Preparation of SNAP_f-Beads for Colocalization Single-Molecule Spectroscopy (CoSMoS) of RNA-Protein Complexes

The SNAP_f-tag is a chemical tag that allows rapid and highly specific covalent labeling of proteins even in the full complexity of the cellular environment. The SNAP_f-tag has been instrumental to study native RNA-protein complexes at single-molecule resolution in their cellular environment as efficient labeling of the RNAs and proteins of interest is essential for this colocalization single-molecule spectroscopy (CoSMoS) technique. However, removal of excessive benzylguanine dye after the labeling reaction has remained challenging. Here, we describe a strategy to remove excessive benzylguanine dye using SNAP_f-tag coated beads as sponges.