Salt-induced protein resistance of polyelectrolyte brushes studied using fluorescence correlation spectroscopy and neutron reflectometry
Salt-induced protein resistance of polyelectrolyte brushes studied using fluorescence correlation spectroscopy and neutron reflectometry
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DOI：
10.1039/b410805a
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发表时间：
2004-01-01
影响因子：
3.3
通讯作者：
Ballauff, M
中科院分区：
文献类型：
--
作者：
Czeslik, C;Jackler, G;Ballauff, M
我们使用双光子激发荧光相关光谱(FCS)和中子反射仪原位研究了盐浓度对蛋白质与聚电解质刷结合程度的影响。在中性pH条件下，牛血清白蛋白(BSA)与聚丙烯酸(PAA)刷子的结合特性表明，蛋白质和PAA刷子都带有负电荷。在FCS实验中使用球形PAA刷子，而在中子反射实验中使用平面PAA刷子作为蛋白质底物。研究发现，在低离子强度下，在静电斥力作用下，BSA与球形和平面型PAA刷子都有很强的结合。BSA体积分数PRO。根据中子反射率确定的LE，表明BSA分子深入PAA刷子。然而，对FCS数据的分析表明，当氯化钠浓度增加到100 mM时，球形PAA刷状粒子的蛋白质亲和力急剧下降。这一观测结果与平面PAA电刷的中子反射率测量结果是一致的。在没有蛋白质的情况下获得的反射率曲线与PAA刷子与含有500 mM氯化钠的BSA溶液接触时测得的反射率曲线几乎重叠，这表明平面PAA刷子在这种较高的盐浓度下具有蛋白质抗性。这项研究的结果为一种新型的蛋白质抗性界面提供了证据。虽然蛋白质与PAA刷子的结合可能由反离子的释放主导，但随着溶液离子强度的提高和空间相互作用使蛋白质分子从界面上排斥，这种驱动力消失。一般来说，通过在相对较小的范围内改变蛋白质溶液的离子强度来改变PAA刷子的蛋白质亲和力，似乎对生物技术应用是有用的。
We used two-photon excitation fluorescence correlation spectroscopy (FCS) and neutron reflectometry to study in situ the effect of salt concentration on the degree of protein binding to polyelectrolyte brushes. The binding of bovine serum albumin (BSA) to poly(acrylic acid) (PAA) brushes was characterized at neutral pH values where both the protein and the brushes carry a negative charge. Spherical PAA brush particles were used in the FCS experiments, whereas a planar PAA brush served as protein substrate in the neutron reflectometry experiments. It has been found that BSA binds strongly to both the spherical and the planar PAA brushes under electrostatic repulsion at low ionic strength. The BSA volume fraction pro. le, as determined from the neutron reflectivities, indicates a deep penetration of the BSA molecules into the PAA brush. However, the analysis of the FCS data reveals that the protein affinity of the spherical PAA brush particles decreases drastically when increasing the concentration of sodium chloride to a few 100 mM. This observation is in line with the measured neutron reflectivities of the planar PAA brush. The reflectivity curve obtained in the absence of protein is virtually overlapping with that measured when the PAA brush is in contact with a BSA solution but containing 500 mM sodium chloride which suggests protein resistance of the planar PAA brush at this elevated salt concentration. The results of this study provide evidence for a new kind of protein-resistant interfaces. Whereas protein binding to the PAA brush is likely to be dominated by the release of counterions, this driving force vanishes as the ionic strength of the solution is raised and protein molecules are repelled from the interface by steric interactions. In a general view, the "switching'' of the protein affinity of a PAA brush by varying the ionic strength of the protein solution over a relatively small range may appear to be useful for biotechnological applications.