Fig. 1

Multimodal measurements enabled by ABPP. a Generic format of an activity-based probe, including a reactive group for irreversible binding to an enzyme target, a binding group that biases the probe toward a particular class of enzymes and/or a spacer region that can impart cell permeability, and a reporter group to enable multimodal readout of probe labeling. b The activity-based probes are added directly to living cells or cell lysates and irreversibly bind target proteins. Click chemistry enables the addition of biotin for enrichment and quantitative liquid chromatography–mass spectrometry (LC–MS) of probe targets. Alternatively, fluorophores are added by click chemistry for gel analysis of target proteins, imaging to quantify uptake and distribution of labeling, and/or cell sorting to quantify uptake