College of Chemistry, Nankai University, Tianjin, 300071, People's Republic of China.
J Phys Chem B. 2012 Oct 11;116(40):12227-34. doi: 10.1021/jp304796p. Epub 2012 Oct 1.
The design of a bioactive surface with appropriate wettability for effective protein immobilization has attracted much attention. Previous experiments showed that the adsorption of hydrophobic protein HFBI onto a polydimethylsiloxane (PDMS) substrate surface can reverse the inherent hydrophobicity of the surface, hence making it suitable for immobilization of a secondary protein. In this study, atomistic molecular dynamics simulations have been conducted to elucidate the adsorption mechanism of HFBI on the PDMS substrate in an aqueous environment. Nine independent simulations starting from three representative initial orientations of HFBI toward the solid surface were performed, resulting in different adsorption modes. The main secondary structures of the protein in each mode are found to be preserved in the entire course of adsorption due to the four disulfide bonds. The relative binding free energies of the different adsorption modes were calculated, showing that the mode, in which the binding residues of HFBI fully come from its hydrophobic patch, is most energetically favored. In this favorable binding mode, the hydrophilic region of HFBI is fully exposed to water, leading to a high hydrophilicity of the modified PDMS surface, consistent with experiments. Furthermore, a set of residues consisting of Leu12, Leu24, Leu26, Ile27, Ala66, and Leu68 were found to play an important role in the adsorption of HFBI on different hydrophobic substrates, irrespective of the structural features of the substrates.
具有适当润湿性的生物活性表面设计对于有效固定蛋白质引起了广泛关注。先前的实验表明，疏水性蛋白 HFBI 吸附到聚二甲基硅氧烷（PDMS）基底表面可以逆转表面固有的疏水性，从而使其适合固定第二种蛋白质。在这项研究中，进行了原子分子动力学模拟以阐明 HFBI 在水相环境中在 PDMS 基底上的吸附机制。从 HFBI 相对于固体表面的三个代表性初始取向开始进行了九次独立的模拟，导致了不同的吸附模式。由于四个二硫键，在整个吸附过程中发现每种模式中蛋白质的主要二级结构都得以保留。计算了不同吸附模式的相对结合自由能，表明 HFBI 的结合残基完全来自其疏水性斑块的模式在能量上最有利。在这种有利的结合模式下，HFBI 的亲水区完全暴露于水中，导致修饰后的 PDMS 表面具有高亲水性，这与实验结果一致。此外，一组由 Leu12、Leu24、Leu26、Ile27、Ala66 和 Leu68 组成的残基被发现无论基底的结构特征如何，在 HFBI 吸附到不同疏水性基底上都起着重要作用。
