Michael Smith Laboratories and the Biological Engineering, University of British Columbia, Rm. 301, 2185 East Mall, Vancouver, British Columbia, Canada V6T 1Z3.
Biotechnol Bioeng. 2012 Mar;109(3):615-29. doi: 10.1002/bit.24349. Epub 2011 Dec 25.
The Zonal Rate Model (ZRM) has previously been shown to accurately account for contributions to elution band broadening, including external flow nonidealities and radial concentration gradients, in ion-exchange membrane (IEXM) chromatography systems operated under nonbinding conditions. Here, we extend the ZRM to analyze and model the behavior of retained proteins by introducing terms for intra-column mass transfer resistances and intrinsic binding kinetics. Breakthrough curve (BTC) data from a scaled-down anion-exchange membrane chromatography module using ovalbumin as a model protein were collected at flow rates ranging from 1.5 to 20 mL min(-1). Through its careful accounting of transport nonidealities within and external to the membrane stack, the ZRM is shown to provide a useful framework for characterizing putative protein binding mechanisms and models, for predicting BTCs and complex elution behavior, including the common observation that the dynamic binding capacity can increase with linear velocity in IEXM systems, and for simulating and scaling separations using IEXM chromatography. Global fitting of model parameters is used to evaluate the performance of the Langmuir, bi-Langmuir, steric mass action (SMA), and spreading-type protein binding models in either correlating or fundamentally describing BTC data. When combined with the ZRM, the bi-Langmuir, and SMA models match the chromatography data, but require physically unrealistic regressed model parameters to do so. In contrast, for this system a spreading-type model is shown to accurately predict column performance while also providing a realistic fundamental explanation for observed trends, including an observed increase in dynamic binding capacity with flow rate.
区域速率模型（ZRM）先前已被证明能够准确地解释在非结合条件下操作的离子交换膜（IEXM）色谱系统中洗脱带展宽的贡献，包括外部流动非理想性和径向浓度梯度。在这里，我们通过引入柱内传质阻力和固有结合动力学的术语，将 ZRM 扩展到分析和模拟保留蛋白的行为。使用卵清蛋白作为模型蛋白，在从 1.5 到 20 mL min(-1)的流速范围内，从小型阴离子交换膜色谱模块中收集突破曲线（BTC）数据。通过仔细考虑膜堆内外的传输非理想性，ZRM 被证明为表征潜在蛋白质结合机制和模型提供了有用的框架，用于预测 BTC 和复杂的洗脱行为，包括在 IEXM 系统中动态结合容量随线性速度增加的常见观察结果，以及使用 IEXM 色谱模拟和缩放分离。通过全局拟合模型参数，评估 Langmuir、双 Langmuir、立体质量作用（SMA）和扩展型蛋白质结合模型在关联或从根本上描述 BTC 数据时的性能。当与 ZRM 结合使用时，双 Langmuir 和 SMA 模型可以匹配色谱数据，但需要回归模型参数不切实际，才能做到这一点。相比之下，对于该系统，扩展型模型能够准确预测柱性能，同时为观察到的趋势提供合理的基本解释，包括观察到动态结合容量随流速增加而增加。
