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 本研究于277.15K、pH=7的条件下，通过蒙特卡洛（Monte Carlo）模拟，对由二甲基丙烯酰胺（DMA）、三聚氰胺基团（MG）和N-丙烯酰氧基琥珀酰亚胺（NAS）构成的聚合物基质上的IgG抗体Fc片段（Fc fragment）的交联反应进行了分析。吉布斯自由能与偶极矩结果表明，该反应可通过范德华相互作用自发进行。此外，定量结构-活性关系（QSAR）分析显示，表面面积与体积参数可用于实现Fc片段的物理吸附，该结论通过静电势图（MESP，Molecular Electrostatic Potential Map）的电子分布得到验证：图中可观察到亲核区域（蓝色）与亲电区域（红色），而分配系数（Log P）则反映了该过程的溶解性。随后，本研究针对Fc/聚合物基质体系中铽离子（Tb³+）在277.15K、pH=7条件下的吸附行为展开分析，结果发现Fc片段呈现出由铽离子诱导产生的平躺式最优几何构型，该过程伴随电子排斥作用、范德华力，且由半胱氨酸（Cys）残基形成的氢键构建了极性结构，这一结论通过Log P为负值得到佐证。最后，通过表面面积与体积参数分析发现，铽离子吸附过程的表面面积与体积随温度升高而增大。