Chun P W
Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville 32610, USA.
J Biol Chem. 1995 Jun 9;270(23):13925-31.
The Planck-Benzinger thermal work function, delta W zero(T), represents the heat-flux term which is responsible for breaking or forming the noncovalent bonds in macro-molecular interactions, while the temperature-invariant chemical bond energy, delta H zero(T zero), gives molecules the cohesiveness to form macromolecular structures. A method is described for evaluating delta H zero(T zero) at different temperatures for ribonuclease A at low pH in the standard state, in order to determine the effect of pH on the thermodynamic stability of this protein. Ribonuclease A at pH 1.13 has a delta H zero(T zero) value of 58 kcal mol-1; at pH 2.50, delta H zero(T zero) is 58, at pH 2.77, 59, and at pH 3.15, 60 kcal mol-1. In the conformational thermal transition of ribonuclease A at pH 2.8, the compensatory temperature ranges from 50 to 320 K, and delta H zero(T zero) is approximately 5-6 kcal mol-1. This widening temperature range is typical of the unfolding process. Such differences in the magnitude of the temperature-invariant chemical bond energy can be attributed to specific changes in the solvent ordering in the immediate domain of ribonuclease A.
普朗克 - 本津格热功函数ΔW₀(T)表示热通量项，它负责在大分子相互作用中破坏或形成非共价键，而与温度无关的化学键能ΔH₀(T₀)赋予分子形成大分子结构的内聚力。本文描述了一种在标准状态下评估低pH值时不同温度下核糖核酸酶A的ΔH₀(T₀)的方法，以确定pH对该蛋白质热力学稳定性的影响。pH为1.13时的核糖核酸酶A的ΔH₀(T₀)值为58千卡/摩尔；在pH 2.50时，ΔH₀(T₀)为58，在pH 2.77时为59，在pH 3.15时为60千卡/摩尔。在pH 2.8时核糖核酸酶A的构象热转变中，补偿温度范围为50至320 K，且ΔH₀(T₀)约为5 - 6千卡/摩尔。这种温度范围的拓宽是展开过程的典型特征。温度不变的化学键能大小的这种差异可归因于核糖核酸酶A紧邻区域中溶剂有序性的特定变化。
