Near-Infrared-Light-Activatable Proximity Labeling of Bead-Binding Proteins

Photocatalytic proximity labeling has recently undergone significant advances as a valuable tool for understanding protein–protein and cell–cell interactions. This paper reports the first photocatalytic protein-labeling approach in which the reaction can be controlled using near-infrared (NIR) light (810 nm). Magnetic affinity beads with encapsulated sulfur-substituted silicon (IV) phthalocyanine, which produces singlet oxygen upon NIR irradiation, were prepared. We have developed a method in which the histidine residues of proteins bound to the ligands on the beads are selectively oxidized and labeled by the nucleophilic labeling reagent while minimizing nonspecific adsorption to the dye. Beads with aryl sulfamide, lactose, or CZC-8004 ligands immobilized on their surface can be used to label proteins that bind these ligands, as well as their protein–protein interaction partners.