A cyanine fluorophore 2-[4-N,N-diphenylaminostyryl]-β-naphthothiazolium propylsulfonate, N3, was synthesized. The asymmetric probe N3 displayed aggregation-induced emission (AIE) characteristic in DMSO/H2O mixtures, whereas it presented twisted intra-molecular charge transfer (TICT) non-emissive state in Dioxane/H2O (Diox/H2O) mixtures. Both the AIE and TICT state could be modulated by proteins, exhibiting switch effect. In DMSO/H2O mixtures with 90% water fractions (fw), protein molecules adsorbed upon the aggregated crystalline nanoparticles of N3 and spread over the surface, thus the strong fluorescence emission of N3 was quenched. The different degree of quenching among proteins revealed that the adsorption of proteins on N3 aggregate particles arose from both hydrophobic and electrostatic interactions. The quenched ratio (I0/I) vs the concentration of positively protein lysozyme (Lys) gave a Langmuir type curve. In Diox/H2O mixtures with 90% fw, the addition of bovine serum albumin (BSA) led to the reduction of non-emissive TICT state and made the fluorescence emission of N3 switch on. The large difference of N3 fluorescence emission toward BSA over other proteins including human serum albumin allowed us to establish a sensitive probe for BSA. An ON-OFF and OFF-ON dual-modal red-emitting fluorescence probe for proteins was established.

中文翻译：

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基于 AIE 或 TICT 状态调制的蛋白质双模态红光荧光探针

合成了花青荧光团 2-[4-N,N-二苯基氨基苯乙烯基]-β-萘噻唑鎓丙磺酸盐，N3。不对称探针 N3 在 DMSO/H2O 混合物中表现出聚集诱导发射 (AIE) 特性，而在二恶烷/H2O (Diox/H2O) 混合物中呈现扭曲的分子内电荷转移 (TICT) 非发射状态。AIE 和 TICT 状态都可以被蛋白质调节，表现出开关效应。在含有 90% 水份 (fw) 的 DMSO/H2O 混合物中，蛋白质分子吸附在聚集的 N3 结晶纳米粒子上并扩散到表面，从而淬灭 N3 的强荧光发射。蛋白质之间不同程度的淬灭表明蛋白质在 N3 聚集体颗粒上的吸附来自疏水和静电相互作用。淬灭比 (I0/I) 与阳性蛋白溶菌酶 (Lys) 的浓度给出了朗缪尔型曲线。在 90% fw 的 Diox/H2O 混合物中，牛血清白蛋白 (BSA) 的添加导致非发射 TICT 状态的降低并使 N3 的荧光发射开启。与其他蛋白质（包括人血清白蛋白）相比，对 BSA 的 N3 荧光发射的巨大差异使我们能够为 BSA 建立灵敏的探针。建立了一种用于蛋白质的ON-OFF和OFF-ON双模态发红光荧光探针。与其他蛋白质（包括人血清白蛋白）相比，对 BSA 的 N3 荧光发射的巨大差异使我们能够为 BSA 建立灵敏的探针。建立了一种用于蛋白质的ON-OFF和OFF-ON双模态发红光荧光探针。与其他蛋白质（包括人血清白蛋白）相比，对 BSA 的 N3 荧光发射的巨大差异使我们能够为 BSA 建立灵敏的探针。建立了一种用于蛋白质的ON-OFF和OFF-ON双模态发红光荧光探针。