How many stereocentres does the tripeptide shown contain in total? Count every stereocentre in all residues, including side chains, and give your answer as an integer.

The residues are Gly-Thr-Ile. Glycine is achiral (0). Threonine has two stereocentres (C-alpha and the carbinol carbon) and isoleucine has two (C-alpha and the beta carbon). The total is 0 + 2 + 2 = 4, confirmed by RDKit.