An efficient excitation energy transfer (EET) cassette, i.e.Ir-Np-OH, has been constructed by connecting an Ir(III) complex phosphor as an acceptor to a naphthalimide fluorophore as a donor. Ir-Np-OH emits dual emissions, with one highly dependent on oxygen concentration and the other completely independent. Thus, Ir-Np-OH exhibits a sensitive and quantitative response to oxygen level in a ratiometric way. The linear response of Ir-Np-OH ranges from 0% (0 mmHg) to 10% (76 mmHg) oxygen tension, which matches very well with intracellular oxygen levels. And the ratiometric oxygen sensing of Ir-Np-OH is completely reversible. Also, importantly, Ir-Np-OH possesses a subcellular targetability specifically toward endoplasmic reticulum (ER), as proved by the co-localization imaging experiment. This feature of Ir-Np-OH should be noted, because generally speaking, it is much more challenging for small-molecule probes to target ER than other subcellular organelles, e.g. mitochondria. By using Ir-Np-OH, an apparent increase in oxygen level from 5.17% (39.29 mmHg) to 7.29% (55.40 mmHg) is monitored in ER of live MCF-7 cells, during the 30 minute stimulation with Rotenone, a typical inhibitor of the mitochondrial respiratory chain. In addition, upon ER stress directly induced by TG (Thapsigargin), the gradual increase in oxygen concentration is also clearly detected. These results confirm that Ir-Np-OH is a promising tool for oxygen-related cellular and chemical biology.

中文翻译：

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用荧光团-磷能量转移盒定量监测内质网中的氧变化†

通过将作为受体的Ir（III）络合物磷光体作为供体的萘二甲酰亚胺荧光团连接，构建了有效的激发能转移（EET）盒，即Ir-Np-OH。Ir-Np-OH会产生双重排放，一种高度依赖于氧气浓度，另一种完全独立于氧气。因此，Ir-Np-OH以比例方式表现出对氧含量的灵敏和定量响应。Ir-Np-OH的线性响应范围为0％（0 mmHg）到10％（76 mmHg）氧气张力，这与细胞内的氧气含量非常匹配。Ir-Np-OH的比例氧感测是完全可逆的。另外，重要的是Ir-Np-OH共定位成像实验证明，它具有专门针对内质网（ER）的亚细胞靶向性。应该指出Ir-Np-OH的这一特征，因为通常来说，小分子探针比其他亚细胞器（例如线粒体）靶向ER更具挑战性。通过使用Ir-Np-OH，在活体MCF-7细胞的ER中监测了氧水平从5.17％（39.29 mmHg）到7.29％（55.40 mmHg）的明显增加，其中典型的抑制剂鱼藤酮刺激了30分钟线粒体呼吸链。另外，在由TG（Thapsigargin）直接诱导的ER应力下，也清楚地检测到氧气浓度的逐渐增加。这些结果证实了Ir-Np-OH 是与氧有关的细胞和化学生物学的有前途的工具。