Isothermal titration calorimetry (ITC) is a widely used tool to experimentally probe the heat signal of the formation of the protein corona around macromolecules or nanoparticles. If an appropriate binding model is applied to the ITC data, the heat of binding and the binding stoichiometry as well as the binding affinity per protein can be quantified and interpreted. However, the binding of the protein to the macromolecule is governed by complex microscopic interactions. In particular, due to the steric and electrostatic protein–protein interactions within the corona as well as cooperative, charge renormalization effects of the total complex, the application of standard (e.g., Langmuir) binding models is questionable and the development of more appropriate binding models is very challenging. Here, we discuss recent developments in the interpretation of the Langmuir model applied to ITC data of protein corona formation, exemplified for the well-defined case of lysozyme coating highly charged dendritic polyglycerol sulfate (dPGS), and demonstrate that meaningful data can be extracted from the fits if properly analyzed. As we show, this is particular useful for the interpretation of ITC data by molecular computer simulations where binding affinities can be calculated but it is often not clear how to consistently compare them with the ITC data. Moreover, we discuss the connection of Langmuir models to continuum binding models (where no discrete binding sites have to be assumed) and their possible extensions toward the inclusion of leading order cooperative electrostatic effects. Graphical Abstract Schematic plot of the ITC experiment and the binding cooperativity of protein corona formation revealed from computer simulations.

中文翻译：

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探测带电大分子周围的蛋白质电晕：通过结合模型和计算机模拟解释等温滴定量热法

等温滴定量热法 (ITC) 是一种广泛使用的工具，用于通过实验探测大分子或纳米粒子周围蛋白质电晕形成的热信号。如果将适当的结合模型应用于 ITC 数据，则可以量化和解释结合热和结合化学计量以及每个蛋白质的结合亲和力。然而，蛋白质与大分子的结合受复杂的微观相互作用控制。特别是，由于电晕内的空间和静电蛋白质 - 蛋白质相互作用以及整个复合物的协同电荷重整化效应，标准（例如，Langmuir）结合模型的应用是有问题的，并且开发更合适的结合模型非常具有挑战性。这里，我们讨论了应用于蛋白质电晕形成 ITC 数据的朗缪尔模型解释的最新进展，以溶菌酶包被高电荷树突状聚甘油硫酸酯 (dPGS) 的明确定义为例，并证明可以从拟合中提取有意义的数据如果分析得当。正如我们所展示的，这对于通过分子计算机模拟来解释 ITC 数据特别有用，其中可以计算结合亲和力，但通常不清楚如何将它们与 ITC 数据一致地进行比较。此外，我们讨论了朗缪尔模型与连续结合模型的联系（其中必须假设没有离散的结合位点）以及它们对包含领先顺序协同静电效应的可能扩展。