Department of Chemical Engineering, Columbia University, 500 W 120th St., New York, New York 10027, USA.
Langmuir. 2011 Oct 4;27(19):11873-82. doi: 10.1021/la202585r. Epub 2011 Sep 6.
A central paradigm that underpins our understanding of the interaction of proteins with solid surfaces is that protein adsorption leads to changes in secondary structure. The bound proteins tend to denature, and these non-native, adsorbed structures are likely stabilized through the loss of α-helices with the concomitant formation of intermolecular β-sheets. The goal of this work is to critically assess the impact this behavior has on protein desorption, where irreversible conformational changes might lead to protein aggregation or result in other forms of instability. The adsorption, desorption, and structural transitions of lysozyme are examined on fumed silica nanoparticles as a function of the amount of protein adsorbed. Surprisingly, the data indicate not only that adsorption is reversible but also that protein desorption is predictable in a coverage-dependent manner. Additionally, there is evidence of a two-state model which involves exchange between a native-like dissolved state and a highly perturbed adsorbed state. Since the in situ circular dichroism (CD) derived secondary structures of the adsorbed proteins are essentially unaffected by changes in surface coverage, these results are not consistent with previous claims that surface-induced denaturation is coverage dependent. Inspired by results from homopolymer adsorption experiments, we speculate that more local descriptors, such as the number of amino acids per chain that are physically adsorbed on the surface, likely control the desorption process.
一个支撑我们对蛋白质与固体表面相互作用理解的核心范例是，蛋白质吸附会导致二级结构的变化。结合的蛋白质往往会变性，这些非天然的吸附结构可能通过失去α-螺旋并伴随形成分子间β-折叠而稳定下来。这项工作的目的是批判性地评估这种行为对蛋白质解吸的影响，其中不可逆的构象变化可能导致蛋白质聚集或导致其他形式的不稳定性。溶菌酶在烟雾状二氧化硅纳米颗粒上的吸附、解吸和结构转变作为吸附蛋白质量的函数进行了研究。令人惊讶的是，数据不仅表明吸附是可逆的，而且蛋白质解吸是可预测的，且依赖于覆盖率。此外，有证据表明存在一种两态模型，涉及在类似天然的溶解态和高度受扰的吸附态之间的交换。由于原位圆二色性（CD）衍生的吸附蛋白质的二级结构基本上不受表面覆盖率变化的影响，这些结果与以前声称的表面诱导变性依赖于覆盖率的说法不一致。受均聚物吸附实验结果的启发，我们推测，更局部的描述符，例如物理吸附在表面上的每条链的氨基酸数量，可能控制解吸过程。
