Latour Robert A
Department of Bioengineering, 501 Rhodes Engineering Research Center, Clemson University, Clemson, South Carolina, 29634.
J Biomed Mater Res A. 2015 Mar;103(3):949-58. doi: 10.1002/jbm.a.35235. Epub 2014 Jun 3.
The Langmuir adsorption isotherm provides one of the simplest and most direct methods to quantify an adsorption process. Because isotherm data from protein adsorption studies often appear to be fit well by the Langmuir isotherm model, estimates of protein binding affinity have often been made from its use despite that fact that none of the conditions required for a Langmuir adsorption process may be satisfied for this type of application. The physical events that cause protein adsorption isotherms to often provide a Langmuir-shaped isotherm can be explained as being due to changes in adsorption-induced spreading, reorientation, clustering, and aggregation of the protein on a surface as a function of solution concentration in contrast to being due to a dynamic equilibrium adsorption process, which is required for Langmuir adsorption. Unless the requirements of the Langmuir adsorption process can be confirmed, fitting of the Langmuir model to protein adsorption isotherm data to obtain thermodynamic properties, such as the equilibrium constant for adsorption and adsorption free energy, may provide erroneous values that have little to do with the actual protein adsorption process, and should be avoided. In this article, a detailed analysis of the Langmuir isotherm model is presented along with a quantitative analysis of the level of error that can arise in derived parameters when the Langmuir isotherm is inappropriately applied to characterize a protein adsorption process.
朗缪尔吸附等温线提供了一种最简单、最直接的方法来量化吸附过程。由于蛋白质吸附研究中的等温线数据似乎常常能很好地拟合朗缪尔等温线模型，因此尽管对于这类应用而言，朗缪尔吸附过程所需的条件可能一个都不满足，但人们常常还是根据其来估算蛋白质的结合亲和力。导致蛋白质吸附等温线常常呈现出朗缪尔形状的物理过程，可以解释为是由于蛋白质在表面上的吸附诱导铺展、重新定向、聚集和团聚随溶液浓度变化而发生的改变，而不是像朗缪尔吸附所要求的那样，是由于动态平衡吸附过程。除非能够确认朗缪尔吸附过程的要求，否则将朗缪尔模型拟合到蛋白质吸附等温线数据以获得诸如吸附平衡常数和吸附自由能等热力学性质，可能会提供与实际蛋白质吸附过程几乎无关的错误值，应该避免这种做法。在本文中，我们对朗缪尔等温线模型进行了详细分析，并对朗缪尔等温线不适当地用于表征蛋白质吸附过程时，在推导参数中可能出现的误差水平进行了定量分析。
