Department of Chemistry, Beijing Key Laboratory of Microanalytical Methods and Instrumentation, Tsinghua University , Beijing, 100084, P.R. China.
Anal Chem. 2017 Jan 17;89(2):1238-1243. doi: 10.1021/acs.analchem.6b03813. Epub 2017 Jan 3.
A colorless and nonfluorescent spirolactam derivative, RhB-RK, was synthesized by amide condensation between the carboxyl group of rhodamine B (RhB) and the amino group of cell-penetrating peptide (CPP). The fluorescence intensity of RhB-RK sharply increased as the pH value decreased from 8.0 to 4.9, demonstrating sensitive and reversible response to intracellular pH distribution. This CPP probe was completely water soluble, had low cytotoxicity, was membrane permeable, and was suitable for pH measurement in various organelles by choosing organelle-specific CPP sequences. Interestingly, CPPs acted not only as carriers but also as indispensable parts of fluorophores here. The presence of active groups on the peptides potentially allows for modification with additional dyes to construct multifunctional and ratiometric probes for cell imaging.
一种无色非荧光螺环酰胺衍生物 RhB-RK 通过罗丹明 B（RhB）的羧基与穿膜肽（CPP）的氨基酰胺缩合反应合成。当 pH 值从 8.0 降低到 4.9 时，RhB-RK 的荧光强度急剧增加，对细胞内 pH 分布表现出灵敏且可逆的响应。该 CPP 探针完全水溶性、细胞毒性低、膜通透性好，并可通过选择细胞器特异性 CPP 序列，适用于各种细胞器中的 pH 值测量。有趣的是，CPP 不仅作为载体，而且作为荧光团的不可或缺的组成部分发挥作用。肽上的活性基团的存在可能允许与其他染料进行修饰，构建用于细胞成像的多功能和比率型探针。
