Cho K C, Poon H T, Choy C L
Biochim Biophys Acta. 1982 Feb 18;701(2):206-15. doi: 10.1016/0167-4838(82)90115-7.
The reversible thermal denaturation of four metmyoglobin derivatives, aquomet, cyanomet, azidomet and fluoromet in both the alkaline pH and acidic pH region, has been examined by optical spectrophotometry. The data are analyzed in terms of a two-state model to extract the thermodynamic parameters delta G, delta H, delta S and delta Cp characterizing the transition. The results are consistent with Brandts' phenomenological model of protein denaturation. Among the derivatives examined, cyanomet, azidomet and fluoromet are about 3 kcal/mol, 2 kcal/mol and 0.2 kcal/mol, respectively, more stable than aquometmyoglobin. The observed differences are found to be inconsistent with the hypothesis that the stability is mainly governed by the spin state of the iron atom. In addition, the enthalpic and entropic contributions in delta G are extracted and the differences in delta G for the various derivatives are found to arise from minor changes in delta H and T delta S. Assuming the final denaturated state to be universal, these changes reflect the effect of ligands on the conformational energy of the native protein.
通过光学分光光度法研究了四种高铁肌红蛋白衍生物，即水合高铁肌红蛋白、氰化高铁肌红蛋白、叠氮高铁肌红蛋白和氟高铁肌红蛋白在碱性和酸性pH区域的可逆热变性。根据二态模型对数据进行分析，以提取表征转变的热力学参数ΔG、ΔH、ΔS和ΔCp。结果与布兰特斯的蛋白质变性现象学模型一致。在所研究的衍生物中，氰化高铁肌红蛋白、叠氮高铁肌红蛋白和氟高铁肌红蛋白分别比水合高铁肌红蛋白稳定约3千卡/摩尔、2千卡/摩尔和0.2千卡/摩尔。发现观察到的差异与稳定性主要由铁原子的自旋状态决定这一假设不一致。此外，提取了ΔG中的焓和熵贡献，发现各种衍生物的ΔG差异源于ΔH和TΔS的微小变化。假设最终变性状态是通用的，这些变化反映了配体对天然蛋白质构象能量的影响。
