Several applications arise from the confinement of proteins on surfaces because their stability and biological activity are enhanced. It is also known that the way in which a protein adsorbs on the surface is important for its biological function since its active sites should not be obstructed. In this study, the adsorption properties of hen egg-white lysozyme, HEWL, into a negatively charged silica pore is examined by employing a coarse-grained model and constant-pH Monte Carlo simulations. The role of electrostatic interactions is taken into account via including the Debye–Hückel potentials into the Cα structure-based model. We evaluate the effects of pH, salt concentration, and pore radius on the protein preferential orientation and spatial distribution of its residues regarding the pore surface. By mapping the residues that stay closer to the pore surface, we find that the increase of pH leads to orientational changes of the adsorbed protein when the solution pH gets closer to the HEWL isoelectric point. Under these conditions, the pK_a shift of these important residues caused by the adsorption into the charged confining surface results in a HEWL charge distribution that stabilizes the adsorption in the observed protein orientation. We compare our observations to the results of the pK_a shift for HEWL available in the literature and to some experimental data.

中文翻译：

---

溶菌酶吸附到带电限制孔中

一些应用源于将蛋白质限制在表面上，因为它们的稳定性和生物活性得到了增强。还已知蛋白质吸附在表面的方式对其生物学功能很重要，因为它的活性位点不应被阻塞。在这项研究中，通过采用粗粒度模型和恒定 pH 值蒙特卡罗模拟，研究了母鸡蛋白溶菌酶 HEWL 对带负电荷的二氧化硅孔的吸附特性。通过考虑静电相互作用的作用将 Debye-Hückel 势包括到基于 Cα 结构的模型中。我们评估了 pH 值、盐浓度和孔半径对蛋白质优先取向及其残基在孔表面的空间分布的影响。通过绘制更靠近孔表面的残基，我们发现当溶液 pH 值接近 HEWL 等电点时，pH 值的增加会导致吸附蛋白的方向发生变化。在这些条件下，由吸附到带电限制表面中引起的这些重要残基的 p K _a偏移导致 HEWL 电荷分布稳定了观察到的蛋白质方向的吸附。我们将我们的观察结果与 p K _a的结果进行比较 转移到文献中的 HEWL 和一些实验数据。