Proximity Histidine Labeling by Umpolung Strategy Using Singlet Oxygen

Area of Science:

• Chemical Biology
• Organic Chemistry
• Biochemistry

Background:

• Electrophilic reagents are commonly used for histidine labeling.
• A need exists for alternative histidine functionalization strategies, particularly those enabling rapid and selective labeling.

Purpose of the Study:

• To report an umpolung strategy for histidine functionalization.
• To demonstrate rapid and selective protein labeling using singlet oxygen (¹O₂).
• To apply this method for nanometer-scale proximity labeling.

Main Methods:

• Utilized a nucleophilic small molecule, 1-methyl-4-arylurazole, for histidine labeling.
• Generated singlet oxygen (¹O₂) under controlled conditions.
• Employed a photocatalyst localized near a ligand-binding site for antibody Fc-selective labeling on magnetic beads.

Main Results:

• Achieved selective histidine labeling with the nucleophilic urazole under ¹O₂ generation.
• Demonstrated rapid antibody Fc-selective labeling using a localized photocatalyst.
• Identified three specific histidine residues around the binding site via liquid chromatography-mass spectrometry.

Conclusions:

• The developed umpolung strategy offers a new approach for histidine functionalization.
• Singlet oxygen-mediated histidine labeling is effective for rapid and selective protein labeling.
• This technique is suitable for nanometer-scale proximity labeling applications.