Figure 1. Multi-species SPT labeling strategy.

CTB-QD705 labels specifically up to 5 ganglioside G_M1molecules through direct binding of CTB to G_M1 (left). CoA-QD655 is covalently coupled to GPI-anchored protein CD59^ACP in presence of the enzyme ACP synthase (center). SAV-QD605 targets biotinylated EGFR^BLAP. The BLAP-tag is biotinylated during the secretory transport pathway when cells are grown in presence of biotin and are co-expressing bacterial biotin ligase (BirA-IgGκ-KDEL) [53].