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Molecular aspects of glycine clustering and phase separation in an aqueous solution during anti-solvent crystallization
CrystEngComm ( IF 3.1 ) Pub Date : 2020-07-06 , DOI: 10.1039/d0ce00542h
Akira Kitayama 1, 2, 3, 4 , Kazunori Kadota 4, 5, 6 , Yuichi Tozuka 4, 5, 6 , Atsuko Shimosaka 1, 2, 3, 4 , Mikio Yoshida 1, 2, 3, 4 , Yoshiyuki Shirakawa 1, 2, 3, 4
Affiliation  

The anti-solvent crystallization behavior of the glycine aqueous and ethanol system was addressed through molecular dynamics simulation of a non-equilibrium state. A rectangular simulation cell was assigned to mimic the instant of the first contact state of the aqueous phase (solvent) and ethanol (anti-solvent). Here, glycine zwitterions began to aggregate into clusters with the invasion of ethanol into the aqueous phase, caused by the dehydration and supersaturation of the area. The number and size of clusters gradually increased with the formation and collapse of the clusters with time progression as liquid structures. The cluster structure reacted to the degree of supersaturation and exhibited higher probability of structured interaction modes, especially in ethanol rich areas. Pre-determination of the crystal polymorph during liquid–liquid phase separation was suggested for this water and ethanol anti-solvent system with the glycine zwitterion as the simplest amino acid, which contained multiple interaction sites. These findings agree with the experimental results and support the precursor behavior of nucleation and mechanism in the two-step nucleation theory and liquid–liquid phase separation.

中文翻译:

反溶剂结晶过程中水溶液中甘氨酸聚集和相分离的分子方面

通过非平衡态的分子动力学模拟,研究了甘氨酸水溶液和乙醇体系的抗溶剂结晶行为。分配了一个矩形模拟单元来模拟水相(溶剂)和乙醇(抗溶剂)的第一接触状态的瞬间。在这里,由于该区域的脱水和过饱和,甘氨酸两性离子开始聚集成簇,乙醇入侵水相。随着团簇的形成和崩溃,团簇的数量和大小随着液体结构的发展而逐渐增加。团簇结构对过饱和程度起反应,并显示出更高的结构化相互作用模式可能性,尤其是在乙醇富集的地区。对于该水和乙醇反溶剂系统,建议以甘氨酸两性离子为最简单的氨基酸(包含多个相互作用位点)对液相和液相分离过程中的晶体多晶型物进行预先测定。这些发现与实验结果吻合,并支持了两步成核理论和液-液相分离中成核的前驱行为和机理。
更新日期:2020-08-10
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