Department of Physics, The Chinese University of Hong Kong , Shatin, N.T., Hong Kong.
J Phys Chem B. 2017 Apr 20;121(15):3394-3402. doi: 10.1021/acs.jpcb.6b08589. Epub 2016 Dec 8.
Molecular dynamics simulations of nanoparticles (NPs) are increasingly used to study their interactions with various biological macromolecules. Such simulations generally require detailed knowledge of the surface composition of the NP under investigation. Even for some well-characterized nanoparticles, however, this knowledge is not always available. An example is nanodiamond, a nanoscale diamond particle with surface dominated by oxygen-containing functional groups. In this work, we explore using the harmonic restraint method developed by Venable et al., to estimate the surface charge density (σ) of nanodiamonds. Based on the Gouy-Chapman theory, we convert the experimentally determined zeta potential of a nanodiamond to an effective charge density (σ), and then use the latter to estimate σ via molecular dynamics simulations. Through scanning a series of nanodiamond models, we show that the above method provides a straightforward protocol to determine the surface charge density of relatively large (> ∼100 nm) NPs. Overall, our results suggest that despite certain limitation, the above protocol can be readily employed to guide the model construction for MD simulations, which is particularly useful when only limited experimental information on the NP surface composition is available to a modeler.
纳米粒子（NPs）的分子动力学模拟越来越多地用于研究它们与各种生物大分子的相互作用。这种模拟通常需要详细了解所研究的 NP 的表面组成。然而，即使对于一些特征明确的纳米粒子，也不一定能获得这种知识。纳米金刚石就是一个例子，它是一种表面主要由含氧官能团组成的纳米级金刚石颗粒。在这项工作中，我们探索了使用 Venable 等人开发的调和约束方法来估计纳米金刚石的表面电荷密度（σ）。根据 Gouy-Chapman 理论，我们将纳米金刚石的实验测定的 Zeta 电位转换为有效电荷密度（σ），然后使用后者通过分子动力学模拟来估计 σ。通过扫描一系列纳米金刚石模型，我们表明，上述方法为确定相对较大（>∼100nm）NP 的表面电荷密度提供了一种直接的方案。总的来说，我们的结果表明，尽管存在某些限制，上述方案仍可以很容易地用于指导 MD 模拟的模型构建，当模型构建者只能获得 NP 表面组成的有限实验信息时，这尤其有用。
