College of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454003, China.
Appl Biochem Biotechnol. 2012 Oct;168(3):592-603. doi: 10.1007/s12010-012-9801-x. Epub 2012 Jul 15.
The interaction between papain and two typical ionic liquids (ILs), 1-octyl-3-methylimidazolium chloride ([C(8)mim]Cl) and 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl), was investigated by using fluorescence spectroscopy technique at a pH value of 7.4. The results suggested that ILs could quench the intrinsic fluorescence of papain probably via a static quenching mechanism. The binding constants were determined by employing the fluorescence quenching method. They were very small compared with that of volatile organic solvents, indicating that only very weak interaction between ILs and papain existed. The Gibbs free energy change (∆G), enthalpy change (∆H), and entropy change (∆S) during the interaction of papain and ILs were estimated. Negative values of these parameters indicated that the interaction between ILs and papain was a spontaneous process, also implying that hydrogen bonding and van der Waals forces played important roles in the interaction processes.
采用荧光光谱法研究了木瓜蛋白酶与两种典型的离子液体（1-辛基-3-甲基咪唑氯盐([C(8)mim]Cl)和 1-丁基-3-甲基咪唑氯盐([C(4)mim]Cl)）在 pH 值为 7.4 时的相互作用。结果表明，离子液体可能通过静态猝灭机制猝灭木瓜蛋白酶的固有荧光。采用荧光猝灭法测定了结合常数。与挥发性有机溶剂相比，这些结合常数非常小，表明离子液体与木瓜蛋白酶之间仅存在非常弱的相互作用。估算了木瓜蛋白酶与离子液体相互作用过程中的吉布斯自由能变化（∆G）、焓变（∆H）和熵变（∆S）。这些参数的负值表明离子液体与木瓜蛋白酶之间的相互作用是一个自发过程，这也意味着氢键和范德华力在相互作用过程中起重要作用。
