Masked acid chlorides for proximity labelling of RNA

A non-radical proximity labelling platform - BAP-seq - is presented that uses subcellular-localized BS2 esterase to convert unreactive enol-based probes into highly reactive acid chlorides in situ to label nearby RNAs. When paired with click-handle-mediated enrichment and sequencing, this chemistry enables high-resolution spatial mapping of RNAs across subcellular compartments.