生物含磷大分子与铀酰相互作用模拟计算研究

Simulated calculation of interaction between uranyl and biological macromolecules with phosphorous

摘要:

【目的】针对UO₂²⁺主要在生物细胞表面生成微纳米片状磷酸氢铀酰矿化体这一前期研究基础。【方法】本文采用模拟计算的方法，探究了磷脂(生物共有)、脂多糖(革兰氏阴性菌特有)、磷壁酸(革兰氏阳性菌特有)、植酸(植物特有)4种生物壁膜及胞外含磷大分子(biological macromolecules with phosphorous，BCP)与UO₂²⁺之间的相互作用力、作用能和间距等。【结果】蒙特卡罗分析结果表明：在弱酸性(UO₂²⁺)、中性至弱碱性(UO₂²⁺与CO₃^2–共存)两种体系下，BCP对UO₂²⁺的吸附均容易发生，吸附能分布在–109 kcal/mol至–114 kcal/mol之间。分子动力学结果显示，UO₂²⁺与BCP接触时，U原子主要与BCP的含P基团作用。在UO₂²⁺体系下，U-P距离较短的是脂多糖和植酸(6.662Å和6.539Å)；而UO₂²⁺与CO₃^2–体系中，U-P距离较短的是磷壁酸和磷脂(5.225Å和12.472Å)，这与BCP结构及其对UO₂²⁺的作用力有关。两种体系下，脂多糖对UO₂²⁺作用占主导的是静电力；磷壁酸和植酸对UO₂²⁺作用起主导的是范德华力；磷脂与UO₂²⁺作用时，范德华力与静电力相当。【结论】BCP与UO₂²⁺作用过程中，主要是磷酸基团对UO₂²⁺存在较强的亲和力和作用力，其在铀-磷的生物矿化过程中扮演成核位点的重要角色。

Abstract:

[Objective] Micro-nano flake hydrogen-autunite can be rapidly formed on the surface of biological cells. [Methods] Through simulated calculation, we investigated the interaction between uranyl and the biological macromolecules containing phosphorus (BCP) of phospholipid (ubiquitous in organisms), lipopolysaccharide (unique to Gram-negative bacteria), teichoic acid (unique to Gram-positive bacteria), and phytic acid (unique to plants), the interaction energy, and the distance between related atoms. [Results] According to the Monte Carlo analysis, the adsorption energy of teichoic acid, lipopolysaccharide, phospholipid and phytic acid fell between –109 kcal/mol and –114 kcal/mol in the pure uranyl system and the uranyl-carbonate system, and the energy was mainly relaxation deformation adsorption energy (E_deformation). Considering the adsorption ability and adsorption probability, lipopolysaccharide showed the best ability, followed by phospholipid, phytic acid and teichoic acid. The molecular dynamics relaxation showed that U atom mainly interacted with the group containing P in BPC in the case of uranyl interacting with BCP. In the pure uranyl system, U-P distance was the shortest in the presence of lipopolysaccharide and phytic acid (6.662 Å and 6.539 Å, respectively). In the uranyl-carbonate system, the U-P distance was the shortest in the presence of teichoic acid and phospholipid (5.225 Å and 12.472 Å, respectively). This can be explained with the structure of BCP and the acting force on uranyl. To be specific, in both systems, the dominant force of lipopolysaccharide acting on uranyl was electrostatic force, and that of teichoic acid and phytic acid was van der Waals force. As for the forces of phospholipid acting on uranyl, the van der Waals force was comparable to the electrostatic force. [Conclusion] To sum up, the phosphorus atoms in the phosphate groups have affinity for uranium atoms in uranyl in the process of interaction between the four biological macromolecules containing phosphorus and uranyl ions.