Exploration of the Reactivity of Multivalent Electrophiles for Affinity Labeling: Sulfonyl Fluoride as a Highly Efficient and Selective Label.

Here we explored the reactivity of a set of multivalent electrophiles cofunctionalized with a carbohydrate ligand on gold nanoparticles to achieve efficient affinity labeling for target protein analysis. Evaluation of the reactivity and selectivity of the electrophiles against three different cognate binding proteins identified arylsulfonyl fluoride as the most efficient protein-reactive group in this study. We demonstrated that multivalent arylsulfonyl fluoride probe 4 at 50 nm concentration achieved selective affinity labeling and enrichment of a model protein PNA in cell lysate, which was more effective than photoaffinity probe 1 with arylazide group. Labeling site analysis by LC-MS/MS revealed that the nanoparticle-immobilized arylsulfonyl fluoride group can target multiple amino acid residues around the ligand binding site of the target proteins. Our study highlights the utility of arylsulfonyl fluoride as a highly effective multivalent affinity label suitable for covalently capturing unknown target proteins.