Ingr Marek, Kutálková Eva, Hrnčiřík Josef, Lange Reinhard
Tomas Bata University in Zlín, Faculty of Technology, Department of Physics and Materials Engineering, nám. T. G. Masaryka 5555, 76001 Zlín, Czechia; Charles University in Prague, Faculty of Science, Department of Biochemistry, Hlavova 2030, 12843 Prague 2, Czechia.
Tomas Bata University in Zlín, Faculty of Technology, Department of Physics and Materials Engineering, nám. T. G. Masaryka 5555, 76001 Zlín, Czechia.
J Theor Biol. 2016 Dec 21;411:16-26. doi: 10.1016/j.jtbi.2016.10.001. Epub 2016 Oct 4.
High pressure methods have become a useful tool for studying protein structure and stability. Using them, various physico-chemical processes including protein unfolding, aggregation, oligomer dissociation or enzyme-activity decrease were studied on many different proteins. Oligomeric protein dissociation is a process that can perfectly utilize the potential of high-pressure techniques, as the high pressure shifts the equilibria to higher concentrations making them better observable by spectroscopic methods. This can be especially useful when the oligomeric form is highly stable at atmospheric pressure. These applications may be, however, hindered by less intensive experimental response as well as interference of the oligomerization equilibria with unfolding or aggregation of the subunits, but also by more complex theoretical description. In this study we develop mathematical models describing different kinds of oligomerization equilibria, both closed (equilibrium of monomer and the highest possible oligomer without any intermediates) and consecutive. Closed homooligomer equilibria are discussed for any oligomerization degree, while the more complex heterooligomer equilibria and the consecutive equilibria in both homo- and heterooligomers are taken into account only for dimers and trimers. In all the cases, fractions of all the relevant forms are evaluated as functions of pressure and concentration. Significant points (inflection points and extremes) of the resulting transition curves, that can be determined experimentally, are evaluated as functions of pressure and/or concentration. These functions can be further used in order to evaluate the thermodynamic parameters of the system, i.e. atmospheric-pressure equilibrium constants and volume changes of the individual steps of the oligomer-dissociation processes.
高压方法已成为研究蛋白质结构和稳定性的有用工具。利用这些方法，人们对许多不同的蛋白质研究了包括蛋白质解折叠、聚集、寡聚体解离或酶活性降低在内的各种物理化学过程。寡聚蛋白质解离是一个能够完美利用高压技术潜力的过程，因为高压会使平衡向更高浓度移动，从而使它们通过光谱方法更易于观察。当寡聚形式在大气压下高度稳定时，这一点尤其有用。然而，这些应用可能会受到实验响应不够强烈、寡聚平衡对亚基解折叠或聚集的干扰的阻碍，也会受到更复杂的理论描述的阻碍。在本研究中，我们开发了描述不同类型寡聚平衡的数学模型，包括封闭型（单体与无任何中间体的最高可能寡聚体之间的平衡）和连续型。我们讨论了任意寡聚化程度下的封闭型同型寡聚平衡，而对于二聚体和三聚体，仅考虑了更复杂的异型寡聚平衡以及同型和异型寡聚体中的连续平衡。在所有情况下，所有相关形式的分数都作为压力和浓度的函数进行评估。可以通过实验确定的所得转变曲线的关键点（拐点和极值），作为压力和/或浓度的函数进行评估。这些函数可进一步用于评估系统的热力学参数，即大气压平衡常数和寡聚体解离过程各个步骤的体积变化。
