Fukada H, Takahashi K
J Biochem. 1980 Apr;87(4):1111-7.
Calorimetric measurement was made on the reduction of the three disulfide bonds of insulin by dithiothreitol (DTT). The reaction was performed at 298 K in three different buffer solutions of pH 9.6. The observed heat changes were corrected for the enthalpy of proton release from the buffer components and the net heat of reaction of insulin with DTT was determined to be delta H0 = 51.5 +/- 1.4 kJ(mol insulin)-1. By subtracting the enthalpy of DTT oxidation (Fukada, H. & Takahashi, K. (1980) J. Biochem. 87, 1105--1110), the standard enthalpy of reduction of insulin was found to be delta H = 78.8 +/- 7.9 kJ(mol insulin)-1. Using the enthalpy change for reduction of random-coil proteins by dithioerythritol (Johnson, R.E., Adams, P., & Rupley, J.A. (1978) Biochemistry 17, 1479-1484), the enthalpy change associated with the conformational change of insulin alone was evaluated to be delta H = 74 +/- 2 kJ(mol insulin)-1 (or 13 J(g protein)-1, a value very similar to that observed for the denaturation of other globular proteins.
用二硫苏糖醇（DTT）还原胰岛素的三个二硫键进行了量热测量。反应在298K下于三种不同的pH 9.6缓冲溶液中进行。对观察到的热变化进行了缓冲液成分质子释放焓的校正，胰岛素与DTT反应的净反应热确定为ΔH0 = 51.5±1.4kJ（每摩尔胰岛素）-1。通过减去DTT氧化的焓（深田浩和高桥健（1980年）《生物化学杂志》87卷，1105 - 1110页），发现胰岛素还原的标准焓为ΔH = 78.8±7.9kJ（每摩尔胰岛素）-1。利用二硫赤藓糖醇还原无规卷曲蛋白质的焓变（约翰逊，R.E.，亚当斯，P.，& 鲁普利，J.A.（1978年）《生物化学》17卷，1479 - 1484页），单独与胰岛素构象变化相关的焓变评估为ΔH = 74±2kJ（每摩尔胰岛素）-1（或13J（每克蛋白质）-1，该值与其他球状蛋白质变性时观察到的值非常相似。
