通过自由能计算和分子动力学模拟理解合成杂质如何影响草甘膦的溶解性和晶体生长
Understanding How Synthetic Impurities Affect Glyphosate Solubility and Crystal Growth Using Free Energy Calculations and Molecular Dynamics Simulations
AI总结：
本文通过分子动力学模拟和自由能计算，揭示甘氨酸如何通过吸附和增强溶解性影响草甘膦的结晶过程，为工业优化和环境评估提供分子层面的见解。
摘要：
草甘膦是全球最广泛使用的除草剂，其结晶过程通过复杂的分子间相互作用进行，这些相互作用强烈受到合成杂质的影响。在分子层面理解这一过程对于优化生产、确保产品质量和评估环境影响至关重要。本文采用直接共存分子动力学模拟和自由能计算，阐明了甘氨酸（一种常见的合成副产物）如何调节草甘膦在水溶液中的溶解性和晶体生长。我们的模拟发现，甘氨酸通过两种主要机制阻碍晶体生长。首先，直接共存模拟显示甘氨酸优先吸附在晶体表面，阻碍草甘膦的附着并减缓生长。其次，自由能计算表明甘氨酸增强了草甘膦的溶解性，降低了过饱和驱动力以将其纳入晶体相。实验测量证实了我们的预测，确认了甘氨酸系统中溶解性增强和晶体生长动力学减缓。这些发现表明，通常被视为惰性杂质的甘氨酸通过促进其溶解而主动破坏草甘膦的结晶。更广泛地说，这种整合的计算-实验方法突显了分子模拟在解析杂质效应、界面现象和溶液热力学在结晶中的能力，为优化工业规程和预测相关环境条件下农药行为提供了分子层面的见解。
英文摘要：
Glyphosate, the most widely used herbicide worldwide, crystallizes through complex intermolecular interactions that are strongly influenced by synthesis-derived impurities. Understanding this process at the molecular scale is critical for optimizing production, ensuring product quality, and assessing environmental impact. Here, we employ direct coexistence molecular dynamics simulations and free energy calculations to elucidate how glycine-a prevalent synthesis byproduct-modulates glyphosate solubility and crystal growth in aqueous solutions. Our simulations identify two major mechanisms by which glycine hinders crystallization. First, direct coexistence simulations show that glycine preferentially adsorbs at crystal surfaces, hindering glyphosate attachment and slowing growth. Second, free energy calculations demonstrate that glycine enhances glyphosate solubility, reducing the supersaturation driving force to incorporate into the crystal phase. Experimental measurements corroborate our predictions, confirming both enhanced solubility and reduced crystallization kinetics in glycine-bearing systems. These findings establish that glycine-typically considered an inert impurity-actively disrupts glyphosate crystallization by promoting its dissolution. More broadly, this integrated computational-experimental approach highlights the power of molecular simulations to disentangle impurity effects, interfacial phenomena, and solution thermodynamics in crystallization, providing molecular-level insights for optimizing industrial protocols and predicting agrochemical behavior under relevant environmental conditions.
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