作者:Cecilia Bombelli、Federico Bordi、Stefano Borocci、Marco Diociaiuti、Raffaella Lettieri、Francesca Limongelli、Giovanna Mancini、Simona Sennato
DOI:10.1039/c1sm05333g
日期:——
Four cationic amphiphilic fluorescent probes were synthesized and fully characterized. All amphiphiles feature a pyrrolidinium headgroup and a hydrocarbon tail tagged with a pyrene residue, and differ in the connection between the headgroup and the tagged tail, and in the hydrophilic/hydrophobic balance, two being single tail surfactants and the others twin type surfactants. The aggregation features were investigated by electrical conductivity, fluorescence, dynamic light scattering and transmission electron microscopy experiments. The obtained results show that changes in the molecular structure of the monomer, by affecting the aggregation behavior, have a strong influence on the conformation of the fluorophore inside the aggregate, and hence on its fluorescence features in aggregating conditions. In particular, the formation of pyrene dimers and/or excimers was observed only for the twin type surfactants, thus suggesting that a second alkyl chain is crucial for warranting a specific orientation of the pyrene moiety suitable for dimers or excimers formation. Moreover, the different linkage of the pyrene moiety to the alkyl chain in the twin type surfactants results in a remarkable difference in the organization of the aggregates they form, in fact only in the aggregates formed by one of the two surfactants the pyrene moiety is exposed at the lipid–water interface.
合成并全面表征了四种阳离子表面活性剂荧光探针。所有表面活性剂均具有吡咯烷铵头基和带有芘残基的碳氢尾,并且在头基与带标尾之间的连接以及亲水/疏水平衡上有所不同,其中两个是单尾表面活性剂,其他两个是双链表面活性剂。通过电导率、荧光、动态光散射和透射电子显微镜实验研究了它们的聚集特性。结果表明,单体分子结构的变化通过影响聚集行为,对聚集体内荧光团的构象产生强烈影响,从而影响其在聚集条件下的荧光特性。特别地,只有在双链表面活性剂中观察到芘二聚体和/或激发态二聚体的形成,这表明第二条烷基链对于保证芘基适当的取向以形成二聚体或激发态二聚体至关重要。此外,双链表面活性剂中芘基与烷基链的不同连接方式导致它们形成的聚集体组织存在显著差异,实际上,只有在其中一个表面活性剂形成的聚集体中,芘基才暴露在脂质-水界面上。