Sorption of proteins by slightly cross-linked polyelectrolyte hydrogels: Kinetics and mechanism
Sorption of proteins by slightly cross-linked polyelectrolyte hydrogels: Kinetics and mechanism
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DOI：
10.1021/jp035821f
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发表时间：
2004-01-29
影响因子：
3.3
通讯作者：
Zezin, AB
中科院分区：
文献类型：
--
作者：
Kabanov, VA;Skobeleva, VB;Zezin, AB
研究了微交联聚N，N-二甲基-N-乙氨基乙基甲基丙烯酸酯水凝胶在无盐和盐水溶液中对细胞色素c、溶菌酶和鱼精蛋白等蛋白质的吸附作用。当pH低于等电点时，聚阴离子水凝胶吸收蛋白质；当pH高于等电点时，聚阳离子水凝胶吸收蛋白质。结果是，高度膨胀的原始水凝胶转变为相对致密的交联聚电解质-蛋白质复合体。微交联聚电解质水凝胶对蛋白质的吸附是一个化学吸引的扩散过程。这一过程的驱动力来自于蛋白质与聚电解质网络的相反电荷段之间的聚电解质间偶联反应的自由能的增加。显然，蛋白质摄取的机制与早先提出的线性聚电解质相似。它包括蛋白质分子从聚电解质网络的一个片段到另一个片段的“接力-竞赛”转移，而不是通过聚电解质间交换反应进行径向混合。结果，在该过程的中间阶段形成了由外部弱膨胀的复合壳和高度膨胀的水凝胶核组成的“核-壳”结构。吸附速率由聚电解质间交换反应的速率决定，即在络合物-水凝胶内部边界上形成自由碎片的聚电解质网络(空位)的速率。空缺的数量取决于这一边界的面积。在中性无盐溶液中，水凝胶吸附蛋白质的动力学曲线不能用Fickian扩散项来拟合，而可以用前沿非均相反应的动力学方程来表示。同时，随着盐浓度的增加，蛋白质吸附动力学符合Fick扩散定律。
Sorption of proteins such as cytochrome c, lysozyme or protamine by slightly cross-linked poly(acrylic acid) and bovine serum albumin by slightly cross-linked poly(N,N-dimethyl-N-ethylaminoethyI methacrylate bromide) hydrogels in salt-free and saline aqueous solutions was studied. The polyanionic hydrogel uptakes the proteins at pH below their isoelectric points while polycationic one at pH above them. As a result highly swollen original hydrogel transforms into relatively compact cross-linked polyelectrolyte-protein complex. Sorption of proteins by slightly cross-linked polyelectrolyte hydrogels is a chemically drawn diffusion process. The driving force of the process comes from the gain in the free energy of the interpolyelectrolyte coupling reaction between the protein and oppositely charged segments of the polyelectrolyte network. Apparently the mechanism of protein uptake is similar to that earlier proposed for linear polyelectrolytes. It involves a "relay-race" transfer of protein molecules from one fragment of polyelectrolyte network to the other without radial mixing via interpolyelectrolyte exchange reaction. As a result "core-shell" constructs consisting of an outer weakly swollen complex shell and a highly swollen hydrogel core are formed at intermediate stages of the process. The rate of sorption is determined by the rate of the interpolyelectrolyte exchange reaction, that is the rate of the formation of free fragments of polyelectrolyte network (vacancies) on the inner complex-hydrogel boundary. The amount of vacancies depends on the area of this boundary. Kinetic curves of protein sorption by hydrogels in neutral salt-free solutions could not be fitted under the terms of Fickian diffusion but can be expressed in terms of the kinetic equation derived for a frontal heterogeneous reaction. At the same time kinetics of protein sorption obeys to Fick's diffusion law when the salt concentration increased.