– (+)-JQ1 maleimide, featuring a cysteine-reactive maleimide linked to the BRD4 ligand, JQ1, via a PEG2 linker, serves as a probe suitable for the COFFEE method (COvalent Functionalization Followed by E3 Electroporation). This approach facilitates the covalent attachment of (+)-JQ1 maleimide to VHL, followed by electroporation into live cells, where the E3 ligase complexes with intracellular BRD4 to prompt its degradation.