Department of Bioengineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka 940-2188, Japan.
J Phys Chem B. 2012 Feb 16;116(6):1927-32. doi: 10.1021/jp209686e. Epub 2012 Feb 6.
Thermodynamic properties, including volumetric properties, provide important information on protein stability and folding. Pressure perturbation calorimetry (PPC) is an effective technique for evaluating the temperature dependence of the thermal expansion coefficient, α(p), of biomaterials. Recently, the thermal N-to-D transition of cytochrome c at nearly pH 4 was found to be a three-state transition including a molten globulelike intermediate state. In this study, the thermal N-to-D transition of cytochrome c was examined by PPC measurements with a three-state model. As far as we know, this is the first report of a three-state analysis of PPC, since two-state analyses are traditionally applied. The V(p) of the MG1-like intermediate state in the N-to-D transition at pH 4 was found to be the value between the partial volumes of the N and D states, suggesting an increase of the hydrophobic hydration in this intermediate state.
热力学性质，包括体积性质，为蛋白质稳定性和折叠提供了重要信息。压力微扰量热法（PPC）是评估生物材料热膨胀系数α(p)温度依赖性的有效技术。最近，细胞色素 c 在接近 pH 4 时的热 N 到 D 转变被发现是一个包括类伸展球蛋白中间状态的三态转变。在这项研究中，通过 PPC 测量和三态模型研究了细胞色素 c 的热 N 到 D 转变。据我们所知，这是 PPC 三态分析的第一份报告，因为传统上应用的是二态分析。在 pH 4 时，N 到 D 转变中类 MG1 中间状态的 V(p)被发现介于 N 态和 D 态的部分体积之间，表明该中间状态的疏水性水合作用增加。
