“…However, in many cases it may be necessary to combine or replace a suppressor-based methodology with other approaches [17] including SNAP-tag technology, FlaSH-tag approaches, GFP fusions, classical Cys modifications, [18] and even semisynthetic methods such as expressed enzymatic or native protein ligations. [19] For example, ncAA approaches are not suitable when backbone modifications are examined, pulsechase experiments are required, large nonnatural segments need to be introduced, when protein immobilization is required or when subsequent modification may not work owing to low concentrations. Therefore, despite the current success, this is just the beginning of an emerging field that requires chemistry compatible with biological systems.…”