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Emergence of non-monotonic deep cavity cavitand assembly with increasing portal methylation
Molecular Systems Design & Engineering ( IF 3.2 ) Pub Date : 2019-09-27 , DOI: 10.1039/c9me00076c
Alexander Saltzman 1, 2, 3, 4 , Du Tang 1, 2, 3, 4 , Bruce C. Gibb 2, 3, 4, 5 , Henry S. Ashbaugh 1, 2, 3, 4
Affiliation  

Octa-acid (OA) and tetra-endo-methyl octa-acid (TEMOA) are deep cavity cavitands that readily form multimeric complexes with hydrophobic guests, like n-alkanes, in aqueous solution. Experimentally, OA displays a monotonic progression from monomeric to dimeric complexes with n-alkanes of increasing length, while TEMOA exhibits a non-monotonic progression from monomeric, to dimeric, to monomeric, to dimeric complexes over the same range of guest sizes. Previously we have conducted simulations demonstrating this curious behavior arises from the methyl units ringing TEMOA's portal to its hydrophobic pocket barring the possibility for two alkane chains to simultaneously bridge between two hosts in a dimer. Here we expand our prior simulation study to consider the partially methylated hosts mono-endo-methyl octa-acid, 1,3-di-endo-methyl octa-acid, and tri-endo-methyl octa-acid to examine the emergence of non-monotonic assembly behavior. Our simulations demonstrate a systematic progression of non-monotonic assembly with increasing portal methylation. This behavior is traced to the progressive destabilization of 2 : 2 complexes (two hosts assembled with two guests) rather than stabilizing other potential host/guest complexes that could be formed.

中文翻译:

门脉甲基化程度增加的非单调深腔空泡组件的出现

辛酸(OA)和四甲基辛酸(TEMOA)是深腔空洞体,它们在水溶液中容易与疏水性客体(如构烷烃)形成多聚体复合物。实验上,OA显示出从单体到二聚体的单调进展,n为-链烷烃的长度增加,而TEMOA在相同的客体尺寸范围内显示出从单体到二聚体,再到单体到二聚体的非单调进展。以前,我们已经进行了模拟,证明这种奇怪的行为是由于在TEMOA的入口到其疏水性口袋的甲基单元而引起的,这种甲基单元阻止了两个烷烃链同时在二聚体中的两个主体之间桥接的可能性。在这里,我们扩展了先前的模拟研究,以考虑部分甲基化的主体单--甲基八酸,1,3-二--甲基八酸和三--甲基八酸检查非单调组装行为的出现。我们的模拟表明非单调组装系统的进步与门甲基化的增加。此行为可追溯到2:2复合物(两个主体由两个来宾组装)的逐步不稳定,而不是稳定可能形成的其他潜在主体/客体复合物。
更新日期:2019-09-27
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