L-Azidonorleucine hydrochloride, an unnatural amino acid, serves as a surrogate for Methionine. It is utilized for labeling mammalian cell proteins and identifying a broad range of methionyl-tRNA synthetase (MetRS) mutants.

CHO cells transfected with pMaRSC and incubated with L-Azidonorleucine (Anl; 1.5 mM; 6 h) are fixed, permeabilized, and treated with alkyne-TAMRA. The TAMRA fluorescence exclusively in the mCherry-expressing cells is observed, consistent with cell-selective incorporation of Anl into cellular proteins[1].

When L-Azidonorleucine (ANL) is administered via the drinking water, an average daily L-Azidonorleucine intake of 0.9 mg/day/g of body weight for 21 d when aiming to label and identify neuronal populations of the brain are recommended. Lower dosages or shorter labeling times might be used for the labeling of other cell types. When L-Azidonorleucine is administered by i.p. injection, the testing different L-Azidonorleucine doses in the range of 4-400 mM are recommended. A 400 mM dosage administered by i.p. (i.p. volume: 10 ml/kg) once per day for 1 week is recommended for labeling some neuronal populations (such as excitatory neurons of the hippocampus). Lower dosages (e.g., 4 mM) can potentially be used for labeling other cell types or when longer labeling periods are desired[2].