Sreenivasachary Nampally, Lehn Jean-Marie
Laboratoire de Chimie Supramoléculaire, Institut de Science et d'Ingénierie Supramoléculaires (ISIS), Université Louis Pasteur, 8 Allée Gaspard Monge, BP 70028, 67083 Strasbourg Cedex, France.
Proc Natl Acad Sci U S A. 2005 Apr 26;102(17):5938-43. doi: 10.1073/pnas.0501663102. Epub 2005 Apr 19.
The guanosine hydrazide 1 yields a stable supramolecular hydrogel based on the formation of a guanine quartet (G-quartet) in presence of metal cations. The effect of various parameters (concentration, nature of metal ion, and temperature) on the properties of this gel has been studied. Proton NMR spectroscopy is shown to allow a molecular characterization of the gelation process. Hydrazide 1 and its assemblies can be reversibly decorated by acylhydrazone formation with various aldehydes, resulting in formation of highly viscous dynamic hydrogels. When a mixture of aldehydes is used, the dynamic system selects the aldehyde that leads to the most stable gel. Mixing hydrazides 1, 9 and aldehydes 6, 8 in 1:1:1:1 ratio generated a constitutional dynamic library containing the four acylhydrazone derivatives A, B, C, and D. The library constitution displayed preferential formation of the acylhydrazone B that yields the strongest gel. Thus, gelation redirects the acylhydrazone distribution in the dynamic library as guanosine hydrazide 1 scavenges preferentially aldehyde 8, under the pressure of gelation because of the collective interactions in the assemblies of G-quartets B, despite the strong preference of the competing hydrazide 9 for 8. Gel formation and component selection are thermoreversible. The process amounts to gelation-driven self-organization with component selection and amplification in constitutional dynamic hydrogels based on G-quartet formation and reversible covalent connections. The observed self-organization and component selection occur by means of a multilevel self-assembly involving three dynamic processes, two of supramolecular and one of reversible covalent nature. They extend constitutional dynamic chemistry to phase-organization and phase-transition events.
鸟苷酰肼1在金属阳离子存在下基于鸟嘌呤四重奏（G-四重奏）的形成产生稳定的超分子水凝胶。研究了各种参数（浓度、金属离子性质和温度）对该凝胶性质的影响。结果表明，质子核磁共振光谱可对凝胶化过程进行分子表征。酰肼1及其组装体可通过与各种醛形成酰腙而可逆地修饰，从而形成高粘性的动态水凝胶。当使用醛的混合物时，动态体系会选择能导致形成最稳定凝胶的醛。将酰肼1、9与醛6、8按1:1:1:1的比例混合，生成了一个包含四种酰腙衍生物A、B、C和D的组成动态库。该库的组成显示出酰腙B的优先形成，其产生的凝胶最强。因此，由于G-四重奏B组装体中的集体相互作用，在凝胶化压力下，鸟苷酰肼1优先清除醛8，凝胶化改变了动态库中酰腙的分布，尽管竞争酰肼9对醛8有强烈偏好。凝胶的形成和组分选择是热可逆的。该过程相当于基于G-四重奏形成和可逆共价连接的凝胶化驱动的自组织，在组成动态水凝胶中进行组分选择和放大。观察到的自组织和组分选择是通过涉及三个动态过程（两个超分子过程和一个可逆共价性质的过程）的多级自组装实现的。它们将组成动态化学扩展到相组织和相变事件。
