Target identification and occupancy measurement of necrosis avid agent rhein using bioorthogonal chemistry-enabling probes

Necrosis is an important biomarker, which only occurs in pathological situations. Tracking of necrosis avid agents is of crucial importance toward understanding their mechanisms. Herein, we developed a modular probe strategy based on bioorthogonal copper-free click chemistry. Structural modification of rhein with transcyclooctene (TCO) led to the identification of rhein-TCO2 as the most active probe with specific necrosis affinity. In a systematic evaluation, the colocalization of rhein-TCO2 in the nucleus (exposed DNA and rRNA) of necrotic cells was observed. This work provides a foundation for the development of target-identified of rhein compounds, and binding to exposed DNA and rRNA may be an important target of rhein compounds in necrotic cells.