Department of Chemical and Biomolecular Engineering, 4 Engineering Drive 4, National University of Singapore, Singapore 117576.
J Phys Chem B. 2010 Mar 11;114(9):3077-84. doi: 10.1021/jp906433u.
Cationic and anionic poly(fluorenyleneethynylene-alt-benzothiadiazole)s (PFEBTs) are designed and synthesized via Sonagashira coupling reaction to show light-up signatures toward proteins. Due to the charge transfer character of the excited states, the fluorescence of PFEBTs is very weak in aqueous solution, while their yellow fluorescence can be enhanced by polymer aggregation. PFEBTs show fluorescence turn-on rather than fluorescence quenching upon complexation with proteins. Both electrostatic and hydrophobic interactions between PFEBTs and proteins are found to improve the polymer fluorescence, the extent of which is dependent on the nature of the polymer and the protein. Changes in solution pH adjust the net charges of proteins, providing an effective way to manipulate electrostatic interactions and in turn the increment in the polymer fluorescence. In addition, the effect of protein digestion on the fluorescence of polymer/protein complexes is probed. The results indicate that electrostatic interaction induced polymer fluorescence increase cannot be substantially reduced through cleaving protein into peptide fragments. In contrast, hydrophobic interactions, mainly determined by the hydrophobicity of proteins, can be minimized by digestion, imparting a light-off signature for the polymer/protein complexes. This study thus not only highlights the opportunities of exerting nonspecific interactions for protein sensing but also reveals significant implications for biosensor design.
通过 Sonagashira 偶联反应设计和合成了阳离子和阴离子聚（芴基乙炔-苯并噻二唑）（PFEBTs），以显示针对蛋白质的点亮特征。由于激发态的电荷转移特性，PFEBTs 在水溶液中的荧光非常弱，而其黄色荧光可以通过聚合物聚集得到增强。PFEBTs 与蛋白质结合时表现出荧光开启而不是荧光猝灭。发现 PFEBTs 与蛋白质之间的静电和疏水相互作用均能提高聚合物的荧光，其程度取决于聚合物和蛋白质的性质。溶液 pH 值的变化调节蛋白质的净电荷，为操纵静电相互作用并进而增加聚合物荧光提供了一种有效方法。此外，还研究了蛋白质消化对聚合物/蛋白质复合物荧光的影响。结果表明，通过将蛋白质切割成肽片段，不能显著减少静电相互作用诱导的聚合物荧光增加。相比之下，疏水相互作用主要由蛋白质的疏水性决定，可以通过消化最小化，从而赋予聚合物/蛋白质复合物熄灭特征。因此，这项研究不仅突出了发挥非特异性相互作用进行蛋白质检测的机会，而且还为生物传感器设计提供了重要启示。
