Mediating Electrostatic Binding of 1-Butyl-3-methylimidazolium Chloride to Enzyme Surfaces Improves Conformational Stability
Mediating Electrostatic Binding of 1-Butyl-3-methylimidazolium Chloride to Enzyme Surfaces Improves Conformational Stability
复制标题
DOI：
10.1021/jp404760w
复制
发表时间：
2013-08-01
影响因子：
3.3
通讯作者：
Kaar, Joel L.
中科院分区：
文献类型：
--
作者：
Nordwald, Erik M.;Kaar, Joel L.
我们最近开发了一种通用方法，通过调整含酶的正负表面电荷的比率来提高酶在离子液体（IL）中的效用。在这项工作中，研究了酶表面电荷比对氯化 1-丁基-3-甲基咪唑鎓 ([BMIM][Cl]) 与胰凝乳蛋白酶和脂肪酶的生物物理相互作用的影响，以在分子水平上了解这种方法。荧光猝灭测定结果表明，[BMIM] 阳离子的结合程度随着正负表面电荷比率的增加而降低（胰凝乳蛋白酶和脂肪酶分别为 7 倍和 3.5 倍）。构象稳定性测定进一步显示热力学稳定性与酶表面电荷比以及[BMIM]结合之间的密切相关性。作为这种相关性的证据，琥珀酰化和乙酰化导致胰凝乳蛋白酶在 10% (v/v) [BMIM] [Cl] 中分别稳定 17.0 和 6.6 kJ/mol，而阳离子化使胰凝乳蛋白酶不稳定 3.6 kJ/mol。综合起来，这些结果表明，改变表面电荷比介导了酶周围 IL 分子的组织，即 [BMIM] 和 [Cl]。优先排除[Cl]，特别是通过降低正负表面电荷的比率，与增加的酶稳定性相关。因此，这些结果更广泛地深入了解了离子液体通过电荷修饰的稳定机制。
We have recently developed a general approach to improve the utility of enzymes in ionic liquids (ILs) via tuning of the ratio of enzyme-containing positive to negative surface charges. In this work, the impact of enzyme surface charge ratio on the biophysical interaction of 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) with chymotrypsin and lipase was investigated to understand this approach at the molecular level. Results of fluorescence quenching assays indicated that the extent of binding of the [BMIM] cation decreased (7- and 3.5-fold for chymotrypsin and lipase, respectively) as a function of increasing ratio of positive to negative surface charges. Conformational stability assays further showed a close correlation between thermodynamic stabilization and enzyme surface charge ratio as well as [BMIM] binding. As evidence of this correlation, succinylation and acetylation resulted in the stabilization of chymotrypsin in 10% (v/v) [BMIM] [Cl] by 17.0 and 6.6 kJ/mol, respectively, while cationization destabilized chymotrypsin by 3.6 kJ/mol. Combined, these results indicate that altering the surface charge ratio mediates the organization of IL molecules, namely, [BMIM] and [Cl], around the enzymes. Preferential exclusion of [Cl], in particular, via lowering of the ratio of positive to negative surface charges, correlated with increased enzyme stability. Accordingly, these results more broadly provide insight into the mechanism of stabilization in ILs via charge modification.