Designer Aromatic Cations for Photoinduced Protein Ligation, Imaging, and Intracellular Labeling at Extended...

Area of Science:

• Chemical Biology
• Biochemistry
• Organic Chemistry

Background:

• Photoinduced protein labeling is crucial in chemical biology.
• Existing methods often require high-energy light, limiting applications.
• A previous study introduced biarylpyridinium salts for biocompatible photoinduced electron transfer (PET) protein labeling.

Purpose of the Study:

• To design novel aromatic cation salts for photoinduced protein labeling using longer wavelengths of light.
• To maintain a sterically minimal profile for the new probes.
• To explore structure-reactivity relationships for optimized probe design.

Main Methods:

• Systematic study of structure-reactivity relationships in donor-acceptor pyridinium salts with extended conjugation.
• Design and synthesis of novel aromatic cation salts, particularly those with chromene-based donor groups.
• Application of probes for live cell imaging and photoinduced protein labeling using green light.
• Mass spectrometry-based proteomic analysis to identify labeled proteins and cellular localization.

Main Results:

• Identified a constrained trans-stilbene relationship as critical for protein labeling.
• Developed probes with chromene-based donors exhibiting robust labeling, high fluorescence quantum yields, and state-dependent photophysical properties.
• Achieved wash-free, live cell imaging and photoinduced labeling with green light using two distinct probes.
• Mass spectrometry revealed distinct proteomic enrichment from mitochondria and endoplasmic reticulum with minimal overlap (<10%).

Conclusions:

• The developed probes enable photoinduced protein labeling with lower-energy light in complex proteomes.
• These probes offer new capabilities for photophysical state-dependent reactivity and measurements.
• The probes facilitate targeted labeling within specific cellular organelles, advancing chemical biology tools.