Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, 37007 Salamanca, Spain.
Int J Biol Macromol. 2013 Oct;61:390-5. doi: 10.1016/j.ijbiomac.2013.07.019. Epub 2013 Aug 2.
The thermal stability of the matrix protein (M protein) of Newcastle disease virus (NDV) has been investigated using high-sensitivity differential scanning calorimetry (DSC) at pH 7.4. The thermal folding/unfolding of M protein at this pH value is a reversible process involving a highly cooperative transition between folded and unfolded monomers with a transition temperature (Tm) of 63 °C, an unfolding enthalpy, ΔH(Tm), of 340 kcal mol(-1), and the difference in heat capacity between the native and denatured states of the protein, ΔCp, of 5.1 kcal K(-1) mol(-1). The heat capacity of the native state of the protein is in good agreement with the values calculated using a structure-based parameterization, whereas the calculated values for the hypothetical fully-unfolded state of the protein is higher than those determined experimentally. This difference between the heat capacity of denatured M protein and the heat capacity expected for an unstructured polypeptide of the same sequence, together with the data derived from the heat-induced changes in the steady-state fluorescence of the protein, indicates that the polypeptide chain maintains a significant amount of residual structure after thermal denaturation.
已使用高灵敏度差示扫描量热法（DSC）在 pH 值 7.4 下研究了新城疫病毒（NDV）基质蛋白（M 蛋白）的热稳定性。该 pH 值下 M 蛋白的热折叠/去折叠是一个涉及折叠和去折叠单体之间高度协同转变的可逆过程，其转变温度（Tm）为 63°C，解折叠焓，ΔH（Tm）为 340 kcal mol(-1)，并且蛋白质天然态和变性态之间的热容量差，ΔCp 为 5.1 kcal K(-1) mol(-1)。蛋白质天然态的热容与使用基于结构的参数化计算的值非常吻合，而计算的蛋白质假设完全展开态的值高于实验测定的值。变性 M 蛋白的热容与相同序列无规多肽的预期热容之间的这种差异，以及蛋白质稳态荧光热诱导变化得出的数据表明，多肽链在热变性后仍保持大量的残余结构。
