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This study introduces a new photosensitized protein labeling method using pyridinium salts activated by a quinolinium scaffold. This efficient technique enables rapid labeling in minutes, even within live cells.

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Area of Science:

  • Biochemistry
  • Chemical Biology
  • Proteomics

Background:

  • Protein labeling is crucial for studying biomolecular functions.
  • Existing methods often face limitations in speed, efficiency, or compatibility with biological systems.

Purpose of the Study:

  • To develop a novel photosensitized strategy for efficient and mild protein labeling.
  • To optimize the sensitizer structure for rapid labeling at low concentrations.
  • To evaluate the system's compatibility with complex biological environments, including live cells.

Main Methods:

  • Utilized N-substituted pyridinium salts activated by a 2,4-diaryl-N-methyl quinolinium scaffold.
  • Performed structure-reactivity relationship studies to optimize sensitizer performance.
  • Conducted mechanistic studies involving photo-induced electron transfer.
  • Applied the method to individual biomolecules, complex proteomes, cell lysates, and live HeLa cells.
  • Employed chemical proteomics for protein enrichment and identification.

Main Results:

  • Developed an optimized photosensitized protein labeling system.
  • Achieved protein labeling within minutes at micromolar reagent concentrations.
  • Demonstrated high selectivity (93%) for Tryptophan residues in lysate-level studies, enriching 319 proteins.
  • Successfully labeled proteins in live cells, identifying 101 proteins, predominantly in the nucleus.
  • Confirmed catalysis occurs in multiple cellular compartments via imaging.

Conclusions:

  • The developed photosensitized strategy offers a rapid, efficient, and mild approach for protein labeling.
  • The system exhibits excellent compatibility with various biological contexts, from isolated biomolecules to live cells.
  • This method provides a powerful tool for chemical proteomics and cellular imaging, enabling deep insights into protein function and localization.