T m of a protein from dilute aqueous solutions to the neat IL. Unfolding gives rise to an endothermic contribution to the heat capacity of the solution, which can be probed by differential scanning calorimetry (DSC).…”

“Nonsolvent” Applications of Ionic Liquids in Biotransformations and Organocatalysis

“…[23e, 27,28] Some RTILs were used successfully as additives (0.1-1 %) in the desymmetrization of prochiral malonate diesters under the catalysis of pig liver esterase (PLE; Table 1). [29] The appropriate combination of a cosolvent (isopropanol, 10 %) with a catalytic amount of certain RTILs (0.1-1 %) led to a significant increase in the rate of the enzymatic reaction and in the enantioselectivity of PLE for the substrate.…”