新型1,3-二丁基咪唑离子液体中脂肪酶催化折分(R,S)-1-苯乙醇

设计合成6种采用不同1,3-二丁基咪唑阳离子和六氟磷酸(PF6-)或双三氟甲烷磺酰亚胺(TFSI-)阴离子的离子液体.以脂肪酶催化拆分1-苯乙醇为模型反应,分别考察介质、水含量和温度对反应的影响.结果表明,在1,3-二异丁基咪唑六氟磷酸盐(D(i-C4)Im]PF6])离子液体介质中酶的活性和反应性明显高于其它离子液体和正己烷.因此,D(i-C4)Im]PF6]被确定为反应介质.在最佳条件下,初始反应速率是1.93μmol?mg-1?min-1,1-苯乙醇的转化率达50%,对映体过量值eep99%,酶的半衰期为348h,酶重复使用10次后活性没有明显减少.此外,圆二色谱、内源荧光光谱和光学显微镜研究表明,酶在D(i-C4)Im]PF6]中保温6d后氨基酸残基的裸露程度略有增加,但其二级结构仍保持稳定,且以天然的折叠球形态存在.

Resolution of(R,S)-1-Phenylethanol Catalyzed by Lipase in Novel 1,3-Dibutylimidazolium Ionic Liquid

Six ionic liquids consisting different 1,3-dibutylimidazolium cation and hexafluorophosphate () or bis(trifluoromethanesulphonyl)imide (TFSI^－) anion were designed and synthesized in the laboratory. The resolution of (R,S)-1-phenylethanol by Pseudomonas cepacial lipase was chosen as the model reaction to study on effects of the reaction medium, water content and temperature on the reaction. The results showed the activity of lipase in the ionic liquid 1,3-di-isobutylimidazolium hexafluorophosphate abbreviated as D(i-C₄)Im]PF₆] has obviously better activity and reactivity than these in other ionic liquids and hexane. Accordingly, the ionic liquid D(i-C₄)Im]PF₆] was chosen as the medium for the reaction. Under optimal condition, initial rate of lipase, the conversion of 1-phenylethanol, ee value of (R)-1-phenylethyl acetate and half life time of the lipase was 1.93 μmol•mg^－1•min^－1, 50%, 99% and 348 h, respectively. Moreover, circular dichroism, fluorescence spectrum and optical microscope analysis have demonstrated after the incubation of lipase in the ionic liquid D(i-C₄)Im]PF₆] for 6 d the lipase exhibited an slightly increasing exposure level of amino-acid residue, however, its secondary structure is of excellent stability also and exists as its native ball enzyme conformation.