Determinants of Cyanuric Acid and Melamine Assembly in Water
Determinants of Cyanuric Acid and Melamine Assembly in Water
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DOI：
10.1021/la201415d
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发表时间：
2011-07-19
期刊：
影响因子：
3.9
通讯作者：
Bong, Dennis
中科院分区：
文献类型：
--
作者：
Ma, Mingming;Bong, Dennis
虽然已知三聚氰胺 (M) 及其衍生物对氰尿酸 (CA) 的识别在水和有机溶剂中都会发生一段时间，但对水中 CA/M 组装的分析尚未见报道 (Ranganathan, A.; Pediredcli, V. R; Rao, C. N. R J. Am. Chem. Soc. 1999, 121, 1752-1753; Mathias, J. P.;西马内克 (Simanek)，C. T.；怀特塞德斯 (G. M. Symp)，1994 年，157-166；麦克唐纳 (J. C.)；怀特塞德斯 (G. M. J. Chem)，1994 年。 2382-2391; Mathias, J. P.; Seto, C. T.; Whitesides, G. M. Polym. Prepr. 1993, 34, 92-93; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1993, 115, 905-916; Zerkowski, J. A.; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1992, 114, 5473-5475; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1990, 112, 6409-6411; Wang, Y.; Wei, B.; Wang, Q, J. Chem. Cryst. 1990, 20, 79-84; 10 Cate, M. G. J.; Crego-Calama, M.; Reinhoudt, D. N. Chem.-Eur. 2004, 10, 3632-3639。我们结合使用溶液相 NMR、等温滴定和差示扫描量热法 (ITC/DSC)、低温透射电子显微镜 (cryo-TEM) 和合成化学，研究了 CA/M 的组装以及可溶性三价 CA 和 M 衍生物 (TCA/TM) 在水性溶剂中的组装。虽然母体杂环在水中共沉淀，但三价系统表现出更受控和协作的组装，其在比母体更低的浓度下发生，并产生稳定的纳米颗粒悬浮液。亲本系统和三价系统的组装严格按照 1:1 进行，并在中性 pH 水中以放热、质子转移偶联过程进行。尽管 CA 和 M 被认为是有机溶剂中的典型氢键基序，但我们发现它们在水中的组装很大程度上是由热函有利的表面积埋藏驱动的，类似于核酸识别中观察到的情况。目前，很少有合成系统能够在水中进行强大的分子识别，并且不依赖于天然识别基序，这可能是由于对水中识别过程的不完全理解。这项研究建立了一个详细的概念框架来考虑水中的 CA/M 杂环识别，这使得未来设计在水中起作用的分子识别系统成为可能。
While the recognition of cyanuric acid (CA) by melamine (M) and their derivatives has been known to occur in both water and organic solvents for some time, analysis of CA/M assembly in water has not been reported (Ranganathan, A.; Pediredcli, V. R; Rao, C. N. R J. Am. Chem. Soc. 1999, 121, 1752-1753; Mathias, J. P.; Simanek, E. E.; Seto, C. T.; Whitesides, G. M. Macromol. Symp. 1994, 77, 157-166; Zerkowski, J. A.; MacDonald, J. C.; Seto, C. T.; Wierda, D. A.; Whitesides, G. M. J. Am. Chem. Soc. 1994, 116, 2382-2391; Mathias, J. P.; Seto, C. T.; Whitesides, G. M. Polym. Prepr. 1993, 34, 92-93; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1993, 115, 905-916; Zerkowski, J. A.; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1992, 114, 5473-5475; Seto, C. T.; Whitesides, G. M. J. Am. Chem. Soc. 1990, 112, 6409-6411; Wang, Y.; Wei, B.; Wang, Q, J. Chem. Cryst. 1990, 20, 79-84; ten Cate, M. G. J.; Huskens, J.; Crego-Calama, M.; Reinhoudt, D. N. Chem.-Eur. J. 2004, 10, 3632-3639). We have examined assembly of CA/M, as well as assembly of soluble trivalent CA and M derivatives (TCA/TM), in aqueous solvent, using a combination of solution phase NMR, isothermal titration and differential scanning calorimetry (ITC/DSC), cryo-transmission electron microscopy (cryo-TEM), and synthetic chemistry. While the parent heterocycles coprecipitate in water, the trivalent system displays more controlled and cooperative assembly that occurs at lower concentrations than the parent and yields a stable nanoparticle suspension. The assembly of both parent and trivalent systems is rigorously 1:1 and proceeds as an exothermic, proton-transfer coupled process in neutral pH water. Though CA and M are considered canonical hydrogen-bonding motifs in organic solvents, we find that their assembly in water is driven in large part by enthalpically favorable surface-area burial, similar to what is observed with nucleic acid recognition. There are currently few synthetic systems capable of robust molecular recognition in water that do not rely on native recognition motifs, possibly due to an incomplete understanding of recognition processes in water. This study establishes a detailed conceptual framework for considering CA/M heterocycle recognition in water which enables the future design of molecular recognition systems that function in water.