Self-consistent field theory of protein adsorption in a non-Gaussian polyelectrolyte brush
Self-consistent field theory of protein adsorption in a non-Gaussian polyelectrolyte brush
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DOI：
10.1103/physreve.73.011802
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发表时间：
2006-01-01
影响因子：
2.4
通讯作者：
Stuart, MAC
中科院分区：
文献类型：
--
作者：
Biesheuvel, PM;Leermakers, FAM;Stuart, MAC
为了描述球形蛋白质分子在聚电解质电刷中的吸附，我们使用爱德华兹自洽场方程的强拉伸近似，并结合非高斯电刷的修正。为了描述这种大小变化很大的（球状）物质（离子、刷状聚电解质片段、球状蛋白质分子）混合物中的化学势，我们使用了为球形颗粒的多分散混合物导出的boublikk - mansoori - carnahan - starling - leland状态方程。在这种方法中，聚电解质链被描述为一串珠子，珠子的大小与链的直径有关。我们使用一维泊松方程来描述静电场，并包括电刷多离子和蛋白质分子的可电离性。该模型解释了在pH值高于蛋白质等电点时，聚酸刷中大量蛋白质吸附的实验观察结果，这是由于蛋白质分子在进入刷时的电荷反转。我们发现在刷子边缘附近蛋白质浓度明显最低。随着pH值的增加，蛋白质转移的屏障变得更大，但当我们增加离子强度时，这种屏障变得更小，这种差异可能与实验观察到的这两种情况下蛋白质释放率的差异有关。自由能分析表明，电刷中小离子的释放和电刷电离度的增加是类电荷电刷中蛋白质吸附的两个驱动力。
To describe adsorption of globular protein molecules in a polyelectrolyte brush we use the strong-stretching approximation of the Edwards self-consistent field equation, combined with corrections for a non-Gaussian brush. To describe chemical potentials in this mixture of (globular) species of widely varying sizes (ions, brush polyelectrolyte segments, globular protein molecules), we use the Boublik-Mansoori-Carnahan-Starling-Leland equation of state derived for polydisperse mixtures of spherical particles. The polyelectrolyte chain is described in this approach as a string of beads with the beads of a size related to the chain diameter. We use the one-dimensional Poisson equation to describe the electrostatic field and include the ionizable character of both the brush polyions and the protein molecules. This model explains the experimental observation of high amounts of protein adsorption in a polyacid brush for pH values above the isoelectric point of the protein as being due to charge reversal of the protein molecules upon entry in the brush. We find a distinct minimum in protein concentration near the edge of the brush. With increasing pH this barrier to protein transfer becomes larger, but much less so when we increase the ionic strength, a difference that might relate to an experimentally observed difference in the protein release rate in these two cases. A free energy analysis shows that the release of small ions from the brush and the increase of brush ionization are the two driving forces for protein adsorption in a like-charged brush.