Fig. 1. Precedent and proposed linker for cysteine-specific dual protein bioconjugation. (a) 7-Oxanorbornadiene derivatives for cysteine-selective modification and retro Diels–Alder cleavage.20–22 (b) [2.2.1]Azabicyclic vinyl sulfones highlight the site of cysteine-selective modification, the second reactive handle for bioorthogonal labelling in cells and the explored point-of-attachment.
