Figure 1

Siglec-9 peptide. (a) Sequence alignment of the C2₂ domain of Siglec-9 and peptide. Coloured in orange is Arg284 (R3) and in magenta Arg290 (R9). The conserved residues between Siglec-9 and the peptide are in bold. The first Cys and terminal Lys in the peptide are the only non-conserved residues. Cys forms a disulfide bridge to Cys14 (Cys295 in Siglec-9) to form the cyclic peptide. Residues in the peptide marked with a star were subjected to mutations. The alignment figure was generated with ESPrit⁴⁵. (b) Molecular structure of the Siglec-9 cyclic peptide. The PET tracer is attached to the terminal Lys (dashed box).