THE KINETICS OF THE THERMAL-DENATURATION OF COLLAGEN IN UNRESTRAINED RAT TAIL TENDON DETERMINED BY DIFFERENTIAL SCANNING CALORIMETRY
THE KINETICS OF THE THERMAL-DENATURATION OF COLLAGEN IN UNRESTRAINED RAT TAIL TENDON DETERMINED BY DIFFERENTIAL SCANNING CALORIMETRY
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DOI：
10.1006/jmbi.1994.0035
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发表时间：
1995-01-27
影响因子：
5.6
通讯作者：
BAILEY, AJ
中科院分区：
文献类型：
--
作者：
MILES, CA;BURJANADZE, TV;BAILEY, AJ
本文表明，胶原纤维变性内体的位置和形状受不可逆速率过程的动力学控制。这是通过测量在不同温度下等温保持的大鼠尾腱的变性速率来证明的，从而确定诸如活化焓和熵的速率常数特性，并由此预测吸热位置和形状。与实际扫描结果的比较显示出良好的correspondence.Isothermal测量的胶原蛋白变性的速率，连续使用量热法测量，用于确定浸泡在水和0.5 M乙酸的肌腱中的胶原蛋白变性的速率常数。将速率常数的温度依赖性拟合到三个速率过程模型，之前在理论上进行了研究：D和z公式、Arrhenius方程和绝对速率理论例如，在水中活化焓为0.518（+/-0.016）MJ mol（-1），活化熵为1.485（+/-0.049）kJ mol（-1）K-1，而在乙酸中相应的数值分别为1.306（+/-0.099）MJ mol（-1）和4.142（+/-0.323）kJ mol（-1）K-1。这些特点进行了讨论的热激活的一个区域的分子，合作单位。活化焓与量热变性焓的比值表明，当原纤维在乙酸中溶胀时，胶原分子基本上独立地起作用时，合作单位为66（+/-5）个残基长。另一方面，完整的原纤维在水中得到26（+/-1）个残基长的合作单位。合作单位尺寸减小的原因是它被纤维中的其他分子包围，因此被纤维中的其他分子稳定。值得注意的是，所建议的合作单位几乎完全位于胶原纤维的“间隙"区域内，分子呈四分之一交错排列。我们相信，合作单位将代表一个域，是免费的稳定羟脯氨酸残基。实际上，这样的结构域存在于从Gly 877到Pro 941的三螺旋的C末端附近，即65个残基。在乙酸中，活化类似于溶液中胶原分子的活化。合作单元中的所有α链间氢键都被破坏，并且在该短区域中的单独链在热碰撞的作用下自由地四处甩动，相对不受分子间相互作用的阻碍。在浸泡在水中的肌腱中，胶原蛋白分子更紧密地聚集在原纤维中，并且活化状态的可能构象的数量受到分子间相互作用的限制。这将合作单位的大小减少到约26个氨基残基。
This paper shows that the position and shape of the denaturation endothem of collagen fibrils are governed by the kinetics of an irreversible rate process. This was proved by measuring the rate of denaturation in rat tail tendons held isothermally at different temperatures, thereby determining rate constant characteristics such as the activation enthalpy and entropy and predicting endotherm position and shape therefrom. Comparison with actual scanning results showed good correspondence.Isothermal measurements of the rate of collagen denaturation, measured continuously using a calorimetric method, were used to determine rate constants for collagen denaturation in tendons immersed in water and 0.5 M acetic acid. The temperature dependence of the rate constants were fitted to the three rate process models, previously examined theoretically: the D and z formulation, the Arrhenius equation and the absolute rate theory For example, in water the activation enthalpy was 0.518 (+/-0.016) MJ mol(-1) and the activation entropy 1.485 (+/-0.049) kJ mol(-1) K-1, while in acetic acid the corresponding figures were 1.306 (+/-0.099) MJ mol(-1) and 4.142 (+/-0.323) kJ mol(-1) K-1. These characteristics are discussed in terms of the thermal activation of a region of the molecule, the co-operative unit. The ratio of the activation enthalpy to the calorimetry enthalpy of denaturation indicated a co-operative unit that was 66 (+/-5) residues long when fibrils were swollen in acetic and the collagen molecules acted essentially independently On the other hand the intact fibrils in water gave a co-operative unit of 26 (+/-1) residues long. The reason for the reduction in size of the co-operative unit is that it is surrounded, and therefore stabilized by other molecules in the fibre. It is interesting to note that the suggested co-operative unit lies almost entirely within the ''gap'' zone of the collagen fibril in its quarter-staggered arrangement of molecules. We believe that the co-operative unit would be represented by a domain that is free of stabilising hydroxyproline residues. Indeed such a domain exists near the C terminus of the triple helix from Gly877 to Pro941, i.e. 65 residues. In acetic acid, activation is similar to that of collagen molecules in solution. All the inter alpha-chain hydrogen bonds in the co-operative unit are broken and the separate chains in this short region are free to flail around under the action of thermal collisions relatively unimpeded by intermolecular interactions. In tendons bathed in water, the collagen molecules are more tightly packed together in fibrils and the number of possible conformations of the activated state is limited by inter-molecular interactions. This reduces the size of the co-operative unit to about 26 amino residues.