Fig. 4. Switchable small molecule motifs for controlling peptide conformation. (a) Azobenzene-based linker for peptide cyclisation, UV light induces formation of the cis-isomer, which reverts to the trans-state when subjected to visible light. (b) Diarylethene-based cyclisation linker which adopts the “closed” form upon UV irradiation, switching back to the “open” form facilitated by visible light. (c) Iminoboronate-mediated peptide cyclisation, linkage readily cleaved by acidification (pH 6), oxidation (peroxynitrite) or treatment with α-nucleophiles (hydrazine). Small molecule components are highlighted in red.
