Hladílková Jana, Callisen Thomas H, Lund Mikael
Division of Theoretical Chemistry, Lund University , P.O.B. 124, SE-22100 Lund, Sweden.
Novozymes A/S , Krogshoejvej 36, DK-2880 Bagsvaerd, Denmark.
J Phys Chem B. 2016 Apr 7;120(13):3303-10. doi: 10.1021/acs.jpcb.5b12225. Epub 2016 Feb 10.
Surface adsorption of Thermomyces lanuginosus lipase (TLL)-a widely used industrial biocatalyst-is studied experimentally and theoretically at different pH and salt concentrations. The maximum achievable surface coverage on a hydrophobic surface occurs around the protein isoelectric point and adsorption is reduced when either increasing or decreasing pH, indicating that electrostatic protein-protein interactions in the adsorbed layer play an important role. Using Metropolis Monte Carlo (MC) simulations, where proteins are coarse grained to the amino acid level, we estimate the protein isoelectric point in the vicinity of charged surfaces as well as the lateral osmotic pressure in the adsorbed monolayer. Good agreement with available experimental data is achieved and we further make predictions of the protein orientation at hydrophobic and charged surfaces. Finally, we present a perturbation theory for predicting shifts in the protein isoelectric point due to close proximity to charged surfaces. Although this approximate model requires only single protein properties (mean charge and its variance), excellent agreement is found with MC simulations.
对广泛应用于工业的生物催化剂嗜热栖热放线菌脂肪酶（TLL）在不同pH值和盐浓度下的表面吸附进行了实验和理论研究。在疏水性表面上可实现的最大表面覆盖率出现在蛋白质等电点附近，当pH值升高或降低时吸附都会减少，这表明吸附层中蛋白质之间的静电相互作用起着重要作用。使用将蛋白质粗粒度到氨基酸水平的 metropolis 蒙特卡罗（MC）模拟，我们估计了带电表面附近的蛋白质等电点以及吸附单层中的横向渗透压。与现有实验数据取得了良好的一致性，并且我们进一步预测了蛋白质在疏水和带电表面的取向。最后，我们提出了一种微扰理论，用于预测由于靠近带电表面而导致的蛋白质等电点的变化。尽管这个近似模型只需要单一的蛋白质性质（平均电荷及其方差），但与MC模拟结果吻合得很好。
