Adsorption of terbium ion on Fc/dymethylacrylamide: application of Monte Carlo simulation

Abstract The crosslinking of the Fc fragment (IgG antibody) on a polymer matrix about of dimethylacrylamide (DMA), melamide group (MG) and n-acryloxy succinimide (NAS) was analyzed through Monte Carlo simulation at 277.15K and pH 7, in where Gibs free energy and the dipole moment indicated the spontaneity of the reaction through van der Waals interactions. In addition, the QSAR properties determinated that both the surface area and the volume allow to carry out the physical adsorption of the Fc fragment that was verified through the electronic distribution of the electrostatic potential maps (MESP) where the nucleophilic zones (blue color) and electrophilic (red color) were observed, while the partition coefficient (Log P) indicated the solubility of the process. Subsequently, the analysis of the adsorption of the terbium ion (Tb+3) at 277.15K and a pH 7 in Fc/polymeric matrix was carried out, observing that the Fc fragment presented a flat-on optimization geometry attributed to the Tb+3 that generates electronic repulsions, as well as van der Waals forces, hydrogen bonds derived from the Cys aminoacids formed a polar structure and that was corroborated by the Log P negative. Finally, the surface area and volume determined that Tb+3 adsorption showed an increase in surface area and volume with temperature.

摘要 本研究针对以二甲基丙烯酰胺（dimethylacrylamide, DMA）、蜜胺基团（melamide group, MG）与N-丙烯酰氧基琥珀酰亚胺（n-acryloxy succinimide, NAS）构成的聚合物基质上的Fc片段（IgG抗体）的交联反应，于277.15K、pH=7条件下开展蒙特卡洛模拟（Monte Carlo simulation）分析。研究通过吉布斯自由能（Gibbs free energy）与偶极矩（dipole moment），证实该反应可通过范德华相互作用（van der Waals interactions）自发进行。此外，定量构效关系（Quantitative Structure-Activity Relationship, QSAR）分析结果表明，表面面积与体积参数可支撑Fc片段的物理吸附过程，该结论通过静电势图（Molecular Electrostatic Potential Maps, MESP）的电子分布得到验证：图中可观测到亲核区域（蓝色）与亲电区域（红色）；而分配系数（partition coefficient, Log P）则反映了该过程的溶解性。随后，本研究针对Fc/聚合物基质在277.15K、pH=7条件下对铽离子（terbium ion, Tb³+）的吸附过程展开分析，观测到Fc片段因铽离子产生的电子排斥作用呈现平躺式优化几何构型；同时，范德华力与源自半胱氨酸（cysteine, Cys）的氢键共同形成了极性结构，该结果通过Log P为负值得到佐证。最后，通过表面面积与体积参数分析可知，铽离子吸附过程的表面面积与体积随温度升高而增大。