Colocalization of NP1024 and FP-2 in malaria parasite-infected erythrocytes in vitro. FP-2 (first column): images were collected with excitation at 405 nm and emission at 422 nm; NP1024 (second column): images were collected with excitation at 488 nm and emission at 520 nm; Merge (third column): co-localization was observed between NP1024 and the fluorescently labeled secondary antibody (points 1, 2, 4, 5, 6, 7 and 8). Exquisite colocalization between the green fluorescence of NP1024 and the red fluorescence of the secondary antibody of FP-2 was clearly observed. In some erythrocytes, there was only the red fluorescence and not the green fluorescence visible (points 3 and 9), indicating that there was no interference between these two fluorescent signals and NP1024 could not enter into all erythrocytes at the concentration chosen. In general, NP1024 entered into erythrocytes and directly bound to FP-2, which was highly expressed in the trophozoite stage of the parasites.

Zhu L, Shan L, Zhu J, Li L, Li S, Wang L, Wang J, Zhang S, Zhou H, Zhang W, Li H. Discovery of a natural fluorescent probe targeting the Plasmodium falciparum cysteine protease falcipain-2. Sci China Life Sci. 2020 Feb 9.