N-Acryloylindole-alkyne (NAIA) enables profiling new ligandable hotspots in chemoproteomics experiments and imaging thiol oxidation

We report a new class of compounds, N-acryloylindole-alkynes (NAIAs), as promising cysteine-reactive probes for proteome-wide cysteine profiling and imaging of thiol oxidative modifications. NAIAs showed superior cysteine reactivity owing to delocalization of π electrons of the acrylamide warhead over the whole indole scaffold, resulting in its activation for faster reaction with cysteines. This allows NAIAs to ligand functional cysteines more effectively than IAA, as well as to image oxidized thiols in cells facing oxidative stress by confocal fluorescence microscopy. In MS-based ABPP experiments, NAIAs successfully captured a new pool of ligandable cysteines and proteins even compared to the current state-of-the-art cysteine profiling data. Competitive ABPP experiments further demonstrate the ability of NAIA to discover hit compounds targeting these new cysteines and proteins. This work should initiate development of new cysteine-reactive probes, particularly those with activated acrylamide, for advancing cysteine imaging and profiling, and covalent ligand screening for drug research.