Chemistry Program, Savannah State University, Savannah, GA 31404, USA.
Biotechnol Lett. 2010 Aug;32(8):1109-16. doi: 10.1007/s10529-010-0262-4. Epub 2010 Apr 3.
Three new ether-functionalized hydrophobic ionic liquids (ILs) were synthesized. Two proteases (subtilisin and alpha-chymotrypsin both covalently immobilized on chitosan) exhibited high synthetic activity (1-3 micromol/min x g) and selectivity (>97-99%, esterification over hydrolysis) in these ILs containing 10-15% (v/v) water during the transesterification of N-acetyl-L-phenylalanine ethyl ester with 1-propanol. However, the same reaction in t-butanol or [BMIM][Tf(2)N], with water contents higher than 2% (v/v) yielded low synthetic activities (0.2-1 micromol/min g in t-butanol) and/or poor selectivity (<40%). The high synthetic activities of proteases in ether-functionalized ILs at high water contents are explained by two reasons: (1) the hydrogen-bond donors in ILs (R(1)-O-R(2)) and chitosan (-OH) controlling the thermodynamic water activity of the reaction system, and (2) the protective role of the ether chain in reducing the cation-protein interaction.
合成了三种新的醚官能化疏水性离子液体 (ILs)。两种蛋白酶（固定化在壳聚糖上的枯草杆菌蛋白酶和α-糜蛋白酶）在这些 ILs 中表现出高的合成活性（1-3 μmol/min·g）和选择性（>97-99%，酯化反应比水解反应高），其中水含量为 10-15%（v/v），在 N-乙酰-L-苯丙氨酸乙酯与 1-丙醇的转酯化反应中。然而，相同的反应在叔丁醇或 [BMIM][Tf(2)N] 中，水含量高于 2%（v/v）时，合成活性较低（叔丁醇中为 0.2-1 μmol/min·g），选择性较差（<40%）。在高含水量的醚官能化 ILs 中，蛋白酶具有高的合成活性，可以用两个原因来解释：（1）ILs 中的氢键供体（R(1)-O-R(2)）和壳聚糖（-OH）控制反应体系的热力学水活度，（2）醚链的保护作用降低了阳离子-蛋白质的相互作用。
