Deposition of colloid particles on protein layers: Fibrinogen on mica
Deposition of colloid particles on protein layers: Fibrinogen on mica
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DOI：
10.1016/j.jcis.2011.01.009
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发表时间：
2011-04-15
影响因子：
9.9
通讯作者：
Sadowska, M.
中科院分区：
文献类型：
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作者：
Adamczyk, Z.;Nattich, M.;Sadowska, M.
采用胶体颗粒沉积法对云母上扩散运输过程中受控吸附产生的纤维蛋白原单层进行了表征。通过调整吸附时间和体积Fb浓度，可获得理想表面浓度的单层膜。通过原子力显微镜对吸附在底物表面的单分子进行计数，直接测定了Fb的表面浓度。结果表明，在pH为3.5和pH为7.4的条件下，Fb在云母上均发生不可逆吸附，吸附速率受体输运控制。用流势法研究了用这种方法制备的Fb单层膜的电动力学性质。确定了Fb单层膜的zeta表观电位与复盖度的关系。结果表明，当pH为3.5时，当Fb覆盖率超过0.16时，云母基质的初始负zeta电位转化为正zeta电位。另一方面，当pH值为7.4时，fb覆盖云母的zeta电位在整个覆盖范围内保持为负。另外，采用胶体沉积法研究了带正电荷和带负电荷的聚苯乙烯乳胶颗粒（直径约800 nm）在Fb单层膜中的电荷分布。在显示负zeta电位的衬底上观察到负乳胶颗粒的异常沉积。假设吸附位点由两个和三个Fb分子组成，pH分别为3.5和7.4，这些实验结果根据波动理论进行了定量解释。这些结果表明，当pH为7.4时，Fb分子上的电荷分布是不均匀的，以正电荷斑块的存在为特征，而平均zeta电位为负，为-19 mV。胶体沉积法在研究Fb单分子膜方面的实用性在涉及正胶乳颗粒的沉积实验中得到进一步证明。结果表明，在相当大的纤维蛋白原覆盖范围内，正负极乳胶颗粒都可以吸附在Fb覆盖的表面上，从而表现为超吸附表面。胶体沉积法可以在其他方法无法达到的范围内测定Fb的体积浓度。(C) 2011爱思唯尔公司版权所有。
Colloid particle deposition was applied to characterize fibrinogen (Fb) monolayers on mica, which were produced by controlled adsorption under diffusion transport. By adjusting the time of adsorption and the bulk Fb concentration, monolayers of desired surface concentration were obtained. The surface concentration of Fb was determined directly by AFM enumeration of single molecules adsorbed over the substrate surface. It was proven that Fb adsorbed irreversibly on mica both at pH 3.5 and at pH 7.4 with the rate governed by bulk transport. The electrokinetic properties of Fb monolayers produced in this way were studied using the streaming potential method. The dependence of the apparent zeta potential of Fb monolayers was determined as a function of the coverage. It was shown that for pH 3.5 the initial negative zeta potential of the mica substrate was converted to positive for Fb coverage exceeding 0.16. On the other hand, for pH 7.4, the zeta potential of a Fb-covered mica remained negative for the entire coverage range. The charge distribution in Fb monolayers was additionally studied using the colloid deposition method, in which negatively and positively charged polystyrene latex particles (ca. 800 nm in diameter) were used. An anomalous deposition of negative latex particles on substrates exhibiting a negative zeta potential was observed. Results of these experiments were quantitatively interpreted in terms of the fluctuation theory assuming that adsorption sites consisted of two and three Fb molecules, for pH 3.5 and 7.4, respectively. These results suggested that for pH 7.4, the distribution of charge on Fb molecules was heterogeneous, characterized by the presence of positive patches, whereas the average zeta potential was negative, equal to -19 mV. The utility of the colloid deposition method for studying Fb monolayers was further demonstrated in deposition experiments involving positive latex particles. It was shown that for a rather broad range of fibrinogen coverage, both the positive and the negative latex particles can adsorb on surfaces covered by Fb, which behaved, therefore, as superadsorbing surfaces. It was also concluded that the colloid deposition method can be used to determine the Fb bulk concentration for the range inaccessible for other methods. (C) 2011 Elsevier Inc. All rights reserved.